Anaerobic Digest

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Courtesy of BioCycle Magazine

Washington, DC: NOSB Considers Digestate Use Petition

The National Organic Standards Board (NOSB) of the U.S. Department of Agriculture (USDA) has agreed to consider a petition from Cenergy USA, the makers of Magic Dirt™, to allow use of digestate from anaerobic digestion plants in organic agriculture. Magic Dirt is made from digested dairy manure fibers. The soil amendment products are currently registered and sold in 22 states. Cenergy filed its petition with NOSB in April 2016 to request that digestate be removed from the “raw manure” category. As part of its review of the petition, the NOSB Crops Subcommittee requested the development of a third-party technical evaluation report for anaerobic digestate. The draft report was published in May 2017. This technical report will support the NOSB’s review of this petition, and attempts to address specific focus areas requested by the NOSB Crops Subcommittee (citations included to assist in finding the text in the report):

  • Define anaerobic digestion (AD) and its end products. (Origin of the Substance)
  • Describe commercially available AD technologies and how the different technologies affect the end products. (Evaluation Question 2)
  • Discuss differences between anaerobic digestate products and compost. (Evaluation Question 11)
  • Provide a summary of all methods in use for creating this material, with feedstocks, ingredients, and end products. Any materials (e.g., acids, bases, microorganisms, etc.) typically added during the anaerobic digestion process should be described, including a discussion about the fate of these additives (e.g., if they are used up, removed, or contribute to the nutrient profile for the end product). (Evaluation Question 2)
  • Explain a typical nutrient cycle for the feedstocks into end products from these processes, focusing on nitrogen. (Action of the Substance)
  • Describe available data concerning pathogen (e.g., E. coli, Salmonella) control using AD and describe documented microbiological risks from use of AD products. (Evaluation Question 10)

The NOSB is expected to discuss the petition and accept public comment at its next meeting scheduled for October 31-November 2, 2017, in Jacksonville, Florida. The final meeting agenda and any documents from the NOSB Crops Subcommittee will be available for public comment in September 2017. More information is available on the meeting webpage.

Toronto, Ontario: Government Explores Plan To Promote RNG

As it winds down its incentives for projects that use biogas to generate electricity, the government of Ontario, Canada is exploring a plan to promote renewable natural gas (RNG). The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), under the auspices of its 2016 Climate Action Plan, recently released a discussion paper on the environmental and financial potential for RNG derived from anaerobic digestion of food and agriculture wastes as a transportation fuel. The paper invited public comments on the strategy as well as proposals for demonstration projects that would be supported by public funding.

The aim is a four-year program to develop agriculture-based projects producing RNG to replace diesel fuel in heavy-duty trucks — a carbon-intensive form of transport, says Chris Duke, of OMAFRA’s Environmental Management Branch. “We want to ensure that we hear what the opportunities and challenges are for the different sectors and make sure the program is responsive to the realities of project development.”

According to the discussion paper, proposed projects “would demonstrate commercial opportunities with different business models such as scale, sources of energy feedstocks, type of technology, location, and ownership of facilities and fleets” and to “help agriculture, food, and bioprocessing businesses develop demonstration projects to produce RNG, and to support businesses to transition their vehicles and fuelling infrastructure to use RNG.”

When fully developed, the program would still need to be approved by the province, and funding would depend on the revenue generated by a greenhouse gas cap-and-trade program launched this year, also as part of the Action Plan. In fact, the RNG program would compete for funds with a wide variety of climate change programs.

The focus is on transportation, rather than injecting RNG into the pipeline grid for general natural gas replacement, because that sector accounts for 30 percent of Ontario’s greenhouse gas emissions, of which 30 percent comes from heavy-duty diesel trucks, explains Duke. And while Ontario’s emissions as a whole fell by roughly six percent between 1990 and 2014, emissions from the transportation sector grew by 27 percent. Ontario is developing a renewable fuel standard, aimed at a five percent reduction in emissions from gasoline by 2020.

Cost would be an issue, adds Duke. While conventional natural gas is a little over half the cost of equivalent diesel, RNG would be the same price. And there is a price premium on trucks fueled by natural gas versus an equivalent diesel truck. So the program would also look at the economics of blending conventional natural gas and RNG, as well as sharing the cost of converting a truck from diesel to natural gas, or buying a new natural gas model.

According to the Canadian Biogas Association, Ontario — Canada’s most populous province — is home to about 40 anaerobic digester projects that use their biogas to generate electricity. Only one, the City of Hamilton’s Woodward Avenue Wastewater Treatment Plant, upgrades some of its biogas to RNG. In 2016, the Canadian Gas Association announced an industry target of five percent RNG in the national natural gas pipeline distribution system by 2025 and 10 per cent by 2030.

Philadelphia, Pennsylvania: City Request For Codigestion Information

The Philadelphia Water Department (PWD) has released a request for information (RFI) for acceptance of preprocessed food waste at the city’s wastewater treatment plants. Proposals are due August 4, 2017. The PWD seeks to expand the feedstock used in its anaerobic digesters at the Southwest and Northeast Water Pollution Control plants. Currently, the plants create biogas that is used on-site for heat and power generation as well as fuel for other facilities. One motivation to explore codigestion is to contribute to the city achieving its zero waste goal by 2035.

