“I think we’re going to enable a larger-scale use and adoption of it that could be meaningful to agriculture,” he says, adding: “These will become basically soil production facilities.” 

Concerns

Determining how well vermifiltration and other manure management approaches work will require more time and more research, experts say. 

Katharine Dickson, an agricultural emissions scientist who recently finished a postdoctoral program at UC Davis, says there should be in-the-field accounting to ensure that any of these methods are working as well as hoped—or to the degree government policy programs assume. All of which is tricky to achieve given the dynamic biological processes playing out in live animals and microbial communities on open farms, she adds.

“Vermifiltration, for example, depends on a live earthworm population whose performance is sensitive to temperature, moisture, and toxicity, and can shift with seasonal conditions or changes in herd size and manure characteristics on a given farm,” Dickson said in an email. 

The use of carbon credits to earn money from vermifiltration projects raises a different set of potential concerns. Most notably, if the methane decreases aren’t as significant as assumed, the projects could receive more credits than they deserve. 

There are more complicated issues as well. For the carbon credit system to make any real difference in the net amount of greenhouse gas in the atmosphere, it must produce emissions reductions that wouldn’t have occurred without that financial incentive. If it was going to happen anyway—as a result, say, of rich grants, legal pressures, or looming policies—the buyer of the credits can’t legitimately claim to have made any progress on its own climate emissions, says Grayson Badgley, a research scientist at CarbonPlan.

On that point, if California agriculture doesn’t meet its looming methane reduction targets, the carrots the state offers could be replaced by sticks: The California Air Resources Board recently began discussing rules that would force, rather than nudge, the sector to meet the 40% reduction required under the 2016 law.

“If lots of dairies are cleaning up their act ahead of pending regulation, it really does seem like the regulation, not offsets, is driving that action,” Badgley wrote in an email. “Trying to collect as many offsets prior to that deadline might adhere to the rules of the market, while still raising questions about whether those rules have enabled real climate action.”