Professor Kirk Semple, Matt Riding (LEC) and colleagues from LEC, CEH and The James Hutton Institute
Dr Ben Herbert and Lois Ricketts (Stopford Projects Ltd)
Land Conditioning Products from
Bio-energy Generation
Developing a suite of novel soil conditioners and plant fertilisers from ash and digestate waste
streams originating from biomass energy generation.
1. Project Rationale
Sustainable forms of energy generation using
biomass such as gasification and anaerobic digestion
(AD) are rapidly growing, and forecast to generate
15% of the UK's energy demand by 2020. AD alone
has the potential to deliver over 40 TWh of
renewable energy, equivalent to over 10% of the
UK's domestic gas demand. As such, waste from
energy generation, including ashes and digestate,
are produced in large volumes and are likely to grow.
The dominant disposal route for ash from
gasification plants is to ash lagoons and landfill;
whilst digestates, derived from AD, are typically
disposed of to land at no cost. However, in the face
of rising pressures on environmental resources,
rising landfill taxes and accompanying waste-
minimisation legislation, alternative options for
waste reuse are increasingly being sought.
3. The Technology
Anaerobic digestion (AD) converts organic waste
materials into biogas and digestate. Biogas, consisting
of methane (60%) and carbon dioxide (40%) can be
used to generate heat and power, or purified and
injected into the gas network. Digestate can be used
as an organic fertiliser and soil conditioner. The AD
process is entirely natural and is carried out by micro-
organisms already present in the waste streams,
which thrive in an oxygen-free environment.
Consequently, the process takes place in large, air-
tight vessels which are designed to maximise biogas
generation and recovery.
Gasification is an emerging thermal conversion
technology that is being used to generate energy from
carbonaceous materials. The process operates under
sub-stoichiometric oxygen conditions, using a
carbonaceous feedstock, to produce low energy
synthesis gas (syn gas), comprising of hydrogen,
carbon monoxide, and a process ash. This gas can
then be used as a fuel to generate electricity or as a
precursor for chemical synthesis and fuel production.
1000
10000
100000
1000000Nitrogen
Water
Soluble
Phosphor
us as P2O5
Water
Soluble
Potassium
as K2O
Calcium
Magnesiu
m
Sulphur
Ash a Ash b Ash c Ash d Ash e
0.1
1
10
100
1000
10000
100000
1000000
Aluminium
Arsenic
Boron
Cadmium
Chlorine
Copper
Iron
Manganese
Molybdenum
Nickel
Selenium
Silicon
Sodium
Zinc
7. The Vision
Widespread adoption of this
technology could result in a
sustainable substitute for
conventional chemical fertilizers, in
turn significantly reducing the
carbon footprint of the agrochemical
industry. Furthermore, utilising the
growing waste stream of biomass
by-products to promote the growth
of crops, including energy crops, will
close the production loop for
biomass to energy generation
enabling a cradle to cradle approach.
5. Micro- and Macro-Nutrients
Previous studies have demonstrated that biomass-ash and digestate can be
useful nutrient sources for crop plants in nutrient limited conditions. Although
virtually nitrogen free, ash is rich in many micro- and macro-nutrients. These are
profiled for ash from a variety of sources in the star plots (left). Contrastingly,
anaerobic digestate is a rich source of trace metals and nitrogen, as well as
relatively stable forms of C, which may improve soil structure and enhance C-
sequestration within soil. Further work profiling the nutrient content of
digestate is currently being conducted.
It is hypothesised that a combination of ash and digestate may be regarded as
comprehensive nutrient provider and soil conditioner.
Micro-nutrient Variability (mg/kg)Macro-nutrient Variability (mg/kg)
6. Partnering with
Business
The project is engaging with strategic
industry partners, and operating both
academically and commercially
throughout the energy from biomass
and agrochemical space. This enables:
• Effective understanding of the
market
• Meeting the requirements of the
end user
• Accelerate product development
• Incorporation of policy and
regulation into scientific research
2. Key Aims
The objective of this project is to radically change the way in which biomass energy
producers can support a circular economy, through utilising bio-energy waste streams to
develop soil conditioners and plant fertilisers, facilitating new ways to mesh commercial
ideas with positive environmental benefits. This will be achieved through four aims:
1) Assess the environmental impacts of applying a waste derived product to land
2) Optimize a novel soil conditioning material derived from bio-energy waste (ash and
digestate)
3) Develop a land conditioning product with a significantly reduced environmental
impact to that of conventional mineral based fertilisers.
4) Close the nutrient cycle and ensure food security
A) Technical AssessmentLiterature Datasets
Chemical Composition
Physico-Chemical Analysis
Environmental Samples
Crops Trials
Product manufacture
B) Environmental AssessmentCarbon Sequestration
Nutrient Cycling
Bioavailability
Toxicity
Biodiversity
Biogeochemistry
Carbon/Water Foot Printing
C) Health AssessmentEmissions
Exposure
Food Chain Transfer
Ecosystem Impact
Human Health
Waste TypesAnaerobic Digestate
Biomass Ash
Waste CompositionChemical Composition
Metals, Nutrients, Elemental
Bioavailability & Speciation
Physical Characterisation
Waste ArisingsMarket
Quantities
Disposal Costs
Forecasting
FormulationChemical/Physical Composition
analysis
Technology TrialsGlasshouse Performance Trials
Crop Health and Yield
Product Efficiency
Soil Condition
Performance Benchmarking
Technology Optimisation
RegulationField Trials
Product Registration
Technology ApplicationMarket
Quantities
Forecasting
PolicyRenewable Energy Directive
Landfill Directive
Government Incentives
Waste Incineration Directive
Resource Recovery
RegulationResource Recovery from waste
Waste Re-use
Waste to Product
Waste to Land
Public PerceptionConsumers
Supermarkets
Supply Chains
Attitude to Waste
“Nimbyism”
Soil ConditionersFormulations/Compositions
Performance
Cost
ApplicationsCrop Type
Soil Type
Application Period
RegulationProduct Registration
Efficiency Trials
MarketMarket Size
Value
Forecasting
4. Project Development
424400
4656000
0.00E+00
5.00E+05
1.00E+06
1.50E+06
2.00E+06
2.50E+06
3.00E+06
3.50E+06
4.00E+06
4.50E+06
5.00E+06
Thermal Treatment Anaerobic Digestion
By-product Source
To
nn
es
ye
ar
-1
20
112
0
20
40
60
80
100
120
Thermal Treatment Anaerobic Digestion
Nu
mb
er
of
Pla
nts
Plant Type
A Whole Systems Approach
Legal, Environmental and Social Considerations
Scoping Research DevelopmentNumber Bio-energy
Plants
Quantity of Waste
Generated by Plant Type
Macro- and micro-nutrient content of ash derived from bioenergy plants representative of a number of different feedstocks
and plant types.
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