SmartFerm digesters at Monterey Regional Waste Management District's ’s integrated waste management complex.

March 18, 2013 | General

Anaerobic Digest

 BioCycle March 2013, Vol. 54, No. 3, p. 19

Marina, California: Pilot Anaerobic Digester For SSO

The Monterey Regional Waste Management District (MRWMD) and Zero Waste Energy, LLC (ZWE) held an open house in late January to unveil a pilot-scale dry anaerobic digester installed at the MRWMD’s integrated waste management complex (just north of the City of Marina) to process up to 5,000 tons/year of commercial source separated organics (SSO). When BioCycle visited several weeks later, construction was being completed on the fully enclosed aeration bay for organics receiving and storage. All of the other components were installed, including four SmartFerm digesters, the monitoring and process control skid, biogas collection bladders, percolate capture and recirculation tank and a combined heat and power unit supplied by 2G Energy. The system is designed to generate 100kW of electricity or up to 3,200 cu. ft./ton of biogas with 58 to 60 percent methane content.

SmartFerm digesters at Monterey Regional Waste Management District's ’s integrated waste management complex.

SmartFerm digesters at Monterey Regional Waste Management District’s ’s integrated waste management complex.

MRWMD’s Board approved an agreement with ZWE to furnish and install the system under a 5-year demonstration program. ZWE financed the system completely in exchange for the tipping fee revenue for the food waste and yard trimmings processed in the digester, along with revenues from the electrical power sales to the adjacent wastewater treatment plant. “We were looking for a site to install a demonstration plant, and this opportunity came up with MRWMD,” says Dirk Dudgeon, Senior Vice-President of ZWE. From the District’s perspective, having the digester facility on site provides an opportunity to gain experience with this technology.
“We did a commercial waste characterization study last summer of materials coming to our landfill,” says William Merry, General Manager of MRWMD. “About 40 to 50 percent of the waste in the loads we audited were organics. Even though the District’s landfill has about 150 years of capacity and the District is well above the state-mandated 50 percent diversion, the District Board believes we need to continue on a pathway to more sustainable practices. It’s the right thing to do.”
While the starting ratio of food waste to green waste is typically 50:50, the mix can go as high as 70 percent food waste and 30 percent green waste, notes Dudgeon. Each digester unit can hold 60 to 65 tons of material. The SmartFerm system operates in the thermophilic temperature range. Aeration trenches are built into the floor. As soon as the digester door is sealed following loading, the system operates aerobically until the material reaches 125° to 130°F. At that point, the percolate is introduced, and the system switches over to the anaerobic process. “Because our technology operates at thermophilic temperatures, PFRP is achieved in the 25- to 28-day retention time,” adds Dudgeon. For digester start-up, ZWE is seeding the percolate tank with liquid cow manure, and processing dry manure in the digesters.

Washington, DC: Biogas Investment Tax Credit Act Of 2013

Representatives Ron Kind (D-WI) and John Lewis (D-GA) recently introduced the Biogas Investment Tax Credit Act of 2013 (HR 860), which would provide a 30 percent investment tax credit (ITC) for qualifying biogas technologies. This bill would add biogas to the list of renewables that already receive a 30 percent federal investment tax credit. According to Patrick Serfass, Executive Director of the American Biogas Council (ABC), projects that inject renewable natural gas into the gas pipeline or use the biogas to power vehicle fleets would benefit from the credit. “This tax credit will help a dairy farmer who makes biogas from cow manure and then uses it to heat the buildings and power the trucks that deliver the milk,” notes Serfass. “Without it, the farmer may not be able to make that investment. The ITC would also facilitate conversion of food waste to biogas that can be injected into natural gas pipelines.”
While biogas projects that generate electricity are eligible for a production tax credit under Section 45 of the federal tax code, currently no comparable tax incentive exists for the production of biogas when used for purposes other than electricity generation, adds Serfass. “During this turbulent time in Congress, the introduction of HR 860 reflects the importance that biogas can play in our nation’s energy mix.” To learn more about other legislative initiatives that could benefit bioenergy, see “Bioenergy Policy Outlook For 2013” (January 2013). The nonprofit American Biogas Council represents over 167 companies dedicated to maximizing the production and use of biogas from organic waste. To learn more, visit

Skaneateles, New York: Improving Economics Of Farm Digestion

Twin Birch Farm, a dairy operation with approximately 1,170 cows located in Skaneateles, began operating a hard covered, plug flow, anaerobic digester with mixing in September 2006. The system was designed by AnAerobics and Twin Birch Farm. It now has seven 30 kW Capstone microturbines; power generated is used on the farm or exported back to the local utility via a net metering agreement. Digested manure solids are used as freestall bedding. Last August, a demonstration-scale biogas conditioning system was installed at Twin Birch Farm by American Biogas Conditioning to reduce hydrogen sulfide levels in the biogas using a biological desulphurization system. The New York State Energy Research and Development Authority (NYSERDA) has been working with American Biogas for several years, and provided $470,000 to help the company develop and test this energy-efficient technology at Twin Birch Farm as well as several other digesters in the state. The conditioning system is designed to reduce H2S levels from 4,000 parts per million (ppm) to 100 ppm, and is expected to reduce processing costs.

