ROBERT REED CRAWLED UP on a massive pile of food scraps and yard trimmings and sat down. He buried his hands and rooted around a bit, grinning at his colleague, Kirk Steed. But instead of responding with a grimace of distaste, Steed merely smiled.
“Nice,” he said.
And it was nice. That’s because the pile wasn’t an oozing, reeking mass of disintegrating banana peels and moldy pasta from the back of the fridge. It was a dark, slightly moist pile of odorless granular material. Yes, it had once been literal garbage — but now it was transformed into utterly different stuff: compost.
And because it had been transformed, it not only was sensorially inoffensive — it had real value as a nutrient-rich soil amendment.
Due largely to geopolitics, interest in compost is spiking in the farming community. Modern nitrogen and phosphate fertilizers are mostly created from natural gas, so one of the best places to make it is the Middle East, where gas is plentiful and cheap. The countries around the Persian Gulf produce about one-third of the world’s artificial fertilizers, and that crucial supply is now bottled up thanks to the war with Iran.
“It’s really squeezing the farmers,” said Reed, the spokesman for Recology, one of the largest trash management companies in California and an innovator in composting green waste. “Compost enriches soil over the long-term and greatly enhances its structure and water-retention properties. Growers are aware of this, of course — and now with the war on and fertilizer in short supply, they want as much as they can get. We’re selling or giving away all we can make.”
And for the record, Recology makes a lot of compost. The company partnered with the city of San Francisco to launch an inaugural curbside pick-up program for green waste in the city in 1996. In the subsequent 30 years, almost 3 million tons of San Francisco’s compostable material has been diverted from landfills to farms, parks and gardens. Today, Recology operates eight composting facilities along the West Coast, collectively processing 1.5 million tons of compostable green waste annually.
Spreading worldwide
San Francisco’s — and Recology’s — success in establishing large composting programs has drawn increasing national and global attention.
“Today, Recology provides curbside composting collection service to about 100 California cities,” said Reed, “and cities across the country are following suit. New York City, Portland [Oregon], Seattle, Denver and Austin all have programs, and 135 countries have sent delegations to San Francisco to learn about urban composting.”
San Francisco’s program also motivated France to pass a national law requiring every city to encourage composting for all homes and businesses, said Reed. And in California, urban composting got a huge boost with the 2024 passage of Senate Bill 1383, which required most cities and counties to provide organic waste collection; the legislation also incentivized jurisdictions to donate finished compost to local farmers.
Reed observed the benefits of city-scale composting are manifold: the programs conserve landfill space, reduce landfill methane emissions, sequester carbon in the soil rather than releasing it as planet-warming CO2 into the atmosphere, and — perhaps most notably — provide farmers with a sustainable source of fertilizer.
Steed, a Recology general manager who oversees two of the company’s composting facilities, said artificial fertilizers and compost must be viewed differently. Chemical fertilizers, he said, “are like steroids for a guy who’s bodybuilding. He takes them, and boom — big muscles, and fast. But there are often health complications. Compost is more analogous to someone who works out for long-term fitness and conditioning, not a huge build. The objective is health — for the soil and the crops.”
That’s also how Zoe Davis, the owner and operator of Full Circle Farm, sees it. Davis produces row crops, fruit, cut flowers and eggs on her 5-acre property near Gilroy, and she uses a lot of Recology compost — about 80 tons a year.
“My career was in microbiology, and to a large extent it still is,” said Davis. “The only difference is that I used to work in a lab, and now I work on a farm.”
“Compost enriches soil over the long-term and greatly enhances its structure and water-retention properties. Growers are aware of this, of course — and now with the war on and fertilizer in short supply, they want as much as they can get. We’re selling or giving away all we can make.”
Robert Reed, Recology
Davis explained that compost doesn’t “feed” plants directly, as artificial fertilizers do.
