DESCRIPTION to commercial offera biogas plant for conversion of organic wastes to biogas

Cleaning Recycling & Organic Fertilizer

2008

No 1 1.1 1.2 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 3 3.1 3.2 3.3 3.4 3.5 INTRODUCTION Project targets Technical and economic ground TECHNOLOGY

CONTENTS

P. 3 3 3

Biological bases of anaerobic digestion Characteristics of raw materials and final products Technological scheme selection Structural scheme of organic wastes digestion Technological schemes of organic wastes digestion into biogas, heat and electricity Technological process description Material balance (biogas, energy resources, biofertilizer) Energy balance, consumption heat and electricity Equipment calculation and selection Production control CONSTRUCTION Biogas plant for anaerobic digestion components Constructions of biogas plant Energy distribution Biogas plant administration Biogas plant placement APPENDIXES

4 6 6 8 9 11 12 13 14 17

19 22 26 26 27

1 2

Economics Biofertilizer utilization

28 30

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1 INTRODUCTION

Customer: domestic wastes sorting enterprise. Localization: Syria. Functionality condition: year-round. Object: biogas plant for anaerobic digestion of organic wastes.

1.1 Project targets

1 Biogas plant construction for electricity, heat and organic fertilizer from organic wastes. 2 Utilization of organic wastes with obtaining ecologically neutral zone. 3 Implementation of progressive ideas, world experience for biogas production and utilization accordingly regulations. 4 Ensuring of cost recovering in less than 3 years, and ecological safety for environment and maintenance staff.

1.2 Technical and economic ground

Methanogenic digestion anaerobic biological process occurs with the aim of different microorganisms that convert most organic compounds into methane, carbon dioxide and environmental neutral biofertilizer under moderate conditions (temperature 25-55 , humidity 7098%). In the past century industrial technology of methanogenic fermentation reached substantial development. Application of heating and heat insulation to methantanks gave possibility to stable and permanent biogas production the whole year independent of weather conditions. Combination of gas generating equipment with automatization supply the customers with biogas under minimal labour inputs. Modern gas power engines, burning down biogas, produce heat and electricity with high efficiency. Biogas plant of middle output, supplying itself with energy, paybacks in 1,5-3,5 years at expense of energy sources and fertilizer selling. As the energy resources and fertilizer prices are rising every year the benefits of using BGP will grow too. In the project domestic organic wastes is used for anaerobic digestion. The biogas yield from these wastes is about 150 m3 per 1000 kg with high methane content 65-75 %. Such a biogas plant will produce a lot of energy.

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2 TECHNOLOGY

2. Biological bases of anaerobic digestion

Biogas production technology is based on biological process of anaerobic digestion of organic compounds. Anaerobic digestion passes at hermetically closed camera (bioreactor). The process can be characterized the equation: 5132NS (Organic compounds) + 32 34+2+NH4HCO3 + 2S At the first stage of digestion compounds are hydrolyzed with the aim of acidogenic bacteria. During hydrolysis complex organic compounds are broken down to simpler ones (proteins, carbohydrates, lipids). At the second stage one part of the simpler compounds are decomposed to acetic acid, carbon dioxide and molecular hydrogen under influence of heteroacetogenic bacteria. The other part with conjunction of acetate transforms to organic acids. Obtained compounds serve as substrates for methanogenic bacteria at the third stage. This stage passes by 2 ways A and B, with participation of different bacteria. These two groups of bacteria convert compounds producing at first and second stage into methane, water and carbon dioxide (pic. 1). Thus, the anaerobic digestion occurs with the aim of bacteria and comprise the conversion of complex compounds to biogas and water. For trophic demands all mentioned bacteria are divided on 3 groups: 1 group hydrolytic or acidogenic (first stage). Proteolitic, cellulolitic, strict and facultative anaerobes belong the group 1. To the group 2 homoacetic bacteria belong (second stage). The group 3 is attributed to methanogenic bactreria (subgroup A) chemolititrophic bacteria turning carbon dioxide and hydrogen to methane and water. Bacteria (subgroup B) turn formic and acetic acid and methanol to methane and carbon dioxide (stage 3B). Except natural substrates anaerobic microorganisms decompose phenols and sulfuric compounds. Depending on the composition of digestive mass and predominance of certain bacteria the content of bioreactor changes its redox-potency and pH.

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Organic wastes First stage hydrolisis Acidogenic bacteria Aminoacids, fats, carbohydrates Second stage hydrolysis, oxidation

Acetogenic bacteria Acetic acid, organic acids, H2, CO2 C1-compounds

Third stage methanogenic digestion

Methanogenic bacteria A Methanogenic bacteria B CH4, CO2

Picture. 1. Scheme of biological transformation organic compounds under anaerobic conditions.

As a result of biological decomposition proteins, lipids, carbohydrates are obtained: Organic acids acetic, butiric, propionic, formic, caproic, lactic; Alcohols and cetones methanol, ethanol, isopropyl, glycerol, butanol, acetone; Gases methane, carbon dioxide, hydrogen, ammonia, hydrogen sulfur; Enzymes - cellulase; Vitamins riboflavin (2), cyancobolamine (12).

