Anaerobic Digestion
- Biological
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Calcite added to the manure system as bedding conditioner and barn floor traction will precipitate out of digesters and cover fixed film components in a digester. Don’t add lime to a manure processing system without a method for calcium removal.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
A conical bottom to facilitate solid removal may prevent solids from remaining in the digester bottom even after a drainpipe is opened. Sediment will accumulate even with flow promoted from outside to the center with a flat bottom.
- AA Dairy
Digested separated manure solids were used for bedding for a short time. Mastitis incidents rose in the milking herd and the bedding was the first potential cause that was eliminated. The risk of additional mastitis makes the use of the manure solids as bedding a detriment.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Corrugated Plastic Drainage Tubing can be used as a fixed film media. Four inch diameter CPDT placed 8 feet on end in a ten foot diameter tank provided 11,965 square feet of surface area on the corrugated pipes, 433 square feet on the walls, and 86 square feet on the floor surface area. Other proprietary media may also work. Increasing the surface area to increase the biological activity is the goal of the fixed film.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Foaming issues occurred as changes to the digester feed rate occurred and when the diet of the cows changed. Foam can be controlled with a foam cutter sprayed on the surface at a concentration of 100ppm. Other adoptions to reduce the impact of foaming were raising the gas inlet and increasing the water trap in the gas line.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
Shock loading of a digester with high energy food waste will create substantial amounts of foam. Loading the digester incrementally throughout the day reduces the potential for foam.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Pumping tie stall manure with long hay is still problematic. Farms that need to pump manure for further processing may need to chop bedding and not use the manure as a disposal for refused hay. One point two gallons of water added near the impellor increases the pumping rate of undiluted manure from a tie stall barn.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
The mixed digester performs well and offers flexibility in operation accepting various consistencies of manure and food waste mixtures. By mixing the influent into the total volume of the digester, the biomass that has been built up in the digester can attack all the new feed. Even though some of the influent goes out of the digester the first day, the total volatile solids reduction is significant and the volatile acids (indicators for odor production) are low.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
A grinder pump will convert any remaining longer particles of manure into pieces less than 1/4th of an inch. Smaller particles will cause less plugging of heat pipes and provide better digestion.
- Noblehurst Farms
Demonstration of a community manure digester project
Maintaining temperature control during the winter is important. Frozen manure and manure that was too wet was bypassed from the digester. When the digester feed was reduced the gas production slowed and less heat was available to heat the influent and maintain the temperature. Either added external energy would be needed to maintain the digester temperature or the digester would need several months and warmer weather to recover.
- Noblehurst Farms
Demonstration of a community manure digester project
The thermometers were installed reading 3 degrees higher than reality. Checking and calibrating the instrumentation should be an important step in start up procedures.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
Odor control can be achieved by a digester system. The odors are negligible when the volatile acid levels leaving the digester are below 500 ppm. As the digester experiences difficulties with temperature or retention time the volatile acids leaving the digester may be higher and odors may occur.
- Manure and Effluent Handling
- Noblehurst Farms
Demonstration of a community manure digester project
Similar to the town of Perry, the disadvantage of the expense of manure transportation to the community site and transportation of the effluent back to each farm was a huge cost for the community system to overcome.
- Town of Perry
Feasibility of anaerobic digestion for multiple farms
The disadvantage of the expense of manure transportation to the centralized site and transportation of the effluent back to each farm was a huge cost for the centralized system to overcome. The energy produced at the centralized site could only be used at the central site to replace electricity at the retail price. Sending the electricity back to the farms would mean paying a wheeling fee to the utility according to NYS law.
- Twin Birch
The digester was designed with a hard top to collect the gas at 12 inches of water column pressure to push gas into the compressor. The greater the pressure the more difficulties there are in sealing a digester. Digesters operating at high pressures should be pressure tested as part of the startup procedure. Use proven technologies to seal digesters. Separate any equipment as much as possible from gas sources.
- Freund
Translucent ridged greenhouse material was used to cover the digester after the original fabric cover failed. The biogas is withdrawn from the digester under a slight vacuum to prevent leakage of biogas outside the digester. This allows observations of foam levels in the digester.
- Noblehurst Farms
Demonstration of a community manure digester project
Concrete hard tops operating under pressure are very difficult to seal. Leaks of biogas cause loss of gas production and odors on the farm. Pressure testing before filling with manure is time consuming and expensive but apparently needed to ensure that the sealant has been properly applied.
