Courtesy : www.cdfa.ca.gov

Composting whitepaper

In the 2015-16 proposed budget, Governor Brown recognized the importance of soil
health and directed the California Department of Food and Agriculture (CDFA) to coordinate a
new initiative to support and enhance this critical resource. The budget language stated “As the
leading agricultural state in the nation, it is important for California’s soils to be sustainable and
resilient to climate change. Increased carbon in soils is responsible for numerous benefits
including increased water holding capacity, increased crop yields and decreased sediment
erosion. In the upcoming year, the Administration will work on several new initiatives to
increase carbon in soil and establish long term goals for carbon levels in all California’s
agricultural soils. CDFA will coordinate this initiative under its existing authority provided by the
Environmental Farming Act”.
Consistent with the Governor’s initiative, now titled the Healthy Soils Initiative, CDFA
worked with several state agencies to identify short and long-term actions that could improve
soil health in California to ensure agricultural sustainability and food security
(. One of the
actions identified was to incentivize management practices that build the carbon content in
soils. Increasing the carbon content of soils has been scientifically shown to lead to greater
agricultural sustainability and ensure food security, especially in light of climate change. CDFA
plans to implement a cost-share incentives program using Conservation Practice Standards
established by the United States Department of Agriculture (USDA) Natural Resources
Conservation Services (NRCS). The CDFA program would include soil health-promoting
management practices that also reduce greenhouse gas (GHG) emissions. Most candidate
practices that could meet these goals are identified in the recently developed COMET-Planner
tool1
. COMET-Planner provides estimates of GHG reductions from each included practice,
which serve as an input to the California Air Resources Board (ARB)’s process of developing a
quantification methodology (QM) that will meet the needs of the California Climate
Investments program.
One agricultural practice with considerable soil health improvement and GHG reduction
potential is the application of compost to croplands and rangelands. Incentivizing the use of this
practice can indirectly achieve large GHG emission reductions2 by increasing demand, spurring
expansion of composting facilities and organic waste diversion from landfills that produce
methane. Methane is a GHG with a 100-year global warming potential 28 times that of carbon
dioxide. Aerobic composting allows the carbon in plant and animal source materials to be
stabilized into carbon compounds that generally decompose slowly after the compost is applied
to land. Land application of compost also directly stimulates biological processes, including
increases in soil microbial and plant biomass3,4, that sequester carbon into stable long-term
organic matter fractions5,6. Increases in these organic matter fractions offer numerous benefits
such as increasing the water and nutrient retention capacity of soils, providing a reservoir of
nutrients for plants, improving aeration, improving water infiltration, reducing soil erosion, and
supporting the abundance and diversity of soil organisms, which can improve plant health.
CDFA must determine application rates of compost that would be supported by an
incentive program. CDFA will not be able to support unlimited rates of compost application
requested by farmers and ranchers given the limited amount of funding available as incentives,
as well as the need to ensure that environmental concerns are addressed. The amount of
4
anticipated greenhouse gas reduction corresponding to developed application rates can then
be estimated based on a model recognized by ARB7
.
CDFA recognizes that ARB is ultimately responsible for developing the quantification
methodology (QM) associated with any program funded through the California Climate
Investments program, also known as funding from the Greenhouse Gas Reduction Fund. As
such, this report describes some quantitative analyses that may support the development of a
QM for the CDFA incentive program, rather than furnishing the QM tool that will be used.
Methodology
On July 17, 2015, CDFA convened a meeting of the Environmental Farming Act Science
Advisory Panel (EFA SAP) to discuss the application of compost to California croplands and
rangelands. The EFA SAP is a group of farmers and scientists who provide scientific guidance to
the Secretary of CDFA and is a platform for public comment. The EFA SAP functions under the
authority of the Environmental Farming Act of 1995
. The July 17th
meeting was open to the public and attended by a variety of stakeholders. Attendees at the
meeting recommended that CDFA convene a subcommittee of compost experts (from
academia and state agencies) to evaluate and propose compost application rates, which could
then be considered for review by the EFA SAP, subject to public comment and proposed to the
Secretary of CDFA to implement as part of any future Healthy Soils Incentive Program.
On August 28, 2015, CDFA convened a meeting of a compost subcommittee. The group
consisted of university researchers in soil science, compost management and agronomy and
included scientists from several pertinent state agencies such as CalRecycle, CDFA and the
Central Valley Regional Water Quality Control Board (a complete list of participants can be
found at the end of this report). The goal of this meeting was to determine compost application
rates that could be supported by a CDFA Incentives Program given the diversity of cropping
systems in California. A second meeting of the subcommittee was held on September 30, 2015.
Several literature reviews were conducted to evaluate the best available science that would
support compost application rates for a CDFA Incentives Program for discussion at the two
subcommittee meetings.
A second Environmental Farming Act Science Advisory Panel (EFA SAP) meeting on this
topic was convened on January 15, 2016. A draft report of the results from the subcommittee
meetings was presented to the members. Public comment on the report was solicited at this
meeting, as well as through a four-week public comment period extending through February
12, 2016.
The Results section below summarizes the proposed compost application rates
recommended by the subcommittee and takes into consideration public comments received.