BioCycle May 2006, Vol. 47, No. 5, p. 60
New York State Energy conference analyzes digester results with retention times, feedstocks, microturbines, pathogen and odor reduction, plus role of primary barriers, green power and carbon credits.
Mary Schwarz

NEW YORK STATE Energy Research and Development Authority (NYSERDA) held its 6th Annual Innovations in Agriculture Conference in March in Syracuse, giving information on innovations to the farmers of the future. NYSERDA is seeking to develop energy alternatives that include methane and cellulose ethanol production and providing incentives for farmers to take a risk.
The first day of sessions was devoted entirely to anaerobic digesters for converting manure into electricity. Brian Aldrich, from the Manure Management Program at Cornell University, presented information on the status of anaerobic digesters in New York. There are currently six operating digesters, four that are down for clean out or refurbishing, one in start-up (for duck manure on Long Island), and four under construction. Three centralized/community digesters for collection from multiple dairies are in the design/financing phase, and nine are in various stages of funding/negotiation. The first generation of digesters from 1978-1985 were kind of a failure – there were seven starts, all of which never made it, but the second generation of digesters, starting in 1997 with AA Dairy, had a whole new set of issues to face: improving financial climate, green power, carbon credits, potential for codigestion with food waste, standards for monitoring and data collection, and especially safety. There are case studies on nine of these second generation digesters on the Cornell Manure Management website: http://www.manuremanagement.cornell.edu/HTMLs/CaseStudies.htm.
Curt Gooch, Senior Extension Associate in Animal Science at Cornell University, presented the results of monitoring five of the New York farm anaerobic digesters in those case studies:
o AA Dairy, a 1,000 cow dairy in Candor, NY, uses a plug flow digester with a 40-day retention time. The gas from digestion produces electricity to power the farm. The solids are composted and sold to the public and the liquid effluent is used for irrigation. It was estimated that the total annual cost/savings of the digester on this farm was a $38/cow benefit. Biogas production was metered on this farm; on average, about 43.8 cu. ft./cow/day was produced. The monthly energy generated allowed for about 9 months of surplus, or the exact amount needed to run AA Dairy for 16 months.
o Farber Dairy Farm located in the Catskills is a 150-cow dairy that separates before digesting. The solids are spread, used as bedding or composted and sold. The gas is burned through a boiler and used for heating the digester; no electricity is generated. It was estimated that the total annual cost/savings of the digester on this farm was a $106/cow loss. (“Cost/savings” essentially is the net cost or net benefit/cow. A negative number indicates the system controls odors but does not provide an economic benefit from energy production, explained Gooch.
o Noblehurst Farm, an 1,100 cow dairy in Livingston County, uses a plug flow, twin digester, and then separates their solids. The biogas is used to generate electricity and heat the digester and the solids are used as bedding for some of the cows. The total annual cost/savings of the digester on this farm were estimated to be a $24/cow loss.
o Dairy Development Institute, an 850-cow dairy in Homer, uses a plug flow digester with a 21-day retention time. The plan is to use the biogas in microturbines to produce electricity for the farm with any excess being sold back to the grid. The microturbines will also recover heat to maintain the temperature of the digester. There have been some start-up problems and so the total annual cost/savings of the digester on this farm was a $22/cow loss.
o Matlink Farm, a 675-cow operation in Clymer, has a mixed digester using manure and food waste. The gas produced is used for electricity; much more biogas is produced with food waste than with manure alone. The total annual cost/savings of the digester on this farm were estimated to be a $293/cow benefit. Matlink Farm was always above the amount needed to run the farm for the 16 months that biogas production was metered.
For all five farms, testing showed excellent pathogen reduction in the manure after digestion, about a 30 percent decrease in solids, 30 percent increase in ammonia nitrogen, 20 percent decrease in organic nitrogen, and no change in phosphorus.
There was a panel discussion of farmers using digesters. All participants said that they put in the digester for odor control and that gas production was secondary to that. They also said that running a digester properly takes a lot of time and that there are many hurdles to overcome especially with mechanical issues. Comments included:
o Bob Aman, from AA Dairy, said they are still not producing gas the way they should be. They need to review/refurbish the system and take care of what they feed the cows as that can have an effect on biogas production. In addition, gases and ammonia are very corrosive on metal.
o Larry Jones, Dairy Development Institute, is using microturbines that are owned by the gas company and maintained by them as well. In return, Jones gets to buy the electricity at a reduced rate.
o Connie Patterson, Patterson Farms, is looking for other uses of biogas because they are producing so much. She says making gas by taking food wastes is profitable.
o Mike Frederickson from Ridgeline Dairy says they are producing 50 percent more power than they use on the farm. They are looking for ways to team up with other businesses, like taking food waste instead of it going to the landfill or selling/giving power to other businesses.
