Methane From Agriculture Is a Big Problem. We Explain Why. | Civil Eats

Methane From Agriculture Is a Big Problem. We Explain Why.

Agriculture and waste are the largest sources of the greenhouse gas, which scientists say is one key to limiting catastrophic warming fast.

a farmer looks at his beef cows and wonders how they produce so much methane.

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When it comes to cutting emissions in the food system to prevent catastrophic climate change, methane is key. Tackling carbon dioxide (CO2) emissions has long been the focus of most climate action because CO2 accounts for 80 percent of all greenhouse gas (GHG) emissions in the U.S. and can persist in the atmosphere for hundreds—or even thousands—of years. In contrast, methane makes up only about 10 percent of GHG emissions in the U.S. (and 20 percent globally) and only sticks around for about a decade.

However, its global warming potential is an estimated 25–35 times greater than CO2 over a 100-year period, and methane concentration in the atmosphere has been increasing rapidly since 2007, much faster than CO2. And yet, because of its short-term lifespan, experts say cutting methane emissions now could help prevent catastrophic short-term outcomes, as we wait for more long-term investments in CO2 emissions reductions to pay off.

In other words, if we compared responses to the climate crisis to responses to a hunger crisis, cutting methane would be emergency food aid and cutting carbon dioxide would be raising wages and ending systemic racism.

“Since methane is such a potent greenhouse gas, the nice thing about reducing [those] emissions is that you can slow warming more quickly,” said Richard Waite, a senior research associate at the World Resources Institute (WRI) who studies the food system’s climate impacts.

Here’s a breakdown of the methane problem within the U.S. food system and a look at the most effective solutions.

Animal Agriculture: Problem & Solutions

Between 1990 and 2019, emissions of all three greenhouse gases from agricultural production (not including land use) went up. But while CO2 and nitrous oxide (N₂O) emissions both increased by about 10 percent, methane emissions went up 17.5 percent. Methane from enteric fermentation—burps from ruminant animals, primarily dairy and beef cattle—is the number-one source of emissions, and experts say the best short-term solution is to tweak what those animals eat.

“If we compared responses to the climate crisis to responses to a hunger crisis, cutting methane would be emergency food aid and cutting carbon dioxide would be raising wages and ending systemic racism.”

“Ultimately it’s about . . . how can you make livestock feed more digestible,” said Mamta Mehra, a researcher at Project Drawdown.

Researchers are looking into that question from various angles, and a few feed additives are already in use, although most are still being studied for efficacy or have yet to be approved by regulators. Recently, Brazil and Chile approved the use of Bovaer, an additive also referred to by the name of its active ingredient, 3-NOP, which is made from nitrate and alcohol. Trials have shown that it could reduce methane emissions between 20 to 90 percent, although there are some questions about how long the effects might last.

Feed additives made from a red seaweed called asparagopsis taxiformis have also shown potential to reduce enteric methane emissions, but questions remain about whether the seaweed can be harvested or grown sustainably at the scale necessary. Enteric fermentation can also be reduced on pastures that include a diverse mixture of grasses and legumes, and research is underway to identify the best combination of plant species for low-emissions grazing.

The other major source of methane emissions from animal agriculture comes primarily from concentrated animal feeding operations (CAFOs). In the U.S., those emissions are the third-largest source of greenhouse gases from agriculture. Over the last two decades, as the dairy and pork industries have both moved toward larger, more concentrated production systems with liquid waste lagoons, those emissions have grown the fastest, increasing by 68 percent between 1990 and 2019.

The most popular solution to this issue to date is to build methane digesters, which capture emissions while also producing energy. Digesters can cut emissions from CAFOs, but opponents point to their high costs and other drawbacks, such as their potential to accelerate consolidation and concentration in industrial animal agriculture, which can have other negative effects on the environment and local communities.

Mehra said Project Drawdown is looking at alternative methods for managing manure, especially on smaller farms, such as covering lagoons and reducing the quantity of waste stored at a time. Solutions that acidify the waste or introduce oxygen also showed promise. Of course, moving away from liquid waste altogether would also eliminate that source of methane emissions, but that would require a massive transition to pasture, and there are other factors to consider on that front.

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Marcia DeLonge, a senior scientist in the Food & Environment Program at the Union of Concerned Scientists, said when cattle eat grass alone, the roughage can increase enteric methane emissions, and N₂O emissions from manure on pastures can increase. However, if the pasture is well-managed, COcan be stored in the soil, reducing overall emissions and providing other ecosystem benefits. Emissions related to growing grain for feed are also eliminated. It’s a good example, she said, of how while zooming in on methane is important, it’s also crucial to examine its impacts within a holistic context.

“In agriculture and food systems, methane, nitrous oxide, and carbon dioxide all matter so much, and they interact within systems,” she said. “When you introduce solutions that can improve the footprint of one, sometimes you can increase another one inadvertently.” For that reason, she adds, it’s important to keep an eye on them all.

The intersecting impacts of different greenhouse gases, for example, is why groups like WRI recommend prioritizing cutting beef consumption in higher-income countries like the U.S. as one of the most effective food-and-climate solutions. Doing so would cut enteric methane emissions from cattle while also cutting N₂O and CO2 emissions from feed production and land use. Waite calculated that if meat consumption from ruminants in countries that currently overeat meat declined to about 50 calories a day—or 1.5 burgers per person per week, to about half of current U.S. consumption levels—10 billion people could eat without any expansion onto new land, avoiding the CO2 emissions from deforestation.