These products are intermediates and can be found inside bioreactor. Final products of anaerobic biodegradation of organic compounds are: biogas (methane content > 55%, carbon dioxide < 45%, hydrogen sulfur < 2%, hydrogen < 1%); fermented substrate containing water, cellulose residues, small quantity of bacteria biomass and inorganic substances (nitrogen, phosphorus, potassium, sulfur and others).

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2.2 Characteristics of raw materials and final products

Designing biogas plant should reprocess:

Organic domestic wastes: 350 tons per day, dry matter content 50%. Functionality condition: year-round.

2.3 Technological scheme selection

In the world practice of biogas production one stage substrate conversion scheme is manly used. At the scheme all biological processes pass in one bioreactor with agitation. The maximal biogas yield in case of full decomposition of organic substances shown at table 1. Table 1 Organic substances Lipids Proteins Cardohydrates Biogas yield, m /kg dry matter 1,11,3 0,60,9 0,70,83

Methane content in biogas, % 80-90 75-80 50-60

In the project two stage substrate conversion scheme is offered. This technology was checked and adjusted at facilities of German company INNOVAS GmbH during more than 10 years. Technology process division is made accordingly to microbial conversion stages. In the first bioreactor hydrolysis and partial acidogenesis of organic substances occur. In the second one acidogenesis completes and acetic acid, carbon dioxide and methane begin to form. The two stage scheme comparing to one stage, helps better control organic substances conversion and receive stable biogas formation with high efficiency and low time and energy loses. Many companies implement simpler one stage technology. But two stage technology more economical. Under the same conditions of digestion time and energy consumption at one stage technology lower biogas volume can be produced. And otherwise for the same biogas yield at two stages scheme needs less time and energy. Full mechanic agitation at one stage needs twice more agitators and electricity than at two stage scheme. At organic wastes quality deviation biogas yield sharply decrease at one stage technology while two stage technology much more stable and allow to regulate biogas production at both stages. Final products of anaerobic fermentetion leaves the bioreactor by different ways. Biogas containing 70-80% of methane after primary cleaning and drying is transmitted to co-generation unit under constant pressure of 5 kPa for electricity and heat production. In case of using biogas as natural gas an additional biogas cleaning has to be made. At the biogas cleaning the excessive carbon dioxide is eliminated and purified methane collects at gasholder.

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Fermented substrate is reasonably to separate onto two fractions liquid (filtrate) and solid (fugate). Fugate is ready for use organic fertilizer (pic.2). Filtrate can be used in different ways for dilution of incoming wastes to the necessary water content, nourishing plants at fields or after its aerobic cleaning to the allowed level releasing to natural basins.

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2.4 Structural scheme of organic wastes digestion

Picture 2 8

2.5 Technological schemes of organic wastes digestion into biogas, heat and electricity

Technological scheme of organic waste digestion with methane production

Organic wastes

1

Wastes homogenizationHomogeneity degree

Substrate preparingFiltrate

2Water content 86-92% t + 20-25

Substrate hydrolysis 3t +25-28 , 5-6 8 days, agitation

2

MethanogenesisFermented substrate

4t +33-38 , 7-8 20 days, agitation

Biogas

Biogas cleaning 5H2S, CO2, moisture content, Wobbe number

7Filtrate

Fermented substrate separationDry matter content 30%

2 Solid biofertilizer (fugate)

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Technological scheme of organic waste digestion with electricity and heat production

Organic wastes

1

Wastes homogenizationHomogeneity degree

Substrate preparingFiltrate

2Water content 86-92% t + 20-25

Substrate hydrolysis 3t +25-28 , 5-6 8 days, agitation

2

Methanogenesis 4t +33-38 , 7-8 20 days, agitation

Biogas

Fermented substrate

Biogas cleaning 5H2S, CO2, moisture content, Wobbe number

6

Electricity, heat productionPower generation t heating water 60

7Filtrate

Fermented substrate separationDry matter content 30%

Solid biofertilizer (fugate)