- Freund
The digester was designed with a center-dividing wall to move the manure down one side and up the other. During construction an opening was created in the dividing wall that allowed short-circuiting of the manure and little treatment and biogas production.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Foaming issues occurred as changes to the digester feed rate occurred and when the diet of the cows changed. Foam can be controlled with a foam cutter sprayed on the surface at a concentration of 100ppm. Other adoptions to reduce the impact of foaming were raising the gas inlet and increasing the water trap in the gas line.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
Foaming can occur when changes occur such as: the diet of the cows the temperature of the digester, and additions of other organic loading. Spraying water over the foam can control foaming. A water source and spray device near the effluent tank is useful.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
As foaming occurs, it often flows into the pipe chase where the gas collection pipes leave the digester. They have water basins set to provide the pressure needed to keep the cover inflated. Foam flowing out creates a mess. Providing a drain for the pipe chases and a solid bottom and water supply makes clean up easier. Removing the top of the pipe chase allows easy access and good ventilation for those working in the area.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
Although the food waste brings in additional solids to the digestion system fewer solids are in the effluent than when just manure is digested. The extra energy of the food waste apparently makes it possible for additional solids destruction. Solids were broken down in the effluent storage as well. The existing manure storage was about one half full of manure solids when digested effluent was introduced. After two years of operation, the solids in the storage are almost all gone without excessive agitation.
- Freund
Utilizing the biogas to run a boiler to heat a grid of pipes allowed the farm to introduce frozen chunks of manure into a preheat chamber. As the manure is thawed the pipe grid keeps the frozen chunks from moving into the digester until they are melted.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
The mixed digester performs well and offers flexibility in operation accepting various consistencies of manure and food waste mixtures. By mixing the influent into the total volume of the digester, the biomass that has been built up in the digester can attack all the new feed. Even though some of the influent goes out of the digester the first day, the total volatile solids reduction is significant and the volatile acids (indicators for odor production) are low.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
The plug-flow digester relies on the proper moisture content of the influent. Dairy manure as produced will not separate into floatable and settable solids very easily. When extra moisture is added, the floatable and settable solids sort out inside the digester, leaving a floating crust and a deposit. As these two portions of the digester get larger they will decrease the usable volume and the hydraulic retention time. Lower retention times will decrease biogas production and fail to reduce the odors in the effluent.
- Spring Valley
Sand laden dairy manure (SLDM) can be removed with a retrofitted gutter cleaner running at the heated inlet. As sand is dropped out the chain driven gutter cleaner is turned on coming out of the digester though air lock to load a manure spreader with SLDM. A ramp still exists to be able to drive down into the storage to remove any solid manure or sand that is not removed by the gutter cleaner.
- AA Dairy
Service support for the engine, generator, electrical inter-tie, and other parts are still not provided by one entity leaving the farm to find the best and quickest solution to a variety of problems. At times the small problem that goes unfixed for a time can lead to more difficult problems. There is an opportunity for a maintenance specialist to assist farms in running the systems that are part of an anaerobic digestion manure treatment process.
- Spring Valley
Inoculation of the manure in a long-term storage can reduce the odors of the manure. Originally discovered serendipitously, the system treating only a small portion of the manure in a controlled temperature digester can reduce the odor of all the manure given time. This means that for a low capital cost odor control can be achieved.
- Noblehurst Farms
Demonstration of a community manure digester project
Complete engine skids and gas handling skids that have been factory installed to meet the specifications of the specific installation provide design and construction convenience. The systems are put together with compatible equipment and controls so on farm hassles are reduced.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
Temperature control of the digester is critical. Air locks in the heat pipes can prevent the proper circulation of the heated water inside the digester to heat the incoming manure to 100˚ F and to keep it at that temperature throughout the 20 day retention time. Temperature gauges, if they work properly, show the lack of heat, however, if the temperature gauges are not calibrated, then the lack of heat in the digester may go undetected. Groundwater impingement on the bottom of the digester can take a significant amount of heat away from the digester making it hard to heat. When flows to the digester are curtailed, the amount of heat to the digester needs to be adjusted since heat will not be needed for incoming manure. Without adjustment higher temperatures than desired may result.
- Noblehurst Farms
Demonstration of a community manure digester project
Maintaining temperature control during the winter is important. Frozen manure and manure that was too wet was bypassed from the digester. When the digester feed was reduced the gas production slowed and less heat was available to heat the influent and maintain the temperature. Either added external energy would be needed to maintain the digester temperature or the digester would need several months and warmer weather to recover.
