December 12, 2006
Blame Cows Before Cars For Greenhouse Gases

Cows have been getting too little blame and SUVs too much blame for the rise of atmospheric greenhouse gass concentrations.

A new report from FAO says livestock production contributes to the world's most pressing environmental problems, including global warming, land degradation, air and water pollution, and loss of biodiversity. Using a methodology that considers the entire commodity chain, it estimates that livestock are responsible for 18 percent of greenhouse gas emissions, a bigger share than that of transport. However, the report says, the livestock sector's potential contribution to solving environmental problems is equally large, and major improvements could be achieved at reasonable cost.

Based on the most recent data available, Livestock's long shadow takes into account the livestock sector's direct impacts, plus the environmental effects of related land use changes and production of the feed crops animals consume. It finds that expanding population and incomes worldwide, along with changing food preferences, are stimulating a rapid increase in demand for meat, milk and eggs, while globalization is boosting trade in both inputs and outputs.

Grazing uses a quarter of the land surface of the Earth. Think about what that means as populations increase and humans all over the world use rising affluence to move out into newly created suburbs. Land supplies are inadequate. The human race has gotten too big.

Deforestation, greenhouse gases. The livestock sector is by far the single largest anthropogenic user of land. Grazing occupies 26 percent of the Earth's terrestrial surface, while feed crop production requires about a third of all arable land. Expansion of grazing land for livestock is a key factor in deforestation, especially in Latin America: some 70 percent of previously forested land in the Amazon is used as pasture, and feed crops cover a large part of the reminder. About 70 percent of all grazing land in dry areas is considered degraded, mostly because of overgrazing, compaction and erosion attributable to livestock activity.

To the fans of biomass energy: Hasn't enough of the Amazon already been lost to pasture land? Do we need to make it worse by promoting the destruction of the rain forests in the name of biomass energy environmentalism?

Livestock are responsible for 37% of anthropogenic methane (i.e. methane produced as a result of human activities).

FAO estimated that livestock are responsible for 18 percent of greenhouse gas emissions, a bigger share than that of transport. It accounts for nine percent of anthropogenic carbon dioxide emissions, most of it due to expansion of pastures and arable land for feed crops. It generates even bigger shares of emissions of other gases with greater potential to warm the atmosphere: as much as 37 percent of anthropogenic methane, mostly from enteric fermentation by ruminants, and 65 percent of anthropogenic nitrous oxide, mostly from manure.

Methane is probably the biggest greenhouse gas problem with livestock. As a greenhouse gas methane is about 21 times more potent than carbon dioxide by weight. Rising world affluence translates into rising demand for meat and that means more cows, sheep, and other methane producers.

But methane from livestock strikes me as (at least in theory) a much more tractable problem than carbon dioxide from fossil fuels burning. The potential exists to capture dairy cow methane when they are in buildings. Also, feeds greatly differ in their effects on methane production and cow bacteria balances could be manipulated to lower methane production. Biotechnology could drastically cut back on livestock methane production.

The use of fossil fuels in agriculture is more problematic for the same reason that the use of fossil fuels is so intractable in other human activities. Until other energy sources become cheaper than fossil fuels the rising demand for livestock and fancier food in general is going to cause a rising demand for fossil fuels.

Livestock compete with wild animals for land area. As the human race becomes more affluent the amount of animal biomass that will be wild is going to decline. This'll drive more species to extinction. (So will medical treatments that allow humans to live in high disease areas.)

The sheer quantity of animals being raised for human consumption also poses a threat of the Earth's biodiversity. Livestock account for about 20 percent of the total terrestrial animal biomass, and the land area they now occupy was once habitat for wildlife. In 306 of the 825 terrestrial eco-regions identified by the Worldwide Fund for Nature, livestock are identified as "a current threat", while 23 of Conservation International's 35 "global hotspots for biodiversity" - characterized by serious levels of habitat loss - are affected by livestock production.

The full text of the UN Food and Agricultural Organization report Livestock's long shadow is downloadable as a PDF file.

Share |      Randall Parker, 2006 December 12 10:45 PM  Climate Trends

David A. Young said at December 13, 2006 9:31 AM:

This is a valid concern, but in the LONG run, the Meat-O-Matic will tend to work to minimize this problem. The technology for growing meat in vats (or whatever) is just beginning to arrive, but it offers so many potential advantages (economic, environmental, nutritional, and culinary) that I think it's market share will increase exponentially as it matures. Not that I'm saying we should ignore the problem until the Meat-O-Matic arrives on store shelves -- just that we should factor this consideration into our long-range thinking, and perhaps do what we can to encourage the technology. Tax breaks for companies doing research in this area would be a good start, for example.

rsilvetz said at December 13, 2006 9:53 AM:

As a greenhouse gas methane is about 21 times more potent than carbon dioxide by weight.