Electricity, heat

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2.6

Technological process description

1. Wastes homogenization. Wastes are moved to homohenizator, that grinds its to homogeneous state. At the homogeneous state wastes do not layer and are easier to mix on the following operations. 2. Substrate preparing. Homogeneous wastes are loaded to the receiving tank where substrate accumulates in quantity enough for 2-3 days continuous biogas plant operation. The wastes are diluted to 86-92 % water content, mixed and if necessary preheated to +20.+25 at receiving tank. Heavy particles sediment at the bottom of the tank during mixing. For dilution of wastes water, sewage of food industry or filtrate after separation of fermented substrate can be used. 3. Substrate hydrolysis. From receiving tank prepared substrate is moved by the means of pump to hydrolysis bioreactor. Where it is heated to temperature +25+28 and mixed during 8 days. The by-product of hydrolysis is carbon dioxide that releases to the atmosphere through a biofilter. Carbon dioxide can be collected and pumped into gas vessel. 4. Methanogenesis. From hydrolysis bioreactor transported by overflow to methanogenic bioreactor where organic substances under anaerobic microbial digestion converts into methane and carbon dioxide. Substrate remains at the bioreactor for 20 days at temperature +33.+38 under periodical mixing. Releasing biogas accumulates under gasholder over the bioreactor and transports by a ventilator to cleaning stage. 5. Biogas cleaning. Biogas preparation is used for lowering hydrogen sulfur and moving away excessive water vapor. Hydrogen sulfur is oxidized directly at the bioreactor by air oxygen according to equation: H2S + 1/2O2 = S + H2O. For the purpose to gas medium of bioreactor compressed air is added in quantity of 4-6% from biogas yield. Free sulfur formed by oxidation accumulates at constructions inside bioreactor. Thereby hydrogen sulfur content decreases more than 50% and the final concentration turn to 0,11,0% depending on primary concentration. After that gas is cooled to +6+10 in tube laid at the necessary deep in the underground and water vapor condenses. Condensed water flows to the collector and dried biogas moves to external gasholder. This precleaning is enough for burning down biogas in co-generators. But for using biogas as a substitution of natural gas it should be cleaned additionally for: - increasing calorific efficiency over 32 000 kJ/m3; - lowering mass concentration of hydrogen sulfur to 0.02 %. Ballast carbon dioxide together with impurities can be removed at industrial gas cleaning systems. Cleaned biogas contains 90-97 volume % of methane and can be used as natural gas. Cleaned methane from biogas may be delivered to domestic consumers or gas refuel stations.

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6. Electricity, heat production. Biogas is burned for production of energy resources in co-generators of different constructions. Generally biogas is burned at reciprocating engines or gas turbines, that activate electric generators. Exhausting gases give heat to circulating water at different heat-exchangers. Smaller part of generated heat 5-40% is used for warming up substrate in receiving tank and bioreactors. 7. Fermented substrate separation. Residue after anaerobic digestion is pumped to the separation site. A separator divides fermented substrate onto solid fraction (dry matter content 25-35%) and liquid fraction (dry matter content 1-2%). Liquid fraction (filtrate) partially or fully returns to receiving tank for incoming wastes dilution. Surplus filtrate accumulates in lagoon and can be used for irrigation as a liquid fertilizer or after cleaning let it out to natural basins. Solid fraction (fugate) is ready for use organic fertilizer like compost. It is transported to special area for storage and selling to consumers. 2.7 Material balance (biogas, energy resources, biofertilizer)

Biogas production Based on incoming data calculations of quality and quantity of biogas gives such results (see table 2). Table 2 Substrate No Substrate quantity, tons per day 1 Domestic organic wastes DM 50% 350 Biogas yield, m per ton of substrate3

Biogas yield, m3

Biogas yield, m3

4 content %

per day

per hour

300

96 000

4 000

70 %

Finally anaerobic digestion of organic wastes will give up to 4000 m3 per hour with methane content 70%.

Energy resources production Biogas after precleaning is the gaseous fuel that have lower calorific efficiency than natural gas (36-40 MJ/m3 or 10-11 kWh/m3) and can release 20-25 MJ/m3 or 5,5-7,0 kWh/m3 of heat energy. Burning biogas in co-generators produce electric energy (up to 45%) and heat energy (about 50 % of total heat energy). Calculation of energy resources release is given at table 3.

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Table 3 Biogas yield, m3 per hour 4 000 Calorific efficiency, kWh/m3 7,0 Total combustion heat per hour, kWh/m3 28 000

Electric power, kWh 12 600

Heat power, kWh 14 000

Fertilizer production Calculation of fermented substrate, filtrate, fugate and returning filtrate are given at table 4. Table 4 Amount, tons per day Biogas yield, m3 per day Fermented substrate, tons per day Dry matter in fermented substrate, tons per day Fugate, tons per day Filtrate, tons per day

Substrate Domestic organic wastes, DM 12%

1500

96 000

1 395

75

250 (DM 30%)

1 145 (return)

Fugate is enriched with mineral and organic components which are in form appropriate for nourishing soils. Commonly biogas plant will produce 90 000 tons per year of solid biofertilizer. For dilution of incoming 350 tons to dry matter content 12% it is necessary 1150 tons of water. Thus all filtrate can be returned to receiving tank for wastes dilution.

2.8 Energy balance, consumption heat and electricity The biogas plants equipment requires energy for operation. The main energy consumers at biogas plant are homogenizators engine, transporting pumps, agitators, separator. Initial data for energy consumption estimation is technological lines productivity and equipment power. For the first planning let develop a biogas plant consisting of 12 equal biogas stations. Each station is equipped with all demanded technological units for conversion wastes to biogas and fugate. The productivity of the station by prepared substrate (DM 12%) will be 125 tons per day or 30 tons per day of incoming organic wastes (DM 50%). Area planning and equipment optimization will be done at designing. Estimated calculation results for electric energy consumption of one biogas station are given at table 5.