- Noblehurst Farms
Demonstration of a community manure digester project
The twin digester construction to avoid an excessively long digester and reasonable spans for the concrete top is a viable design. This should make it possible to shut down and start up each side independently and therefore easier. It is hard to divide the influent equally to the two digesters; a flow meter along with the control device may be needed.
- AA Dairy
The weir wall consisting of timbers set across the concrete opening at the outlet of the digester failed. Until repairs were made the outlet reception pit needed to be kept full to prevent the loss of gas.
- Separation
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
A conical bottom to facilitate solid removal may prevent solids from remaining in the digester bottom even after a drainpipe is opened. Sediment will accumulate even with flow promoted from outside to the center with a flat bottom.
- AA Dairy
Digested separated manure solids were used for bedding for a short time. Mastitis incidents rose in the milking herd and the bedding was the first potential cause that was eliminated. The risk of additional mastitis makes the use of the manure solids as bedding a detriment.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
The plug-flow digester relies on the proper moisture content of the influent. Dairy manure as produced will not separate into floatable and settable solids very easily. When extra moisture is added, the floatable and settable solids sort out inside the digester, leaving a floating crust and a deposit. As these two portions of the digester get larger they will decrease the usable volume and the hydraulic retention time. Lower retention times will decrease biogas production and fail to reduce the odors in the effluent.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
An external shell and tube heat exchanger made with ¾ inch pipe can work in digesters on separated liquid. An automatic back flush device operating for 26 seconds every 2 hours will keep plugging from occurring. The external heat exchanger allows maintenance to occur without opening up the digester.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Separation ahead of digestion removes 30% of the Biodegradable Volatile Solids. The solids removed are about 1 cubic foot per cow per day, and consist of about 27% solids and are 20% of the mass. The liquids, about 17 gallons and 80% of the mass, consist of about 6% solids. The liquids are able to be pumped after the separator.
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Handling chicken manure as a solid instead of as a liquid has significant advantages in odor control and reduced volume of material. Previously liquid manure was scraped and flushed to a holding pond and then land applied. Adopting the composting system eliminated odors, flies and runoff concerns.
- Composting
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Integrating the manure collection and handling system (belts with ventilation) with the manure treatment system (composting) optimized the total farming operation. The belt and ventilation system between layer cages allowed more birds per building, better ventilation, drying of the manure for ease of handling and preparation for a compost operation without the addition of amendment.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Direct composting with an abundant amendment and a good market may be more profitable than biodrying. If compost can be sold for $10 a cubic yard, and amendment can be obtained cheaply it may make more economic sense to just make good compost and sell it directly instead of using recycled compost as an amendment that minimizes the amount of compost to be sold.
- AA Dairy
Composting marketing has been increasingly successful. This has occurred over time with repeat customers, word of mouth advertising and the use of a website. Prices vary depending on size of the purchase. All the manure solids can be sold.
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Composting continues at lower moisture conditions than previously recommended. Mixed compost that has been composting continues to biologically degrade below moisture levels (40%) that are recommended to start composting. Drying below 20% moisture does control additional composting to a low rate.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
Solid sales marketing needs to be done to sell manure solids. The digested separated solids are homogeneous, dark in color, and have good tilt. They should be preferred over other forms of organic soil amendment. However, without a marketing effort it cannot be assumed that they can be sold at any price. Transportation costs make the market area relatively near to the farm.
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Value added by certification of organic status, pathogen reduction, and processing (pelletizer) helps make the manure management profitable. Documenting the pathogen reduction during composting, certifying and marketing the dried manure as organic and processing and blending the pelletized manure helped meet their customers’ needs and enabled them to charge a higher price for their product.
- Gas Production
- Cornell University
Feasibility study of fuel cells using biogas from anaerobic digestion
Biogas containing H2S and CO2 will need to be cleaned before it can be used by the fuel cell. There are a variety of ways that this can be done. CO2 removal may be the limiting factor on the relatively small sized farm operations.
- Cornell University
Feasibility study of fuel cells using biogas from anaerobic digestion
The capital costs of fuel cells are still too high to justify their use on farms at this time. Potential lower cost manufacturing methods and efficiencies created by mass production may bring the price down.
