History: Anaerobic Digesters at Dairies in California

Before 2002, fewer than five dairies in California operated anaerobic manure digesters. Each dairy used the biogas produced by the digester to run an engine that powered a generator producing electricity for use at the dairy. There were no specific regulatory programs that applied to the digesters, although the Regional Water Boards (RWBs) regulated wastes produced at the dairies, including effluent from the digesters.

Other state and local agencies likewise did not have regulations specific for the digesters, although some of those agencies had regulations applicable to dairies.

In 2002, the California Energy Commission (CEC) provided grant funding for the Dairy Power Production Program (DPPP) to support construction of digesters at additional dairies. The program was administered by Western United Resource Development (WURD), and resulted in construction of digesters at ten dairies¹. The new digesters were also used to power generators, but several dairies negotiated with utility companies to sell excess electricity. However, pricing for the surplus electricity was not favorable to the dairies and many just flared excess biogas.

No new state regulatory programs were developed that applied to the ten digesters constructed under the first round of DPPP funding, nor did local agencies develop any regulations that applied to the digesters.

Starting in 2004, several counties began developing regulatory programs for dairies, but the regulations did not specifically address digesters.

However, starting about 2005, new regulatory programs were enacted that affected the construction of digesters at dairies. Having to understand and comply with the new regulations was very challenging for proponents of digesters at dairies.

Most of the new regulations applied to air emissions in the San Joaquin Valley and in the South Coast Air Pollution Control Districts (APCDs).

The primary affect of the new regulations was to limit the amount of nitrogen oxides (NOx) that could be released by operation of engines used to power generators. At the same time, the Central Valley RWB was developing a new regulatory program for dairies that included more stringent requirements for new lagoons such as those that could be covered to serve as an anaerobic digester. During the period that the Central Valley RWB regulations were under development, persons proposing to construct digesters at dairies in the Central Valley experienced frustrating delays in obtaining design approval from RWB staff.

A second round of CEC grant funding was made available through WURD in October 2006, and nine additional dairies received funding for new digesters. At about the same time, Utility Districts developed policies for the purchase of excess electricity at rates that were more favorable to dairy operators. In May 2007, the Central Valley RWB adopted general Waste Discharge Requirements (WDR) Order R5-2007-0035 for cow dairies; the Order includes requirements applicable to construction and operation of digesters, including application of digester effluent and other wastewater to cropland. Although the APCD and RWB requirements applicable to digesters were now clearly established, the difficulty and cost of complying with the requirements resulted in delays in getting the new digesters operating. As of April 2008, only one of the additional digesters was operational.

In late 2007, a few companies proposed to construct anaerobic digesters at dairies to produce biogas and treat the biogas for injection into Utility District natural gas pipelines. The Central Valley RWB issued individual WDR orders for seven such facilities in January and March 2008. Six of the facilities stated that they would co-digest imported organic feedstocks to enhance biogas production. As of April 2008, none of these facilities were operational.

In December 2010, the Central Valley Water Board certified a final Environmental Impact Report for Waste Discharge Regulatory Program for Dairy Manure Digester and Co-Digester Facilities. The program EIR assesses the environmental impacts associated with manure digester and co-digester facilities throughout the Central Valley. Under the program the Central Valley Water Board has adopted two general orders: a general order for digester and co-digester facilities located on dairies in December 2010, and a general order for centralized digester facilities not located on a dairy in June 2011. The adoption of the general orders enables the Central Valley Water Board to reduce the time required to permit dairy digester projects by at least 75 percent.

¹For additional information on the DPPP and the digesters constructed under the program, go to the California Energy Commission website and search for “DPPP.”