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Table 5 Methane tank agitator Hydrolysis bioreactor agitator Electricity consumer Substratetransporting pump Homogenizators engine Filtrate returning pump 4,0 4,0 1,0 4,0

Receiving tank agitator

Separator

Productivity, m3 per hour Power, kW Equipment number Total power

1,25 5,0 1 5,0

5,2 4,2 1 4,2

10,2 2,7 2 5,4

41,7 10,4 2 20,8

62,5 11,5 2 23,0

5,2 1,7 1 1,7

64,1

The whole biogas plant will spend up to 770 kW per hour that is less than 7% of all generated electricity. Heat energy consumers at biogas plant are receiving tank and bioreactors. Calculation comes from the substrate flow rates per hour and heat losses of ponds to the environment, are given at table 6. Table 6 Amo unt tons per dayHeat loss of relieving tank and hydrolysis bioreactor, kWh Heat loss of methanogenic bioreactor, kWh Total heat demand of one station, kWh Total heat demand of biogas plant, kWh

results

Substrate

Substrate heating

Domestic organic wastes, DM 12%125 283 12,5 13,8 309,3 3 720

Maximal heat demand for warming up reservoirs of biogas plant in cold time of a year will be 30 % from heat power of co-generator burning obtained biogas.

2.9 Equipment calculation and selection

Equipment is defined by incoming waste characteristics and will be done at design works. The list of one biogas station equipment is shown at table 6.

Total, kW

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Table 6 The equipment list of one biogas station Equipment unit Homogenizators engine Substrate-transporting pump Receiving tank agitator Hydrolysis bioreactor agitator Methanogenic bioreactor agitator Separator Filtrate returning pump Supplied power, kW 5,0 4,2 2,7 10,4 11,5 1,7 4,0 Number of units 1 1 2 2 2 1 1

Wastes transporting. Homogenizator load with wastes is done by means of mechanical loader. Homogenized wastes are transmitted by screw conveyer to the receiving tank. Diluted wastes are pumped to the hydrolysis bioreactor. From latter substrate proceeds by overflowing to methanogenic bioreactor. Fermented substrate overflows to separator and filtrate after separation turns back to receiving tank. Fugate is carried out by mechanical loader from separation site to a fertilizer storage area. Biogas station. Biogas station consists of homogenizator, receiving tank, hydrolysis and methanogenic bioreactors, EPDM-gasholder. All reservoirs equipped with 2 agitators and heating system. Gas cleaning. There are several ways of biogas utilization: burning down at a co-generator with heat and electricity production; burning at water or steam boilers with heat power transmitting to heat carreers (steam or water); cleaned gas is transfered to other consumers (refuel stations, industrial and private consumers). After biogas precleaning it can be transmitted to a co-generator directly by tube. For other goals it should be cleaned better. Two techniques of carbon dioxide removal from biogas are employed today: carbon dioxide absorption by liquid, liquefaction of carbon dioxide. The first technique is based on the property of carbon dioxide (density 1.976 kg/m3) to dissolve under pressure in water or special liquid. Lighter methane (density 0.716 kg/m3) dissolves much worse (i. 3).

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Picture 3. Absorption system scheme for 2 removal. Cryogenic technique can produce liquefied carbon dioxide for technical demands. Principal scheme of the second technique is shown at pic. 4.

Picture 4. Cryogenic system for 2 removal. The residual gases like sulfur hydrogen, siloxans and others are removed from biogas in both techniques in special adsorptive columns. Co-generation site. Co-generators are made for simultaneous generation of heat energy in from of hot water of steam and electricity. For burning as much biogas as this biogas plant will produce a biogas turbine with electric generator has to be installed. The power of gas-turbine engine is counted by its electric generation power, heating power is depended on heat transmitting system (water, steam, water-steam, additional combustion chamber). Combined steam and gas turbine produces electricity with the highest efficiency. Heat of exhausting gases feeds a steam boiler. The energy of obtained steam is utilized at separated steam turbine with additional electricity generation (i. 5).

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Picture 5. Combined steam and gas turbine. Heat scheme. 1 Gas turbine engine, 2 Electric generator, 3 Steam turbine, 4 Boiler-utilizer, 5 Condensate tank, 6 Feeding water reservoir, 7 Pump

At the project the following combined steam and gas turbine is offered:Turbine type UGT 10 000 CC1 Number and type of engines 1 UGT10 000 + 1 ST Electric power, kW 13 500 Coefficient of efficiency electric, % 45,8 Natural gas 3 consumption, m per hour 2 980

Separation site. Separation site is equipped with centrifugal separator of, filtrate collection well and submersible pump with 10 m3 per hour productivity and head of 0,3 bar, concrete platform of 20 m2 for temporal storing of fugate.

2.10

Production control

Biogas plant operation is monitored at a computer in the control room. Central control board at the control room make it possible to operate by all units at manual or automatic modes locally or at a distance. Executive machinery of biogas plant is provided with electric equipment: Submersible propeller agitator, rate of rotation less than 100 per minute. Agitator is equipped with asynchronous electric engine 400 V/ 50 Hz. Agitator is applied at reservoirs for substrate mixing. Submersible pump made from stainless steel transports substrate between the sites of biogas plant. Separator dividing fermented substrate is equipped with asynchronous electric engine 400 V/ 50 Hz. Head conduit system transmits substrate and made from faucet high pressure PVC tubes.