- Twin Birch
The digester was designed with a hard top to collect the gas at 12 inches of water column pressure to push gas into the compressor. The greater the pressure the more difficulties there are in sealing a digester. Digesters operating at high pressures should be pressure tested as part of the startup procedure. Use proven technologies to seal digesters. Separate any equipment as much as possible from gas sources.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
The 3” pipe leading to the flare was designed to take excess gas to the flare. When none of the gas is being used the pipe is too small and a blow out in the pipe chase occurs. Keeping the flare lit during windy conditions and when both high and low biogas flows are present is difficult. Two automatic spark producers are needed to provide a spark where a flammable mixture of biogas and oxygen is present.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
Gas handling pipes, flares and enterprises for energy use need to be used for the additional production that a food waste system will require. Pre-planning and analysis of potential food waste should be done to estimate the gas production and the size of the utilization equipment.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
The food waste is high in energy having three times the gas production per unit of mass than manure, yet the nutrient content is comparable to manure so imported nutrients are kept low. Not all farms can take advantage of this. Only farms that have a land base that can accept the extra nutrients should consider this option.
- Cornell University
Feasibility study of fuel cells using biogas from anaerobic digestion
Improved efficiencies in energy conversion would be profitable. Present efficiencies in the 20 to 30 percent range of converting potential energy to electricity are poor. Raising these efficiencies to 40-60 percent by using fuel cells holds a promise of higher returns.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
Gas conditioning for the compressors and micro-turbines is critical. Hydrogen Sulfide and water vapor in the gas present the potential for corrosion. Methods to remove a significant portion of these contaminants are crucial. The compressor may have sensitive components that will corrode. The output from the compressor must be reduced in moisture content and have no excess oil in it or the micro-turbines may fail.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
A 5-day retention time in a fixed film digester will provide odor control as well as 30 cubic foot of biogas per cow per day. The gas production is sufficient to maintain operating temperatures in the digester with a biogas boiler even during the winter.
- Noblehurst Farms
Demonstration of a community manure digester project
Maintaining temperature control during the winter is important. Frozen manure and manure that was too wet was bypassed from the digester. When the digester feed was reduced the gas production slowed and less heat was available to heat the influent and maintain the temperature. Either added external energy would be needed to maintain the digester temperature or the digester would need several months and warmer weather to recover.
- AA Dairy
The weir wall consisting of timbers set across the concrete opening at the outlet of the digester failed. Until repairs were made the outlet reception pit needed to be kept full to prevent the loss of gas.
- Engine
- AA Dairy
The engine selected was based more on the price than the most efficient size. A used engine became available and was put into service. An oversized engine will be inefficient in converting fuel to power at lower operating speeds. Building the digester for 1,000 cows while only operating it at half capacity does cause some inefficiency.
- Noblehurst Farms
Demonstration of a community manure digester project
Burying the exhaust pipe and out letting it some distance from the engine room keeps corrosion away from building and keeps noise down. Internal combustion engines are loud. Sound control may be needed on some sites.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
The waste heat given off by the engine generator is significant. Utilizing the coolant to heat the influent and maintain the digester temperature and using it for heat exchangers for hot water in the calf barn and milking parlor still requires a radiator to dissipate extra heat. Even in the winter the un-insulated engine building is very warm. This makes a very good heated shop and should be used for that function.
- AA Dairy
The noise from the motor in an un-insulated pole barn can be loud. Providing a sound insulated engine room reduces the sound at the farm as well as the sound at a distance. People that had been keeping their window shut from the odors were now complaining about the sound.
- Electric
- Cornell University
Feasibility study of fuel cells using biogas from anaerobic digestion
Improved efficiencies in energy conversion would be profitable. Present efficiencies in the 20 to 30 percent range of converting potential energy to electricity are poor. Raising these efficiencies to 40-60 percent by using fuel cells holds a promise of higher returns.
- AA Dairy
The projected savings from hot water use did not materialize since changing from the existing radiant heat to hot water heat in the parlor would have cost too much. Since the electricity produced by the on farm generation covers the electric needs of the farm there was not a big incentive in making an expensive change.
- Heat
- Freund
Utilizing the biogas to run a boiler to heat a grid of pipes allowed the farm to introduce frozen chunks of manure into a preheat chamber. As the manure is thawed the pipe grid keeps the frozen chunks from moving into the digester until they are melted.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
The waste heat given off by the engine generator is significant. Utilizing the coolant to heat the influent and maintain the digester temperature and using it for heat exchangers for hot water in the calf barn and milking parlor still requires a radiator to dissipate extra heat. Even in the winter the un-insulated engine building is very warm. This makes a very good heated shop and should be used for that function.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
Heat pipes in the barn floor may not keep manure from freezing during weather colder than 5 degrees F. Although heat can be supplied continuously from the heat recovered off the electrical generation system, during sharp cold snaps the in floor heat cannot prevent freezing.
