LIVERMORE ― As state and local agencies look for ways to combat global warming, a local experiment is underway to test the effectiveness of using compost to remove carbon from the atmosphere while improving the quality and productivity of soil.
StopWaste, a public agency governed by the Alameda County Waste Management Authority, the Alameda County Source Reduction and Recycling Board, and the Energy Council, is managing the program, commonly referred to as carbon farming.
City of Livermore Councilmember Bob Carling reported in a recent council meeting that he had received an overview on the process.
“StopWaste has been looking at this carbon farming concept where you take compost, you throw it on to a field, and it helps to fix carbon in the soil to create a healthier soil than what you had,” Carling said in an interview with The Independent. “It doesn’t solve the climate change issue, certainly not. But, it’s something interesting we can do.”
According to the Carbon Cycle Institute, land management is the second largest contributor to carbon dioxide emissions on the planet. Common agricultural practices — such as driving tractors tilling soil, overgrazing, and using fossil fuel-based fertilizers, pesticides and herbicides — result in significant carbon dioxide release.
“Carbon farming is the concept and the practice of putting carbon back in the soil because so much carbon that we have in the air was originally in the earth, in the soil,” explained Kelly Schoonmaker, StopWaste program manager. “We’re in the situation right now where we’ve got a lot of greenhouse gas emissions. We certainly need to get those under control and reduce them. We also already have a lot of carbon in the atmosphere. What carbon farming does, and specifically the practice that we’re looking at, is a one-time compost application. There are many other applications that help the soil sequester carbon, but this one-time application can help the soil capture that carbon from the air and deposit it in the soil for long-term storage.”
The Marin Carbon Project started in Marin County in 2008, and researchers there discovered the potential for rangeland soils to remove carbon from the air and store it for decades, or even centuries. That project has influenced the work currently underway in Alameda County.
Alameda County’s three-year long project went underway in December 2019 when researchers applied a thin layer of compost on a 10-acre sloped section of rangeland owned by StopWaste in the Altamont Hills east of Livermore. While the pandemic and drought have contributed to less-than-ideal conditions, the project is expected to eventually cover about 100 acres.
Schoonmaker said the project has removed about one ton of carbon from the atmosphere per year for each acre that received a single, one-quarter inch application of compost. That closely matches the observations made as part of the Marin Carbon Project, which also completed computer modeling to determine how long the compost benefits will continue. Their research determined that one ton of carbon will continue to be extracted from the atmosphere every year for 30 years. Some benefits of the application will continue for up to a century.
“The goal of our project is to demonstrate to ranchers that they can adopt new practices or adapt existing practices to sequester carbon,” Alameda County Resource Conservation District biologist Hillary Sardiñas said. “Many farmers and ranchers already use climate-beneficial practices, but they may not recognize that what they’re doing can help mitigate climate change.”
The StopWaste project also has a possible secondary benefit. Senate Bill (SB) 1383, signed into law by then-Gov. Jerry Brown in 2016, established several requirements aimed at reducing the volume of short-lived climate pollutants (SLCP) — organic waste like food scraps, yard trimmings, paper and cardboard. According to CalRecycle, SLCP accounts for half of material deposited in landfills, and is responsible for 20% of the state’s methane emissions. Methane is considered a super pollutant that’s 84 times more potent than carbon dioxide. Beginning Jan. 1, 2022, SB 1383 requires cities and counties to purchase compost created from recovered organic waste products to keep the material out of landfills and to create a market demand for the material.
Carling said that the City of Livermore will be required to purchase 10,000 tons of organic mulch annually. If the StopWaste project pans out, some of that material could be used in other carbon farming projects on farms and ranches.
Expanding the organic materials in mulch could have an impact on the quality of the mulch produced, Schoonmaker noted.
“The thing about (SB) 1383 is that you’re going to see a lot more food waste,” she said. “With food waste comes contamination, which is a huge problem. That’s like plastic and glass. I don’t mean toxic stuff. But it’s really hard to screen out, and you can end up with a lot of plastic and glass in certain types of compost. Compost is like any other product — there is a range of quality.”
Schoonmaker went on to note that since food waste contaminants can be difficult to remove from green waste, requirements should be set up that support carbon farming, while also protecting grazing.
“We don’t want to spread plastic and glass everywhere,” she said. “We don’t want people to think this is just open land where we can just chuck all this compost. We want people to use it where it’s got the most benefit.”
While the prospects are promising, there is the potential for other unintended consequences. Carling told of a Livermore rancher who used compost on his rangeland. While it had the intended benefit of producing more grass, drought conditions turned the tall, thick grass into a fire hazard.
“Carbon farming gets you a couple of things,” Carling said. “It addresses SB 1383. Secondly, it helps to fix carbon in the soil to combat climate change to a limited extent. I think it’s an interesting idea.”