Friday, May 9, 2008

Feedlot cows produce more methane than pasture cows

As more researchers work to understand where ghg emissions occur in ag practices, we can begin to parse growing practices to determine which have a lower carbon footprint.

Environmental Health Perspectives posted recent research, Global Farm Animal Production and Global Warming: Impacting and Mitigating Climate Change, that does some of this parsing by combining the results of various related studies.

Here are some emerging facts from that article:
  1. "Animal agriculture sector accounts for approximately 9% of total CO2 emissions, which are primarily the result of fertilizer production for feed crops, on-farm energy expenditures, feed transport, animal product processing and transport, and land use changes (Steinfeld et al. 2006)."
  2. "Burning fossil fuels to produce fertilizers for feed crops may emit 41 million metric tons of CO2 per year (Steinfeld et al. 2006)."
  3. " Farm animals and animal production facilities cover one-third of the planet's land surface, using more than two-thirds of all available agricultural land including the land used to grow feed crops (Haan et al. 1997). "
  4. "Typically, cattle confined in feedlots or in intensive confinement dairy operations are fed an unnatural diet of concentrated high-protein feed consisting of corn and soybeans. Although cattle may gain weight rapidly when fed this diet (Pollan 2002), it can cause a range of illnesses (Smith 1998). This diet may also lead to increased methane emissions."
  5. And this: "The standard diet fed to beef cattle confined in feedlots contributes to manure with a "high methane producing capacity" (U.S. EPA 1998). In contrast, cattle raised on pasture, eating a more natural, low-energy diet composed of grasses and other forages, produce manure with about half of the potential to generate methane (U.S. EPA 1998)."
So feedlot cattle appear to produce twice the methane as pasture due to the diet. I assume this does not include the any methane from fertilizer or feed growing practices.

The first response seems obvious: eat less meat. The counterpoint is that we need protein. We can of course grow more pasture beef, but at current consumption habits we would have to expand land use for cattle quite significantly if we consume meat at current levels. Also, as health efforts (partially) succeed in getting us to reduce our red meat consumption in this country, as economic progress grows in developing nations, particularly China and India, meat consumption increases potentially negating any ghg reduction we have accomplished.

Ugh. So what can we do?

Since the climate is a global issue the pathway forward needs to incorporate global, national, and local concerns:
  1. Reduce feedlot cattle consumption everywhere.
  2. Increase the production of pasture beef.
    1. Which also decentralizes manure production and reduces the necessity of using fossil fuels to create fertilizers, and then transport them to buyers.
  3. Generate large consumer awareness programs in developing nations that as they turn their diets towards more red meat consumption that they request pasture beef.
    1. Other research shows that pasture beef has more omega 3 fatty acids than feedlot beef (will get source).
  4. Encourage trade policies that incentivize the production of low carbon meat.

Secondary source (primary sources in brackets, available in article): Koneswaran G and Nierenberg D, Global Farm Animal Production and Global Warming: Impacting and Mitigating Climate Change, Environmental Health Perspectives Volume 116, Number 5, May 2008,


Hilary Burrage said...

Thank you Tim.

I came across this blog whilst researching for my own website piece on 'Food, Facts & Factoids' (please see article of 5 May'08); and I too conclude that eating less meat is going to be very important for a range of reasons.

Then I posted a question about this on LinkedIn (still current, as I write this). I have been rather surprised by the responses of some people who have taken the time to reply - there's certainly a range of views about what constitutes a 'food fact'!

Best wishes,

Eric said...

Interesting, Tim.

Here in Sweden I'm working with biogas projects where we capture the methane content of the manure and "flare it off" (actually selling it as a vehicle fuel and replacing fossil fuels for addition CO2 reductions). After digestion, the manure is still availble for use as a replacement for artificial fertiliser, but with a reduced smell and more available nitrogen content. Interesting, eh?

I'm not saying that biogas will save our excessive meat consumption. But when it comes to renewable fuels, nothing touches biogas.

Anonymous said...

One point in favor of "Feedlot Cows" (even if I find the image of a cow grazing much more pleasing) is the fact that methane / manure capture is easier for non-pasture-cattle due to the fact that they emit most of it in closed quarters.

So the real question would be if "feedlot cows" on farms with biogas facilities emit less Greenhouse Gases than "pasture cows" if biogas use and it's emission balance (less CH4, more CO2, replacing fossil fuels for heat/power produced) is included.

Just a thought...

Tim Crosby said...

Good comments. Thanks all.

The methane digester idea is one to fully consider. I know folks working on digesters up here (NW WA state). One trick, though, is that once you remove the methane you still have a large quantity of concentrated waste to deal with. Yes it is manure fertilizer, as it was before the methane process; but it can still be in quantities larger than local farms can handle. And if you add in the cost of transporting it you can hurt the profitability of the methane digester.

Thanks again,


Anonymous said...

We can eat as much beef as we want. We just have to do it sustainably. That word needs defining but, if feedlot manure has a higher methane producing capacity,so much the better. Now if we closed the loop, we would site a digester and gas capture to burn that free gas to poser something, like a generator.
In China they use the pig manure gas to fire the stove to cook the pig! The leftover solids do present another issue, I will admit!

Anonymous said...

Hey Tim, now we can burn the poop for electricity, too.

Adam said...

I think it's important to note that this figure refers only to methane from manure, not that produced by enteric fermentation and emitted in the form of burps. The latter produces much more methane than the former, and it may be that pastured cows actually produce more methane than feedlot cows that way. (See, for example,

Anonymous said...

Yes, grass-fed cattle burp far more methane than grain-fed manure piles produce in confinement situations. Interestingly, if one could feed grain on the open range, you would end up with far less from both sources. It would be very difficult to do that.

JMO, but cattle are eventually toast. It's unsolvable.

Anonymous said...

Rather interesting blog you've got here. Thanks for it. I like such themes and everything that is connected to them. I definitely want to read more soon.

Combined Cycle Operator Training said...

The first response seems obvious: eat less meat. The counterpoint is that we need protein.

Anonymous said...

Hey - I am definitely glad to discover this. Good job!

AgAlberta said...

Actually, as an animal scientist, I can tell you that it is a fact that a ruminant (beef) produces more volatile fatty acids and therefore methane as a result of bypassed urea when fed on a forage or legume diet. In this case, pasture would result in higher methane production by a substantial amount. Numerous papers, including one by Basarab et al. and Okine, show that diets high in grain based components are very effective at lowering CH4 emissions. I think it is important to recognize the use of pasture in growing beef because it uses a feed not accessible to humans and many other animals in domestic agriculture (grass) to grow a protein source that is very dense and high in CLA.