Anaerobic Digest

August 15, 2012 | General

Anaerobic Digest

BioCycle August 2012, Vol. 53, No. 8, p. 18

New York, New York: Energy Vision Sees Greener New York Highways

A fact sheet produced by Energy Vision, a nonprofit based in New York City that promotes clean energy fuels such as renewable natural gas (RNG), focuses on how to convert New York State’s 2.5 million mostly diesel-powered trucks and buses over to biobased fuels made from the organic waste stream. New York has the fourth largest collective dairy herd in the nation and is home to a $3 billion/year food processing industry as well as more than 600 sewage treatment plants, making the state an excellent candidate for reliable biogas production.
The fact sheet, “A Greener Transportation Fuel for the Empire State?” makes the case that RNG-fueled vehicles are necessary not just to reduce reliance on fossil fuel, but for public health reasons. Diesel emissions “have been classified as a known carcinogen” and the soot particles affect respiratory health, says the fact sheet. It states that one in eight New York City adults suffers from asthma (30 percent above the national average), and asthma is the leading cause of child hospitalization in the city. The New York state transportation sector contributes 41 percent of all CO2 emissions. RNG vehicles emit 88 percent less CO2 than diesel. Energy Vision’s “greener transportation future” calls for retooling existing infrastructure — from engines to filling stations — to accommodate natural gas made from organic waste, aka “frack-free” RNG.

Dubuque, Iowa: City Opts For AD Over Incineration

Faced with a decision on whether to replace its aging sewage sludge incinerator with a newer model or switch to anaerobic digestion for biosolids treatment at Dubuque’s 10 mgd Water & Resource Recovery Center (W&RRC), the city opted for the latter. The city hired Strand Associates to conduct technical, economic and carbon footprint analyses of these two technologies as well as other competing technologies.  Although anaerobic digestion was more expensive on an upfront-cost basis, Dubuque selected this alternative because it better met the city’s commitment to sustainability, including greenhouse gas, energy and overall carbon footprint reduction. The integration of anaerobic digestion is expected to bring the plant’s energy costs down significantly. Biogas generated from the anaerobic digestion process will initially be used in the boilers to heat the digester and buildings; cogeneration using microturbines is also planned and will boost total generation capacity to 1 MW. Recovered heat will meet the needs of the digesters and several buildings.  It’s anticipated that the plant may eventually be able to provide for all of its electrical needs as well as a surplus.
Construction of the digesters is expected to be completed by January 2013. Total project completion is scheduled for February 2014. A receiving station is being installed for FOG and other substrates. “A lot of flexibility is designed into the receiving station and digestion facilities so that the plant can receive very soluble as well as high solid substrates,” says Randy Wirtz of Strand Associates. The city also evaluated bringing in source separated food waste from cafeterias and other generators.  In the future, this material may be brought to the W&RRC digestion facilities to produce even more biogas. Digested biosolids are anticipated to meet Class A (Class 1, in Iowa) standards and will be land applied on local farmland.

Toronto, Canada: Digester Planned For Toronto Zoo

Bolstered by a $40,000 Toronto Community Foundation Green Innovation Award and a $115,000 grant from the Community Energy Partnership Program, the nonprofit ZooShare Biogas Co-operative Inc., can move toward its goal of building a 500 kW community-owned biogas plant at the Toronto Zoo. Plans include turning the manure output of the animals, combined with regional grocery store waste, into electricity, heat, fertilizer and revenues for the zoo. The funding plan calls for the majority of capital costs to be financed through the sale of community bonds to individuals from around the city of Toronto, which will pay 7 percent annual returns and mature in 7 years.
While a technology partner has yet to be chosen, says ZooShare Executive Director Daniel Bida, the project — estimated to cost $5.4 million at buildout — will include a pasteurizer as well as several input storage tanks in front of the primary digester. “This is because the zoo can’t have any outside storage of undigested material, so everything that arrives has to be put into the tanks,” explains Bida. Feedstocks will include about 3,000 tons of zoo-generated manure and 14,000 tons of grocery store waste annually — including produce and fats, oils and grease (FOG), he adds, noting power generated will be sold to the Ontario grid under the province’s feed-in tariff (FIT) program. New rules surrounding the FIT were favorable to the venture as they put greater emphasis on community projects and increased rates paid to biogas while wind and solar were cut by 15 to 25 percent. In addition to selling power to the grid, revenues are anticipated through tipping fees and the sale of fertilizer (the digested feedstocks) to garden centers. A companion greenhouse is tentatively planned for the site. “With an open-access development model, a focus on education, a strong web presence and a high-profile location, ZooShare could potentially help millions of people each year learn more about the value of their organic waste and the potential of community-owned biogas,” says Bida.