Which makes one wonder exactly what will happen when natural processes unleash the methane sitting in the depths of the ocean...

Oh, and along with the cows, one shouldn't forget the bogs, the termites and every other ubiquitous bio process that puts out methane. Forget, again, that the precession and nutation of the Earth in orbit and nutation, along with solar output rise and fall, are the determining factors on whether this ball of rock is ice-coated or not...

Yeah, right, we need some complicated international CO2 treaty to prevent global warming.... this one ain't in our control folks...

me said at December 13, 2006 1:28 PM:

If monocultures are less efficient than mixed grass ecosystems, why does anyone feed cattle corn rather than letting them graze.

Marvin Meyer said at December 13, 2006 1:30 PM:

All ICE autos are basically "pumps", of the 4 stroke kind,.. racing at 7000 revs per minute. It can be calculated out by time and lbs/hr of fuel consumption plus volumetric efficiency of the displacement of the cyclinders how much based on the worlds 800 million autos. and other factors.
I can't believe cows "are a bigger share". The bigest share by far will be the release of Co2 from the northern tundra/ musket "IF" the global warming temps rise enough to thaw the north.

According to Lester Brown of EPI.


Randall Parker said at December 13, 2006 4:32 PM:


I think it depends on which soil one is talking about. Some soil is so marginal, terrain so sloped, and/or the water so limited that you might as well let mixtures of grasses grow on it. Of course, if you do that and harvest it for biomass energy you can't use the grass to feed cattle or sheep.

But cattle do graze. I'm not a livestock expert by any means. But it is my impression that lots of cattle spend months grazing and then get fattened up at the end before slaughter with grain. My guess: They can't get as many calories per day grazing.

Robert Silvetz,

In the longer run we'll need massive fleets of satellites to reflect light toward or away from the Earth as part of a program of global climate engineering. We can prevent a big freeze or a big melt that way.

David A. Young,

It is the medium to long term that we need to be worried about for the environment. Before we get really advanced tech I want a high quality of life and lots of wilderness and species survival.

Of course, in the longer run we also have a population explosion problem to deal with as natural selection selects for people who want more children and biotech stops death from aging.

There's no end of troubles.

Robert Schwartz said at December 13, 2006 6:00 PM:

You guys laughed when Ronald Reagan blamed the trees. I don't see you laughing now.

JMG3Y said at December 14, 2006 6:16 AM:

A good reference is a chapter section Other Greenhouse Gases in in Spencer Weart's on-line book The Discovery of Global Warming .

One component of consideration - the atmospheric half-life of methane is much less than that of carbon dioxide.

Tood said at December 14, 2006 7:27 PM:

You would think those PETA nuts would use this to drive their goals of vegetarianism.

That is, if they were actually interested in their stated goals. Read this.

Corky Boyd said at December 14, 2006 7:49 PM:

Has anyone sugggested catalytic converters for cows. This would break the methane down into CO2 and water and be far less damaging. We put catalytic converters on auto exhasts to break down hydrocarbons, why not cows?

More seriously, I do remember some research on products that reduce flatulence in cattle. Can't remember the product, but it was possibly alpha-galactosidase enzyme, the active ingredient of Beano. You will still get CO2 because the vegetable matter in the manure will eventually break down into CO2 and water becuase of the fungi cycle, but much of the more dangerous methane will be avoided.

Many people are unaware that there are two complementary cycles involved in the natural creation of hydrocarbons (photosynthesis cycle)and their breakdown (fungi cycle). A steady state forest that has reached maturity does not add net oxygen to the atmosphere. Photosynthesis produces hydrocarbons (wood) from CO2 and water. As trees reach maturity and die, fungi break down the wood (rot) into the same constituents, CO2 and water. The mature forest carbon sink remains constant. Strange as it may seem, using forest products in a way their breakdown is delayed or avoided (such as home construction or furniture) actually increases the worldwide carbon sink, and keeps it out of the atmosphere.

The same is true with cows added to the cycle, if no methane is produced. Grazing grasses would have the same zero net CO2 oxygen balance of a forest if cattle weren't present. Cattle manure and the cattle themselves become the carbon sinks from eating the grass. The cattle, their manure, our manure etc. will eventually be broken down into their origins, CO2 and water. The product to be avoided is methane.

Avoiding meat is not the answer. Reducing the methane is.

back40 said at December 15, 2006 9:03 AM:

"If monocultures are less efficient than mixed grass ecosystems, why does anyone feed cattle corn rather than letting them graze"

To make them fat, change the flavor of the fat, change the color of the fat, and increase milk production. It's the Twinky diet, rich in carbohydrates.

