September 12, 2007 | General

Small Dairy Pioneers Anaerobic Digestion

Dairy with less than 300 head of cattle installs complete mix digester capable of processing off-farm waste streams.
Nora Goldstein
BioCycle September 2007, Vol. 48, No. 9, p. 54
In January 1990, two brothers, Paul and Fritz Klaesi, moved their families from Switzerland to Canada to settle on Fepro Farms, a dairy operation in Cobden, north of Ottawa, Ontario, Canada. “I was a farmer, and my brother Paul worked for an electrical utility,” says Fritz Klaesi. “I knew a farmer who had a small-scale digester that he used for heating. I saw some Swiss literature that discussed a new development that would make anaerobic digestion feasible for small farms. Previously, the technology was only targeted at bigger dairy farms, e.g., with a minimum of 400 to 500 cows.”
After many years of studying digester designs and analyzing the economics – including sale of electricity generated by the biogas – the Klaesi brothers retrofitted their existing circular manure pit to install a continuous flow, complete mix digester in 2003. They followed Swiss design literature, and built an elliptical-shaped digester vessel covered with a fixed membrane. The cement walls of the digester were insulated; plastic pipes were installed in the floor so that heated water can be circulated to maintain the digester at a mesophilic temperature range. “We have about one mile worth of plastic piping to control the temperature of the digester,” says Klaesi. “A heat exchanger – utilizing heat recovered from the gas engine – heats the water to 75° – 80°C, and it returns at about 50° – 55°C. If the temperature in the digester falls below 40.2°C, the system automatically adds heat.”
Fepro Farms has about 300 animal units in total, with about 140 milking cows. The 500 cubic meter (m3) digester vessel has two vertical agitator units that operate on a timer. Total cost of the system was about $250,000 “plus a lot of work,” says Klaesi. “We calculated a 10-year payback, and save between $1,000 to $2,000/month in power bills.” Manure enters the digester at 8 to 9 percent solids. Digested manure at about 7 percent solids flows into the remaining manure pit and is land applied (or stored during winter months). “Odors when landspreading the digested manure are about 80 to 90 percent less than before,” he adds, “and there is a 99 percent reduction in pathogens. The key to successful operations are mixing and temperature. If the digester contents aren’t mixed, a fiber would rise from the material and build a crust so that the methane could not be captured.”
In May, after nearly two years of applications, consultations and education, the Klaesi brothers received the first ever issued Ontario Ministry of the Environment Provisional Certificate of Approval for a Waste Disposal Site permitting them to process 5,000 metric tons per year of off-farm organic residuals originating in the provinces of Ontario and Quebec. Allowable materials include a variety of agricultural residues (organic waste from crop drying, products approved for livestock feeding); by-products from ethanol and biodiesel plants; aquaculture manure; food processing waste of plant or animal origin; leaf and yard waste as well as herbaceous plant waste from greenhouses, nurseries, etc.; fats, oils and grease of plant or animal origin and accompanying food residuals collected from grease interceptors and/or grease traps at food production, food processing and/or food wholesale and retail facilities; paunch manure; fish and fish processing waste; and, flocculation and scum waste from dissolved air flotation (DAF) systems at large food and meat processors.
The certificate’s Waste Disposal Site designation is restricted to an area of 1,500 square meters, encompassing the following storage and processing areas: In-ground liquid off-farm waste storage tank with maximum capacity of 50 m3; an off-farm waste pasteurizer with maximum holding capacity of 4 m3; and a covered storage pad for dry materials such as leaves and yard waste with a maximum storage capacity of 50 m3. It addresses only processes and procedures directly related to the introduction of off-farm organic residuals to the digester and does not interfere with any of the normal farm practices.
Organic Resource Management, Inc. (ORMI), Canada’s largest grease trap pumping service provider operating in Ontario, Quebec and British Columbia, provided consultation with respect to the regulatory developments and the technicalities of digester management for off-farm organic residuals. ORMI has lobbied for the introduction of anaerobic digesters into Canada for several years as a recycling solution for the organic residuals it collects from nearly 8,000 customers. Digesters are widely used in Europe for these residuals, says Douglas Carruthers, ORMI’s Vice President, Corporate Development. “Knowledge gained through our extensive research of that European experience was useful in the regulatory arena in Ontario. The Klaesi brothers pioneering example has been a key driver helping to demonstrate a successful win-win solution for the various regulators.” In July, the Klaesi brothers and ORMI executed a 20-year, exclusive off-farm residuals delivery contract for the Febro Farms digester.
With anticipation of receiving the Certificate of Approval, the Ontario Ministry of Agriculture, Food and Rural Affairs awarded Fepro Farms a grant to purchase a 50 m3 underground storage tank to receive fats, oils and grease (FOG) and food wastes from ORMI, and an above ground pasteurization tank where any digester feedstock that may be of animal origin is held at 70°C for one hour before being metered into the digester. A Houle unit pumps the feedstock into the pasteurization tank.
