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IMPROVING THE VALUE AND SUSTAINABILITY OF LAYING HEN MANURE MAY 2019

A BRITISH FREE RANGE EGG PRODUCERS ASSOCIATION SUSTAINABILITY SCHEME REPORT

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A BRITISH FREE RANGE EGG PRODUCERS ASSOCIATION SUSTAINABILITY SCHEME REPORT 03

Contents Executive Summary 04

1 Introduction 08 1.1 Poultry manure: resource or waste? 09 1.2 Changing legislative requirements 10 1.3 Alternative uses of poultry manures 11 1.4 Aims of this report 12 2 Key legislation and impacts on land spreading 14 2.1 Nitrate vulnerable zones (NVZs) 15 2.2 Environmental permitting 19 2.3 Farming rules for water 21 2.4 Clean air strategy 22 3 Fertiliser values of poultry manure 23 3.1 Nutrient content of poultry manures 25 3.2 Poultry manure values 27 3.3 Maximizing fertiliser value - housing and management factors 28

4 Alternative uses of poultry manure 32

4.1 Incineration 34 4.2 Drying and pelleting 46 4.3 Composting 55 4.4 Anaerobic digestion 64

5 Conclusions 78

6 Photographs 86

Authors Jason Gittins Jon Walton ADAS Unit 10D, Cefn Llan Science Park, Aberystwyth SY23 3AH

EXECUTIVE SUMMARY

This report provides a practical guide for farmers who are currently spreading poultry manure onto their own land, exporting it to land operated by others or considering alternative uses for it. The background is a changing legislative and policy landscape which is likely to impact in future upon both manure utilisation methods and new poultry housing systems. The Farming Rules for Water (announced by Defra in 2018) seek to tackle diffuse pollution from agriculture and include new requirements on land spreading and preventing pollution risk. The Clean Air Strategy (launched by Defra early in 2019) sets out new rules to minimise pollution from organic and inorganic fertiliser use. It introduces the issue of mandatory design standards for new poultry housing.

Added to this are the impacts of recent trends in the free range sector. In certain parts of the country, there are now large numbers of farms with free range egg production enterprises. Locally, this can mean a surplus of poultry manure relative to fertiliser requirements on neighbouring land and therefore additional manure haulage costs. For producers who are currently land-spreading poultry manure, this report has estimated the current value of key nutrients contained (nitrogen, phosphorus and potassium). At 50% manure dry matter content, the value is likely to be between £20 and £26 per tonne according to application time and method. A key variable is the dry matter content of the manure. Further calculations show that at 80% dry matter, the value rises to £41 per tonne. These prices relate to the value of the nutrients contained

05A BRITISH FREE RANGE EGG PRODUCERS ASSOCIATION SUSTAINABILITY SCHEME REPORT

in the manure and they therefore exclude the costs of haulage and land-spreading. In a review of alternative uses for poultry manure, the report considers manure incineration, drying and pelleting, composting and anaerobic digestion. The outputs from these processes can be summarised as either i) a dry, solid product which is easier to store, handle and spread than ‘fresh’ poultry manure and therefore has greater potential value or ii) a fuel which can be used to generate electricity or heat, together with a residual product which also has a saleable value. The report provides a concise profile of each process and the conclusions section includes a ‘side-by-side’ comparison in the form of a single table. A brief outline of each process is provided below. 1 Incineration Dry manures (over 55% dry matter) can be incinerated to provide on-farm heat or to generate electricity that can be used either on-farm or exported to the grid. Payments may be received from government incentive schemes such as the Feed in Tariff (FIT) and the Renewable Heat Incentive (RHI). The residual ash also has a saleable value. Capital costs are high and therefore this method is likely to be

considered only by very large free range producers (over 100,000 birds) or by local groups operating on a collaborative basis. 2 Drying and pelleting Drying laying hen manure increases its nutrient value and makes it easier to handle. The process can use air from the poultry house or waste heat from other sources such as anaerobic digestion or incineration. Drying systems can be set up next to the poultry house and the smallest available is considered suitable for 12,000 birds. Once dried, pelleting the manure can then add further value through sale as a fertiliser for commercial or domestic use. Pelleting systems are more expensive to install and run than drying systems and it is considered that a minimum of around 64,000 birds would be needed to justify the costs. 3 Composting Poultry manure can be composted but it needs to be combined with a carbon-rich material to optimise the process. The economic model for composting normally relies on a gate fee being charged for incoming raw materials such as ‘green waste’. This can provide a substantial part (or all) of the revenue received. Although the compost itself has useful fertiliser value, the prices obtained for it are often

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low. Low capital cost ‘windrow’ systems can be used for composting and this can be undertaken outdoors on a concrete base or within an existing building, if available. However the process is likely to be quicker and better controlled if more expensive ‘in-vessel’ systems are used. 4 Anaerobic digestion Anaerobic digestion takes organic materials (generally wastes) and in anaerobic conditions, produces gas which is used for energy generation. The digestion process makes a more homogenous and stable product from the original feedstock and this can be used as a fertiliser. The high nitrogen content of poultry manure generally limits its inclusion within a feedstock mix to 20% although new technological developments aim to allow the use of up to 100% poultry manure in future. In addition, laying hen manure contains calcium grit which is unsuitable for use in AD unless the system enables grit extraction. The report finds that in general, capital costs of ‘alternative’ manure utilisation systems are high and that there is a lack of systems tailored to smaller producers. The Clean Air Strategy indicates that future support may be available to farmers (although the details are not yet available) and assistance with capital

costs could encourage and hasten change in the sector. For on-farm systems that produce heat (such as incineration and anaerobic digestion), there are opportunities to use a proportion of this to provide warmth to free range houses at certain times of the year. This could provide added benefits including reduced ammonia and drier manure and litter. If high capital costs continue to make investment in alternative uses for manure ‘out-of-reach’ for smaller producers, there may be increased interest in collaborative approaches. A model could be developed whereby a manure handling facility is established at a central site, serving the needs of a number of local producers, who would all supply manure to it. Such an approach could also become increasingly attractive if future controls mean that farmers cannot continue indefinitely with their current land spreading activities.


1 INTRODUCTION

1.1 Poultry manure: resource or waste?Poultry manure and used litter are inevitable by-products of free range egg production. They can be viewed either as a valuable resource – for use on farm or sold to third parties - or alternatively as a waste to be disposed of. It is well-known that manure and used litter from poultry is a valuable source of the plant nutrients nitrogen, phosphorus, potassium and sulphur. When spread to land, these nutrients reduce the need for manufactured nutrients to be applied to meet optimum plant demand. Poultry manures also provide additional benefits, such as helping to improve soil structure. However, manure application to land must be carefully managed in order to maximise fertiliser values, to minimise nutrient losses to the environment and to ensure that odour

emissions and potential fly infestations are avoided. For producers with little or no additional land for spreading, suitable arrangements must be made with recipient neighbouring farmers. In some areas with high poultry populations and limited available land this may be difficult and the potential saleable value of the manure can be offset by high transport costs.


In England, poultry manure spreading is closely controlled in nitrate vulnerable zones (NVZ). Poultry farmers who are outside NVZ area but who operate with an environmental permit (exceeding 40,000 bird places) are subject to similar requirements. Further controls were announced by Defra in the form of the Farming Rules for Water (April 2018)1 and the ‘Clean Air Strategy’2 (January 2019) which includes plans for further legislation to reduce ammonia emissions.

Considered together, existing and planned new legislation is likely to impose extra control over poultry manure spreading to land. This may require additional and therefore more distant land to be made available, with consequential increases in transport costs. With this in mind, some producers are now considering alternative uses of poultry manure both to ‘future-proof’ their businesses and to achieve additional income from the laying hen manure produced.

1.2 Changing legislative requirements

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1 www.gov.uk/government/publications/farming-rules-for-water-in-england 2 www.gov.uk/government/publications/clean-air-strategy-2019

Alternative uses of poultry manure and used litter have been under consideration for many years. However interest has recently increased, partly due to the likelihood of additional land spreading controls. Farmers with larger flock sizes may face more difficulties in finding local land for spreading. However these may be best-placed to adopt alternative manure uses, due to economies of scale. The main processes used to produce alternative products from manures include incineration, drying, pelleting, composting and digesting.

To date, these systems have been adopted by very few egg producers and the vast majority still use traditional land–spreading for their manures. By contrast, there has been more uptake of alternatives to land-spreading in the broiler sector, including the construction of large power-generating plants in the east of England which use broiler litter as a raw material. This probably reflects differences in the nature and analysis of manures from laying hens and litters from broilers and the different scale of the two sectors.

1.3 Alternative uses of poultry manures


This report provides a practical guide for farmers who are currently spreading poultry manure onto their own land, exporting it to land operated by others or considering alternative uses. Current legislation and future developments are described in more detail in Section 2 to set out the ‘framework’ against which land-spreading will be undertaken in future. The focus here is on legislation in England as it relates to conventional (i.e. not organic) free range systems. Some differences may apply in other countries within the UK both at present and in future.

In Section 3, we consider the fertiliser value of poultry manures and the financial benefits of applying these to land. The extent, practical implications and reasons for variability due to differences in manure dry matter and seasonal effects is set out.