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Gas outlet system is built from PE tubes buried under ground. Systems and sites of designing biogas plant with equipment are controlled by commands come from programmed controller. Two operational modes are used at biogas plant: time-programmed management of technological phases synchronized between different systems, management by control and measuring devices, this mode is reserved for limited and damage dangerous technological parameters. Synchronizing signals comes to central programmed controller from all units of biogas plant. The controller samples all equipment of biogas station and display collected information. At display one can see all constructions and sites equipped with electric drives and sensors of medium. All gathered parameters are registered. Emergency devices controls maximal and minimal levels in reservoirs, pressure at gas conductive tubes, methane concentration at closed rooms. In case of accident occurring emergency signal sounds for 30 minutes and if accident has not been eliminated the alarm signal transmits to the central post of a nearest service department.

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CONSTRUCTION

3.1

Biogas plant for anaerobic digestion components

The main componets of biogas plant accordingly Germans two stage technology of INNOVAS GmbH. wastes transporting system; receiving tank for 2 day of accumulation; hydrolysis bioreactor for 8 days substrate remaining; methanogenic bioreactor for 20 days substrate fermenting; biogas cleaning system; fermented substrate separation site; area for storage solid biofertilizer for 3 months; reserve lagoons for 1 month. Construction characteristics are calculated at initial data and given at table 7. Table 7 No 1 2 3 4 5 Constructions Receiving tank, m3

Volume/square 250 10003

Dimensions, m 86 16 6 20 6 120 100 150 112 4

Construction number 12 12 12 1 1

Hydrolysis bioreactor, m3 Methanogenic bioreactor, m Store area, m2

1500 12 000 45 000

Reserve lagoon, m3

Three reservoirs form a one biogas station. One biogas station occupies an area of 60 30 m2 or 0.2 hectare. Total biogas plan consisting of 12 biogas stations with lagoons and cleaning systems will occupy an area up to 8 hectares (i. 6). Biogas plant with gas co-generators will take less area up to 5 hectares (i. 7). Solid biofertilizer store area will take additionally 1.2 hectares.

Two plans of biogas plant corresponding to the final product output in form of methane or electricity are given at pic. 6,7.

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Picture 6. Plan of biogas plant for methane production.

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Picture 7. Plan of biogas plant for heat and electricity production. .

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3.2

Constructions of biogas plant

Receiving tank is a concrete round reservoir of 8 m diameter and 6 m height with concrete overlap. The reservoir has agitators and heating system for warming up substrate to +20+25 0, and digged into the ground at all height for heat insulation (i. 8).

Picture 8. Receiving tank.

Hydrolysis bioreactor is a round reservoir made of concrete or stainless steel of 16 m diameter and 6 m height, digged on 3 m into the ground, equipped with agitators and heating system for optimal temperature maintaining. As a result of hydrolysis and fermentation carbon dioxide releases that is removed by tubes at the upper part of the bioreactor (i. 9).

Picture 9. Hydrolysis bioreactor.

Methanogenic bioreactor is a concrete round reservoir of 20 m diameter and 6 m height. The reservoir is overlapped with wood bars and planks covered with EPDM-membrane for biogas precleaning and accumulation. The bioreactor has agitators and heating system for keeping substrate at mesophilic conditions +33+38 0. The reservoir is digged on 3 m and isolated with foam plastic. Fermented substrate overflows to the separation system during filling operations. Released biogas outlets from the upper part of bioreactor by gas tubes (pic. 10).

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iture 10. Methanogenic bioreactor.

Gas cleaning system. Biogas flows from bioreactor at minimal pressure of 20 mBar (maximal pressure 50 mBar). Removal excessive moisture is made by cooling biogas. At +8 0 water vapor condenses with residual water content of 10 mg per 1 m3. Cooling system is tubing system put underground on 1-2 m deep and 50 m long. Condensed water drains to collection tank for the 3% tube incline (pic. 11). Dried biogas comes to gasholder and feeding system of co-generators.

Picture 11. Biogas drying system.

There emergency devices at gas transporting system. Gas burner is actuated at pressure 10% over nominal (at 55 mBar) - (i. 12). Safety valve responses at gas pressure over 20% of nominal (at 60 mBar).

Picture 12. Gas burner.

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Cryogenic biogas cleaning system is made as separated modules. The modules can be settled at concrete bases outdoor (pic. 13).

Picture 13. Cryogenic module for carbon dioxide removal.

Separation site is a concrete platform with separator near the methanogenic bioreactor (i. 14). Filtrate flows down into concrete well and fugate dumps to concrete plate beneath the separator.

Picture 14. Separator.

Biogas accumulation system contains of EPDM-gasholders over bioreactors and separated plastic film gasholder (pic. 15) or steel gasholders for high pressure gas storage.

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Picture 15. Plastic film gasholders.

Lagoon for filtrate reserve collection can be made from concrete or plastic film (i. 16).

Picture 16. Plastic film lagoon.