- Twin Birch
The heating system had several flaws. The heat balance of the digester system is vital. Designs need to address the heat recovery from the biogas, methods to heat the incoming manure, and correct estimates of the maintenance heat needed to maintain a constant temperature in all weather conditions.
- AA Dairy
The projected savings from hot water use did not materialize since changing from the existing radiant heat to hot water heat in the parlor would have cost too much. Since the electricity produced by the on farm generation covers the electric needs of the farm there was not a big incentive in making an expensive change.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
A grinder pump will convert any remaining longer particles of manure into pieces less than 1/4th of an inch. Smaller particles will cause less plugging of heat pipes and provide better digestion.
- Twin Birch
Drains to control the water table around the digester to prevent buoyancy of the empty digester and to control heat loss were not designed. All in ground structures should have drainage systems in the backfill to reduce heat loss and prevent floatation.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
Temperature control of the digester is critical. Air locks in the heat pipes can prevent the proper circulation of the heated water inside the digester to heat the incoming manure to 100˚ F and to keep it at that temperature throughout the 20 day retention time. Temperature gauges, if they work properly, show the lack of heat, however, if the temperature gauges are not calibrated, then the lack of heat in the digester may go undetected. Groundwater impingement on the bottom of the digester can take a significant amount of heat away from the digester making it hard to heat. When flows to the digester are curtailed, the amount of heat to the digester needs to be adjusted since heat will not be needed for incoming manure. Without adjustment higher temperatures than desired may result.
- Noblehurst Farms
Demonstration of a community manure digester project
The thermometers were installed reading 3 degrees higher than reality. Checking and calibrating the instrumentation should be an important step in start up procedures.
- Noblehurst Farms
Demonstration of a community manure digester project
Maintaining temperature control during the winter is important. Frozen manure and manure that was too wet was bypassed from the digester. When the digester feed was reduced the gas production slowed and less heat was available to heat the influent and maintain the temperature. Either added external energy would be needed to maintain the digester temperature or the digester would need several months and warmer weather to recover.
- Management of Anaerobic Digestion
- Noblehurst Farms
Demonstration of a community manure digester project
Similar to the town of Perry, the disadvantage of the expense of manure transportation to the community site and transportation of the effluent back to each farm was a huge cost for the community system to overcome.
- Town of Perry
Feasibility of anaerobic digestion for multiple farms
Benefits of a centralized system include economies of scale for the design, construction, and operation. Although more complex, a centralized system (since it would have to provide for influent from several farms instead of one) would still be easier to design than four separate systems on the individual farms. Constructing one combined system would be cheaper than constructing four separate systems on four separate sites. Operating and maintaining one system would be cheaper and could use more specialized management than each farm operating and maintaining a digester.
- Town of Perry
Feasibility of anaerobic digestion for multiple farms
The recommended choice was to have the individual sites cooperate on one designer and setting up a cooperative maintenance agreement. Some of the cost saving can be obtained without having to transport the manure and having each farm replace electricity produced for retail electricity used on each farm.
- Twin Birch
Choosing an engineering company to design and build the digester can be confusing. It is important to review the experiences and references of the
- Spring Valley
Incremental improvements of the system to match the capital expenditures with benefits provided can be part of the system. First, by building the small digester to achieve odor reduction, then adding a cover to collect the gas emissions from the manure storage to flare. Adding an engine to utilize the gas for on-farm power production and finally adding heat recovery to provide more than ambient temperatures to the main manure storage to facilitate digestion. Each of these components can be added incrementally.
- Twin Birch
The cost estimate for this project was under $500,000. The actual cost to date has been over $1,000,000. Obtain realistic cost estimates and include plans for exigencies.
