February 17, 2013 | General

Anaerobic Digest

BioCycle February 2013, Vol. 54, No. 2, p. 17

Madison, Wisconsin: Report Assesses Viability Of AD At Swine Operations

While installation of anaerobic digesters has been increasing at a steady rate on dairy farms, swine operations have lagged behind, with only about two dozen in operation in the U.S. A new report issued by the Energy Center of Wisconsin (ECW), “Anaerobic Digestion On Swine Operations: Assessing Current Barriers and Future Opportunities,” analyzes what is suppressing adoption of AD by swine facilities and identifies possible routes to increase use of the technology. Authors Joe Kramer of ECW and Amanda Bilek of the Great Plains Institute focused their analysis on four states: Illinois, Iowa, Minnesota and North Carolina. According to U.S. EPA’s AgSTAR program, these states have 4,000 swine operations that are of sufficient size to add an AD system, but there are only nine operational projects across all four states (6 in North Carolina, 2 in Iowa and 1 in Illinois). Kramer and Bilek interviewed swine industry stakeholders, anaerobic digester developers and other experts to gain insights into perceptions and other factors that affect use of anaerobic digesters at swine operations.
One significant barrier identified is the structure of the swine industry itself. “Growing operations have very narrow profit margins which limit their ability and inclination to invest in additional processes beyond the primary farm functions,” explain Kramer and Bilek. “Therefore, they tend to be minimally staffed, and structures are designed to maximize cost-effectiveness of manure handling and storage. …. The primary barrier is that for most operations an AD and combined heat and power (CHP) system does not appear economically favorable with current market conditions and current perceptions of costs and benefits. … In addition, many of the benefits to the farm, the neighborhood and environment are external to the market and not directly monetized.” Another barrier is current manure collection practices. In the Midwest, growing operations have evolved to minimize the costs of complying with structural and storage regulations, leading to use of barns with slatted floors and deep pit storage of manure beneath, which is then pumped out to fields once or twice per year. “The addition of a digester to these farms would be costly and would require additional structures and a change in on-farm practices,” notes the report. In North Carolina, swine operations have traditionally used flush collection of manure (creating greater volume because of dilution) and storage in open lagoons. Minnesota and North Carolina have current policies on the books that limit or prohibit the construction of manure lagoons.
Kramer and Bilek conclude that if the economic barrier to installing AD systems at swine operations could be overcome, other barriers will fall. The foremost change needed is to improve the economics of digester systems for swine growers. In addition to higher rates for electricity generated by AD biogas, they discuss new incentives that could create a monetary value for renewable thermal energy projects (or the thermal component of CHP), add biogas resource carve outs in existing or new renewable energy standards, add CHP as a qualified resource to meet state energy efficiency standards, and implement more robust standard offer purchase programs. Also suggested are: Colocation with other industrial facilities, such as an ethanol plant or a food processing plant, which could provide a customer for excess heat from the CHP system and might also provide an additional waste stream for codigestion; and Utilization of emerging technologies to concentrate nutrients or create fertilizer products that could add to revenues or directly reduce costs of nutrient management. Kramer and Bilek also recommend development of “concise, unbiased and understandable documentation of successfully installed swine AD systems” and “medium-and long-term changes such as promoting policies that encourage diversion of organics from landfills, developing low-cost systems and technology solutions, identifying regulatory changes that would increase incentives for biogas, and providing examples of swine AD projects that are receiving value from carbon credits.” The report can be downloaded at