1.4 Aims of this report

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In Section 4, we provide a concise review of alternative uses for poultry manures, using a standard format and covering key requirements, commercial opportunities and costs.

Finally the conclusions are presented in Section 5 with a ‘side-by-side’ summary comparison of the alternative uses considered. The Executive Summary (at the start of the report) is a self-contained section which provides an overview of the whole report.


2 KEY LEGISLATION AND IMPACTS ON LAND SPREADING

These are areas that have been designated as being at risk of agricultural nitrate pollution. They were first identified over 20 years ago but since then, the area included has expanded. NVZ areas currently account for around 55% of all land in England. An online tool is available, allowing farmers to determine whether a particular area of land is included within an NVZ area3. Within NVZ areas the maximum amount of nitrogen that can be applied to land is specified as a legal requirement. Specific rules are in place in relation to the application of organic manures. These relate to the total amount applied, the timing of spreading and any areas of land which cannot be used for spreading. Full details can be found on the UK government website4 but a practical summary of NVZ requirements is provided below.

2.1.1 Use of organic manures In NVZ areas, a maximum of 170kg per hectare of nitrogen can be applied via organic manures5 (e.g. from poultry) on a holding in each calendar year. This includes any manure that is directly deposited by outdoor livestock. On that basis, if poultry manure is spread onto grassland grazed by cattle during the year, account must be taken of the manure directly deposited by the cattle. This maximum amount (170kg per hectare) is the limit that applies as an average across the whole holding and separate to this is an annual field limit. The field limit is 250kg per hectare from organic manures spread in NVZ areas. This excludes

2.1 Nitrate vulnerable zones (NVZs)


3 https://environment-agency.cloud.esriuk.com/farmers/ 4 https://www.gov.uk/government/collections/nitrate-vulnerable-zones#nvz-designations-2017-to-2020 5 The term ‘organic manures’ generally refers to livestock manures and other organic wastes. It should not be taken to refer only to organic systems of livestock production

This section considers relevant current legislation and the likely impacts of new requirements. It is clear that legislative controls are gradually tightening with regard to land-spreading of manures and this may encourage more egg producers to consider other options for manure processing and utilisation.

nitrogen from any manures deposited by grazing animals. 2.1.2 Closed periods for spreading and storage requirements Manure and litter from laying hens cannot be spread in NVZ areas at certain times of the year. The length of the ‘closed period’ depends upon the nature of the soil and whether the spreading is on grass land or tillage (cultivated) land. Table 1 below sets out the closed periods that apply.

In addition, NVZ rules state that no more than 8 tonnes of poultry manure per hectare (likely to be equivalent to a total of around 150kg of nitrogen at 40% dry matter) may be applied in a single application from the end of the closed period until the end of February. At least three weeks must be allowed between successive applications.

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6 Sandy soils are defined at https://www.gov.uk/guidance/using-nitrogen-fertilisers-in-nitrate-vulnerable-zones#where-you- cant-spread-manufactured-fertilisers-or-organic-manures

Table 1. Summary of closed period in NVZ areas in England

Grassland Tillage land

Sandy or shallow soils6 1 September to 31 December 1 August to 31 December

All other soils 15 October to 31 January 1 October to 31 January

2.1.3 Soil incorporation Poultry manure spread onto bare soil or stubble (unless sown with seed) must be worked into the soil as soon as practical and within 24 hours at the latest. 2.1.4 Non-spreading conditions and locations Poultry manure must not be spread on fields that are waterlogged, flooded or covered in snow, nor on land that has been frozen for more than 12 of the previous 24 hours. It must not be spread within 50 metres of a spring, well or borehole or within 10 metres of surface water. 2.1.5 Outside NVZ areas In areas of England which are outside an NVZ, the application of poultry

manures to land is covered in a Code of Good Agricultural Practice and also by ‘Farming rules for water’ (see section 2.3 below. Section 5.4 of the Code of Good Agricultural Practice7 states that land applications should be limited to no more than 250kg of ‘total nitrogen’ per hectare in any 12 month period (paragraph 394). This is higher than the holding limit within an NVZ area. This figure excludes direct deposition of manure from grazing animals which is included within NVZ limit. The Code also sets out ‘good practice’ in relation to the timing of manure applications to land, restrictions on areas for spreading and application techniques.


7 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/268691/ pb13558-cogap-131223.pdf

Failure to comply with the terms of the Code does not inevitably result in prosecution outside NVZ areas but it may be taken into account by the Environment Agency in England, when exercising their powers.

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Larger free range egg production units which hold an environmental permit (over 40,000 bird places on a site) are subject to requirements on manure management planning. Precise requirements depend on whether the manure is spread onto the farm’s own land or if it is exported to others. If the farm is also in an NVZ area, the records being kept for NVZ purposes should be sufficient to meet permitting requirements. 2.2.1 Permitted farms - on-site spreading Application rates of poultry manures must not exceed 250 kg per hectare in any 12 month period, which is equivalent to the field limit set in NVZ areas. A manure management plan must be implemented and reviewed at least

every four years, recording the weight and nutrient content of manures applied to each field. Manures should be analysed at least once during the production cycle; analyses to include total and available nitrogen and total phosphorus. Soils should be analysed for total phosphorus at least every five years. Additional requirements include incorporation of manures spread onto un-cropped land or bare soils within 24 hours. Restrictions are in place to avoid spreading during adverse conditions (e.g. no spreading onto waterlogged or frozen land) and on unsuitable land (e.g. steeply-sloping).

2.2. Environmental permitting


2.2.2 Permitted farms - off-site spreading Even when manure is exported to other farms, the permit holder (i.e. the egg producer) is still expected to take measures to minimise pollution risks. Records should be kept of the quantities of manure removed and the relevant dates, including the name and address of the recipient and details of the land area available. Where a contractor or other third party takes the manure, they must confirm that manure will be spread in accordance with the Defra Code of Good Agricultural Practice8. Also, they must confirm that spreading will be in accordance with a manure management plan for the receiving land. Finally, there should be contingency plans in place in case

the land becomes unavailable for spreading or movement restrictions are in place. This could require additional on-farm manure storage or the use of other land for spreading.

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8 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/268691/ pb13558-cogap-131223.pdf

These were introduced by Defra in April 20189 with the aim of tackling diffuse water pollution from agriculture and setting a consistent baseline of good practice for agriculture in England. The key requirements are as follows: • The application of organic manures to cultivated land must be planned in advance to meet soil and crop nutrient needs and not exceed these levels. • Planning must take into account where there is a significant risk of pollution and the results of testing for phosphorus, potassium, magnesium, pH and nitrogen levels in the soil. Analyses must be undertaken at least every 5 years.

• Manures must not be stored on land or applied to land within 10 metres of inland fresh water or within 50 metres of a spring, well or borehole. • Manures must not be applied if the soil is waterlogged, flooded or snow- covered; if it has been frozen for more than 12 hours in the previous 24 hours and if there is a risk of causing pollution. • Reasonable precautions must be taken to prevent significant soil erosion and runoff from the application of organic manure or from poaching by animals.

2.3 Farming rules for water


9 The Reduction and Prevention of Agricultural Diffuse Pollution (England) Regulations 2018

Defra’s ‘Clean Air Strategy’10 was launched in January 2019, setting out the UK government’s plans to reduce ammonia emissions from farming. Whilst it focuses on tackling air pollution in England, the strategy notes the ‘shared goals’ of the UK as a whole and so similar developments may be anticipated in Scotland, Wales and Northern Ireland. In the sections that are relevant to manures from the free range egg production sector, Defra state that: ‘We will regulate to reduce ammonia emissions from farming. We will: 1. Introduce rules on specific emissions reducing practices including; • A requirement for all solid manure spread to bare land (other than that

managed in a no-till system) to be incorporated rapidly (within 12 hours) with legislation to be introduced in the shortest possible time frame; • Mandatory design standards for new poultry housing. The standards will be designed in collaboration with industry experts and will include design features to improve animal health and welfare and minimise environmental pollution to air (including greenhouse gas emissions), water and land as far as practicable; 2. Regulate to minimise pollution from organic and inorganic fertiliser use, seeking advice from an expert group on the optimal policy approach’.

2.4 Clean air strategy

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10 https://www.gov.uk/government/publications/clean-air-strategy-2019

No details of how and when these rules will come into force have been given, but the introduction of new rules for the design of new poultry houses could have important implications. The strategy also states: • ‘We will consult on each policy as quickly as possible to provide farmers, farm suppliers and farm service providers with certainty on the investments needed’; • ‘We will require and support farmers to make investments in the farm infrastructure and equipment that will reduce emissions’.

A further action contained within the strategy states that Defra will require and support farmers to make investments in the farm infrastructure and equipment that will reduce emissions. At present, no further details are available on the possible scope and extent of the support referred to.


3 FERTILISER VALUES OF POULTRY MANURE

Typical nutrient contents of poultry manures at a range of different dry matter percentages are shown in Table 2. The dry matter content of layer manure is variable but the trend towards fewer single-tier systems and more multi-tiers with belt manure removal has led to a greater proportion of layer manure with dry matter contents greater than 50% according to Defra data11.

Total nitrogen, phosphate, potash, sulphur and magnesium contents all increase (on a ‘weight per tonne’ basis) as the manure dry matter rises. The data in Table 2 make no distinction between single-tier and multi-tier systems at a given dry matter content.