Co-generator unit is installed at disaggregated building. Main components of co-generaton unit are gas-burning engine, electric generator, engine cooling system and automatization module (i. 17). In the project of biogas plant combined steam and gas turbine is offered for the maximal electricity production.

Picture 17. General view of combined steam and gas turbine.

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Heat-exchanging system consists of heat insulated tubes and heat-exchangers (i. 18), filled with a heat carreer - water. Water is heated by exhausting gases from co-generator and warms substrate at receiving tank and bioreactors. Surplus heat can be used for private and industrial houses heating or drying raw materials.

Picture 18. Heat-exchangers.

Control post is situated in a separated building on the concrete base with twenty-four hour working place with computer monitoring and a control board. The electric cabinet is mounted in the same building.

3.3 Energy distribution Energy supply system distributes electric power between consumers accordingly with their functional and territorial character. Biogas plant uses a small part of generated electricity to itself demands (5-7%) and transmits the rest to the consumers. In the case of methane production biogas plant should have a small gas generator for feeding its electric equipment. Powerful electric units pumps, agitators, separator have its own electric service panel.

3.4 Biogas plant administration

Organic wastes are loaded to the homogenizator once a day or more frequent. Homogenized wastes transports by a screw to receiving tank. Where wastes are accumulated, diluted to 88-90% of moisture content and mixed at time-programmed mode. Substrate feeding system of bioreactors is activated by a program 8-12 times per day. Fermented substrate is unloaded with the same periodicity. There is an emergency system to empty reservoirs if their overfill occurs. Biogas plant is controlled with the aim of sensors and accordingly to commands from central control board.

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Biogas flows continuously from outlet tube, equipped with condenser and safety devices. Safety devices are responses to extreme data from sensors. A co-generators module has autonomous automatic system that provides stable electricity generation at the power range 75-100% of nominal. Excessive biogas removes through emergency and safety devices. A separator can work at unloading time or several hour every day. Fugate is transported from separation site by mechanic loader, filtrate is pumped to the lagoon.

3.5 Biogas plant placement

The biogas plant should be built at the periphery of the waste sorting plant for safety distance not less than 200 m. The best building site location is upland to relief and not in the lowland and near ground water outlet to avoid accumulation of hazardous factors. Building site if possible should not be interrupted with trees or broken ground and has a precipitation drain. Constructions are installed by zones collected by technological features for tubes length reduction. A necessary span should be provided between technological zones for laying tubes, automobile passage and normal loading at the ground. A depth for all constructions have to be the same. A height may vary but emission tubes have to be 1 m higher than the highest building. Roads for mechanic transportation should have hard lean-to cover 3,5 m wide. Footpaths should go to all spots where operating personnel may come. Biogas plant have a perimeter net fence on concrete supports. At the biogas station control room, electric service panel, fire safety post have to be provided.

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APPENDIX 1 ECONOMICS

Economical calculations are approximate and can be exacted corresponding to waste composition, combination of heat/electricity demands, implementation different biogas cleaning system and co-generators, perspective costs of heat, electrical energy and fertilizers. For permanent biogas plant work operating personnel should be engaged. Personnel make monitoring and if necessary corrections actions. Expected natural gas cost is taken as 0,20 Euro per 1 m3. http://www.eia.doe.gov/emeu/cabs/Syria/Electricity.html Version 1. Biogas plant producing methane.

Capital expenditure Biogas plant Gas cleaning system Reserve lagoon Total capital expenditure Current expenditure Equipment, biorectors maintains Electricity costs, biogas cleaning maintain Personnel salary Total current expenditure Profits Productivity Units Biogas (methane - 70%) Natural gas equivalent (methane - 90%) 2 quotes Solid biofertilizer Lump sum Net income Pay-off period, year m3 t t 10,4 3 100 27 150 000 566 000 90 000 0,20 12 15 m3 4 000 35 000 000 per hour Productivity per year Price, EUR

EUR 16 000 000 6 500 000 800 000 23 300 000

190 000 390 000 30 000 610 000

Total, EUR

5 430 000 6 800 000 1 350 000 13 580 000 12 970 000 1,8

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Version 2. Biogas plant for production of heat and electric power. Expected electricity cost is taken as 0,03 Euro per 1 MW.

Capital expenditure Biogas plant Combined steam gas turbine generator Reserve lagoon Total capital expenditure Current expenditure Equipment, biorectors maintains Electricity costs, biogas cleaning maintain Personnel salary Total current expenditure Profits Productivity Units Biogas (methane - 70%) Electricity Heat energy 2 quotes Solid biofertilizer Lump sum Net income Pay-off period, year m3 MW MW t t 10,4 4 000 11 10 34 500 000 95 000 86 000 566 000 90 000 30 10 12 15 per hour Productivity per year Price, EUR

EUR 16 000 000 12 000 000 800 000 28 800 000

170 000 80 000 30 000 290 000

Total, EUR

5 700 000 860 000 6 800 000 1 350 000 14 710 000 14 420 000 2,0

The energy resources and fertilizer prices are rising every year. So the benefits of using biogas plants will grow proportionally.

