Composting, the process by which plant matter and food waste is broken down into soil, has long been recognized as a key component in developing a nutrient-rich base for organic farming. But recent research, as explored at the second annual Food Waste Solution Summit put on by the San Diego Food System Alliance last week, suggests benefits of the practice could extend far beyond the reach of farms and gardens.
"When food waste makes its way into landfills, it's producing significantly more greenhouse-gas emissions than it would otherwise," said Dr. Marcia DeLonge, an agroecologist with the Union of Concerned Scientists, during a presentation. Meanwhile, "healthy soils tend to be more productive and absorb more carbon."
DeLonge shared some findings of researchers affiliated with the Marin Carbon Project, a research project ongoing in Northern California for nearly a decade.
In 2008, researchers selected two sites, one coastal and one in the state's inland valleys, and spread one-half inch of compost over portions of range land used for grazing cattle. Taking no further action, the condition of the sites has been the subject of an ongoing study since.
"We found that the composted areas, year after year, resulted in 40 to 70 percent increases in forage [plant material consumed by grazing livestock]. This was something that the cows noticed," DeLonge continued, slides behind her showing herds of cattle largely concentrated in areas that received the compost treatment while avoiding nearby areas that hadn't received the added topsoil.
In addition to recording "measurable, significant increases in soil carbon," which was the project's goal, DeLonge said researchers "also found increases in the amount of water holding capacity of soils which, in a drought-affected area is absolutely huge."
While improved productivity of range land and the additional water retention (which keeps top soil moist longer after rains, allowing plant roots to tap into the water and remain healthy) were both beneficial, the Marin researchers were focused on the ability of composted soil to trap carbon deposits in the atmosphere. According to the group's estimates, if one half of the state's range land were to receive the same half-inch treatment as the test sites (whose effects are expected to be impactful for "several decades"), the compost would be able to scrub between 21 and 42 metric tons of carbon from the atmosphere annually. At the higher end, this is equivalent to the carbon released from all electricity generation in the state.
Given the potential benefits of composting, it could be expected that the practice would be highly encouraged, especially by government bodies with the green-friendly focus of California. But local composters report they're having difficulties in launching or expanding their programs.
Richard Flammer, a composting consultant with Hidden Resources who moderated a later panel discussion at the summit, said factors including low "tip fees" at local landfills, a lack of composting facilities near population centers, lack of coordination among a host of different waste service providers, and "poorly-written or nonexistent zoning and local land use restrictions" all contribute to a relatively low participation rate in composting across the county.
"We have an interesting situation that's probably not replicated anywhere else — there are three million people in San Diego County, but we also have 250,000 acres of farm land," said Eric Larson, executive director of the San Diego County Farm Bureau, a nonprofit advocacy group for farmers. "Usually you have either an urban or a rural setting, but here we have two important components for a compost cycle located together.
"Composting is actually essential to farmers remaining in business. In San Diego we don’t have much organic matter in our soils because we don't have much rainfall," Larson continued. "But the farmers I talk to feel like they're 'rogue composters,' because the regulations in the county restrict the capacity to bring feed stock onto the farm."
Current regulations were developed in the 1970s partially as a result of rural land owners accepting green waste for "recycling" but instead allowing large piles of dried brush and debris to accumulate. Absent any efforts to hasten the process of decomposition, the masses posed a fire hazard and would take years to naturally decompose.
As a result, local farmers are only supposed to use materials generated on-site for composting, though Larson says many privately admit to bringing in used livestock bedding or food waste from outside to supplement their own efforts to generate soil.
Joe Farace, a program manager with the county's Planning and Development Services department, said he was aware of difficulties the ban on off-site waste posed to farmers and community gardens.
"We realize that there are issues with regulations as they're currently written," Farace told panel attendees. "But I think we also realize the benefit of composting — its improvement on the overall food system as well as the reduction in greenhouse gas component."
Farace said revisions to existing laws were "slotted into future planning programs." Meanwhile, two pieces of state legislation passed in 2014 could hasten the move toward more widespread composting.
One, Assembly Bill 1826, is already taking effect. Since April 1, businesses that produce more than eight cubic yards of waste per week have been required to separate food scraps and landscape trimmings and arrange for recycling — the law has already spawned several boutique waste-management businesses to compete with existing trash collectors, a few of whom were at the summit marketing their services. While large facilities like supermarkets and shopping malls are already affected, many smaller and mid-size businesses including most of the restaurant industry will be affected when the threshold for compliance drops to four cubic yards of waste weekly in 2017.
Assembly Bill 1594, meanwhile, won't fully take effect until 2020. At that point, it will overturn part of a 1996 law that, while mandating 50 percent of waste collected be diverted from local landfills, allowed green waste that still ended up in dumps as "alternative daily cover" to be counted as officially "diverted."
Both laws will result in a significantly higher proportion of organic matter being moved from trash dumps to recycling facilities, meaning compost may soon be big business.