3.1 Nutrient content of poultry manures


* Data taken from the Nutrient management Guide (RB209), AHDB (2017)

11 Defra (2015). Analysing the characteristics of UK pig and poultry manures and slurries. Defra project report SCF0202.http://sciencesearch.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location =None&ProjectID=19376&FromSearch=Y&Publisher=1&SearchText=SCF0202&SortString= ProjectCode&SortOrder=Asc&Paging=10#Description

The value of manure and used litter from free range laying hens as a fertiliser is based mainly upon its nutrient content. However moisture content is also important because it determines the extent to which nutrients are concentrated or diluted. This has implications for transport costs, ease of handling and the likely occurrence of odour complaints and fly infestations. In this section, we consider typical nutrient contents, the extent of variation and the value of poultry manure as a fertiliser.

Dry matter (%)

Total nitrogen (kg N/t)

Total phosphate (kg P2O5/t)

Total potash (kg K2O/t)

Total sulphur (kg SO3/t)

Total magnesium (kg MgO/t)

20 9.4 8.0 8.5 3.0 2.7

40 19.0 12.0 15.0 5.6 4.3

60 28.0 17.0 21.0 8.2 5.9

80 37.0 21.0 27.0 11.0 7.5

Table 2. Typical nutrient content of poultry manure (fresh weight basis)*

Differences in manure nitrogen production from single-tier and multi-tier systems have been assessed using the ENCASH software tool12. This allows farmers to calculate the nitrogen production in manure based on specific dietary inputs and systems for housing and manure management.

The results, set out in Table 3 predict that levels of nitrogen per hen are higher in multi-tier than in single-tier systems, due to higher dry matter content and less nitrogen loss in the form of ammonia. They also show that levels are higher when covered stores are used as opposed to field heaps.

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12 www.planet4farmers.co.uk/Content.aspx?name=ENCASH 13 ENCASH estimates are based on a production cycle of 420 days (16 to 76 weeks), 325 eggs/bird and a protein content in feed of 16.5%. Estimates used a feed conversion value of 2.65kg of feed per kg egg mass for single-tier systems and 2.54kg of feed per kg egg mass for multi-tier, given expected differences in feed intake between systems

Free range system Manure storage Manure nitrogen production (kg nitrogen/1000 birds)

Multi-tier Covered store 649

Multi-tier Field heap 583

Single-tier Covered store 592

Single-tier Field heap 537

Table 3. ENCASH13 estimates of manure nitrogen production from single-tier and multi-tier ree range layer systems

The MANNER-NPK software tool14 was used to assess the value of nutrients supplied by laying hen manure applications at a dry matter content of 50%. The total nutrient value ranged from £20 per tonne to £26 per tonne, depending on application timing and

the extent of the delay between application and incorporation into the soil (Table 4). The values do not include any allowance for transport or spreading costs, both of which could be around £4-5 per tonne.

3.2 Poultry manure values


14 http://www.planet4farmers.co.uk/Manner.aspx 15 MANNER-NPK estimates are based on a total application to a sandy loam soil of layer manure at 12 tonnes per hectare, either incorporated by plough within 6 hours of application or left on the soil surface (i.e. not incorporated). Estimates were made for manure applied in central England (annual rainfall of 650 mm) on 1 September, growing an early sown winter cereal crop or on 1 March growing a spring sown cereal. Manure dry matter and nutrient contents were the average values of the most recent laying hen manure data (Defra, 2015). Nutrient price data was based on the AHBD GB fertiliser price data averaged over April 2018-March 2019; ammonium nitrate (34.5% N) at £263 per tonne; triple superphosphate (46% P2O5) at £325 per tonne; muriate of potash (60% K2O) at £273 per tonne

Table 4. MANNER-NPK estimates14 of the nutrient value of laying hen manure (50% dry matter) at land spreading in autumn or spring, and with either i) no rapid soil incorporation or ii) incorporation within 6 hours

Application time

Incorporation within 6 hours

Nitrogen value (£/t)

P2O5 value (£/t)

K2O value (£/t)

Total nutrient value (£/t)

Autumn No 2 11 7 20

Autumn Yes 2 11 7 20

Spring No 5 11 7 23

Spring Yes 8 11 7 26

It is clear that most of the value of the manure is in the phosphate element (£11 per tonne) and in potash (£7 per tonne), especially with an autumn application. Application timing had the biggest impact on manure nitrogen value, with nitrogen supplied by spring applications worth between £3 and £6 per tonne more than autumn applications. Rapid soil incorporation increased the value of spring applied manure by £3 per tonne reflecting the reduction in ammonia loss. There was no impact of soil incorporation on the value of autumn applied manure, as nitrogen saved by reducing ammonia emissions typically leads to increased nitrate leaching losses.

Poultry manure applications are also a source of organic matter which has been shown to improve soil biological and physical functioning. Organic matter additions also improve soil structure which has the potential to improve water retention (especially on light soils), reduce the risk of soil erosion and make cultivations easier. Such benefits have not been quantified but would be considered additional to the values set out in Table 4. Finally, a similar approach based on MANNER NPK was used to estimate manure nutrient values at a range of different dry matter contents, from 20% to 80%. The same assumptions were made as in Table 4 and the results are shown in Table 5 opposite.

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Dry matter (%) Nitrogen value (£/t) P2O5 value (£/t) K2O value (£/t) Total nutrient

value (£/t)

20 5 6 4 15

40 8 9 7 24

60 11 12 10 33

80 14 15 12 41

Table 5. MANNER-NPK estimates of the nutrient value of laying hen manure at a range of different dry matters (20-80%)

Compliance with the Defra Code of Good Agricultural Practice for reducing ammonia emissions16 helps to maximise the fertiliser value of manures. Key points to note are as follows:

• Keeping manure as dry as possible means that a greater proportion of readily available nitrogen is in the uric acid form. This means that nitrogen is less likely to be lost via ammonia volatilisation. During manure storage, there are benefits to covering manure, whether in purpose- built stores, in field heaps and on trailers. From a practical and commercial perspective, drier manure also means lower transport costs. • Apply manure in the spring if possible to avoid nitrogen loss in winter due to leaching. Rapidly incorporating manure to minimise ammonia emissions is beneficial. The majority of ammonia emissions occur within 24 hours of application, hence it is best to incorporate as soon as practically possible, ideally within 6 hours of application.

3.3 Maximising fertiliser value - 3.3 housing and management factors

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16 www.gov.uk/government/publications/code-of-good-agricultural-practice-for-reducing-ammonia-emissions

• Use soil analysis to target manure applications to soils which have a requirement for phosphate and potash. Laying hen manure applications typically supply more phosphate and potash than crops use in one harvest. Regular, repeat applications to the same land over several years has the potential to increase soil phosphorus concentrations in particular to levels which may increase the risk of leaching to local watercourses. • Use AHDB’s Nutrient Management Guide RB20917 to assess crop nutrient requirement and RB209 or MANNER-NPK18 to quantify crop available nutrient supply from manure applications.


17 https://ahdb.org.uk/knowledge-library/rb209-section-1-principles-of-nutrient-management-and-fertiliser-use 18 http://www.planet4farmers.co.uk/

4 ALTERNATIVE USES OF POULTRY MANURE

In this section, we provide a concise review of alternative uses for poultry manures for those interested in exploring options other than land spreading. The output from the processes considered (combustion, drying, pelleting, composting and digestion) can be summarised either as: • A dry, solid product which is easier to store, handle and spread than ‘fresh’ poultry manure and has greater potential value, or • A fuel which can be used to generate electricity or heat, together with a residual product from the manure which also has a saleable value.

For each process, a technical description is provided together with an assessment of key requirements and commercial opportunities for free range producers. Typical costs and returns and potential difficulties are set out, together with possible future innovations and developments. Farm-specific issues such as the location and scale of free range enterprise are also important in determining the likely feasibility of each process. This document is therefore intended to be used as a basis for farmers to begin more detailed discussions based on their own circumstances. Cost indications are based on prevailing prices in early 2019.


