Dairy Digesting & AMMP
Dairy digesters are a renewable technology that uses livestock manure to produce methane, which is a renewable source of electrical energy generation and transportation fuel. The technology has many environmental and social benefits.
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 dairies. 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.
As of April 2008, only one of the additional digesters was operational.
Beginning in 2015, the California Department of Food and Agriculture began to issue grants through the Dairy Digester Research and Development Program (DDRDP). The program provides financial assistance for the installation of dairy digesters in California. DDRDP is funded through the California Climate Investments (CCI) for the reduction of methane from livestock and dairy operations. Since DDRDP launched 118 dairy digester projects have been completed in California. The collective GHG emission reductions estimated from the 118 projects is 21.12 million metric tons of carbon dioxide equivalent (MTCO2e) over 10 years, and the approximate cost to achieve one MTCO2e (10-year) reduction is approximately $28.81. Of this cost, the share of the CCI monies (i.e., the CDFA grant) is approximately $9.26 or 32 percent, and the remainder is achieved through matching funds provided by the grant recipient.
DDRDP grant recipients report economic benefits, including jobs creation to CDFA. Since 2019, CARB has developed the Job Co-Benefit Assessment Methodology and Modeling Tool, which was utilized to estimate jobs benefits provided by projects at the time of application.
For more information or to apply for a DDRDP grant, visit CDFA - OEFI - Dairy Digester (ca.gov)
CDFA’s Alternative Manure Management Program (AMMP) provides financial assistance for the implementation of non-digester manure management practices in California, which will result in reduced greenhouse gas emissions.
Alternative manure management practices involve handling and storing manure in ways that don't include use of an anaerobic digester, and support management of manure in a dry form. Like the DDRDP, AMMP is funded through California Climate Investments for the reduction of methane from livestock and dairy operations.
AMMP supports several project types for which quantification methodology for GHG emission reductions is eligible. Methane is produced when volatile manure solids are stored in wet, anaerobic conditions; consequently, conditions that lead to methane production must currently exist at a dairy or livestock operation in order for methane emission reductions to be achieved through an AMMP project.
While solid separation or conversion from flush to dry scrape manure collection can be a critical component an AMMP project, these practices are not considered to be stand-alone projects because they relate only to how manure is separated or collected. In order to calculate GHG emissions and emission reductions, it is also necessary to identify how the separated or collected manure volatile solids will be treated and/or stored (e.g. open solar drying, composting in vessel).
The storage or further treatment of the collected solids produces methane to varying degrees, as determined by the Methane Conversion Factor (MCF) for each practice. The following manure management practices, i.e., combinations of manure collection and/or separation and storage/treatment methods are currently incentivized through the AMMP:
I. Manure Collection and/or Separation
1. Pasture-based management including (i) conversion of a non-pasture dairy or livestock operation to pasture-based management and/or (ii) increasing the amount of time livestock spend at pasture at an existing pasture operation. Note: All pasture-based management projects must currently manage/store some manure in anaerobic conditions and introduce new practices that reduce the quantity of manure managed under such conditions.
2. Alternative manure treatment and storage practices including: a) Installation of a compost bedded pack barn that composts manure in situ; or b) Installation of slatted floor pit storage manure collection that must be cleaned out at least monthly.
3. Solid separation of manure solids prior to entry into a wet/anaerobic environment (e.g. lagoon, settling pond, settling basin) at a dairy or livestock Page 2 of 2 operation in conjunction with one of the manure treatment and/or drying practices provided below. Eligible solid separation technologies include: a) Weeping Wall (system must have a minimum of at least two cells) b) Stationary Screen c) Vibrating Screen d) Screw Press e) Centrifuge f) Roller Drum g) Belt Press/Screen h) Advanced solid-liquid separation assisted by flocculants and/or bead filters. This practice must be implemented in conjunction with a primary mechanical separator. i) Vermifiltration. This practice must be implemented in conjunction with a primary mechanical separator. Note: Either the installation of a new solid separation system at a dairy or livestock operation that does not currently employ solid separation, or the installation of a new solid separation system with significantly higher separation efficiency than the existing solid separation technology may be eligible.
4. Conversion from a flush to scrape manure collection system in conjunction with one of the manure treatment and/or drying practices provided below.
II. Manure Treatment, Drying and/or Storage
1. Open solar drying of manure (manure is dried in a paved or unpaved open confinement area without any significant vegetative cover where accumulating manure may be removed periodically); 2. Closed solar drying (drying of manure in enclosed environment);
3. Forced evaporation with natural-gas fueled dryers;
4. Daily spread (manure is routinely removed from a confinement facility and is applied to cropland or pasture within 24 hours of excretion);
5. Solid Storage (storage of manure, typically for a period of several months, in unconfined piles or stacks);
6. Composting in vessel (composting in an enclosed vessel, with forced aeration and continuous mixing);
7. Composting in aerated static pile (composting in piles with forced aeration but no mixing);
8. Composting in intensive windrows (with regular turning for mixing and aeration);
9. Composting in passive windrows (with infrequent turning for mixing and aeration)
For more information or to apply for to AMMP, please visit CDFA - OEFI - AMMP (ca.gov)