Are manure digesters actually combating climate change?

dairy cows in freestall barn
(Farm and Dairy photo)

If today’s California is what the rest of America will look like tomorrow, you might want to brace yourself for too little water, too much animal manure, and $4.65-per-gallon gasoline.

And, weird, too, because in California these too-little, too-much, and too-expensive elements have been combined to create what was thought to be a partial cure for climate change.

The first, water, is precious. The same amount of municipally-supplied water that costs $23 a month in Nebraska costs $65 a month in the Golden State. Only 20% of all water, however, flows to 39 million Californians; agriculture gulps the other 80%.

Thirsty crops, right? More like thirsty livestock: “47% of California’s water footprint is associated with the production of meat and dairy,” reports the Sacramento-based Comstock’s Magazine.


Animals and water — no matter the livestock or the state — means manure. In California, that combination also means taxpayer subsidies to build manure handling systems to capture methane generated in anaerobic digesters to be burned by vehicles or put into the natural gas grid.

That recipe sounds like a two-birds-with-one-stone solution to ag’s two growing problems, increased methane pollution from a deepening dependence on confined animal feeding operations and animal ag’s growing role in global climate change — or at least it did until manure digesters were built and monitored.

Their early results were worse than poor, according to a January report on manure digesters by Reuters. In fact, the results were dismal.

“In 2009,” the story noted, “the Obama administration and an industry group, the Innovation Center for U.S. Dairy, pledged to reduce the industry’s greenhouse gas emission by 25% by 2020 over levels in 2007, in part by expanding federal support for new digesters.”

Bigger problems

“Instead, methane emissions in the sector have risen more than 15%, in part driven by growth in herd size … ” In short, one solution — methane-making manure digesters — led to a second, bigger problem, more manure-making cows.

That’s just basic ag economics, explained Rebecca Wolf of Food & Water Watch, an environmental watchdog group, in the Reuters story: “If you start making money off of pollution, you’re not going to stop polluting.”

Indeed, pollution grows with digesters because livestock numbers grow with digesters.

States like Iowa, however, are choosing to ignore the acrid evidence. Recently, Iowa enacted a digester-promoting law that, according to the Cedar Rapids Gazette, not only doesn’t worry about livestock expansion it “allows Iowa animal feeding operations to exceed confinement capacity if [farmers] install an anaerobic digester to treat all manure…”

Uncle Sam wants in the bigger CAFOs/bigger digester game, too.

The Biden Administration’s still-unpassed, $1-trillion-plus Build Back Better program contains a river of federal subsidies to promote “climate mitigation” strategies like manure digesters in the coming years.

Flatten the trend

Some ag researchers, however, want to flatten that rising trend.

In a Dec. 14 podcast titled “On biodigesters — are they a real win-win technology?” three University of Iowa research professors, Silvia Secchi, Chris Jones and Dave Cwiertny, agreed that Iowa’s new focus on digesters as a solution to the state’s overwhelming livestock manure problem almost guarantees more and bigger CAFOs in Iowa and even more unmanageable manure.

“If this is such a winning proposition for farmers,” noted Secchi, an economist and geographer, in the episode, “why should public money be spent on it; why not private investment?”

Secchi goes on to add, “We are rushing headlong into these so-called solutions because they have this ‘feel-good’ factor like ‘soil health’ but don’t yet have the results to prove it.”

California, however, now faces some digester indigestion. Recently, noted Reuters, “Environmental groups petitioned the California Air Resources Board to make [manure digesters] ineligible for [state] credits, arguing their presumed role in combating climate change was inflated and that the credits encourage making more manure.”

Which California — and the rest of the U.S. and its taxpayers —neither need nor want.


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Alan Guebert was raised on an 800-acre, 100-cow southern Illinois dairy farm. After graduation from the University of Illinois in 1980, he served as a writer and editor at Professional Farmers of America, Successful Farming magazine and Farm Journal magazine. His syndicated agricultural column, The Farm and Food File, began in June, 1993, and now appears weekly in more than 70 publications throughout the U.S. and Canada. He and spouse Catherine, a social worker, have two adult children.


  1. The conclusion “digesters lead to more cows” is an apples and oranges comparison. How does the existence of digesters cause the herd to grow? Farmers produce what they can sell profitably (or, all too often… unprofitably!). Common sense would say that if the herd grew, it was because consumer demand grew. It’s also hard to tell from the article what the “15% growth in methane” was related to – is that since 2007? 2009? How much did the US population grow during whatever period in which the 15% in methane growth was measured? Whether methane emissions growth outstripped demand driven by population growth (or not) is a key fact to allow judging whether it is even possible that digesters are helping.

    Of course, a larger herd produces more methane, but why blame it on digesters? Now, if the digesters are leaking methane or are otherwise causing greenhouse gas emissions (for example, maybe they need boatloads of diesel engines to stir the manure), please give the reader the breakout of where digesters’ greenhouse gas emissions come from, not just “animal production produced 15% more methane” which is inaccurate and misleading.

    Now, if the argument is that digester methane contributes to greenhouse gases when burned, then to be intellectually honest, we need to know the numbers on whether it somehow increased the overall amount of natural gas burned. My impression is that the digester methane offsets gas that comes from drilled wells, but I don’t have that data.

    When judging whether digesters are good or bad to have, is vitally important to know what the practical on-the-ground alternative to digesters is. I suspect it is huge heaps of manure or lagoons – both of which simply emit their methane into the atmosphere. Are methane-capturing digesters somehow worse, net greenhouse gas wise, than “no digesters”? The article seems to imply that, but that seems to defy logic.

    An article such as this one should cite the numbers and give sources, not just make broad-brush unsupported assertions about digesters – otherwise the readers may come to the (erroneous? correct?) conclusion that digesters are a bad thing.


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