Composting sequesters carbon and reduces emissions. Is it enough to fight climate change?

San Francisco celebrating 25th year of food scraps collection program

Matt Manna stood in front of a steaming pile of charcoal colored dirt on a tree-lined road near Lodi, watching the dark heap grow as it poured out from the bed of a semitruck.

This wasn’t just any dirt. This was high-grade compost made with San Francisco’s discarded food scraps. The black organic matter was quickly loaded into a smaller vehicle and spread through vineyards that Manna and his family have been farming in California’s Central Valley for generations.

Manna met his compost at the end of its journey. But once it returns to his soils, San Francisco’s food scraps will help bring forth the next crop of walnuts, cherries and wine grapes.

Matt Manna, director of operations at Manna Ranch, stands with a compost pile from San Francisco at one of his vineyard properties in Acampo (San Joaquin County). (Recology photo)

Matt Manna, director of operations at Manna Ranch, stands with a compost pile from San Francisco at one of his vineyard properties in Acampo (San Joaquin County). (Recology photo)

Turns out, The City’s compost is an intrepid traveler. Before being dumped on the side of this two-lane road, these scraps arrived from all over the world as bananas, bell peppers, eggs, and coffee beans. Once eaten and discarded, our food waste is transported to one of the largest composting facilities in the state, a few minutes outside of Tracy, where it begins a carefully monitored, 60-day decomposition process.

This year, San Francisco is celebrating the 25th year of its food scraps collection program — a major component of its zero waste and emissions reduction goals. It’s a program that has helped pave the way for a law that will require composting programs statewide. But as climate change continues to threaten the state with record-breaking temperatures, devastating fire seasons and more extreme droughts, will diverting food scraps from landfills be enough?

“From a climate perspective, we can’t just compost our way out of this mess,” said Alexa Kielty, the zero waste program coordinator at San Francisco’s Department of the Environment. But, she said, reducing The City’s overall waste can make a huge dent in easily avoidable emissions.

A worker monitors incoming compost waste on a receiving pick station at Recology’s Blossom Valley Organics facility in Vernalis (San Joaquin County). (Jessica Wolfrom/The Examiner)

A worker monitors incoming compost waste on a receiving pick station at Recology’s Blossom Valley Organics facility in Vernalis (San Joaquin County). (Jessica Wolfrom/The Examiner)

Compost, known colloquially as “black gold” for its high nutrient and microbial content, is essentially a concoction of decayed organic material that can be added to soil to help plants grow.

“Farmers want it for two reasons,” said Robert Reed, public relations manager for Recology, The City’s waste management company that runs the Blossom Valley Organics composting facility. “It’s going to help them grow more healthy food, and it’s going to help them save water because it softens the soil.”

San Francisco prides itself on being the first in the nation to mandate a citywide composting and recycling program, which started as a community-led initiative in the late 1990s. Today, most San Franciscans are familiar with separating their trash, organics and recyclables into three bins.

It’s a color-coded system that’s helped San Francisco keep 2.5 million tons of compostable material out of landfills since 1996, noted Reed.

Although The City failed to meet its goal to become zero-waste by 2020, a goal it set nearly two decades ago, it’s still considered a leader in large-scale municipal composting. And now, the rest of the state will be forced to follow suit.

Sorting San Francisco compost at Recology’s Blossom Valley Organics facility. (Recology photo)

Sorting San Francisco compost at Recology’s Blossom Valley Organics facility. (Recology photo)

A law going into effect Jan. 1 will require California cities, counties and special districts to reduce organic waste in landfills by 75% and rescue at least 20% of surplus food by 2025.

It’s part of an effort to curtail emissions of short-lived pollutants — things like methane, tropospheric ozone and black carbon that persist for a shorter period in the atmosphere but are known to cause more harmful impacts.

It’s “the biggest change to trash in California since we started recycling in the 1980s,” said Linda Mumma, spokesperson for CalRecycle, the agency that oversees the state’s waste management programs. “Food, yard and other organic waste rotting in landfills is a top source of climate super pollutants in the state, so cutting this waste is a vital part of our fight against climate change.”

Before working at Recology, William Ryan, a site foreman at the Blossom Valley Organics facility, never gave much thought to the sheer volume of waste generated by the Bay Area alone. Now, he sees the scraps we discard every day. “I didn’t realize how important this was until I started working here four years ago,” said Ryan. “It opened my eyes.”

Ryan meets our food waste in the middle of its journey: half-decayed, crammed into bio bags, mixed with milk cartons, coconut husks, and yard trimmings that are separated onsite.

But he also watches our trash transform. Within months, truckloads of sludgy scraps become dark, hot to the touch and buzzing with microbial activity. Black gold.

“We’re taking this, putting it back out into the Earth and it’s growing our food again,” said Ryan. “It’s a constant process, over and over and over.”

Sprinklers help the decomposition process and keep the compost pile’s temperature regulated. (Recology photo)

Sprinklers help the decomposition process and keep the compost pile’s temperature regulated. (Recology photo)

But despite decades of education campaigns, the wrong stuff still ends up here. Stuffed animals, metal scraps, the occasional plastic bag, a glass kombucha bottle. “I think people have underappreciated the learning curve involved,” said Sally Brown, a professor at the University of Washington who studies soils.

Another challenge to getting residents on board with city composting: “the stink factor,” as Kielty calls it. Letting food scraps rot in bins on the kitchen countertops was initially a hard sell, she said. “It’s taken 10 years to sort of normalize it.” But now, she said, “you see your neighbor doing it, you see a business doing it. Everywhere you go. You go to an event. You go to Gay Pride. There are green bins for composting.”

When done right, composting can have significant environmental benefits. It reduces the need for chemical fertilizers and helps soils retain water by increasing what is called bulk density, an indicator of soil compaction, which is critical in a drought-stricken and wildfire-prone state.

“It’s like California Closets for your soil,” said Brown. “Instead of just throwing everything on a heap on the floor, you put it in the appropriate units, and all of a sudden you have a lot more space. So water can soak in much more quickly. And also, there’s a lot more space for water to hang around, so this reduces your irrigation needs.”

When the Hennessey Fire surrounded Matthew Englehart’s Be Love Farm in Vacaville on three sides, the moisture in the compost helped stop the flames in their tracks, said Reed.

Compost can also help sequester carbon in the soil. “For climate change and for healthy soils and for regenerative agriculture, increasing soil carbon is your single most important tool — and the one tool that works the best and the fastest is returning organics to the soil,” said Brown.

  • But for farmers like Manna, using compost just makes good sense. Standing near his tidy rows of just-harvested vines, he said, “you take a lot off these vines, right? So, we got to give them something back. If they don’t get any love back, they don’t keep giving.”

jwolfrom@sfexaminer.com

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