Sacramento, California: Public Utilities Commission Initiates Biomethane Rulemaking

AB 1900, authored by Assemblyman Mike Gatto and passed last fall, went into effect in January 2013. The Act requires the California Public Utilities Commission (CPUC) to develop standards for constituents in biogas to protect human health and pipeline integrity and safety. In February, the CPUC initiated a formal regulatory procedure to make it easier for producers of biomethane to transport the renewable fuel via the state’s utility pipeline grid. “Given California’s large dairy industry and the number of landfill sites that are able to produce biomethane, we have an enormous opportunity to develop this natural resource,” CPUC commissioner Mark Ferron said in a release. The CPUC is also adopting pipeline access rules that “ensure each gas company provides nondiscriminatory open access to its gas pipeline system to any party for the purposes of physically interconnecting with the gas pipeline system and effectuating the delivery of gas,” notes the release.
In support of the CPUC standards development, the California Office of Environmental Health Hazard Assessment (OEHHA) and the Air Resources Board (ARB), in consultation with other state agencies, are required by AB 1900 to undertake certain actions. Specifically, OEHHA is tasked with compiling a list of constituents of concern (constituents) found in biogas that could pose a health risk and that are at levels that significantly exceed the concentrations of those constituents in natural gas. OEHHA is also required to determine health protective levels for these constituents. ARB is tasked with developing realistic exposure scenarios and identifying the associated health risk to utility workers and gas end users; determining the concentrations of these constituents in biogas necessary to protect public health; and identifying monitoring, testing, reporting, and recordkeeping requirements necessary to ensure that health protective levels are maintained.

Turtle Lake, Wisconsin: Cheese Factory Residuals To Biogas Power

The GreenWhey Energy anaerobic digestion facility, designed to process 500,000 gallons/day of wastewater from several local food processors including cheese factories and a soy ingredients plant, is under construction and scheduled for completion in the summer of 2013. The plant has the capacity to produce 3.2 MW of electricity, which will be sold to Xcel Energy. Process heat will be used by the food processors. GreenWhey Energy, Inc., project owners, recently closed on $28.5 million in construction and long-term financing. The company was assisted by Baker Tilly Capital, LLC, a subsidiary of Baker Tilly Virchow Krause, LLP. Project investment included senior loan financing from Caterpillar Financial Services, New Markets Tax Credit financing from CAP Services, Inc., and equity funding from Geo Investors Fund. The project also qualifies for a federal 1603 grant upon completion of construction.

Pittsboro, North Carolina: Biofuel Producer Receives Certification

Piedmont Biofuels — one of the first biodiesel producers that BioCycle reported on — has been certified under the internationally recognized Roundtable on Sustainable Biofuels (RSB) Program following a third-party assessment conducted by SCS Global Services (SCS). Piedmont Biofuels collects used cooking oil from restaurants in the Research Triangle Park area and uses it to produce biodiesel that is sold locally through 7 filling stations. The SCS assessment included an inspection of the biodiesel plant and several of the filling stations as well as verification that the company’s biodiesel reduces greenhouse gas emissions by 70 percent compared to conventional diesel fuel.
“Our mission has always been to lead the sustainability effort in North Carolina through the development and production of clean, renewable fuels,” says Lyle Estill, President of Piedmont Biofuels. “Undergoing independent assessment by SCS and earning RSB certification allows us to validate our sustainable practices. Not all biofuels are created equal and this certification will go a long way toward proving that.” Piedmont Biofuels is located in a previously underutilized industrial area that has been converted into an “eco-industrial park” that houses businesses (including a vermicomposting operation) committed to modeling sustainable business practices.

Wooster, Ohio: $6.5 Million Grant For Bioenergy, Biofuel Research

Ohio State University’s Ohio Agricultural Research and Development Center (OARDC) received a $6.5 million grant from the U.S. Department of Agriculture and the U.S. Department of Energy to test and expand a university-developed anaerobic digestion technology. Awarded through the Biomass Research Development Initiative (BRDI), the three-year grant will also allow researchers to develop technology for converting biogas to liquid hydrocarbon fuels so that it can be used just like gasoline. University partners in the grant include Mississippi State University and the University of Georgia; the main industry partner is quasar energy group, an Ohio-based company that operates a digester on OARDC’s Wooster campus. The main goal of the research is to enhance the integrated anaerobic digestion system (iADs), a patent-pending technology developed by OARDC and operated by quasar. The system combines a commercial liquid biodigester with a dry biodigester to process feedstocks with up to 85 percent solids content, such as yard trimmings, crop residue and lignocellulosic food waste. The first iADs was built in 2012 next to quasar’s digester in Zanesville, Ohio, and can process 8,000 tons of material annually. Grant funds will be used to research production of biogas from three feedstocks: yard trimmings, corn stover and giant miscanthus, a potential bioenergy crop. Researchers at OSU South Centers at Piketon have been testing the crop’s adaptability to Ohio since 2010.
Related research to be conducted under the BRDI grant includes: Evaluate use of the digestate as a fertilizer to grow giant miscanthus on strip-mined land not suitable for traditional crops; Study biogas feedstock logistics, including use of a methane-fueled truck to transport the digestate to the field and bring miscanthus biomass back to the digester; Develop a technology for pretreatment of lignocellulosic biomass to enhance its digestibility, leading to higher biogas production; and Evaluate the microbial community present during the anaerobic digestion of pretreated feedstocks.

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