Dry manures (over 55% dry matter) can be incinerated to provide on-farm heat or to generate electricity that can be used either on-farm or exported to the grid. Payments may be received from government incentive schemes such as the Feed in Tariff (FIT) and the Renewable Heat Incentive (RHI). The residual ash also has a saleable value. Capital costs are high and therefore this method is likely to be considered only by very large free range producers or by local groups operating on a collaborative basis. 4.1.1 Technical description In the past, incineration of poultry manures and used litters was considered a waste activity under the Waste Incineration Directive19. As a result, it was generally not considered feasible or financially

viable in a farm situation. However poultry manure is an animal by-product and since 2014, legislation has allowed the energy to be recovered from animal by-product incineration20. Compliance with regulatory requirements is therefore less onerous in terms of monitoring and reporting and this has made manure incineration a feasible option for some farmers. The process involves burning manure in a combustion unit and recovering the heat which can then be used on the farm to heat the poultry houses or other on-site facilities through hot-water systems. Alternatively, it can be converted to electricity in combined heat and power systems

4.1 Incineration

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19 Directive 2000/76/EC 20 Regulations (EU) 592/2014 and (EU) 2017/1262

(CHP) so that the electricity is either used on-farm or can be exported for off-site sale. Incineration also creates a residue (ash) which represents between 8 and 15% of the weight of the incoming manure. This has a saleable value as a fertiliser. The process that has been shown to be most suitable for poultry manure is based on ‘fluidised bed technology’. This is a proven technique used in other power- generating plants for reliably using relatively inconsistent granular materials as a fuel. It is also well- suited to ‘farm scale’ approaches as it can operate with variable moisture contents in manures although the recommended dry matter content is at least 55%. The drier the material,

the higher the energy production. The floor of the furnace has a sand bed through which air is released by nozzles. An oil or gas burner is used to create initial heat at start-up and also for use during the process if required. Manure is fed into the top of the furnace from a storage bunker. The fluidised beds operate by suspending manure particles on upward-blowing jets of air during the combustion process. The result is a turbulent mixing of gas and solids, similar to a bubbling fluid, providing efficient chemical processes and heat transfer. Incineration temperatures must be monitored to ensure that they are sufficient to meet the requirements


of animal by-products legislation but they can be controlled to avoid the higher temperatures that can create more gaseous nitrogen oxides which may require abatement activity. The flue gas from the process has a temperature of around 850°C and heat is recovered in a boiler section as hot water or steam, depending on the system for use elsewhere on site (to reduce heating costs) or to supply heat to the poultry houses as required. Converting the heat to electrical power is also possible in CHP systems. Power generation can be by a steam engine or alternatively by Organic Rankine Cycle (ORC) technology that works with

pressurised hot water temperatures as low as 150°C. The process is generally considered to be relatively inefficient (in terms of the percentage of energy conversion to power) but it still produces heat that is available for use. ORC uses a closed system and an organic chemical thermal fluid which has a lower boiling point than water. The ash resulting from the incineration process is collected in approximately equal quantities from the bed itself and also as ‘fly ash’ at the end of the process. The nutrient analyses for the two are slightly different but both can be sold as a high pH (alkaline) fertiliser high in phosphorus, potassium and trace elements.

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4.1.2 Commercial opportunities At present, BHSL Hydro21 is understood to supply the only fluidised bed system for poultry farmers who are considering manure incineration. A number of installations are already in operation in the UK, although mainly for use in the broiler sector at present. This equipment is able to meet emissions requirements and it has the remote monitoring infrastructure that can demonstrate compliance. Several different models are available, including CHP systems and these vary in terms of scale and features. The electricity and / or heat produced can be used on the farm and electricity sales to the national grid may also be possible, depending

on farm location and distribution network. For on-farm use, the opportunity could be taken to use a proportion of the heat to warm the poultry houses at certain times of year and / or to dry the manure within them. This could provide additional ‘poultry house-related’ environmental benefits. It could also improve the performance of free range flocks by lower feed use, lower in-house ammonia levels and improved litter quality. Farmers generating electricity and heat from such a system also gain income through government schemes. Details are outlined below and also within the separate case study.


21 www.bhslhydro.com

• Feed in Tariff (FIT) payments for the electricity generated. Different payment rates apply depending on whether the electricity is used on-site (lower rate) or exported into the grid (higher rate). • Renewable Heat Incentive (RHI) payments for the heat produced. Non-domestic rates are set periodically and vary according to the technology used. Established sites can also benefit through the Renewables Obligations Certificates (ROCs) support mechanism but this is now closed to new installations.

The residual ash can be bagged and sold and expected analyses of key nutrients and selected trace elements are set out in Table 6. Ease of handling and the high content of nutrients such as phosphorus and potassium mean that higher sale prices should be achieved for these materials than for ‘standard’ poultry manure. Alternatively, supply to a major producer of branded fertiliser products such as Fibrophos22 is a possibility, given that they already have market outlets and product certifications already in place.

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22 www.fibrophos.co.uk

4.1.3 Key considerations Requirements for facilities that incinerate poultry manure as a fuel are set out in EU legislation23. This limits the scale of operations to a maximum of one tonne of material per day – approximately a total rated thermal input not exceeding five

megawatts. It also specifies that the manure itself must be ‘unprocessed’. The incineration process is regulated by the APHA and it must meet key requirements for time and temperature in the furnace and flue gas (2 seconds at over 850oC or 0.2


23 Commission Regulation 592/2014

Table 6. Expected analysis of key nutrients and selected trace elements in ash from incineration

Bed Ash Fly Ash

Calcium (%) 64 47

Phosphorus (%) 10 16

Potassium (%) 10 15

Zinc (mg/kg) 860 1,380

Manganese (mg/kg) 920 1,640

seconds at over 1100oC.). An environmental permit must be in place for the process and this is regulated by the local authority as a Part A(2)24 activity. Under permit requirements, operators must have in place permanent procedures following the principles of HACCP to identify, measure and control critical control points. An end-of-waste protocol must be in place for the ash produced, with records kept to confirm the disposal method. Planning permission is required prior to starting. In some cases and for certain locations this could be a lengthy process and difficult to obtain, particularly since incineration can be an emotive term and

therefore a concern to local residents. 4.1.4 Costs and returns Whilst legislative change has made manure incineration an option at farm level, the capital costs are still high. This is likely to be a feasible option only for the largest free range egg producers or as the basis for a collaborative approach involving several smaller producers in the same area. A CHP system, together with an in- feed system for the manure, an ORC generator, storage facilities for manure, fuel and ash and a heat distribution system (pumps and pipework) together with suitable building is likely to cost in the region of £2 million. For a non-CHP system,

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24 This category includes a range of different activities, including animal waste incineration

the cost may be reduced by around one-third (to approximately £1.3 million) but the potential income would also be reduced. Initial planning costs are likely to be very variable but they could be in the region of £40,000. Other costs to be considered include labour, insurance, maintenance and fuel for start-up. Some sources have estimated that these could total over £50,000 per year although for existing businesses, some of the labour input would in effect be transferred from previous manure-related activities such as land-spreading. Based on the expected power conversion efficiency of the process, 32 tonnes of manure per 1,000 birds

per year and an electricity value of 12 pence per unit, likely annual returns are around £600 per 1,000 birds. This is equivalent to just under £20,000 per year for each 32,000 bird house. The value of the ash as a fertiliser should also be considered. Based on an estimated sale price for ash of £40 per tonne and this representing 15% by weight of the manure total (i.e. 4.8 tonnes per 1,000 birds), the value is around £6,000 per 32,000 birds on an annual basis


CASE STUDY ON POULTRY MANURE INCINERATION – JAMES BAXTER

James Baxter has 128,000 free range laying hens on his farm near Stranraer in Scotland. He uses an FBC750 Combined Heat and Power (CHP) system from BHSL to incinerate the poultry manure produced, using the energy generated for heating and electricity. Because of the farm location, James does not supply energy to the national grid and so it is all used on farm. James’s decision to opt for manure incineration came after a review of a number of different options as alternatives to land-spreading. He considered anaerobic digestion but identified a number of practical difficulties, concluding that other materials were better-suited to the digestion process than the manure from his laying hens. He also considered other CHP machines, including small scale ‘plug and play’ units, which are often used for power generation in

developing countries. A number of other machines and technologies were considered but these were discounted for reasons including lack of track record of burning laying hen manure, the need to pellet the manure prior to incineration, potentially high maintenance costs and concerns over high emission levels. With a fluidised bed incineration system now in place, James currently burns around 11-12 tonnes of manure each day from his 128,000 hens and sees manure burning as part of an integrated approach with heat being supplied back to the poultry houses to improve the environment and dry the manure in-house on the belts. The electricity generated is used on the farm to reduce utility costs. Residual ash from the process is used as a fertiliser on farm or sold to other farmers but it is expected that it will soon be


sold to fertiliser companies to help them meet their environmental requirements for the use of recycled materials in their products. James has sought to benefit from government incentive schemes such as RHI and ROCS but he has found the accreditation process to be complex and that expected payments were severely delayed. This could have important negative implications for cash flow for businesses reliant on such payments. Key compliance issues for payments included the need for incoming manure not to have been further-processed prior to incineration and there must also be a clear and demonstrable use for the heat and electricity generated. Overall, James considers that £2 million would be a reasonable budget figure for capital costs for such a development and on

that basis accepts that larger bird numbers are needed to justify the investment at present. However the development of smaller (and therefore cheaper) machines in future will happen in future if demand is which may create opportunities for others. Alternatively, installing a unit on a separate industrial or other site with an on-site demand for heat and electricity could be an alternative model for the future. This could then have manure supplied to it by a number of local producers. James estimates that his annual income from the activity is currently around £270,000 per year, based on RHI payments, electricity generated (net of the amount used in the process itself ) and sales of ash as fertiliser. Having carefully worked out the costs and returns, James expects that the equipment costs will be re-paid within around seven

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years. This does not take account of any benefits from improved flock performance which have been observed. These arise from improved environmental conditions, better flock health and higher in-house temperatures in winter, leading to reduced feed use.