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APPENDIX 2 BIOFERTILIZER UTILIZATION Fertilizers are the basis for improving and rising agricultural production. But physical, chemical and biological characteristics of organic wastes and manure are not good to apply them directly. Untreated wastes are used only locally, efficiency of such fertilizers is about 10-15%. Depending on ways and storage duration organic wastes loses 20-50% organic matter and nourishing elements (mainly nitrogen). After anaerobic digestion of organic wastes natural biofertilizer is obtained. It is enriched with bioactive substances, contains a great pool of microelements. The main advantage of biofertilizer comparing to manure compost is balanced content, nourish value and high concentration of humificated substances. Humificated organic substances is favourable medium for soil microorganisms. After biofertilizer introduction activation of nitrogen fixing and other microorganisms is observed. Chemical compositions of solid and liquid biofertilizers produced at the biogas plant from different substrates are given at table 1 and 2 corresponding. Table 1 Chemical composition of biofertilizer from biogas plant. Solid fraction, DM* 20-25% Biofertilizer (fermented substrate) Cow manure Horse manure Poultry droppings Grass Grass silage Maize silage Sugar beet tops Beer grains Distillery wastes (grain) Sugar beet press Slaughter wastes Milk whey Crop wastes Potato wastes Fruit cake, press Organic food wastes Rape press Activated sludge N 4,3-5,0 3,6-3,8 17-18 3,2-3,5 3,5-3,8 3,7-4 2,1-2,3 14-16 16-18 5,0-6,2 10-12 2,5-3,2 8-10 4,5-4,7 6-6,8 5,6-5,8 4,5-5 3,9 -4,2 Chemical composition, kg per ton NH4-N 1,0-1,2 1,0-1,1 3,0-3,5 0,7-1,0 0,5-0,9 1,2-1,3 0,5-0,9 2,0-2,5 1,9-2,3 1,8-2,0 0,4-0,8 1,8-2,0 1,5-1,8 1,6-1,9 2,4-2,2 P2O5 2,7-2,9 4,0-4,3 10-10,9 1,37-1,4 1,25-1,3 1,3-1,4 1,25-1,4 6,0-6,5 6,0-6,3 3,3-3,5 20-25 1,0-1,2 5,6-6,0 2,8-3,5 6,4-6,7 3,23,6 2,6-3,8 2,2-2,9 K2O 7,5-7,8 4,3-4,8 8,0-8,8 4,2-4,8 4,0-4,5 4,2-4,5 3,5-4 5,4-5,5 5,3-5,5 4,2-4,5 3,0-3,5 5,2-5,3 4,6-4,8 5,3-5,8 4,0-4,3 5,6-7 2,1-2,22 MgO 1,3-1,5 1,5-1,8 3,5-4,2 0,5-0,6 0,5-0,6 0,8-1 0,7-0,9 0,6-0,8 0,6-0,8 1,2-1,6 2,5-2,6 0,7-0,8 1,2-1,4 2,1 2,5-2,7 3,2-3,4 0,5-0,27 Table 2

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Chemical composition of biofertilizer from biogas plant. Liquid fraction, DM* 5% Biofertilizer (fermented substrate) Cow manure Poultry droppings Grass silage N 1,8-2,2 7,1-8,2 2,2-2,8 Chemical composition, kg per ton NH4-N 1,0-1,2 3,0-3,5 0,9-1,5 P2O5 0,8-1,6 6,8-7,9 1,9-2,3 K2O 2,2-2,8 5,0-5,6 2,0-2,5 MgO 0,4-0,5 1,5-2,2 0,5-0,7

* DM dry matter content, concentration of main elements can be different depending on the substrate composition. HUMUS Humus plays fundamental role for ecological equilibrium in soils. It is the nutrition medium for ground forming microorganisms, that by-turn stimulate plant nourishing and growth. Humus is formed by organic plant residues, slow-decomposing and totally decomposed organic substances and microbial metabolites. Main part of humus are humus acids, fulvic acids and their salts, humins stable complex compounds of humic and fulvic acids with other soil substances. Humines have great specific surface (600-1000 m2 per g) and adsorptive capacity. Introduction into soil small humus quantity leads to microflora changes, enhancing its metabolic activity and nitrogen fixation. These changes provide enriching soil medium. Soils nourishing with humus fertilizers brings those advantages: improving mobility of soil phosphorus; nitrogen fixation activation, turning to increasing general and protein nitrogen content, advancing carbon dioxide emission by soil; enhancing ammonia and amid nitrogen, phosphorus assimilation by plants; increasing free potassium and aluminium concentration, with decreasing free magnesium, thus humins influence much to cationic contents and dynamics. Principal soil parameter is organic matter content, because organics drastically improve physical, chemical and biological properties of soil and defines soil fecundity. Organic matters provide low heat transmitting that prevents quick heat loses into the atmosphere. Humus in 15-20 times more effective any other organic fertilizer. Specific humus microflora and enzymes are able to recover dead soil with regeneration of all soil functions and return fertility. These valuable properties of humus retains for 3-4 years. Every year a lot of organic matter is lost with harvesting, soil microorganisms number decreases that influence a humus forming rate. For maintaining necessary humus level organic compounds should be added to soils. For the purpose organic wastes or manure are used, but they contains small quantity of humins. That is why more efficient fertilizers have to be used. Substantial quality and quantity growth of harvests can be reached at the case of humus fertilization. From different sources winter wheat gives additionally yield of 15-20%, sugar beet upto 20%, maize 20-30%, potato upto 30%.