- Spring Valley
Retrofitting a fabric cover on existing concrete manure storage allowed the gas produced in the storage to be collected. Reinforced fiber strips supported by a center pole support the cover when the gas pressure is too low
- Noblehurst Farms
Demonstration of a community manure digester project
Concrete hard tops operating under pressure are very difficult to seal. Leaks of biogas cause loss of gas production and odors on the farm. Pressure testing before filling with manure is time consuming and expensive but apparently needed to ensure that the sealant has been properly applied.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Foaming issues occurred as changes to the digester feed rate occurred and when the diet of the cows changed. Foam can be controlled with a foam cutter sprayed on the surface at a concentration of 100ppm. Other adoptions to reduce the impact of foaming were raising the gas inlet and increasing the water trap in the gas line.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
Shock loading of a digester with high energy food waste will create substantial amounts of foam. Loading the digester incrementally throughout the day reduces the potential for foam.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
Gas handling pipes, flares and enterprises for energy use need to be used for the additional production that a food waste system will require. Pre-planning and analysis of potential food waste should be done to estimate the gas production and the size of the utilization equipment.
- AA Dairy
The noise from the motor in an un-insulated pole barn can be loud. Providing a sound insulated engine room reduces the sound at the farm as well as the sound at a distance. People that had been keeping their window shut from the odors were now complaining about the sound.
- AA Dairy
Service support for the engine, generator, electrical inter-tie, and other parts are still not provided by one entity leaving the farm to find the best and quickest solution to a variety of problems. At times the small problem that goes unfixed for a time can lead to more difficult problems. There is an opportunity for a maintenance specialist to assist farms in running the systems that are part of an anaerobic digestion manure treatment process.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
The design of the anaerobic digestion system including manure handling, gas collection, gas utilization, and digester heating should not just be designed by each individual component but designed as a system. This site experienced a beam failure due to lateral loads that were not anticipated by the concrete designer. If the concrete design had been better integrated with the rest of the project they may have realized that lateral loads could develop.
- Noblehurst Farms
Demonstration of a community manure digester project
The thermometers were installed reading 3 degrees higher than reality. Checking and calibrating the instrumentation should be an important step in start up procedures.
- Site Consideration
- Noblehurst Farms
Demonstration of a community manure digester project
Similar to the town of Perry, the disadvantage of the expense of manure transportation to the community site and transportation of the effluent back to each farm was a huge cost for the community system to overcome.
- Town of Perry
Feasibility of anaerobic digestion for multiple farms
Benefits of a centralized system include economies of scale for the design, construction, and operation. Although more complex, a centralized system (since it would have to provide for influent from several farms instead of one) would still be easier to design than four separate systems on the individual farms. Constructing one combined system would be cheaper than constructing four separate systems on four separate sites. Operating and maintaining one system would be cheaper and could use more specialized management than each farm operating and maintaining a digester.
- AA Dairy
The noise from the motor in an un-insulated pole barn can be loud. Providing a sound insulated engine room reduces the sound at the farm as well as the sound at a distance. People that had been keeping their window shut from the odors were now complaining about the sound.
- AA Dairy
Treated separated digested liquid manure from the cow barn when added to the Heifer barn’s manure storage pond reduces the odor in that storage. This means that to control the odors on a farm system not all the manure has to be brought to the digester itself.
- F.A.R.M.E. Institute, Inc.
Anaerobic digester demonstration with biogas fueled micro-turbines
Heavy snow load can collapse the flexible cover on the digester if it falls faster than it can melt. Shoveling the snow off will allow the cover to inflate.
- Environmental Issues of Anaerobic Digestion
- Twin Birch
Power generation problems at this site are due to the corrosive environment. Carefully analyze your facility design to limit potential adverse impacts on equipment.
- Matlink Dairy Farm, Inc.
Anaerobic digester demonstration illustrating environmental benefits
Accepting food waste is highly profitable. The tipping fees make the manure treatment system a profit center for the farm. This is a win-win-win situation. The farm gets a payment to accept the food waste and the extra energy as the volatile solids are converted to methane, the food company has an environmentally responsible and relatively cheap way to get rid of their waste product and the nutrients from the food waste are recycled back to the land while green energy is produced.
- AA Dairy
Treated separated digested liquid manure from the cow barn when added to the Heifer barn’s manure storage pond reduces the odor in that storage. This means that to control the odors on a farm system not all the manure has to be brought to the digester itself.
Composting
- Biology (recipe)
- Earthworks
Demonstration of composting service serving multiple farms
Amendment (waxed cardboard not cleanly available) addition is problematic. Compost amendment (and bedding for the cows, which is used to increase the C: N ratio as well) is almost always the lowest price material. This means quality control of it is poor and if a higher use becomes available it is then marketed to that use and becomes unavailable for compost amendment (or bedding).