Drying laying hen manure increases its nutrient value and makes it easier to handle. The process can use air from the poultry house or waste heat from other sources such as anaerobic digesters or incinerators. Drying systems can be set up next to the poultry house and the smallest available is considered suitable for 12,000 birds. Once dried, pelleting the manure can add further value through sale as a fertiliser for commercial or domestic use. Pelleting systems are more expensive to install and run than drying systems and it is considered that a minimum of around 64,000 birds would be needed to justify the costs. 4.2.1 Technical description - drying Manure is typically dried by directing warm air over a series of manure belts which are arranged on different levels. The process is more suited to

multi-tier than single-tier housing since it can be linked to existing manure belts and conveyors. The drying belts are ideally situated near to a poultry house so that they can utilise the extracted air from the ventilation system. Daily manure removal from the house allows drying to be undertaken as a batch process, starting at the top level of belts. A spreading mechanism is used to distribute the manure evenly. Perforations in the belts allow warm air to circulate, so accelerating the drying process. The manure is carried to the end of the top level and it then drops down to the belt below. This moves in the opposite direction, continuing the

4.2 Drying and pelleting

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drying process until the dried manure finally reaches the bottom level, when it should achieve the required dry matter content. The process is usually fully-automated, operating without direct supervision. At the end, dried manure is removed from the system using an auger or screw conveyor. Using warm air from the poultry house ventilation system provides a very cost-effective approach, utilising heat generated by the hens which would otherwise be lost to the atmosphere. Warm air could also be generated using an external heat source, such as from anaerobic digestion or an incinerator CHP plant. This approach could enable the drying system to be set up in a

building that is distant to the poultry houses. Typically the drying process takes 48 hours to reach a dry matter content of between 80 and 90%. However, the duration depends factors such as the dry matter of the manure at the start and the humidity, temperature and volume of the air used for drying. Pre-drying the manure in the poultry house (i.e. before it enters the drying system) accelerates the drying process. For this, the manure can be left on the manure belts in the house for approximately 48 hours. Alternatively, perforated plastic air tubes can be installed over the manure belts in the house. These use warm air from external fans to pass over the manure.


The drying process reduces the weight of the manure due to the loss of moisture. For example if one tonne of manure with an initial dry matter content of 30% is dried to a dry matter content of 85%, the final weight is likely to be only around one-third of its initial weight. 4.2.2 Technical description - pelleting To improve marketing opportunities, the dried manure can be pelleted in a separate pelleting plant. For this, the manure must have a dry matter content of between 80 and 85%. Typically, a pelleting plant includes a crusher which ensures that the dried manure is broken down into smaller, uniform size particles before it enters the pellet press. After the pelleting

process, a temperature of at least 70oC must be maintained for at least one hour to kill harmful bacteria and pathogens. The pellets are then cooled before they are stored in bulk or packed in bags and then distributed. As a guide, the entire drying and pelleting process is likely to take around three days. 4.2.3 Commercial opportunities Whilst there are few poultry manure drying systems in the UK at present, the technology is well established and commonly-used in countries such as the Netherlands, due to additional legislative requirements for poultry manure in some locations. A number of companies supply equipment for drying or pelleting

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including Big Dutchman, Dorset Group, Facco, Jansen Poultry Equipment, Stronga and VDL Agrotech. The main markets for dried and pelleted poultry manures are as commercial fertilisers for agricultural and horticultural use and land restoration and as garden fertilisers for the domestic market. If required, poultry manure can be blended with other materials to produce a dried or pelleted fertiliser with a specific nutrient profile. It could be used as a fuel for incineration in CHP and other plants. As a fertiliser, the main advantages of dried and pelleted manure are: • Reduced storage and transport costs; in addition to reported

weight reductions, the volume of dried manure may be reduced by 10 - 15%. Pelleting can reduce the volume by a further 50%, leading to further reductions in transport costs. • Higher nutrient values; since these increase (on a ‘kg per tonne’ basis) with higher dry matter content. • Reduced ammonia emissions; regular removal of manure from the poultry house and rapid drying of the manure reduces ammonia emissions. • Higher nitrogen content; as less nitrogen is lost through ammonia emissions, dried manure has


higher nitrogen content than fresh manure. • Reduced odour and fly problems compared to fresh manure, with pelleted product representing a further improvement over ‘dried’. In addition, pelleted manure in particular is a more uniform product, easier to spread and apply to land. This makes it suitable for bagging in small unit sizes, for sale to the general public through retail outlets. However this is likely to be a competitive sector requiring considerable marketing effort. 4.2.4 Key considerations When air from the poultry house is used for drying, the size of the dryer

is mainly based on the number of hens in the house. Typically one square metre of drying belt area is required for between 300 and 420 hens, depending on the local climate (temperature and humidity) and whether plastic or perforated steel belt systems are used. On this basis, a 32,000 bird house would require around 80m2 of drying surface. As an example, this could be provided by five drying layers, each one being 8m x 2m. The minimum house size for drying systems is typically considered by suppliers to be around 12,000 birds. The humidity and the temperature of the poultry house also affects the drying process when ventilated air is used. The lower the air humidity and

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the higher the temperature, the more efficient the drying process. An internal house temperature of between 15 and 20oC is normally sufficient for drying but in free range systems this could be challenging in many parts of the country, especially during winter. A higher volume of air may therefore need to be directed over the manure. Alternatively, the length of the drying process could be extended (e.g. from two to three days) or the manure may be pre-dried within the house. Manure from single tier houses may need additional treatment if it has comparatively high moisture content. One option is to install a separate belt system under the mini-pit slats in a single-tier system,

to remove the manure regularly during the flock cycle. Drying systems can be retro-fitted to an existing poultry house with drying taking place either along the length of the house or at the gable end, depending on the location of air outlets. Ideally the system should be set up so that it can dry manure from more than one house but in free range situations, this may be difficult. Site design, the need to maintain vehicular access (to collect the dried manure) and to maintain bird access to popholes and the range are other practical issues that may arise. Pelleting systems come in a range of capacity sizes from 400 kg per hour (small) to 5 tonnes per hour (large).


Poultry sector suppliers suggest that a minimum of around 64,000 birds is required to operate a small pelleting system economically, unless the manure is blended with another input material, in which case less manure is required. On farms with an environmental permit (over 40,000 hen places), enforcement of any issues in relation to manure drying is the responsibility of the Environment Agency. If ammonia, odour or noise from the plant was considered to be a problem then some form of mitigation may be required. In order to sell pelleted poultry manure as a fertiliser, the plant must meet EU animal by-products

legislation25 and must be approved by APHA. This stipulates temperature requirements (see section 4.2.2) although alternative treatment methods can be used if they have been validated by APHA. 4.2.5 Costs and returns The capital cost for drying systems depends on factors such as the desired dry matter content of the final product, the amount of drying surface required, the heat source used to warm the air and whether pre-drying or air cleaning is required. Larger capacity drying systems are usually cheaper on a ‘per bird’ basis and if one system can dry the manure from multiple houses. On that basis, one supplier estimates a

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25 Regulation (EU) 1069/2009 and Regulation (EC) 142/2011

cost of £2.50 per bird for a system capable of drying manure from 32,000 birds. For 64,000 birds it would be £1.70 per bird and for 128,000 birds it would be £1.30 per bird. Where feasible, retro fitting typically increases the cost of a drying system by around 20% compared to a new- build. In some cases, a pre-drying system may need to be installed so adding further cost. Operational costs vary, but they are usually low given the use of extracted air from poultry houses or waste heat from another activity. Some electricity is required to operate the drying belts. Capital costs for a complete pelleting

plant capable of processing 750 kg per hour of manure (suitable for 200,000 laying hens) were recently estimated to be between £1.30 and £1.55 per bird. On this basis, the cost of drying and pelleting equipment for a farm with 64,000 hens is likely to be in the order of £4 per bird. The energy consumption for pelleting is much higher than it is for drying. Suppliers indicate that a 750 kg per hour plant uses around 80 kilowatt hours of electricity and that the cost of producing one tonne of pellets from dried manure is likely to be between £20 and £35. Dry manure can command a higher price as a fertiliser as it has a higher nutrient value than wet manure. For


example, Table 5 indicates a nutrient value of £41 per tonne at 80% dry matter. It also weighs less, so reducing transport costs and making storage easier. For pelleted product, additional income needs to be obtained in order to offset the higher production costs. In the Netherlands, pelleted poultry manure is said to have market values ranging from between €60 and €250 per tonne, depending on its nutrient content and the target market. In the UK, 20kg bags of pelleted manure retail for around £16 however the producer/supplier may receive only a relatively modest proportion of this.

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Poultry manure can be composted but it needs to be combined with a carbon-rich material to optimise the process. The economic model for composting normally relies on a gate fee being charged for incoming raw materials such as ‘green waste’. This can provide a substantial part (or all) of the revenue received. Although the compost itself has useful fertiliser value, the prices obtained for it are often low. Low capital cost ‘windrow’ systems can be used for composting and this can be undertaken outdoors on a concrete base or within an existing building, if available. However the process is likely to be quicker and better controlled if more expensive ‘in-vessel’ systems are used. 4.3.1 Technical description As a result of increased landfill costs,

composting is widely practised in the UK as a recovery process for a range of different organic materials and these can include poultry manures. The objective is to produce a high quality fertiliser in an easier-to- handle form and to reduce the volume and weight of the material for final transport. Compost has a high organic nitrogen content which should exceed the 70% threshold that enables it to be spread during closed seasons in NVZ areas (see also section 2). An additional benefit of the composting process is an improvement in microbiological quality e.g. by reducing pathogen load. The process involves the conversion

4.3 Composting


of the material to compost in aerobic conditions i.e. with sufficient air (oxygen) supply. It is a natural process resulting from microbial activity which creates heat, with temperatures typically over 70oC within the material itself. To maintain the supply of oxygen which is essential to the process, physical movement of the material is required (turning) unless forced aeration systems are in place. In order to optimise the composting process the following two key variables need to be controlled: • Moisture content. The target should be a starting dry matter content of between 40 and 60% in the material being composted.

