agriculture

cleaning-up-cow-burps-to-combat-global-warming

Cleaning up cow burps to combat global warming

agriculture, cows, methane, Science / /
Cleaning up cow burps to combat global warming

Tony C. French/Getty

In the urgent quest for a more sustainable global food system, livestock are a mixed blessing. On the one hand, by converting fibrous plants that people can’t eat into protein-rich meat and milk, grazing animals like cows and sheep are an important source of human food. And for many of the world’s poorest, raising a cow or two—or a few sheep or goats—can be a key source of wealth.

But those benefits come with an immense environmental cost. A study in 2013 showed that globally, livestock account for about 14.5 percent of greenhouse gas emissions, more than all the world’s cars and trucks combined. And about 40 percent of livestock’s global warming potential comes in the form of methane, a potent greenhouse gas formed as they digest their fibrous diet.

That dilemma is driving an intense research effort to reduce methane emissions from grazers. Existing approaches, including improved animal husbandry practices and recently developed feed additives, can help, but not at the scale needed to make a significant global impact. So scientists are investigating other potential solutions, such as breeding low-methane livestock and tinkering with the microbes that produce the methane in grazing animals’ stomachs. While much more research is needed before those approaches come to fruition, they could be relatively easy to implement widely and could eventually have a considerable impact.

Knowable Magazine

The good news—and an important reason to prioritize the effort—is that methane is a relatively short-lived greenhouse gas. Whereas the carbon dioxide emitted today will linger in the atmosphere for more than a century, today’s methane will wash out in little more than a decade. So tackling methane emissions now can lower greenhouse gas levels and thus help slow climate change almost immediately.

“Reducing methane in the next 20 years is about the only thing we have to keep global warming in check,” says Claudia Arndt, a dairy nutritionist working on methane emissions at the International Livestock Research Institute in Nairobi, Kenya.

The methane dilemma

The big challenge in lowering methane is that the gas is a natural byproduct of what makes grazing animals uniquely valuable: their partnership with a host of microbes. These microbes live within the rumen, the largest of the animals’ four stomachs, where they break down the fibrous food into smaller molecules that the animals can absorb for nutrition. In the process, they generate large amounts of hydrogen gas, which is converted into methane by another group of microbes called methanogens.

The microbes that digest fiber—and those that produce methane—live mostly in the rumen, the first and largest of a cow’s four stomachs.

Enlarge / The microbes that digest fiber—and those that produce methane—live mostly in the rumen, the first and largest of a cow’s four stomachs.

Knowable Magazine

Most of this methane, often referred to as enteric methane, is belched or exhaled out by the animals into the atmosphere—just one cow belches out around 220 pounds of methane gas per year, for example. (Contrary to popular belief, very little methane is expelled in the form of farts. Piles of manure that accumulate in feedlots and dairy barns account for about a quarter of US livestock methane, but aerating the piles or capturing the methane for biogas can prevent those emissions; the isolated cow plops from pastured grazing animals generate little methane.)

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nitrogen-using-bacteria-can-cut-farms’-greenhouse-gas-emissions 

Nitrogen-using bacteria can cut farms’ greenhouse gas emissions 

agriculture, bacteria, Biology, climate change, fertilizer, nitrogen, Science / /

Keeping crops from the greenhouse —

Nitrogen fertilizers get converted to nitrous oxide, a potent greenhouse gas.

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A tractor amidst many rows of small plants, with brown hills in the background.

Fritz Haber: good guy or bad guy? He won the Nobel Prize in Chemistry in 1918 for his part in developing the Haber-Bosch process, a method for generating ammonia using the nitrogen gas in air. The technique freed agriculture from the constraint of needing to source guano or manure for nitrogen fertilizer and is widely credited for saving millions from starvation. About half of the world’s current food supply relies on fertilizers made using it, and about half of the nitrogen atoms in our bodies can be traced back to it.