To "finish" a steer for meat, i.e. create so much fat that it not only is a layer of back bark but lodges between muscle fibers, marbling in other words, an animal must gain weight at a rate of 1.7 pounds a day for 60-90 days. Since a steer can only eat so much volume a day the feed must be rich to do this. Most unimproved grasses and forbs are only this rich for a few months in spring.

Fat produced from a starchy diet is white in color and tastes milder than that produced on a fresh greens diet. It has less beta-carotene which gives grass fat a yellow cast. Corn fat is higher in omega-6 fatty acids and lower in omega-3 fatty acids.

Confinement dairy animals eat corn all their lives, not just for finishing. They never get fat since they excrete so much energy in milk. It's a battle to keep them fat enough to have sufficient body condition to get back in calf, and so freshen for another year of milk production.

Grass dairy animals give less milk and are even harder to freshen. Often they are only milked seasonally, allowed to dry up in winter.

As long as corn is cheap it pencils to feed it to cattle for the above benefits, even though the meat and milk is inferior from a health (and some say aesthetic) perspective. It's an environmental tragedy as well since field cropping is so destructive. Right now there is trouble in cow town since the price of corn has been going up, up, up due in large part to demand for highly subsidized ethanol production.

Polyculture grass and forb ecosystems are more productive than monocultures for all soil types and climates. But, that productivity isn't a one shot deal like an annual grain grass (corn is grass too). You need to harvest it and then let it regrow. This is done repeatedly during the year with production varying with photoperiod even if all other nutrients and water are constant. If you let it get tall and rank production is reduced and it has less quality as well since the plants have more woody material (lignin) to be stiff enough to stand tall. In general, once grass gets over 8" tall it loses food value at a rapid rate.

Since grasses regrow, and stop growing once they get tall, you can have mixed uses. It can be grazed a few times early in the year, and then take a cutting or two with mechanical harvest. This is an old technique, a way to store forage for winter by making grass hay or silage (or baleage), but the hay could just as well be used for cellulosic ethanol production, assuming that technology matures.

It takes knowledge and effort to manage a mixed species, mixed use sward and so realize these theoretical benefits. It's not easy. It's what is often called "management intensive". It isn't so much that it takes intensive labor as that the labor must be done at just the right time and place. Measurement for management information is required to make good and timely decisions. There are graziers that have long traditions of doing this sort of thing, but it is not pervasive. Worse, many indigenous subsistence cultures have been so disrupted that they no longer follow, and sometimes have forgotten, their own best practices.

So, while it is possible to have your grass (for ethanol) and eat it too (for cattle), it seems unlikely that more than a few will have the energy and intelligence to manage such a system. Besides, few want to do the work. If it can't be done sitting down, it is said, there's no money in it.

tdean said at December 15, 2006 11:07 PM:

Parker: "To the fans of biomass energy: Hasn't enough of the Amazon already been lost to pasture land? Do we need to make it worse by promoting the destruction of the rain forests in the name of biomass energy environmentalism?" I don't know about anybody else, but I haven't heard any biomass advocates suggesting we chop down the rain forests. Isn't this what we call a "straw man" argument? How appropriate.

Even the most inefficient ethanol production from corn produces a protein rich byproduct that can be used for animal feed. Only carbohydrates are consumed to produce the ethanol. We seem to be closing in on cellulosic ethanol very quickly so that corn stover and other agricultural and forestry wastes will be used to produce alcohol or hydrocarbon fuels for transportation without affecting food production. And as back40 and the current issue of Science (8 Dec) points out, harvesting polyculture prairy grasses for biofuel produces yields over three times that of monocultures with far less fossil fuel input on abandoned agricultural land. High biodiversity production of biofuels reduce GHGs up to 16 times that of conventional corn and soybean biofuels. So Randall, who is talking about cutting down the rain forests besides you? Try some intellectual honesty for a change.

Even the supposed hubbub about cow farts and global warming is a non-issue. Atmospheric methane concentration has been stable for the last seven years. ( It is possible that there could be massive surprises when the permafrost thaws or methane cathrates on the continental shelves are catastrophically released as they have been in the geologic past, but cow flatulence ain't a problem at this point because atmospheric methane has reached a steady state between production and decomposition. So let's talk about real problems, shall we?

sp said at November 14, 2007 6:29 AM:

Global Warming is bull shit. It is just the cycle of the environment. The world cools down and heats up all the time.

tcjs said at October 2, 2012 9:32 AM:

Thank you tdean for actually doing your research. It's nice to see that the world isn't completely full of retards.

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