Lower dry matter content (i.e. wetter material) can restrict the air supply and the composting mass becomes air-depleted (anaerobic). This stops composting activity, particularly in the initial stages and the process can become odorous. The dry matter content at the end of the composting process is likely to be around 60-70%. • The ratio of carbon to nitrogen in the material to be composted. The optimum ratio is around 20:1 but as poultry manure is comparatively high in nitrogen and low in carbon, it has a C:N ratio of only around 10:1. Because of this, composting poultry manure alone - whilst technically

56

possible - would not be recommended. Ideally, it should be mixed with a carbon-rich material such as straw, wood or general green waste. Whilst the principles of all composting systems are similar, the methods used range from the simple to the much more sophisticated. As a guide, the composting process typically takes between 8 and 12 weeks. Open-air or covered windrow systems in which the material forms an extended pyramid shape normally 1-2 metres high on a concrete base provide the simplest and cheapest approach. Ideally the material should be turned on approximately a weekly basis and more frequently at the start

of the process than at the end. This could be done using general farm equipment although specialist compost-turning machinery is also available. More sophisticated options involve purpose-built, ‘in-vessel’ systems and these can either be vertically or horizontally arranged, the latter being available in modular form so that it can be extended according to capacity requirements. In these systems, the aeration necessary for the composting process to proceed can be undertaken automatically e.g. using systems with aerated floors so that oxygen levels can be controlled. Typically, the material is held ‘in vessel’ for only around two weeks with the remainder of the time then


being spent in windrow or similar systems. Within the poultry sector, Big Dutchman26 are one equipment company with good experience of in-vessel systems, mainly based on developments undertaken elsewhere in Europe. 4.3.2 Commercial opportunities Compost is likely to be more valuable as a fertiliser than raw poultry manure since the dry matter is higher and odours are lower. These benefits alone however are unlikely to offset the additional costs of the composting process at present. Process costs can be minimised by using windrow systems in existing buildings or on hardstanding areas

but at present, the economic model for nearly all composting systems is based on the receipt of a gate fee for incoming material. The compost itself may be supplied to the customer or end user either at a low price or even free of charge. As well as providing the main (or only) source of income, the gate fee material brought in has the added advantage of assisting the composting process by adjusting the carbon to nitrogen ratio. A number of different materials could be brought in for mixing with poultry manure. Commonly-available materials include commercial green wastes from local authority collections, recycling centres, vegetable processors and other

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26 www.bigdutchman.de

farmers. These are likely to attract relatively modest gate fees. Alternatively, more specialised wastes such as gypsum can be used and these normally attract higher gate fees although additional requirements are likely to apply (see below). Locality is likely to have an important bearing on the availability of such materials and on marketing opportunities for the final product. Fresh or part-composted poultry manure could be provided to mushroom growers in certain locations so that they can produce a compost material suitable for mushroom production. However, GB mushroom production has been in decline as imports have increased and so any such opportunities are

likely to be limited. The mushroom growing process is technically challenging and expensive to establish so it is unlikely to be something for poultry producers to consider for themselves. A suitable compost material for mushroom growing could be based on a mix of pre-wetted straw (typically from barley) and poultry manure possibly with some added gypsum. After composting is complete, mushroom growers inoculate it with the appropriate fungus to begin the growing process. 4.3.3 Key considerations For a windrow approach, at least one square metre of floor area is required per tonne of manure or other raw


materials treated. Space allowance should be made for a three month composting process and then for a further three months storage capacity. As a guide, a 64,000 bird free range unit producing 40 tonnes of manure per 1,000 hens per year is likely to require a similar tonnage of another raw material to achieve the correct C:N ratio. Thus the total weight would be equivalent to 80 tonnes per 1,000 hens at the outset. On this basis, at least 2,560m² of floor area would be required for six months capacity. For open-air systems, dirty water storage facilities would be essential so that run-off could be contained. This would also be advisable for composting undertaken within buildings, thus enabling thorough clean-out.

Incoming raw materials may need to be treated prior to composting e.g. shredding of green waste, sorting to exclude foreign bodies and any materials that cannot be composted and so additional space may be needed. An on-farm composting approach, based on the use of existing buildings would not in principle require planning permission although normal planning rules would apply if new buildings were to be constructed. An environmental permit would be required if raw materials are being brought in for composting. The precise requirements would largely depend upon the nature of these raw materials. For example, a process whereby green waste from local

60

recycling centres is mixed with poultry manure is likely to require a standard permit. A bespoke permit would be required if what are considered ‘higher risk’ and more specialist wastes are brought in for mixing with poultry manure. Permits are issued by the Environment Agency and they would need to cover waste management acceptance (i.e. control of incoming materials), the process itself and the final use of the composted material, whether for land spreading or other uses. Odours are a potential problem of the composting process. The likely extent of problems depends upon the materials used, the pH and the moisture content of the manures, as well as the proximity of neighbours.

The use of in-vessel approaches can alleviate odour problems at least in part but these considerably increase capital costs. Compliance with Publicly Available Standard 100 (PAS100)27 is considered essential for those considering a composting process. It is a recognised standard that provides a guarantee of the product and its method of manufacture. Importantly, it means that no further waste regulatory controls are required, so that recipients and end users of the compost do not require their own environmental permit. To achieve PAS100, suitable environmental management and HACCP system must be in place and costs and registrations apply.


27 http://www.qualitycompost.org.uk/standards/pas100

4.3.4 Costs and returns The commercial viability of composting is likely to be driven by the gate fees that can be achieved for incoming raw materials, with revenue from sales of the final product expected to be modest (probably less than £5 per tonne) in most cases. There may however be regional differences, with perhaps greater demand in arable growing areas than elsewhere. Locality can play an important role in determining gate fees but as a guide a fee of around £20-30 per tonne may be received for locally-sourced, easy-to-process green wastes. This can rise to around £80-100 per tonne for wastes that are more difficult to treat and which require more

regulatory and process control. The capital cost of an outdoor composting system situated on a new concrete base is likely to be around £40 per square metre, based on site work, the cost of the concrete and related infrastructure. If an area of 2,560m² of concrete is required for 64,000 birds, the likely cost would therefore be just over £100,000. In vessel systems are much more expensive and likely to start at around £150 per tonne of material to be composted annually. For a system composting 40 tonnes of manure with 40 tonnes of other raw material (i.e. 80 tonnes per week), the annual throughput would be around 4,160 tonnes. At £150 per tonne, the

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equipment cost would be in the order of £625,000. After adding buildings and other infrastructure, the total is likely to be in the region of £1 million.


Anaerobic digestion (AD) is a process which takes organic materials (generally wastes) and in anaerobic conditions, produces gas which is used for energy generation. The digestion process makes a more homogenous and stable product from the original feedstock and this can be used as a fertiliser. The high nitrogen content of poultry manure generally limits its inclusion within a feedstock mix to 20% although technological developments have allowed the use of up to 100% poultry manure in large scale plants. In addition, laying hen manure contains calcium grit which is unsuitable for use in AD unless the system enables grit extraction. 4.4.1 Technical description Anaerobic digestion (AD) is a process which uses a culture of microbes in an air-excluded environment to

digest non-cellulosic substances in organic matter feedstock and produce energy. The raw materials used (i.e. the feedstock) are usually waste organic materials such as food or animal manure, but they could also be a purpose-grown crop. The process produces a gaseous mix (‘biogas’) which can be used to generate heat or electrical energy. This can either be used on-farm or it can be exported offsite e.g. by using an engine-driven generator connected to the grid. The AD process also produces digestate which can be used as a nutrient rich fertiliser. AD tank designs are arranged either vertically or horizontally. Vertical tanks take feedstock through a pipe at the

4.4 Anaerobic digestion

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top of the tank on one side and the digestate leaves through a pipe on the other side, at the bottom. In horizontal plug flow systems, the feedstock travels as a plug of material at the rate it is fed in. It is digested and released at the opposite end. Vertical systems are simple and comparatively cheap to operate, but digestion time is harder to control and optimise. Horizontal plug flow systems are more expensive to set up and operate, but the digestion time can be optimised to improve efficiency. Both ‘wet’ and ‘dry’ AD systems can be used. The wet system is most common, processing feedstocks with between 5 and 15% dry matter whereas dry AD systems can process feedstocks with over 15% dry matter.

The AD process is similar in both systems, with several stages as illustrated in the flow diagram in Figure 1 overleaf.


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Figure 1. Flow diagram of a typical AD system

Feed stock storage and preparation The feedstock is stored and then mixed and blended in a vessel to

provide a regulated mix of feedstock to the digester.

Digestion process The feedstock enters a sealed digester vessel where the material is

broken down anaerobically by microorganisms for a set period, typically around 30 to 40 days.

Most digesters use a continuous flow process. Batch system designs can

be used but are much less common.

Biogas The biogas produced is stored at relatively

low pressure in a container, either in the void space above a digester vessel or in a

separate container alongside.

