BioCycle September 2010, Vol. 51, No. 9, p. 44
The first farm-based facility is under construction, benefiting from a regulatory collaboration between the Massachusetts Departments of Environmental Protection and Agricultural Resources.
MOST farms in Massachu-setts are small and family-owned. These farms contribute to a diversified state economy and, as importantly, to the cultural character of the state. Their continued cultivation is not a simple economic decision evaluated only in bushels, tons and dollars, but one that takes into account the impact of agriculture on the nature of Massachusetts as a place.
And the public knows it. There is a strong farm to plate movement in Massachusetts, with the second highest percentage of direct to consumer sales in the nation and ninth in the nation in terms of direct sale dollars, despite having one of the smallest agricultural economies in the United States in terms of cash receipts. However, as in other states, small dairy operations are subject to the pricing direction that favors industrial-scale milk production, as well as land development, especially residential, that makes “business as usual” manure spreading perceived as an unacceptable nuisance.
Anaerobic digesters can not only make Massachusetts’ dairy industry more competitive, lowering energy costs and further diversifying farm businesses, but they also increase the compatibility of legacy farms with current land-use development trends in the region. One viable option is development of small, distributed anaerobic digesters that match the state’s small, distributed farms, versus current industry trends that advocate much larger facilities on much larger farms. In addition, codigestion of manure with other energy-rich, organic materials helps generate the energy sales necessary to pay for ongoing operations and maintenance costs for digesters on dairy farms in Massachusetts.
This substrate requirement dovetails with goals set by the Massachusetts Department of Environmental Protection (DEP), which has targeted organic residuals from food processing/commercial food preparation as a priority material for waste diversion since 2006. Diverting this material to farm anaerobic digesters is a “two birds, one stone” solution. The state’s 2010-2020 Solid Waste Master Plan references anaerobic digestion (AD) of food waste: “Large amounts of food waste are generated…this material can be a valuable resource, both for producing compost products that can improve soil quality, conserve water, and reduce erosion and as a potential energy source through processes such as anaerobic digestion.” Specific action items in the plan reference AD on farms: “Adding a site assignment exemption for on-farm anaerobic digestion options;” and “Support development of on-farm organics infrastructure such as anaerobic digestion.”
REGULATING A TWO BIRD SOLUTION
Anaerobic digesters often, as admitted by one regulator, “do not fit well within our established laws and rules.” They tend to overlap several regulatory authorities as processing manure brings in the agricultural authority, food residuals the solid waste authority, energy generation the utilities authority, and so on. AGreen Energy, LLC (majority owned by small dairy farms) was the first to permit a codigester in Massachusetts and thus not subject to a formal process. The company first approached the Department of Agricultural Resources (DAR), which directed it to the Department of Environmental Protection (DEP). From there, internally, the agencies developed a regulatory pathway and then shared it with AGreen in a multidepartment meeting in December 2009. A set of complementary permits for air emissions (including air pollutants, noise and odor), material receiving and processing, and fertilizer licensing, were issued as a result of collaboration between the DEP and DAR.
The first leg of the complementary permit is regulating farm-based codigestion as a recycling activity, rather than a solid waste activity. Massachusetts regulations governing solid waste facilities include exemptions for all agricultural manures and agricultural composting of food residuals in small amounts; however, there is no explicit language addressing AD. Instead, an implicit reading of state regulations is used, namely regulations addressing the location and operation of recycling operations. This slips anaerobic digesters into the existing regulatory environment without reinventing the wheel. It also sets out neatly what the regulatory concerns are: air, noise and odor emissions; spill response; material accumulation; etc.
In essence, farm anaerobic digesters are recycling operations that process organic residuals into stabilized digestate that is then spread on agricultural fields as a source of nutrients for agricultural crops. The use of digestate produced from food residuals and manure as a substitute for commercial fertilizers qualifies AD as a recycling process, and qualifies digestate as a commercial fertilizer in the state of Massachusetts. It is this nutritional value present in the stabilized digestate that allows this recycling determination.
This framing of digestion as a process that produces a product, instead of a treatment process for unstable waste, differentiates farm-located AD from potential food residue-only anaerobic digestion facilities. Unless a food residue-only facility has an identified customer for its “recycled fertilizer,” it may be difficult to qualify for the same recycling designation as farm anaerobic digesters. With the weak NPK value of most digestates (estimates for a project in Massachusetts put the NPK value at less than 0.6/0.2/0.5), the cost of trucking and spreading the digestate quickly exceeds the commercial value. With farm-owned anaerobic digesters this trucking cost is internalized and makes use of existing manure spreading equipment.
KEEPING DIGESTERS FARM APPROPRIATE
To prevent small Massachusetts dairy farms from turning into industrial digestion facilities with an accessory dairy barn, there is a limit on the size of farm AD facilities. This is not a new concept as similar restrictions are also in place on farm composting activity. To qualify as a “conditionally-exempt” recycling facility, the digestion facility must process 100 tons or less of material each day. In round numbers, this limits farm digesters (a complete mix digester was assumed) to a working capacity of around 750,000 gallons with a 30-day retention time. This digestion volume could support the manure-only digestion of a herd with well over 1,000 head or a small farm codigesting manure and food residues, but stops short of enabling an extremely large facility of several million gallons.
Farm anaerobic digesters are allowed some breathing room on emission restrictions, especially for NOx and CO (Table 1), but only for (biogas-fed) engines with a nameplate capacity of 500 kW or less and shielded flares with a maximum capacity of 350 scfm. With the high cost associated with meeting emission restrictions outside of this allowance, farm digesters are unlikely to exceed these sizes. This maintains air quality standards for large point polluters, while allowing the distributed deployment of efficient combined heat and power units.
Farm anaerobic digesters, since they produce a renewable fuel used to generate electricity, qualify as Class II Net Metering Facilities in Massachusetts, as long as they have a “generating capacity” of between 60 kW and 1,000 kW. Net metering rates for electricity are much higher than what is available as a standard generator, incentivizing development of facilities of this size.
The first farm anaerobic codigester in Massachusetts (developed by AGreen), located at Jordan Dairy Farms in Rutland, MA, is now wrapping up this permitting process. A 500,000 gallon, complete mix digester supplied by Quasar Bioenergy of Ohio was delivered to the farm at the end of August. Supporting a 375-head milking herd in central Massachusetts, it is expected to generate approximately 280 kW and recycle between 40 and 55 tons/day of organic residues. Another four facilities of the same size are on the drawing board, creating a diversified recycling solution for a diversified farm economy.
Sam Snellings is with AGreen Energy, LLC, a majority farmer-owned anaerobic digester development entity in Massachusetts. He has worked on codigestion regulatory paths in Massachusetts and Florida.