Rice: Problem & Solutions

Rice has a tiny climate impact per gram of protein compared to beef or dairy. Still, it ranks fourth in terms of GHG emissions from agriculture in the U.S. because bacteria that produce methane thrive in flooded paddy fields and a portion of that methane is released into the atmosphere by the plants. This matters in a big way globally, Mehra said, because rice is the third largest crop in the world and provides one-fifth of the calories consumed worldwide.

Improved rice cultivation is among the top 25 solutions,” she said, in terms of overall climate action.

This involves farmers tweaking their practices to flood the fields for a shorter time, using techniques like alternate wetting and drying, reducing tillage and nutrient applications, and improving rice breeding.

Rice can also be grown without flooding, thereby eliminating most methane emissions, using a set of practices called System of Rice Intensification (SRI). The method has been shown to increase yields per acre and it has additional environmental benefits, but it’s primarily practiced on small farms in Africa and Asia because it is so labor-intensive. Researchers and farmers are working on mechanizing versions of SRI in the U.S. and elsewhere to scale up its production.

Food Waste: Problem & Solutions

It’s well known that food that ends up in landfills emits methane as it breaks down. In the U.S., landfills are the third-largest source of methane emissions, and account for about 20 percent of global emissions. While it is difficult to parse out what percentage of that methane comes from food, according to the U.S. Food and Drug Administration, wasted food is the single largest category of material that ends up in municipal landfills.

“If we’re talking about any piece of food waste. . . we’re not just talking about the methane. That food was produced in a way that led to a whole suite of other emissions.”

According to the nonprofit ReFED, roughly 35 percent of food produced in the U.S. in 2019 went to waste, and stemming that tide presents an immense opportunity to cut methane emissions. Solutions that keep food out of landfills (as opposed to just trapping methane, for example) can also eliminate the emissions involved in producing that food.

“If we’re talking about any piece of food waste . . . we’re not just talking about the methane. That food was produced in a way that led to a whole suite of other emissions,” DeLonge explained. “Somebody had to grow that food, it had to be transported, it had to be stored, and maybe refrigerated, etc.” For that reason, reducing food waste is at the very top of the list of Project Drawdown’s climate solutions.

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In low-income countries, the most effective strategies often involve improving storage and transportation infrastructure, while in richer countries like the U.S., they tend to be clustered on the consumer side. ReFED’s ranking of U.S. food waste reduction strategies places smaller portion sizes in restaurants and other food service locations, consumer education campaigns, and centralized composting at the top of the list.

While the problem and solutions are big and complex, the U.N.’s Global Methane Assessment makes it clear that simply implementing the existing strategies would reduce methane emissions 40-45 percent by 2030, the amount the IPCC said was necessary—alongside other greenhouse gas reductions—to limit warming to 1.5°C this century. A large proportion of that reduction could come from farming differently, shifting to lower-meat diets, and wasting less.

The researchers found that doing so would also have co-benefits, including preventing premature deaths and avoiding crop losses caused by the formation of ground-level ozone, another product of methane emissions.

“We have this amazing suite of options, and we can leverage them all. We just need to be really thoughtful about where we implement them,” DeLonge said.

Lisa Held is Civil Eats’ senior staff reporter and contributing editor. Since 2015, she has reported on agriculture and the food system with an eye toward sustainability, equality, and health, and her stories have appeared in publications including The Guardian, The Washington Post, and Mother Jones. In the past, she covered health and wellness and was an editor at Well+Good. She is based in Baltimore and has a master's degree from Columbia University's School of Journalism. Read more >

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  1. Stefhan Gordon
    Enteric methane is a red herring. Thousands of things emit methane via methanogenesis from plankton to trees to shellfish to beaver ponds to termites to cockroaches. Any soil ecosystem or digestive tract that contains methanogenic archaea emits methane......and methanogenic archaea are all over the places in soil ecosystems and animal microbiomes including human microbiomes.

    So why aren't we inundated by all this methane? Because it's broken back down to cyclical Co2 and H2O to a small extent by methanotrophs in soil and to a very large extent by hydroxyl radicals in the troposphere.

    What happens to cyclical CO2? It's fixed again by photosynthesis into a myriad of carbon compounds including the cellulose that ruminants consume. So cattle are cycling and recycling the same carbon over and over again just like what occurs wherever other biogenic methane is emitted.

    One should also note that WRI has received a lot of funding from the BMGF so WRI "coincidently" pushes plant based analogs as options to beef...and "coincidently" these plant based analogs aligned with the investment interests of the BMGF.
  2. Barbara
    A cousin is a generational dairy farmer. For short money built a methane converter. Generated enough electricity to power 3 families homes and the farm and milk parlor. Utilized a fallow field to to semi dry, the now methane free poop, packaged and sells the end product as organic fertilizer. Win win! An easy, ecologically sound, money saver and money producer. If a small farmer could do that then big factory farms could too! Short, sweet and to the point. Why not spend the thousands of dollars for researching “specialized” food (which could end up being as bad as GMO’s) into research into the best converters and grants for building them. Small farms would be able to save money. Large factory farms would be able to make money by selling excess electricity to the power companies. Lots of farmers, large and small would benefit from the fertilizer. Again win win! It’s something that could be implemented in short order. I’ve always been a believer in… work smarter not harder!
    • Bernard Nagelvoort
      Barbara - Take a look at Mason/Dixon Farm near Gettysburg, PA. Built anaerobic digestion system in 1979. 1800 cows then - now 2100. Methane generated burned in Cat converted diesels to produce all electricity needed on farm plus excess to grid.
      Now store effluent in covered ponds for irrigation on cropland producing most of feed for cows - with odors controlled.
      Residual solids from digester recovered in solids separator and marketed
      This is what big factory farms can afford to do, but smaller dairies need $ help.

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