Biogas can be used to generate electricity or to generate heat on site if there is demand.

Biogas can also be treated to improve

quality, enabling it to be exported to the gas grid (this is usually limited to larger plants).

Digestate A wet AD system produces liquid digestate with a dry matter content of approximately

5% to 7%.

Some systems separate the fibre from the liquid digestate using a mechanical separator to provide an additional

solid digestate.

A dry AD system produces stackable solid digestate.

4.4.2 Commercial opportunities The AD process has been used for many years in industry and on some UK cattle and other farms for the last twenty years. Uptake has been driven mainly by the government introducing financial support for infrastructure to generate renewable energy including Renewable Obligation Certificates (ROC), Feed in Tariff (FIT) and Renewable Heat Incentive (RHI). The feedstock for the AD process can be any biodegradable plant or animal matter and so on this basis, poultry manure can be used. Based on the example in Table 7 overleaf (at 20% dry matter), it is clear that poultry manure has a higher gas yield than cattle manure but if used,

inclusion rates for poultry manure are generally limited to around 20% of total feedstock. This is mainly because of its high nitrogen content, which affects the chemistry and the microbial activity of the AD process. The bacteria within the digester may also be unable to break down lignin in plants that may be present in used litter, if this is also added. A further constraint – and the main reason why laying hen manure is rarely included as a feedstock for AD at present – is because it contains high levels of calcium grit which can accumulate in the AD vessel unless the system includes equipment to trap the grit. Existing AD operators are therefore likely to charge a gate fee at present for poultry manure


supplied to them, so this is unlikely to be a preferred option for egg producers at present. The secondary product of AD is digestate (the residual product from the digested feedstock). The volume of digestate produced is typically just less than the volume of the feedstock input so it therefore represents a considerable weight of material. Nitrogen is normally the most significant crop nutrient supplied by

digestate but since most AD plants include only a small proportion of poultry manure in the feedstock, the analysis of the digestate is the result of the ‘mix’, rather than the digested poultry manure alone. Table 8 opposite shows typical nutrient contents for AD digestate based on RB209 figures28.

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28 https://ahdb.org.uk/nutrient-management-guide-rb209

Cattle manure (25% DM)

Poultry manure (20% DM) Maize silage

Gas produced per tonne fresh weight 50m3 85m3 210m3

Table 7. Typical gas yields from different feedstocks


29 Whole digestate is unseparated material. Separated digestate are the two fractions produced after the digestate has gone through a mechanical separator. MANNER-NPK estimates are based on application to a sandy loam soil of farm-sourced digestate at either 50m3 per hectare by band spreading (trailing hose) for whole and separated liquor and 20 tonnes per hectare for separated fibre and incorporated by plough within 6 hours of application. Estimates were made for digestate applied in central England (annual rainfall of 650 mm) on 1 March growing a spring sown cereal. Nutrient price data were based on the AHBD GB fertiliser price data averaged over April 2018-March 2019; ammonium nitrate (34.5% N) at £263 per tonne; triple superphosphate (46% P2O5) at £325 per tonne; muriate of potash (60% K2O) at £273 per tonne.

Type

Dry matter %

Total N

Total P2O5

Total K20

Total MgO

Total SO3

Total nutrient

value (£/m3)kg/m3 or kg/t

Whole 5.5 3.6 1.7 4.4 0.6 0.8 5.1

Separated liquor 3.0 1.9 0.6 2.5 0.4 <0.1 2.6

Separated fibre 24.0 5.6 4.7 6.0 1.8 2.1 7.1

Table 8. Typical nutrient contents and MANNER-NPK estimates of nutrient value of digestate from farm sourced feedstock using RB209 figures29

New AD technology is currently being developed that may offer more opportunity in future for using laying hen manure as a feedstock at farm scale. Within the AgroCycle research project30 (with funding through the EU Horizon 2020 Research and Innovation Programme) Harper Adams University College is seeking to develop a dry AD system capable of using only poultry manure as a feedstock at farm scale. The AD system being trialled uses a low cost, small scale rotating drum digester. This is capable of holding 40m3 of material inside a heated water jacket using energy generated from a boiler which uses some of the biogas generated. It includes a pre-

treatment step to reduce the nitrogen levels in poultry manure. The system is currently being trialled in Ireland and initial results are expected to be published shortly. At a larger scale, a new commercial AD plant is being designed to operate with laying hen manure (only) in England. It is understood that the plant will use 55,000 tonnes of feedstock per year and that the biogas will be used in the gas grid. The system will mix incoming laying hen manure (at 30% dry matter) with the liquid fraction from the digestate after nitrogen is removed from it to produce an ammonia sulphate fertiliser. A separate process is intended to remove the calcium grit from the manure early in the

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30 https://www.harper-adams.ac.uk/research/project/189/sustainable-business-models-in-food-waste-management-in- the-retail-sector

digestion process. The technology has been developed by the American manufacturer DVO31 and the installation is being developed by Rika Biofuels32. 4.4.3 Key considerations AD systems require both feedstock and digestate storage. Liquid feedstock storage requires a vessel such as a slurry store. Solid feedstock, such as poultry manure requires storage in a structure with an impermeable base, retaining walls and drainage collection. Liquid digestate can be stored in a tank of concrete or steel construction, or in an earth lagoon. These generally need to have a cover to control emissions. If the system separates the digestate, the fibre from the liquid

digestate requires additional solids storage. Dry AD systems produce stackable solid digestate which require similar clamp-type storage. Capacity for six months storage is normally required so that the digestate can be applied to crops at optimum plant growth stages. The biogas produced by AD contains impurities which need to be removed before the gas can be used for electricity generation. Gas cleaning systems are offered by most suppliers for this purpose. Further treatment is required to raise the calorific value and remove other contaminants to meet National Grid gas standards, but as this process has a relatively high cost it is limited to larger scale AD plants.


31 http://dvoinc.com 32 www.rikabiofuels.com

Farmers can operate smaller AD systems without an environmental permit, although registration with the Environment Agency is still required. An exemption is given providing that only specified raw materials are used (these materials include manures, slurries and plant tissue) and that the total quantity of waste treated or stored at any time does not exceed 1,250 cubic metres. The digester must have a net rated thermal input of less than 0.4 megawatts. Digestate from farm- based AD plants fed from agricultural sources can be applied to land for use as a fertiliser without a separate exemption33. 4.4.4 Cost and returns Farm-scale biogas plants with wet

digester systems typically range from 250 to 500 kilowatt systems, processing between 10,000 and 20,000 tonnes of farm manures, slurry and crop feedstock per year. The capital investment involved typically ranges from around £1.4m to £2.5m, with return on investment mainly dependent upon income from energy sales, renewable energy support schemes and the sale of digestate. Government support for AD has tended to reduce over the years as the industry capacity has grown. The incentive for developing on-farm AD is now much more dependent on the financial returns that can be achieved from using the biogas as energy on site.

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33 www.gov.uk/guidance/waste-exemption-t24-anaerobic-digestion-at-premises-used-for-agriculture-and-burning- resulting-biogas

CASE STUDY ON ANAEROBIC DIGESTION AND DRYING – CHARLES MEAR

Charles and Jo Mear have a 28,000 bird free range egg production unit together with egg packing facilities and a mill for producing feed using locally-grown wheat. They also manage arable crops on an enterprise of over 80 hectares in Bedfordshire. Business diversification has been a key focus to ensure profitability and most recently, Charles has managed the installation of a solar PV system and subsequently an anaerobic digestion (AD) plant for renewable energy and heat production. The renewable heat from the AD plant is used to dry manure over a belt system supplied by Dorset Green Machine, model MB9. The AD system was installed in 2016 with biogas used for electricity generation through a 165 kilowatt rated output generator. Around 10% of the electricity generated will be used on-farm, the rest is fed into the grid. The digester

is a horizontal plug flow system which is 6 metres wide, 4 metres deep and 42 metres long with a capacity of around 1000m3. The feedstock is 60% maize purpose-grown crops (PGC) and 40% rye PGC grown on their farm or supplied by neighbours. The digester generates 2,500 tonnes per year of solid digestate, after separation from the liquid fraction. The original intention was to include laying hen manure within the feedstock mix with PGC, but the AD system design could not operate with the build-up of calcium grit. The digestion process takes between 60 and 65 days to complete. The digestate is separated through a screw press and the liquid and solid fractions are land spread on the farm for their fertiliser value, replacing bought-in fertilisers. Some is also sold locally as a fertiliser, soil improver or mulch to farmers and allotment groups.


The farm has installed a belt drier to dry the laying hen manure and this operates off the renewable heat from the biogas fuelled CHP generator. Two heat exchangers have been installed to provide heat to the drier. The birds are housed in flat deck systems with verandas on both sides. The laying cycles are staggered, so the farm generates around 300 tonnes of manure every 6.5 months. The drier has a throughput of around 2.4 tonnes per day. The manure entering the system is around 52% DM and it is dried to 85% DM. The dried manure is bagged into 2m2 bags for ease of handling and to reduce dust. A biological air scrubber has been installed to reduce ammonia emissions and dust, although this was not a legal requirement.