Singapore: Global Methane Initiative

The Global Methane Initiative (GMI), launched in 2004 (as the Methane to Markets Partnership), focuses on methane reductions across five primary emission sources: agriculture, coal mines, municipal solid waste (MSW), municipal wastewater and oil and gas systems. The Initiative is a voluntary, multilateral partnership that forms an international network of partner governments, private sector members, development banks, universities and NGOs in order to build capacity, develop strategies and markets and remove barriers to project development for methane reduction in partner countries. The U.S. is one of 41 founding partner countries, and its work on the Agricultural Subcommittee builds off of the US EPA’s experience with the AgSTAR program. Allison Costa, Program Manager for AgSTAR, was recently chosen to serve as one of the subcommittee’s three cochairs, in recognition of U.S. leadership in this sector to build capacity with developing country members and share the agency’s experiences in the anaerobic digestion sector. The subcommittee meets at least annually and holds additional web-based teleconferences to collaborate on joint projects.
The most recent meeting was held July 2 and 3, 2012 in Singapore. The Agriculture Subcommittee moved toward adopting a Statement of Purpose, outlining its mission, specific focal areas for methane reductions within the agriculture field — anaerobic digestion (AD) from livestock and agroindustrial wastes — and roles of participating members. Participants also agreed to begin two new subcommittee projects. One will showcase AD project success stories in each of the member countries; the other will develop a guide to the different policies and incentives available around the world that promote AD projects in this sector. Technical and policy sessions for the upcoming Methane Expo 2013, which will be held in Vancouver, Canada, March 12–15, 2013, were also discussed. For more information about the Initiative and how to participate, visit

Washington, DC: Biogas Legislative Update

Representatives Ron Kind (D-WI) and John Lewis (D-GA) — both members of the House Ways and Means Committee — introduced the very first investment tax credit (ITC) for biogas production, reports the American Biogas Council (ABC). H.R. 6212 proposes to amend the Internal Revenue Code of 1986 to provide a 30 percent ITC for qualifying biogas technologies. The legislation has several key components, including recognition that biogas can be used not just to generate electricity, but as a renewable substitute for natural gas in vehicles, industry and homes. The bill covers a range of biogas technologies, including anaerobic digestion (AD), that produce biogas with a minimum of 52 percent methane content.
At the state level, the California legislature moved forward with SB 1122, which would create a special procurement program for electricity generated from biogas. Across the country, Massachusetts recently adopted legislation that extends the state’s net metering law to cover electricity generated from AD projects.