Heating selected organic residuals to 70°C and holding it for an hour follows the Animal By-Products Regulations adopted by the United Kingdom and the European Union for facilities processing “catering wastes,” which include food waste, DAF scum and FOG. “Ontario decided to follow that standard to maintain the security of our vital farm product world export market in the post ‘mad-cow’ disease world,” notes Carruthers. “And by heating the off-farm residuals to 70°C with the free surplus digester heat and holding it, we expect that cell rupture and the hydrolysis process is accelerated, generating biogas more quickly in the digester. At the digester operating temperature, these concentrated feedstocks break down in less then days, while increasing the amount of biogas and the percentage of methane generated.”
Fully enclosed tanker trucks deliver Fepro Farms between 22 to 30 m3/load of the concentrated off-farm feedstock from ORMI’s Ottawa region customers. “Proprietary pretreatment systems operated at our permitted waste transfer sites yield concentrated feedstocks with total solids as high as 50 percent, the limit where it is still manageable by vacuum truck,” says Carruthers. “The underground farm storage tank is aggressively agitated prior to pumping material into the pasteurizer to ensure a uniform mix. Concentrating the off-farm feedstock allows our farm partners to minimize the necessary increases in digester and final digestate storage capacity required to accommodate imported organic residuals.”
A cubic meter of the concentrated feedstock can yield up to ten times more biogas than dairy manure, he adds. “It has a higher percentage of available carbon than manure because of the undigested plant and animal fats, oils and grease content and the accompanying food particles. This is the case with other commercial and institutional food waste we collect as well.” ORMI has a patented food waste pulper system used at grocery stores and other high-volume generators. The pulp accumulates on-site in large volume storage tanks that are serviced by the company’s vacuum trucks. “Increasing the bulk density of the organics dramatically increases the transportation efficiency,” notes Carruthers. “The pulping and subsequent storage time prepares – by initiating hydrolysis – these organics to be directly delivered to on-farm digesters.”
Klaesi Brothers initially installed a 50kW Hans-Jurgen Schnell diesel engine to convert biogas into electricity. Of the biogas combusted in the generator, 48 percent is captured as heat and 38 percent is converted to electricity. This unit also burns about 8 percent diesel in the engine. There is a 70 m3 heat storage tank, which is used for hot water heating in the homes and the dairy barns. Electricity is currently delivered to the Ontario Hydro grid under a net-metering arrangement that allows the Klaesis to reduce their farm’s monthly consumption cost to near zero.
Since 2003, the Fepro Farm’s 300 animal units have produced sufficient biogas to operate the 50 kW engine approximately 14 hours/day. Anticipating increased biogas production, the Klaesi brothers secured a new 100 kW engine that was recently installed. The existing manure flow and the concentrated off-farm feedstock is expected to run this unit 24/7, more than doubling the original energy output of the Fepro Farms digester with manure. But the net metering agreement does not permit any return to be earned for additional generated energy. Additionally, the grid connection for the farm must be improved to permit export of all the energy it could generate.
If a higher electricity price can be negotiated with the Ontario Ministry of Energy, the Klaesi brothers will consider expanding their digester to process corn silage. The existing manure storage unit would be retooled and insulated, and a gas recovery unit would be installed, creating a two-stage digester. The digestate would be transferred to a separate final storage lagoon. The farm has applied for a grant from the Ontario Ministry of Agriculture, Food and Rural Affairs to upgrade the digester and grid connection to accommodate the digestion of energy crops. “The power price needs to be much better, and we need assistance from the government,” says Klaesi. “Corn silage has a significant amount of biogas potential – about 200 m3 of biogas per metric ton and allows additional ORMI feedstock along with our manure base, further increasing the energy production. There is a widespread interest among Ontario farmers concerning this energy crop demonstration.”
In March 2006, the Ontario Ministry of Energy announced it was launching North America’s first Standard Offer Contract (“SOC”) to facilitate renewable source electricity in-feed to the grid. The contract offers $0.11 per kWh to qualifying generators under 10 MW in size employing wind, water and biogas or bioenergy renewable sources. Solar generated power is paid $0.42 per kWh. As of July 2007, the SOC has proven effective in contracting for 388 MW of wind power; 24 MW of hydro power and 15 MW of landfill methane gas power. In addition, it has stimulated 88 MW of solar power at the higher price. To date, there are no anaerobic digester projects contracted. The Klaesi brothers have not yet signed an SOC.
In August 2007, the Ontario Ministry of Agriculture, Food and Rural Affairs announced the Ontario Biogas Systems Financial Assistance Program, a $9 million investment to help approximately 20 farmers or agrifood businesses develop and build anaerobic digesters. Phase 1 funding covers up to 70 percent of the eligible costs of a feasibility study, to a maximum of $35,000. Phase 2 funding covers up to 40 percent of eligible construction and implementation costs to a maximum of $365,000.
Although, on initial review, the SOC price appears attractive, it has not been sufficient to stimulate farm biogas projects in the absence of any other support programs. The combined capital costs of the digester technology, generator engines and the electricity grid interconnection cannot yet be justified on a business case basis. Perhaps the combination of the new grant program and demonstrated experience by the Klaesi brothers will move the industry forward in 2008.

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