Davis, California: Food Processor Residue Assessment

A report recently posted by the California Biomass Collaborative, “California Food Processing Industry Residue Assessment,” presents the findings of a county-level inventory of food processing industry wastewater and solid residues, which then was used to estimate the amount of energy that these residues could generate from California-based biomass resources. The research project was funded by the California Energy Commission’s PIER (Public Interest Energy Research) program and conducted by Ricardo Amon, Mark Jenner, Rob Williams, Hamed El-Mashad and Steven Kaffka. Food processor sectors investigated included: fruit and vegetable canneries, dehydrated and fresh/frozen fruit and vegetable processors, dairy creameries, wineries, meat processors and almond and walnut processors. Where possible, current waste disposal practices and amounts were identified and the potential availability of resources was assessed.
According to the report, “regression methods using survey data were used to estimate the amount of solids discharged as a function of wastewater, the number of workers and the solids’ moisture content for incomplete observations. Potential energy was estimated using generic feedstock properties and basic assumptions for conversion efficiencies.” Results show 26.3 billion gallons of wastewater (equivalent to 175,000 tons of BOD5) and 3.4 million dry tons of solid residues are produced annually by the industry sectors investigated. Almond hulls and shells account for almost 60 percent of total dry tons of solid residue. “This resource represents a technical energy potential of 560 MW of equivalent electricity with 24.5 million MMBtu of recovered heat,” note the authors. “Almond hulls represent a significant component of the total energy potential identified in the study. However, much of the residue materials have current economic uses and, at current prices, are not available for energy. These materials include almond hulls, walnut shells, cheese whey, and animal by-products. To download the full report, go to

London, England, United Kingdom: Draft Quality Protocol For Biomethane

The European Pathway to Zero Waste and the UK Environment Agency (EA) released a revised draft Quality Protocol that establishes end of waste criteria for production and use of biomethane from anaerobic digesters and landfill biogas for injection into the gas grid or for use in an appliance suitably designed and operated for natural gas. These include compression and spark ignition engines; gas turbines; fuel cells; and heating appliances.
“If these criteria are met, the biomethane will normally be regarded as having been fully recovered and to have ceased to be waste,” explains the revised criteria. “Producers, processors and users are not obliged to comply with the Quality Protocol. If they do not, the material will normally be considered to be waste and waste management controls will apply to its storage, handling, transport and application.” Adds the EA on the webpage where the protocol can be downloaded: “The new quality protocol will also help to establish a consistent set of standards required in order to facilitate direct injection of waste-derived biomethane into the gas grid and use in other appliances. By reducing the regulatory burden on businesses using biomethane from waste sources, we hope to encourage its increased production and use.”
Comments on the current draft will be accepted through February 28, 2013. After this review, the Quality Protocol as drafted will be finalized and then go forward for notification under the European Union Technical Standards and Regulations Directive 98/34/EC.

Elmwood, Ontario: Beef To Biogas At Cattle Feedlot

An anaerobic digester at an 1,800 head cattle feeding operation in Elmwood has been operating at full capacity since last October. According to an article in the November 2012 edition of “Biogas News,” published by the Biogas Association in Ontario, Marl Creek Renewables’ digester is processing solid beef manure and corn silage, combined with a range of off-farm feedstocks. It used the Octaform technology to build the tanks; the two 250 kW CHP units are manufactured/supplied by SEVA Energie. Marl Creek is using hydrolysis to process all off-farm materials before adding them to the digester. “This process provides a high level of stability and is highly efficient, particularly for large batches of feedstock that are inconsistent in their makeup,” notes Biogas News, adding that owner Carl Frook’s business card now reads: “Marl Creek Renewables — Beef to Biogas.” Read the full article at

Washington, DC: Sorghum-Based Ethanol + Biogas For Process Energy = Advanced Biofuel

In late December, the U.S. Environmental Protection Agency announced it is issuing a supplemental rule associated with the Renewable Fuel Standard (RFS) program. This final rule contains a lifecycle greenhouse gas (GHG) analysis for grain sorghum ethanol and a regulatory determination that grain sorghum ethanol qualifies as a renewable fuel under the RFS Program. EPA’s analysis indicates that ethanol made from grain sorghum at dry mill facilities that use natural gas for process energy meets the lifecycle GHG emissions reduction threshold of 20 percent compared to the baseline petroleum fuel it would replace, and therefore qualifies as a renewable fuel. It also contains a regulatory determination that grain sorghum ethanol produced at dry mill facilities using specified forms of biogas for both process energy and most electricity production, has lifecycle GHG emission reductions of more than 50 percent compared to the baseline petroleum fuel it would replace, and that such grain sorghum ethanol qualifies as an advanced biofuel under the RFS program. Western Plains Energy in Oakley, Kansas, which produces ethanol from sorghum, has installed an anaerobic digester supplied by Himark bioGas to generate biogas to fuel the ethanol plant’s boilers. Manure from a nearby 50,000 head feedlot, along with syrup from the ethanol plant, will be codigested to generate biogas. Western Plains intends to qualify its ethanol as an advanced biofuel under the new EPA determination.

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