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Finally, positive impact of humus to the fecundity of soils can be explained as a complex of interrelated processes: improving physical and mechanical soil properties; intensifying soil exchanging processes: adsorption of feeding elements, enhancing its biological activity resulting in better plant nourishing. These processes leads to harvest yields increasing. Accordingly to specified positive indications humus has other valuable properties: large moisture keeping, humidity resistance, mechanical strength, absence of weed seeds, great pool of useful microorganisms, enzymes, antibiotics, growth hormones. Humus also has more standard properties: flowability, moisture content, expected action to the plants, harmless to soils, good interaction with mineral fertilizers. Moreover humus efficiency exceeds that one of any other mineral fertilizers. Humus content after methanogenic digestion of organic wastes is shown at table 3. Liquid biofertilizers can be used for plant sprinkling. Sprinkling is also useful against some harmful insects, parasitizing at fruits and berries. Vital functions of plants closely connected with humic substances the main resource of carbon dioxide for photosynthesis. Despite atmosphere contains considerable carbon dioxide quantity plants during fast growth feel the lack of carbon dioxide for its metabolism. Table 3 Humus content in biofertilizers obtained from different organic wastes (kg of humus per 1 ton substrate) Substrate Fermented substrate (liquid) Fermented substrate (solid) Compost Filtrated sluge Dry matter % in fresh substrate 4-10 25-35 40 10-20 Humus content kg per 1 ton of fresh substrate 6-12 36-54 50-60 10-15

Biofertilizer advantages comparing to other organic fertilizers Biofertilizer by many reasons are better than other organic fertilizer (manure, droppings, peat). Among them: - Weed seeds absence. In pig an cow manure, peat a lot of weed seeds presented. 1 ton of fresh manure have up to 10 000 weed seeds, that even after animal digestion do not lose its growing ability. It results in cereal harvesting loss of 5-7% at 1 hectare. - Pathogenic microorganisms absence. Through organic wastes many dangerous plant diseases are spread. Also manure can possess more than 100 human and animal diseases among than: anthrax, tuberculosis, brucellosis, paratyphoid, murrain, salmonellosis, ascaridiasis and enteric infections. Pig manure have general microbial number from 4,1108 to 3,6109, sporogenous

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anaebobics from 102 to 104, E. coli titre from 105 to 107 per 1 g. Biofertilizers because of special reprocessing at bioreactors are completely free from pathogenic microflora. - Useful microflora presence, that enhances plant growing. Organic wastes generally used for fertilizing have only little useful microorganisms. Manure hold about 109 microorganisms per 1 g, together with pathogenic. In biofertilizers hold microorganisms and no pathogenic. - No adaptation period. Manure and other organics before soil adding demand long period of composting (6-12 months). Valuable components are lost during composting and the rest start bringing advantages in 2-4 years after its introduction. Biofertilizers become useful directly after their implementation. - Stability to washing out useful elements from soil. Up to 80% of organic fertilizers are washed out during one season. So every year it is necessary to add organics into the soils. At the same conditions only 15% of biofertilizers are washed out. So introduction of biofertilizers into soil will work 3-5 years longer than common organic fertilizers. - Maximal nitrogen storage and accumulation. The lack of nitrogen results in lowering harvest yields most plants. Plant growth slows down. Plants become more sensitive to different diseases. Long nitrogen deficiency lead to protein hydrolysis and chlorophyll degradation in plant cells. During long manure composting almost 50% of associated nitrogen can be lost. Thanks for anaerobic fermentation of organic wastes general nitrogen amount completely remains, moreover soluble ammonia nitrogen increases at 10-15%. - Ecological influence. Organic wastes in untreated form bring damage polluting soil and ground water. While biofertilizers are fully ecologically safe for environment. Biofertilizer advantages comparing to mineral fertilizers Mineral fertilizers have negative influence into environment, human and animal health. In solution and grain form mineral fertilizers are assimilated by plants on 35-50% and the rest accumulate as nitrates in soil and plants. Food products from these plants are responsible for gastrointestinal cancer development. Long low nitrates income leads to thyroid gland growth. Nitrates promote increasing cholesterol and decreasing protein in human blood. Biofertilizers assimilates by plants almost on 100% with minimal nitrates concentration in food products. Biofertilizers quantity to introduction. Mineral salts solutions are hardly ever met in natural soils. So common mineral fertilizer dosage has negative effect onto the soil microflora. And working with mineral fertilizers demands exact amounts for usage. Exceeding that quantity disrupt soil structure and year-cycle of soil acidification. Humus as principal part of soil can be added in any amounts. At its implementation there is no soil mineralization thanks to its ecological properties. 1012 - 1014 saprophyte and methanogenic

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