PWD has assessed its digester capacity and determined there is enough for the codigestion process, but now is searching for additional information to implement it. In the request, PWD is asking how collection, pretreatment, quality and delivery would be handled by a potential company to create the highest quality feedstock possible. Collection of food waste will be the vendor’s responsibility; pretreatment will be done before delivery to the digesters. “Pretreatment must be comprehensive enough to remove contaminants, including trash, plastics and other such materials, from the collected food waste stream,” states the RFI. The request asks potential vendors how they would reduce grit content and if they have a pretreatment facility in operation.

Davis, California: University Purchases On-Campus Digester

The University of California in Davis (UC Davis) has purchased an anaerobic digester that has operated on campus since 2014 and plans to open an adjacent composting facility to create a more comprehensive organics management strategy, reports University News. The cost was estimated at $600,000 plus $450,000 for facility upgrades and permitting fees.

The purchase enables UC Davis to maintain an active research program on AD technology and potentially expand research opportunities in compost application for healthy soils and carbon sequestration. The purchase also assists the institution in meeting California’s organics diversion mandates. “The digester has helped demonstrate feasibility of the technology in a medium-sized plant, which was an important reason behind construction of the plant on the UC Davis campus,” noted Camille Kirk, UC Davis’ director of sustainability.

The digester, which opened in April 2014, was built, owned and operated by CleanWorld, with a ground lease from the university. Its location at the closed UC Davis landfill enables blending of the digester biogas with landfill gas for combustion in a microturbine. Organics from the campus dining halls, animal facilities and grounds are processed in the digester.

The university plans to construct a composting facility to manage effluent and waste products from the digester, as well as other organics generated on campus that cannot be digested, and are currently hauled away, adds University News.

Potsdam, New York: USDA Funds Small-Scale AD Research

Clarkson University in Potsdam has been awarded a $500,000 grant from the U.S. Dept. of Agriculture (USDA) National Institute of Food and Agriculture (NIFA). NIFA grants support research and programs that help dairy producers and growers achieve long-term viability, high yield, and labor efficient production of local agricultural products. Clarkson will use the funding to advance anaerobic digestion techniques for small-to-medium-scale dairy farmers, and work in conjunction with the Cornell Cooperative Extension farm dairy specialists to improve manure management and resource recovery.

“This support will allow us to continue our renewable energy and resource recovery project for small-farm anaerobic digesters for North Country farms, in collaboration with the Cornell Cooperative Extension of St. Lawrence County and Syracuse University,” notes Project Director Dr. Stefan J. Grimberg, Professor of Civil and Environmental Engineering at Clarkson. “Our researchers have developed an AD design and application, which demonstrates the economic viability of AD technology for smaller dairy farms. We hope that through our educational outreach, AD technology will be integrated at smaller-scale dairy farms, improving farm viability.”

Grimberg told BioCycle that this grant is a continuation of an earlier grant, under which his team built a demonstration-scale modular horizontal plug flow digester at the Cornell Cooperative Extension farm in St. Lawrence County. That demonstration unit is fed 500 pounds of dairy manure and kitchen waste per day, and digested at 100°F for 25 days.  Under this new grant, the team will recover solids using a screw press and research how the dewatered solids can be composted to make a low pathogen bedding material. Liquid effluent can be used to support vegetable production in the Cooperative Extension greenhouse, and testing will be done on using the biogas in a hydronic heater to provide space heating in the greenhouse.

Toronto, Ontario: Environmental Watchdog Makes AD Recommendations

The Ontario government should “help wastewater treatment sites produce low carbon energy from wastewater, from organics diverted from landfill, and from agricultural biomass,“ stated Dianne Saxe, the Environmental Commissioner of Ontario, an independent “watchdog” officer of the Ontario Legislature in her annual energy conservation report. “The organic material in wastewater is a valuable source of energy that is currently mostly wasted.” In her role, Saxe makes nonbinding recommendations on environmental issues. Her statement is in “Energy from Sewage,” one of eight chapters in the 145-page report, “Every Drop Counts.”

With both the provincial and Canadian government poised to make major investments to rebuild aging treatment facilities, proposed measures in the report include:

  • Simplify regulations for building anaerobic digestion facilities and producing renewable natural gas for the pipeline grid.
  • Make AD and energy-recovering projects eligible for infrastructure funding; the key is “to refocus infrastructure decisions on total lifecycle cost, not just capital cost.”
  • Encourage smaller municipalities to collaborate on building central “host” AD facilities that would process feedstocks from sewage treatment plants and other sources, creating projects large enough to be technically and financially viable.
  • Instruct the provincial regulator, the Ontario Energy Board, to set a renewable natural gas (RNG) content requirement and cost recovery criteria for the three major gas utilities, giving energy recovery projects more financial certainty.

The province appears to already be moving very cautiously in the direction of that last recommendation. The minister of energy recently said he would “encourage” the Board “to move forward in a timely manner to include RNG as a potential fuel that could help reduce greenhouse-gas emissions.” In response, the Board announced that, by the end of 2017, it would develop a new “framework (that) will set out expectations and approach to issues related to including RNG within the distributors’ gas supply portfolios.” Just 28 of Ontario’s 750 treatment plants include AD facilities, but most flare much or all of the biogas produced.

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