- Cornell Waste Management Institute
Evaluation and optimization of composting systems
Pathogen control varies from site to site. This is probably due to recontamination of the compost. Storage and handling methods vary from site to site.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
Tests involving Ascris worms successfully showed that the biodrying method killed pathogens aver a four-day period even with out mixing. The Ascris eggs were placed in a number of locations in an actively composting pile. After removal at four days the eggs were no longer viable. Control Ascris eggs were still viable. The Ascris eggs are often used to simulate the survival of Cryptosporisium oocycts.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
During cold weather negative aeration, sucking air from the top of the pile down into the air channels and up to the fan does work. As the warm saturated air moves out of the piles into the air channels it cools and moisture drops out in the channels. A drainage system with an air lock was designed into the system. However the air passageways had a negative slope at the upper end before they turned vertically up to the fans. This area became blocked plugging the passageway and shutting off the air supply.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
Cold weather positive pressure aeration can cause moisture buildup in the top of the piles. As air is pushed into the composting piles the heat from composting allows the dry air to pick up moisture as it move upward. When the now saturated warm air reaches a point close to the surface of the pile, the air is cooled by the cold ambient temperatures and moisture is released. When this occurs inside the pile the moisture builds up in the top layer. While the bottom dries out the moisture in the top keeps the average moisture content in the pile at an elevated level.
- Methods, Operation
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Integrating the manure collection and handling system (belts with ventilation) with the manure treatment system (composting) optimized the total farming operation. The belt and ventilation system between layer cages allowed more birds per building, better ventilation, drying of the manure for ease of handling and preparation for a compost operation without the addition of amendment.
- Watershed Agricultural Council, Inc.
Demonstrations of fixed film anaerobic digester
Direct composting with an abundant amendment and a good market may be more profitable than biodrying. If compost can be sold for $10 a cubic yard, and amendment can be obtained cheaply it may make more economic sense to just make good compost and sell it directly instead of using recycled compost as an amendment that minimizes the amount of compost to be sold.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
Manure/amendment piles higher than 4 ft have poor air porosity if the amendment has little structure. The amendment used in the biodrying project was chopped hay, old silage and/or composted manure. None of these materials has aggregates that would give the pile porosity at moisture contents above 60%. As the piles composted with forced air and without turning they settled so even as they dried they did not achieve porosity sufficient for the fans to move air through.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
The computerized control system that monitored the variable speed fans and the temperature of the piles did a good job of both controlling the operation and recording the data. Thermocouples in the piles were used with a logic system that could be adjusted for different operating conditions were used successfully
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
The energy from composting and the fans were sufficient to evaporate moisture to reduce 65% moisture content manure/amendment mix to 50% partially composted material with 14 days of controlled aeration and one week of fan drying
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Composting continues at lower moisture conditions than previously recommended. Mixed compost that has been composting continues to biologically degrade below moisture levels (40%) that are recommended to start composting. Drying below 20% moisture does control additional composting to a low rate.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
The fans did not deliver the air pressure they were rated at. The required air movement through the composting piles was not met. Manometer measurements verified that the fans rated at 7 inches of water pressure would only produce a maximum of four inches at the fan outlet.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
Having a Vee manure spreader to mix the amendment with the manure and then unload sidewise into the biodrying shed is a feasible way to create uniform piles. A backboard was needed to prevent the manure from shooting all the way through the shed.
- Cornell Waste Management Institute
Evaluation and optimization of composting systems
Earthen pads tend to have more mineral matter in the compost than compost made on concrete pads.
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration)
Spontaneous combustion is a possibility for material stored in massive piles at moisture conditions above 25% and lower than 40%. Between these moisture levels stored material needs to be piled at low enough heights so the heat from biological reactions can not cause a runaway chemical reaction and combustion.
- Cornell Waste Management Institute
Evaluation and optimization of composting systems
Mixing by front end loader or with a turner both can achieve mature compost. Depending on the final use either system can be used
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
Cold weather positive pressure aeration can cause moisture buildup in the top of the piles. As air is pushed into the composting piles the heat from composting allows the dry air to pick up moisture as it move upward. When the now saturated warm air reaches a point close to the surface of the pile, the air is cooled by the cold ambient temperatures and moisture is released. When this occurs inside the pile the moisture builds up in the top layer. While the bottom dries out the moisture in the top keeps the average moisture content in the pile at an elevated level.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
During cold weather negative aeration, sucking air from the top of the pile down into the air channels and up to the fan does work. As the warm saturated air moves out of the piles into the air channels it cools and moisture drops out in the channels. A drainage system with an air lock was designed into the system. However the air passageways had a negative slope at the upper end before they turned vertically up to the fans. This area became blocked plugging the passageway and shutting off the air supply.