But it also allowed farmers to use this newly abundant synthetic nitrogen fertilizer with abandon. This has accentuated agriculture’s role as a significant contributor to global warming because the emissions that result from these fertilizers is a greenhouse gas—one that has a warming potential almost 300 times greater than that of carbon dioxide and remains in the atmosphere for 100 years. Microbes in soil convert nitrogen fertilizer into nitrous oxide, and the more nitrogen fertilizer they have to work with, the more nitrous oxide they make.

Agriculture also leaks plenty of the excess nitrogen into waterways in the form of nitrate, generating algal blooms that create low-oxygen ‘dead zones’ where no marine life can live.

One way to reduce nitrogen emissions from farms would be to simply use fertilizer more efficiently. But—as we’ve seen with fossil fuels (and antibiotics and plastics)—when humans have a miraculous substance on our hands, we just can’t seem to use it at levels that minimize its impact. We instead seem compelled to throw around as much of the stuff as we can. But even if we were to start using less fertilizer now, we are past time to choose a single technique to curb greenhouse gas emissions; we need to put them all into action.

Denitrifying bacteria reduces levels of nitrous oxide in soil by converting it to the molecular form of nitrogen found in air. They use it as an oxidizer for respiration under conditions with low or no oxygen. So adding these nitrogen-respiring bacteria to soil could help decrease nitrous oxide emissions.

Modifying the microbiome of soil is just as hard as modifying the microbiome in our bodies. So instead of trying to promote the growth of any denitrifying bacteria that might happen to already be in soil, researchers decided to grow them externally and then add them in. Their source was partially treated sewage, called digestate, that was destined as organic fertilizer anyway. Keeping the digestate in oxygen-free conditions enriched their levels of one strain of nitrogen-respiring bacteria.

The researchers homed in on this particular strain because it has the enzyme needed to break down nitrous oxide, but not the enzymes used to make it from other nitrogen compounds. And although it is not the fastest, most efficient strain at nitrogen respiration, it won because it is the most tenacious: It grows to high concentrations even when oxygen is present, and it works well in soil.

When this digestate was mixed into soil, fertilizer-induced emissions were reduced by 50–95 percent, depending on the pH and organic carbon content of the soils. The effect lasted over the entire growing season. The presence of the added nitrogen-respiring bacteria did not seem to affect the indigenous microbiota already present in the soil, and the added bacteria did not carry genes for antibiotic resistance or pathogenicity, which is obviously essential if they are to be used in farming. What hasn’t been tested yet, however, is whether the presence of these bacteria influence the growth of crops.

Using mathematical modeling of future emissions, the researchers concluded that adding these bacteria to soil could reduce nitrous oxide emissions by 60 percent, and if they are added to all liquid manure systems in Europe, Europe could reduce its anthropogenic nitrous oxide emissions by 3 to 4 percent.

Nature, 2024.  DOI: 10.1038/s41586-024-07464-3

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some-states-are-now-trying-to-ban-lab-grown-meat

Some states are now trying to ban lab-grown meat

agriculture, climate change, lab-grown meat, Policy, Science, syndication / /

A franken-burger and a side of fries —

Spurious “war on ranching” cited as reason for legislation.

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tanks for growing cell-cultivated chicken

Enlarge / Cell-cultivated chicken is made in the pictured tanks at the Eat Just office on July 27, 2023, in Alameda, Calif.

Justin Sullivan/Getty Images

Months in jail and thousands of dollars in fines and legal fees—those are the consequences Alabamians and Arizonans could soon face for selling cell-cultured meat products that could cut into the profits of ranchers, farmers, and meatpackers in each state.

State legislators from Florida to Arizona are seeking to ban meat grown from animal cells in labs, citing a “war on our ranching” and a need to protect the agriculture industry from efforts to reduce the consumption of animal protein, thereby reducing the high volume of climate-warming methane emissions the sector emits.

