When Sally Brown finds herself with food scraps and no available compost pile, she takes matters into her own hands.

“I’ll surreptitiously put it outside,” said Brown, a research professor and soil scientist at the University of Washington.

“Compost is a way to effectively feed your soil,“ she said. “When I go someplace where there’s no composting, I get very upset.”

Brown does that because organic material exposed to oxygen — you know, decomposing in a compost pile or surreptitiously tossed behind a bush — creates CO2. But organic material rotting in landfills creates methane, which has a much larger climate impact than CO2. “So getting stuff that rots out of landfills is a very cheap way to quickly reduce carbon emissions,” said Brown. 

At least, in theory. 

Landfills account for roughly 14% of all U.S. methane emissions, according to the Environmental Protection Agency. This means that that slice of the emissions pie could get way smaller if we were better at closing the gap between organic waste producers — households and businesses — and compost users. 

The problem is that most of us don’t live near farms that can readily use the lawn trimmings or avocado skins produced in our homes. That’s where companies like Agromin come in. 

Agromin is one of the largest organics recyclers in California. Bill Camarillo, the company’s co-founder and CEO, said his company handles about 1.2 million tons of organic waste per year but hopes to make that 10 million tons over the next decade. “I’m on a 10 million ton march,” he said. 

In a receiving yard in Santa Paula, California, about an hour from Los Angeles, trucks carrying green waste collected from households and businesses dump material onto large piles. “But as you can see, this material hasn’t been cleaned yet,” said Camarillio.

A couple of employees were pulling plastic bags and other noncompostable garbage out by hand. Once that’s done, the waste gets pushed into a grinder to create more surface area, which helps speed the decomposition process. 

Roughly 80% of Agromin’s revenue comes from something called tipping fees. Cities and private companies that haul waste pay Agromin about $60 per ton to accept the organic material their trucks collect. 

Camarillo said the other 20% of the company’s revenue comes from turning that waste into mulch or soil additives that farmers, landscapers and individual gardeners can buy. “It’s kind of like a vitamin we put back in the ground that’s alive,” he said. 

The material here is mostly yard and farm waste; there were piles of rotting lemons discarded from a nearby grove. 

After cleaning and grinding that material down, Agromin moves it to an adjacent yard for “finishing. “And you’ll notice a distinct difference in odor,” Camarillo said. “Not that this is bad — smells like money to me — but if you go to the other side, it smells very earthy.”

Decomposition naturally raises the temperature enough to kill pathogens. The entire process — from the time the material hits the ground to being ready for application on a farm — takes at least 45 days. “Then, it’s off in a truck going to a ranch somewhere,” Camarillo said. 

One factor driving this industry forward is a California law known as SB 1383, which requires cities to divert more organics from landfills and purchase a certain amount of finished compost based on the number of residents in their communities. It’s meant to pull on both the supply and demand sides of the compost market.

That law has helped Agromin grow its business as a compost broker for jurisdictions trying to comply. 

“So, I’ll just take a city of Ventura as an example,” Camarillo said. “They called me three years ago and said, ‘What am I supposed to do with 8,000 tons of compost?’”

For some jurisdictions, Agromin helps identify ways to use that material, such as on parklands or in city landscaping. For others, they find farmers and other end-users willing to accept the compost.

“We partner with a farmer under a direct service provider agreement, where the farmer agrees to accept the compost from the city that the city buys and will pay for the delivery and the spreading so the city only has to buy the compost,” Camarillo said. 

One thing that helps reduce that costs is putting compost facilities closer to compost users. The Santa Paula facility is actually on farmland owned by a company called Limoneira, which grows citrus and avocados. 

“This is where we are applying all the stuff that comes from Agromin,” said Edgar Gutierrez, Limoneira’s director of farming operations, in a field of avocado plants sitting on mounds of mulchy compost. 

There are visible reminders that the compost there once came from a landscaping operation or someone’s green bin, like a piece of blue plastic or a chunk of a wooden shipping pallet. But mostly, it just looks like dirt. 

“It’s basically giving life to that soil,” said Gutierez. Eventually, that soil will grow avocados — the skins of which we mostly throw away.