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The climate solution in California’s compost and crops

These nature-based solutions are cheaper than climate tech

Autumn In California Wine Country
Rows of composting grape pomace are covered for the winter in Sonoma County’s Alexander Valley on December 13, 2015, near Geyserville, California. 
Photo by George Rose/Getty Images

Scaling up composting, tree-planting, and other sustainable agricultural practices in California could trap about a quarter of the state’s annual carbon dioxide emissions by 2030, according to a new report. These strategies for drawing down greenhouse gases are cheaper and easier to ramp up than technological alternatives, like devices that suck planet-heating CO2 out of the air, and should play a key role in the state’s efforts to address climate change, the report authors argue.

Although it often leads the nation in setting aggressive climate goals, California is also a state with one of the biggest carbon footprints, making it imperative that the state consider a wide range of strategies for reducing emissions. That could include carbon sequestration.

Over the next eight years, the new report finds that California could sequester up to 289 million metric tons of CO2 equivalent on “working lands” — urban areas and lands used for agriculture and livestock. By 2030, that capacity could increase to almost 100 million metric tons of CO2 equivalent sequestered a year. That’s roughly equivalent to shutting down 25 coal power plants for a year.

Accomplishing this would take a lot of big changes in California, the report acknowledges. The majority of that sequestered carbon would come from composting across the state’s croplands and pasturelands. Planting more trees on farms and in cities would also have a significant impact.

“This is a huge opportunity. And it’s something that we know how to do, proven practices that are tried and true,” says Jock Gilchrist, lead author of the report published Monday by the nonprofit organization The Climate Center in collaboration with the nonprofit Carbon Cycle Institute. To make their estimates, the researchers counted up how many acres might be used and multiplied that by the amount of carbon that each acre could absorb each year.

Climate models generally agree that finding ways to pull greenhouse gas emissions from the atmosphere — while at the same time eliminating pollution from fossil fuels — will be necessary to avoid catastrophic levels of climate change, considering how much CO2 we’ve already pumped into the air.

Lately, enthusiasm has been building around technology that can pull CO2 directly out of the air. Microsoft, for example, pledged in 2020 to one day remove more CO2 than the company emits using this approach. Bill Gates’ climate investment fund also plans to funnel billions into developing the nascent technology.

Without those sorts of investments, the technology will likely stay too expensive to deploy at a meaningful scale. As it is, capturing carbon this way can cost upwards of $600 per metric ton — six times more than the cost per ton of CO2 that Gilchrist and his co-authors estimate it would take to use the more nature-based methods outlined in their new report.

The report proposes California allot $29 billion for natural methods of carbon sequestration through 2030. Much of that money would go towards building up facilities for producing and distributing compost, hiring and training staff to manage trees, working with farmers to implement sustainable practices, and giving incentives to farmers to switch to composting.

There are a few different ways composting can make a dent in carbon pollution. Compost is made from food or agricultural waste that might otherwise release greenhouse gases when sent to landfills. Instead, it’s used to nourish crops and grasses for livestock to graze. More productive croplands and pasture and healthier soils, in turn, are better at drawing down and sequestering CO2. Starting this year, California residents and businesses will be required to separate out their food and green waste from other garbage so that it can be composted.

The report also highlights the benefits of agroforestry, the practice of planting trees among crops and pastures. On top of taking in CO2 themselves, these trees can prevent erosion that causes soils to lose carbon. Planting a diversity of crops also improves soil health.

The analysis focuses only on working lands, but there are also more natural “carbon sinks,” like forests and wetlands, that could also play a role in fighting climate change. Those, however, are increasingly at risk from encroaching development and effects of the climate crisis like worsening wildfires and drought.

California’s water woes could also derail some of the strategies in Gilchrist’s report since plants and trees need water to grow and store carbon. Beyond that, the solutions in the new analysis will also need a lot of buy-in from policymakers and California residents.

Those obstacles are significant, says Stephen Hart, a professor of life and environmental sciences at the University of California Merced who was not involved in the analysis. Hart believes the report’s authors overestimated how quickly the state can implement such strategies and worries about whether they can be sustained over time. “The coordination of thousands of farmers, rangeland managers, etc. to meet their suggested targets would like[ly] take an organizational effort unmatched in the State’s history,” he writes in an email to The Verge. He also points out that some farmers concerned about crop yield may not want to switch from high-nitrogen synthetic fertilizers to compost, and worries about the emissions that might come with transporting compost.

While Hart sees efforts outlined in the study playing a small role in California’s climate action plans, he says efforts to draw down carbon shouldn’t take away from the most necessary step to take: stopping pollution from fossil fuels in the first place.

Update 4:20PM Jan. 26: This article has been updated to clarify the roles of the Climate Center and the Carbon Cycle Institute in producing the report.