Agriculture accounts for about 11 percent of the country’s greenhouse gas emissions, according to federal data, with livestock such as cattle making up a quarter of those emissions, predominantly from their burps, which release methane—a potent greenhouse gas that’s roughly 80 times more effective at warming the atmosphere than carbon dioxide over 20 years. Globally, agriculture accounts for about 37 percent of methane emissions.

For years, climate activists have been calling for more scrutiny and regulation of emissions from the agricultural sector and for nations to reduce their consumption of meat and dairy products due to their climate impacts. Last year, over 150 countries pledged to voluntarily cut emissions from food and agriculture at the United Nations’ annual climate summit.

But the industry has avoided increased regulation and pushed back against efforts to decrease the consumption of meat, with help from local and state governments across the US.

Bills in Alabama, Arizona, Florida, and Tennessee are just the latest legislation passed in statehouses across the US that have targeted cell-cultured meat, which is produced by taking a sample of an animal’s muscle cells and growing them into edible products in a lab. Sixteen states—Alabama, Arkansas, Georgia, Kansas, Kentucky, Louisiana, Maine, Mississippi, Missouri, Montana, North Dakota, Oklahoma, South Carolina, South Dakota, Texas, and Wyoming—have passed laws addressing the use of the word “meat” in such products’ packaging, according to the National Agricultural Law Center at the University of Arkansas, with some prohibiting cell-cultured, plant-based, or insect-based food products from being labeled as meat.

“Cell-cultured meat products are so new that there’s not really a framework for how state and federal labeling will work together,” said Rusty Rumley, a senior staff attorney with the National Agricultural Law Center, resulting in no standardized requirements for how to label the products, though legislation has been proposed that could change that.

At the federal level, Rep. Mark Alford (R-Mo.) introduced the Fair and Accurate Ingredient Representation on Labels Act of 2024, which would authorize the United States Department of Agriculture to regulate imitation meat products and restrict their sale if they are not properly labeled, and US Sens. Jon Tester (D-Mont.) and Mike Rounds (R-S.D.) introduced a bill to ban schools from serving cell-cultured meat.

But while plant-based meat substitutes are widespread, cell-cultivated meats are not widely available, with none currently being sold in stores. Just last summer, federal agencies gave their first-ever approvals to two companies making cell-cultivated poultry products, which are appearing on restaurant menus. The meat substitutes have garnered the support of some significant investors, including billionaire Bill Gates, who has been the subject of attacks from supporters of some of the state legislation proposed.

“Let me start off by explaining why I drafted this bill,” said Rep. David Marshall, an Arizona Republican who proposed legislation to ban cell-cultured meat from being sold or produced in the state, during a hearing on the bill. “It’s because of organizations like the FDA and the World Economic Forum, also Bill Gates and others, who have openly declared war on our ranching.”

In Alabama, fear of “franken-meat” competition spurs legislation

In Alabama, an effort to ban lab-grown meat is winding its way through the State House in Montgomery.

There, state senators have already passed a bill that would make it a misdemeanor, punishable by up to three months in jail and a $500 fine, to sell, manufacture, or distribute what the proposed legislation labels “cultivated food products.” An earlier version of the bill called lab-grown protein “meat,” but it was quickly revised by lawmakers. The bill passed out of committee and through the Senate without opposition from any of its members.

Now, the bill is headed toward a vote in the Alabama House of Representatives, where the body’s health committee recently held a public hearing on the issue. Rep. Danny Crawford, who is carrying the bill in the body, told fellow lawmakers during that hearing that he’s concerned about two issues: health risks and competition for Alabama farmers.

“Lab-grown meat or whatever you want to call it—we’re not sure of all of the long-term problems with that,” he said. “And it does compete with our farming industry.”

Crawford said that legislators had heard from NASA, which expressed concern about the bill’s impact on programs to develop alternative proteins for astronauts. An amendment to the bill will address that problem, Crawford said, allowing an exemption for research purposes.