“It feeds the microbes in the soil that break down the nutrients in the compost, making them available to the plants,” she said. “Artificial fertilizers are essentially salts, and they reduce the microbial community, making it almost impossible to build soil health. That’s why you need to apply them directly to each crop each year. Compost, on the other hand, builds and sustains soil fertility over the long term.”
That said, most growers should probably avoid going cold turkey on quitting artificial fertilizers, Davis said.
“You’re going to have an extremely sharp decline in productivity for at least the first year if you do a hard stop,” she said.
The perfect recipe
Making compost on an industrial scale requires a lot of space and heavy equipment; strict processing protocols are also followed to ensure stinky kitchen scraps and leaves proceed in an expeditious fashion to finished compost within 60 days.
Things start off with an “active static pile,” or ASP, said Steed.
“We shred the material to reduce the surface volume, add water to get it to the right moisture level, pile it up, and induce airflow through the pile with a large blower,” Steed said.
As the material is decomposed by microorganisms, it heats up — which is a good thing, given that that it indicates the pile is actively transforming into compost.
“But we don’t want it to get too hot, or it will kill the microorganisms needed to create the final product — or even spontaneously combust,” Steed said.
The material “cooks” in the ASP for 30 days, after which it is pushed into windrows, moistened, and turned by heavy equipment once or twice a week. After “curing” for another 30 days, it is usually ready for final processing.
“You generally can tell when it’s ready by the appearance,” said Steed. “It’s uniformly dark — the materials in an ASP, by contrast, are lighter and more varied in color.”
The finished compost is then screened, separated by size, and graded. Some material is discarded completely due to contamination or inadequate decomposition; it goes to a landfill or is used as a “biocover” on the windrows and piles. Of the mid-grade compost, some is taken by Caltrans or other agencies for landscaping along highways. Some of it goes to farmers.
The top-end product is inoculated with earthworms for further reduction, ultimately producing the crème de la crème of compost — “vermicompost,” the stuff that Reed pawed through. This exclusive product is in particularly high demand by farmers.
Recology also adds soil amendments to their compost on request.
“We can customize the product for different growers,” said Steed as he and Reed strolled through a section of the Jepson Prairie Organics yard heaped with large piles of various materials.
“These are all different amendments,” Steed explained, surveying the stock. “Depending on soil requirements, we can add gypsum, coco coir [coconut husk fiber] sandy loam, redwood fines — whatever is needed.”
A slight improvement
Compost is no panacea for fertilizer shortfalls. With reduced artificial fertilizer availability, global food shortages are a real possibility, and skyrocketing prices are a certainty; there’s simply not enough compost available to completely make up for tight supplies. Compost is also bulky, and handling and spreading it may impose more fuel and labor costs than applying manufactured fertilizers.
But as Steed and Reed observe, compost continually improves soil even as it produces yearly crops, mitigates greenhouse gas emissions and reduces the waste stream going to landfills.
“We’ve shown its benefits, the interest is growing — but there’s a lot more left to do,” Reed said. “About one-third of the waste generated in the U.S. can be — and should be — composted.”
One impediment in accelerating municipal composting is a certain lack of public awareness — or perhaps concern. Contamination — specifically, plastic contamination — is a huge problem for industrial composters. Removing as much plastic as possible from the waste stream is both a priority and headache for Recology at all its composting sites. At Jepson Prairie, lofty piles of plastic await landfill disposal, and scraps of plastic are whipped by the wind across the yard.
“Unfortunately, we can’t control what the public puts into their green waste bins,” said Reed, “and plastic bags and bottles are a major problem. That includes the new so-called ‘compostable’ plastic bags you now see in supermarkets. They’re not compostable. They simply degrade relatively quickly into tiny pieces — microplastics. In some ways, that makes the problem worse.”
All challenges aside, geopolitical tensions, food supply worries and environmental concerns are conjoining to give compost its moment.
“Farmers clearly see the benefits,” said Davis. “We feed the community, and the community feeds the farms through the green waste that they generate. It’s a virtuous circle.”