Charles is developing a market for the residual solids produced on the farm and is conducting trials based on dried manure blends with the digestate solid fraction. The farm engages with local allotments and amateur gardeners and employs a consultant to help develop products and markets. To help with the marketing of the dried organic fertiliser products, Charles is experimenting with methods of further processing including a shredder to reduce the particle size of the chicken manure prior to drying, pellet extrusion and packaging. The farm has Leader Grant support for this. The farm has plans to develop a local community education centre, which will invite local residents and schools to learn and actively participate in the farm project. This is planned in the coming years, with an education room including a heated

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polytunnel facility running off the renewable heat from the generator. The cost of installing the AD plant, the drying system and all associated ancillary equipment (including digestate liquor lagoons, heat exchangers, air scrubbers etc.) was around £1.8 million and it was not without problems. The initial aim was to get 7.2p per kilowatt hour through the RHI scheme. However, due to the design and build company going into liquidation prior to commissioning and rapid changes to government support, Charles has had to accept 3.2 pence. He has received no payments since the plant first became operational in April 2017 and this has had a huge impact on cashflow and therefore on the further development of the business.


5 CONCLUSIONS

For the vast majority of free range egg producers, land spreading their manures and used litters is standard practice at present. The use of alternative methods is currently rare. Producers who have sufficient land for spreading benefit from the fertiliser values of the manures applied and the contribution it makes to the biology and structure of the soil. However regular applications of poultry manure to the same land can result in an over-supply of nutrients and in turn to increased pollution risk. Based on a dry matter content of 50%, we calculate the current nutrient value of poultry manure to be between £20 and £26 per tonne, depending on the time of application and whether it is incorporated into the soil within 6 hours or not. The most valuable nutrients are phosphorus and potassium with the value of the nitrogen

content being greater for spring than for autumn applications. Poultry manures with a higher dry matter content have more value e.g. the nutrient value of an 80% dry matter manure is estimated at £41 per tonne. This range of manure values excludes any costs of transport and spreading. Transport costs can be considerable, particularly for those exporting manures to other farms some distance away. This can erode the theoretical value of the manure (as shown) above and in practice result in little or no income being obtained. In parts of the country where there are high populations of free range hens but comparatively low land fertiliser requirements, this is already leading to concerns about the impacts of local manure surpluses. Legislation and codes of practice are already


in place to control the quantity and timing of poultry manures applied to land. The expectation is that these will become more onerous in future. Key developments are the Farming Rules for Water (2018) and the Clean Air Strategy (2019) which include the following:- • Organic manure applications to be planned to meet soil and crop nutrient needs; • Account to be taken of significant risk areas for pollution; • Reasonable precautions to be taken to prevent runoff from manure applications; • Mandatory design standards for new poultry housing in order to reduce ammonia emissions.

The likelihood is that these developments will exert further controls over land spreading activities. For many farmers, this may mean that even maintaining the ‘status quo’ i.e. continuing un-changed with current land spreading practices will not be possible. Additional land areas will be needed for manures to be spread. In some parts of the country with high poultry populations, the implications are likely to be most severe, particularly for those with insufficient land for spreading under their own control. These developments may lead to renewed interest in uses of manure other than for land spreading. Four alternative options have been considered within this report and Table 9 on pages 83-85 summarises key information relating to each.

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At present, the capital costs of activities such as combustion and anaerobic digestion are very high and therefore they are likely to be considered for ‘own use’ only by the very largest free range egg producers. However, increased interest from farmers in the use of smaller systems may result in new developments in lower capacity equipment, with the prospect of making them more affordable to smaller producers. For combustion and AD, revenue from government schemes is important to financial success. For new enterprises, the future of such schemes and the likely scale of payments should be carefully considered at the outset because prices are regularly reviewed and government policy changes can be made. The latest rates for the Feed in Tariff (FIT)34 and the Renewable Heat Incentive (RHI)35 can be found on the Ofgem

website and these will provide a basis for future decision-making. Evidence from the case studies indicates that payments from these schemes can be much delayed and so this eventuality must be planned and budgeted for. Because of the lack of ‘alternative’ systems that are tailored to smaller producers at present, there may be a stronger case for considering a collaborative approach, whereby a manure handling facility (such as combustion) is established at a central site in order to serve the needs of a number of local producers, who would each supply manure to it. Details of future support that may be available to farmers under the Clean Air Strategy are not yet available but assistance with the capital costs of alternatives to land


34 www.ofgem.gov.uk/publications-and-updates/feed-tariff-fit-tariff-table-1-april-2019 35 www.ofgem.gov.uk/environmental-programmes/non-domestic-rhi/contacts-guidance-and-resources/ tariffs-and-payments-non-domestic-rhi

spreading and with the establishment of collaborative approaches to production and marketing could encourage and hasten change. For manure systems which can produce heat (such as combustion and anaerobic digestion), there are additional opportunities to use a proportion of this to provide heat to free range houses at certain time of the year. This could provide additional benefits in terms of reducing ammonia emissions associated with housing, maintaining dry litter, improving bird welfare and reducing odour risk.

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Table 9. Summary of key features of alternative poultry manure uses

Incineration Drying & pelleting Composting Anaerobic

digestion

Capital costs

High – likely to be between around £1.4m to £2m in total, dependent

on whether a CHP

or a non-CHP system is used

Medium – Drying equipment is

estimated to cost around £2.50 per bird for a house

of 32,000, drying and pelleting

for 64,000 birds is around

£4 per bird

Can be very low if windrow systems

and existing buildings or

concrete bases are used. ‘In

vessel’ systems (equipment

alone) are likely to be around £0.7m (equipment only)

High – typical range is £1.4m

to £2.5m for 250 to 500 kilowatt

systems

Legislative and other key requirements

(other than planning consent)

Animal by-prod-ucts legislation

applies, enforced by

APHA. Environmental permit needed

(Part A2 activity) regu-

lated by the local authority

APHA approval is needed and heat treatment

to 70°C for at least 60 minutes (or equivalent)

is needed

Exempt from environmental

permitting unless bringing in ‘higher risk’

wastes. Mixing poultry manure

with green waste would be exempt.

Compliance with PAS100 is likely to be needed to

ensure that recipients of the compost do not

require their own environmental

permit

Registration needed with Environment Agency but

exempt from environmental

permitting if poultry manures and plant tissues are used; if waste

treated and stored is less than 1250m³ and if net

rated thermal input is less than 0.4 megawatts. Digestate from

farm-based systems can be applied to land

without a separate

exemption

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Table 9 (cont). Summary of key features of alternative poultry manure uses


digestion

Likely scale or minimum

size of operation

Large scale needed (over 100,000 hens)

due to high capital costs – unless smaller

capacity systems become

available in future

Drying systems can be provided

for small units (12,000 birds)

whereas a minimum of

64,000 birds is likely to be needed for pelleting

No lower limit for windrow systems

using existing facilities. At least

medium scale (e.g. 64,000 birds as a minimum) is

likely to be needed for

in-vessel systems

Large scale (over 100,000

birds) likely to be needed

Final products

Energy which can be used to

generate heat or electricity for on-site use or

exported. A residual ash is also produced which can be

sold to fertiliser companies or for land-spreading

Dried ‘bulk’ manure can

attract a slightly higher sale price

than fresh manure, with

lower transport costs. Prices for

pelleted product in Netherlands

vary greatly according to

nutrient content (£50-£220 per tonne). High

prices possible if able to

successfully market bagged

product to retailers

Compost, mainly for use in

agriculture, horticulture or for other land uses. The sale value may be

modest (e.g. £5 per tonne or less) and if so the gate

fee is the main income source

(see below)

Biogas which can be used to

generate heat or electricity for on-site use or exported. The digestate can be spread to

land – nutrient content varies according to

the raw material mix


Table 9 (cont). Summary of key features of alternative poultry manure uses


digestion

Other income sources

For new systems, income can be

obtained through the Feed in Tariff

(FIT) and the Renewable Heat Incentive (RHI)

None

Gate fee charged on the incoming materials needed

for mixing with poultry manure. This could range

from £20 per tonne for green

waste to over £80 for materials that

require more regulatory and process control

For new systems, income can be

obtained through the Feed in

Tariff (FIT) and the Renewable Heat Incentive

(RHI)

Limits and dependencies

The recommended

manure dry matter content is at least 55%

Drying systems are more suited

to use with multi-tier

housing and are cheap to

operate if exhaust air from

the house can be used to dry

the manure. Design of free range sites will determine the

feasibility of this.

Poultry manure alone is not suitable for composting

because of its high nitrogen

content. Mixing with a carbon-rich material is needed to

achieve the optimum C:N ratio

Calcium grit extraction

systems must be used. The high

nitrogen content of poultry

manure generally restricts its

inclusion rate to 20% of an ‘AD mix’. Supply of

laying hen manure to other

AD plants is likely to require ‘gate fee’ payments

photographs

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Photo 1. Case study – James Baxter Photo 2. Typical farm scale wet AD process

Photo 3 Typical drying system set up

Feedstock store

(silage clamp)

Feedstock mixer vessel

Liquid digestate storage

Biogass storage


Photo 4 Small pellet press which can process 400 kg per hour

Photo 5 Distributor spreading manure onto the drying belt Photo 6 Case study – Charles Mear

Manure drying (green building) using waste heat from anaerobic digestion. The dried manure is bagged for easy of handling and storage

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