Madison, Wisconsin: AD Maintenance 101

“Maintenance depends a lot on up-front engineering, type of equipment chosen, or even the supplier,” said Monte Lamer, Clear Horizons Biogas Operations Supervisor for the Dane County community manure digester during a presentation on digester maintenance at a Renewable Energy Education Field Day cosponsored by the Farm Foundation, USDA, US EPA, the Innovation Center for U.S. Dairy and the Wisconsin Bioenergy Initiative of the University of Wisconsin. Digesters run 24/7 and so dependable staffing is critical, Lamer emphasized, adding that maintenance of a digester and all of its systems falls into four basic categories: preventative, predictive and routine, unexpected priority, and emergency maintenance. “Preventative maintenance could be thought of as routine diagnostics of equipment that might be bearing vibrations or temperatures. This is done with the SCADA [supervisory controls and data acquisition] equipment that logs any changes in operation parameters,” thereby alerting operators to small problems before they become big ones. Lamer gave the example of a centrifuge that extracts about 100 gallons a minute out of the Dane County digesters: “Our bearing vibration was slowly climbing and we could see this on our data log-in equipment. We were able to take precautions and bring the vibration in line without any downtime.”
Predictive and routine maintenance includes normal greasing, oil changes or the alignment of a bearing or coupling. Sampling oil in a generator or other piece of equipment also can help determine if maintenance is needed. At the Dane County digester, weekly oil monitoring showed rising silica levels in a genset that was traced back to a cleaning product used at one of the dairies that was ending up in its DAF tank. “It appeared in our gas … and it will actually destroy a genset,” said Lamer. As an example of an unexpected priority, he referenced the untimely replacement of two compressors that fed the two air systems, which in turn operate all the controls at the plant. The ones initially installed were inadequate. Both were upgraded to heavy duty cycle compressors with air dryers. Auto drains were installed to remove condensate that gets into the air system because of the heat in a compressor. (For complete story on the community digester, see “County Clusters Farms for Renewable Power Project,” February 2012.)

Colchester, Vermont: Cow Power Has A New Name

With recent approval of the merger of Central Vermont Public Service Corporation (CVPS) and Green Mountain Power (GMP) by the Vermont Public Service Board (PSB), the state’s dairy manure to kilowatts program has both a new name and expanded territory. Previously the largest investor-owned utility in Vermont, CVPS had covered roughly half the state. Green Mountain Power, Vermont’s No. 2 power producer before the merger, was purchased seven years ago by Montreal-based GazMetro. The Canadian parent company has historically allowed GMP to operate autonomously, the PSB noted in approving the deal. Due to operational efficiencies, ratepayers will receive $144 million in direct benefits over time.
“We’ve changed from CVPS Cow Power to GMP Cow Power,” says program manager David Dunn. “We are going to keep that program going and offer it to our new GMP legacy customers. Before, it was just available to customers in the CVPS territory.” Now it will be available to all GMP customers, pending approval of a new voluntary tariff by Vermont regulators. “We have 11 farms in our program and had worked previously with a GMP project in their territory,” adds Dunn, who ran the program initially under CVPS. “That’s 12 in Vermont, and one more coming online soon if everything goes as planned.” Two smaller projects being developed represent a scale prototype for the whole country, and unlike the state’s more typical Standard Offer (feed-in tariff) Program for projects up to 2.2 MW, will operate on a net metering model similar to smaller solar or wind-turbine projects. These smaller projects offset their usage, based on what they produce, to a group of self-selected accounts. The Standard Offer projects will continue to be based on 20-year agreements, explains Dunn, with contracting farms receiving 14 cents kWh produced, plus an additional 4 cents/kWh voluntarily paid by ratepayers.

London, England: Bullish On Biogas

Bloomberg Businessweek reported that the United Kingdom’s largest food retailers such as Marks & Spencer Group, Tesco and Walmart are diverting their food waste streams to anaerobic digestion, motivated in part by a landfill tax that makes burying organic waste incrementally expensive. Beginning in April 2012, the tax (not including the tipping fee) was 64 pounds (about $98) per metric ton and will increase by 8 pounds (about $12.50) a year. “Diverting food waste from landfill to anaerobic digestion is a no-brainer for the supermarkets — landfill charges and energy costs are only getting more expensive,” Niamh McSherry, a food retail analyst at Berenberg Bank, told Bloomberg. The magazine reports that Marks & Spencer sends almost 90 percent of its food waste to AD facilities in the UK. According to London-based New Energy Finance, electricity from anaerobic digestion currently costs about $142.80/megawatt hour to produce, compared to coal-generated electricity, which costs $78/megawatt hour.

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