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urban-agriculture’s-carbon-footprint-can-be-worse-than-that-of-large-farms

Urban agriculture’s carbon footprint can be worse than that of large farms

agriculture, farming, plants, recycling, Science, Sustainability, urban farming / /

Greening your greens —

Saving on the emissions associated with shipping doesn’t guarantee a lower footprint.

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Lots of plants in the foreground, and dense urban buildings in the background

A few years back, the Internet was abuzz with the idea of vertical farms running down the sides of urban towers, with the idea that growing crops where they’re actually consumed could eliminate the carbon emissions involved with shipping plant products long distances. But lifecycle analysis of those systems, which require a lot of infrastructure and energy, suggest they’d have a hard time doing better than more traditional agriculture.

But those systems represent only a small fraction of urban agriculture as it’s practiced. Most urban farming is a mix of local cooperative gardens and small-scale farms located within cities. And a lot less is known about the carbon footprint of this sort of farming. Now, a large international collaboration has worked with a number of these farms to get a handle on their emissions in order to compare those to large-scale agriculture.

The results suggest it’s possible that urban farming can have a lower impact. But it requires choosing the right crops and a long-term commitment to sustainability.

Tracking crops

Figuring out the carbon footprint of urban farms is a challenge, because it involves tracking all the inputs, from infrastructure to fertilizers, as well as the productivity of the farm. A lot of the urban farms, however, are nonprofits, cooperatives, and/or staffed primarily by volunteers, so detailed reporting can be a challenge. To get around this, the researchers worked with a lot of individual farms in France, Germany, Poland, the UK, and US in order to get accurate accounts of materials and practices.

Data from large-scale agriculture for comparison is widely available, and it includes factors like transport of the products to consumers. The researchers used data from the same countries as the urban farms.

On average, the results aren’t good for urban agriculture. An average serving from an urban farm was associated with 0.42 kg of carbon dioxide equivalents. By contrast, traditional produce resulted in emissions of about 0.07 kg per serving—six times less.

But that average obscures a lot of nuance. Of the 73 urban farms studied, 17 outperformed traditional agriculture by this measure. And, if the single highest-emitting farm was excluded from the analysis, the median of the urban farms ended up right around that 0.7 kg per serving.

All of this suggests the details of urban farming practices make a big difference. One thing that matters is the crop. Tomatoes tend to be fairly resource-intensive to grow and need to be shipped quickly in order to be consumed while ripe. Here, urban farms came in at 0.17 kg of carbon per serving, while conventional farming emits 0.27 kg/serving.

Difference-makers

One clear thing was that the intentions of those running the farms didn’t matter much. Organizations that had a mission of reducing environmental impact, or had taken steps like installing solar panels, were no better off at keeping their emissions low.

The researchers note two practical reasons for the differences they saw. One is infrastructure, which is the single largest source of carbon emissions at small sites. These include things like buildings, raised beds, and compost handling. The best sites the researchers saw did a lot of upcycling of things like construction waste into structures like the surrounds for raised beds.

Infrastructure in urban sites is also a challenge because of the often intense pressure on land, which can mean gardens have to relocate. This can shorten the lifetime of infrastructure and increase its environmental impact.

Another major factor was the use of urban waste streams for the consumables involved with farming. Composting from urban waste essentially eliminated fertilizer use (it was only 5 percent of the rate of conventional farming). Here, practices matter a great deal, as some composting techniques allow the material to become oxygen-free, which results in the anaerobic production of methane. Rainwater use also made a difference; in one case, the carbon impact of water treatment and distribution accounted for over two-thirds of an urban farm’s emissions.

These suggest that careful planning could make urban farms effective at avoiding some of the carbon emissions of conventional agriculture. This would involve figuring out best practices for infrastructure and consumables, as well as targeting crops that can have high carbon emissions when grown on conventional farms.