- Management of Composting
- AA Dairy
Composting marketing has been increasingly successful. This has occurred over time with repeat customers, word of mouth advertising and the use of a website. Prices vary depending on size of the purchase. All the manure solids can be sold.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
The computerized control system that monitored the variable speed fans and the temperature of the piles did a good job of both controlling the operation and recording the data. Thermocouples in the piles were used with a logic system that could be adjusted for different operating conditions were used successfully
- Earthworks
Demonstration of composting service serving multiple farms
Coordinating the composting operation and farm operation can be difficult due conflicting motives and separate management. The low profit margins in both the farm and the compost markets increase the importance of good management.
- Cornell Waste Management Institute
Evaluation and optimization of composting systems
Earthen pads tend to have more mineral matter in the compost than compost made on concrete pads.
- Site Consideration
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
The energy from composting and the fans were sufficient to evaporate moisture to reduce 65% moisture content manure/amendment mix to 50% partially composted material with 14 days of controlled aeration and one week of fan drying
- Earthworks
Demonstration of composting service serving multiple farms
Soil stabilization over a large area (although cheaper than concrete) is still significant. Since composting requires access to the site for placement of the material mixing and collection an all weather surface is important to avoid ruts and added mineral matter to the compost.
- Environmental Issues of Composting
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration)
Ammonia release from high nitrogen chicken manure during composting can be significant. Composting at a low carbon to nitrogen ratio will cause nitrogen loss as ammonia. To conserve nitrogen the C: N ratio should be above 40. Drying without complete composting can result in high nitrogen levels in the resulting product.
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Value added by certification of organic status, pathogen reduction, and processing (pelletizer) helps make the manure management profitable. Documenting the pathogen reduction during composting, certifying and marketing the dried manure as organic and processing and blending the pelletized manure helped meet their customers’ needs and enabled them to charge a higher price for their product.
- Cornell Waste Management Institute
Evaluation and optimization of composting systems
Pathogen control varies from site to site. This is probably due to recontamination of the compost. Storage and handling methods vary from site to site.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
Tests involving Ascris worms successfully showed that the biodrying method killed pathogens aver a four-day period even with out mixing. The Ascris eggs were placed in a number of locations in an actively composting pile. After removal at four days the eggs were no longer viable. Control Ascris eggs were still viable. The Ascris eggs are often used to simulate the survival of Cryptosporisium oocycts.
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Handling chicken manure as a solid instead of as a liquid has significant advantages in odor control and reduced volume of material. Previously liquid manure was scraped and flushed to a holding pond and then land applied. Adopting the composting system eliminated odors, flies and runoff concerns.
- Marketing
- AA Dairy
Composting marketing has been increasingly successful. This has occurred over time with repeat customers, word of mouth advertising and the use of a website. Prices vary depending on size of the purchase. All the manure solids can be sold.
- Cornell Waste Management Institute
Evaluation and optimization of composting systems
The production of compost on-farm results in varying quality over a range of characteristics. The C: N ratio, nutrient content, maturity, organic content, moisture content, and pathogen control vary from site to site. There are a variety of standards that compost or soil amendment could be marketed under. The varying quality of the compost and the differing standards (and no standards) in the marketplace make marketing the compost problematic.
- Kreher’s Poultry Farms
Poultry waste drying and composting demonstration
Value added by certification of organic status, pathogen reduction, and processing (pelletizer) helps make the manure management profitable. Documenting the pathogen reduction during composting, certifying and marketing the dried manure as organic and processing and blending the pelletized manure helped meet their customers’ needs and enabled them to charge a higher price for their product.
- Cornell Waste Management Institute
Evaluation and optimization of composting systems
Pathogen control varies from site to site. This is probably due to recontamination of the compost. Storage and handling methods vary from site to site.
- Watershed Agricultural Council, Inc.
Demonstrations of biodrying
Tests involving Ascris worms successfully showed that the biodrying method killed pathogens aver a four-day period even with out mixing. The Ascris eggs were placed in a number of locations in an actively composting pile. After removal at four days the eggs were no longer viable. Control Ascris eggs were still viable. The Ascris eggs are often used to simulate the survival of Cryptosporisium oocycts.
Related Pages
Section Links
|