GREEN POWER AND CARBON CREDITS
The late afternoon session of the conference was devoted to green power and carbon credits. Janet Joseph, NYSERDA, gave an overview of the Renewable Portfolio Standard. The objective is to increase the percentage of renewable or “green” energy serving the New York retail load, to ensure that 25 percent of energy is from renewable sources by the year 2013. The customer-sited tier of RPS is for entities that are producing < 1MW electricity – this is where fuel cells, solar power, wind power and manure digesters fall. The incentive for these to produce excess electricity will fall into two types of payments: (1) Capacity payments – up front payment based on the capacity of the digester – to help with capital cost of putting in a digester; or (2) Production payments – based on kilowatt hours of actual electricity production in excess of use at a rate of $0.07/kwh. This is still in the planning stages; some issues that still need to be resolved include eligibility, net metering, ownership of attributes, feedstocks and total funding.
Ron Rausch from the New York State Department of Ag and Markets spoke about the status of the Region Greenhouse Gas Initiative, which has the objective of reducing CO2 emissions in industrial plants. The plan includes an agricultural methane offset standard where digester operators can receive credits for methane reduction, but not carbon credits. Ed Heslop from Environmental Credit Corp. explained that a carbon credit is a certified, verified emission reduction. Digesting to capture methane, then burning the gas, reduces greenhouse gases. This process makes you eligible for a carbon credit, which can be sold for cash. Environmental Credit Corporation can join the Chicago Climate Exchange for the farm, verify carbon credits, and then trade credits for money. Farms with digesters placed into service after January 1, 1999 are eligible for this service. A typical project can get about 3,500 credits/yr and the estimated value of carbon credits is $1-2/credit.
SUCCESSFUL MODELS
The morning session of the second day was on successful models from the industry perspective. Dave Palmer from Cow Power, Inc spoke about how digesters create a natural environment for the bugs to do what they need to do. Kamyeh Zadeh from ECO Technology Solutions, LLC specializes in developing, managing and deploying the best new energy and energy-related technologies that focus on conservation and distributed generation. Robert Foxen from Global Common talked about designing a centralized digester for a cluster of farms in Cayuga County. Global Common is a renewable energy development company focusing on biomass. They provide all of the project financing.
Mike Safty from RCM Digesters says they try to provide simple, effective designs with the least amount of maintenance to the farmer. They are flexible in construction and design. He says the trick to digesters is to keep them warm and fed properly. Steve Hoyt from Saratoga Biogas says their systems are different because they can use high-energy inputs (corn silage, gases, grains, food waste, etc.). They can use a combination of inputs including manure and can produce large amounts of energy even with fewer cows. Their systems are based on German experience where there are over 600 digesters. Bert Spaeth of Siemens Buildings Technologies, Inc. says they offer start-to-finish operations, including monitoring. Most of their clients are separating solids prior to digesting. Composting solids and using them as bedding, is currently worth more than the electricity generated. They then digest the liquid and the gas goes through a scrubbing system to reduce H2S and separate the moisture out, and then it goes to a generator to produce electricity.
This panel was asked: “What are the primary barriers to getting more digesters in New York State, and what can we do to get more?” The basic answer was cost – digesters need to be made affordable and the cost of conventional electricity needs to be high (for it to be profitable) and/or incentives need to remain. There may need to be more creative financing – low interest loans or grants. They think that costs may come down as more units are built.
BEDDING AND COMPOST
Jean Bonhotal and Ellen Harrison of the Cornell Waste Management Institute (CWMI) spoke about a project on manure solids as dairy cow bedding. Composting of dried manure solids (DMS) is really just a thermophilic stage, not designed to produce mature compost. The goal is to make use of the solids after separation in the most economic way possible. There will be six farms in the study using different bedding scenarios. One farm will have cows bedded on DMS directly from the separator, cows on DMS that have been partially composted and cows on sand. The other five farms all use only DMS, but one is separating, then composting in a drum composter prior to use; two are separating, then drying in piles prior to use; one is separating (the liquid gets digested), then drying in windrows prior to use; and the other one is digesting, then separating, drying in piles and using. Researchers will be sampling the bedding (both used and unused) for bacterial pathogens (mastitis causing organisms) and compositional analysis, and will be checking the unused bedding (DMS) for Johnes (mycobacterium avian paratuberculosis – MAP). An economic analysis – including energy savings (less manure hauling, less importation of bedding) – also will be conducted. The panel of farmers using DMS stated that using DMS requires a state of constant experimentation. Management is the key – and it is important not to blame DMS for mastitis and somatic cell count (SCC) problems.
The conference wrapped up with sessions on regulatory requirements for digesting food organics, manure storage, manure management safety, emerging air emissions issues and farm bill and NYSERDA funding. The program agenda, PowerPoint presentations, posters, and attendee list for NYSERDA’s 6th annual Innovations in Agriculture conference can be found at http://www.manuremanagement.cornell.edu/HTMLs/6thAgConf.htm.
Mary Schwarz is in the Department of Crop & Soil Sciences at the Cornell Waste Management Institute (CWMI) in Ithaca, New York. She is working on the dried manure solids bedding project at CWMI. Visit the website http://cwmi.css.cornell.edu/.