But any negatives are softened by a couple of additional considerations. One is that even the worst-performing produce seen in this analysis is far better in terms of carbon emissions than eating meat. The researchers also point out that many of the cooperative gardens provide a lot of social functions—things like after-school programs or informal classes—that can be difficult to put an emissions price on. Maximizing these could definitely boost the societal value of the operations, even if it doesn’t have a clear impact on the environment.

Nature Cities, 2019. DOI: 10.1038/s44284-023-00023-3  (About DOIs).

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a-locally-grown-solution-for-period-poverty

A locally grown solution for period poverty

agave, agriculture, materials science, Science, Sustainability / /

Absorbant agave —

A Kenyan tinkerer and Stanford engineer team up to make maxi pads from agave fibers.

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Image of rows of succulents with long spiky leaves and large flower stalks.

Enlarge / Sisal is an invasive species that is also grown agriculturally.

Women and girls across much of the developing world lack access to menstrual products. This means that for at least a week or so every month, many girls don’t go to school, so they fall behind educationally and often never catch up economically. 

Many conventional menstrual products have traditionally been made of hydrogels made from toxic petrochemicals, so there has been a push to make them out of biomaterials. But this usually means cellulose from wood, which is in high demand for other purposes and isn’t readily available in many parts of the globe. So Alex Odundo found a way to solve both of these problems: making maxi pads out of sisal, a drought-tolerant agave plant that grows readily in semi-arid climates like his native Kenya.

Putting an invasive species to work

Sisal is an invasive plant in rural Kenya, where it is often planted as livestock fencing and feedstock. It doesn’t require fertilizer, and its leaves can be harvested all year long over a five- to seven-year span. Odundo and his partners in Manu Prakash’s lab at Stanford University developed a process to generate soft, absorbent material from the sisal leaves. It relies on treatment with dilute peroxyformic acid (1 percent) to increase its porosity, followed by washing in sodium hydroxide (4 percent) and then spinning in a tabletop blender to enhance porosity and make it softer. 

They tested their fibers with a mixture of water mixed with glycerol—to make it thicker, like blood—and found that it is as absorbent as the cotton used in commercially available maxi pads. It was also as absorbent as wood pulp and more absorbent than fibers prepared from other biomaterials, including hemp and flax. Moreover, their process is less energy-intensive than conventional processing procedures, which are typically performed at higher temperatures and pressures. 

In a cradle-to-gate carbon footprint life cycle analysis, including sisal cultivation, harvesting, manufacturing, and transportation, sisal cellulose microfiber production fared roughly the same as production of cellulose microfiber from wood and much better than that from cotton in terms of both carbon footprint and water consumption, possibly because cotton requires so much upstream fertilizer. Much of the footprint comes from transportation, highlighting how useful it can be to make products like this in the same communities that need them.

Science for the greater good

This is not Odundo’s first foray into utilizing sisal; at Olex Techno Enterprises in Kisumu, Kenya, he has been making machines to turn sisal leaves into rope for over 10 years. This benefits local farmers since sisal rope and even sisal fibers sell for ten times as much as sisal leaves. In addition to making maxi pads, Odundo also built a stove that burns sawdust, rice husks, and other biodegradable waste products. 

By reducing wood stoves, he is reducing deforestation and improving the health of the women who breathe in the smoke of the cookfires. Adoption of such stoves have been a goal of environmentalists for years, and although a number of prototypes have been developed by mostly male engineers in developed countries, they have not been widely used because they are not that practical or appealing to the mostly female cooks in developing countries—the people who actually need to cook with them, yet were not consulted in their design.

Manu Prakash’s lab’s website proclaims that “we are dedicated toward inventing and distributing ‘frugal science’ tools to democratize access to science.” Partnering with Alex Odundo to manufacture menstrual products in the low-income rural communities that most need them seems like the apotheosis of that goal.

Communications Engineering, 2023. DOI:  10.1038/s44172-023-00130-y

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