Sunday, August 12, 2012

Cattle "Emissions"


Ancestral Health Symposium 2012 is now history. The symposium took place at the Harvard Law School August 9th-11th. Not a bad gig for a forage agronomist! The title of my presentation was The Reality of Ruminants and Liebeg’s Barrel: Examining the New ‘Conventional Wisdom'. All of the presentations were video taped, and will be freely available.
My title slide. Cattle mob grazing a pasture under center pivot irrigation.
Photograph by Dawn Gerrish.
One of the themes of this year’s symposium was sustainability. I don’t see that term in the simplistic way many do, in part because I remember being told by leaders of the sustainable agriculture movement that “animals have no place in sustainable ag!”

The truth is that the production of animal products from perennial forages is the sustainable agricultural system. Many, however, are concerned about the carbon dioxide and methane “emissions” from livestock in general, and cattle in particular. Some folks don’t seem to understand that a cow grazing grass can only emit carbon that was originally in grass, and that the carbon in grass has to have come from the atmosphere. So it’s a cycle not an “enrichment.” But there’s more to it than that!

Under the following assumptions:

Carbon:Nitrogen ratio = 17 and 3.4% N, giving 57.8 % C
3% of body weight daily dry matter (DM) intake; 1,000 lb cow = 30 lb DM per day
70% utilization - 30 lb DM eaten / 0.70 = 42.8 lb DM offered
Equal above and below ground DM distribution
90% of C consumed is “emitted” 

We’d see:

42.8 lb DM above ground, 42.8 lb DM below ground – 85.6 lb DM total
57.8% C in DM – 49.5 lb C total
17.3 lb C consumed
15.6 lb C emitted

Thus, for every pound of carbon “emitted” by a cow on grass, 3.2 pounds of carbon are fixed in plant roots, uneaten plant debris, or the cow herself or her calf. Even if we say that 100% of carbon she ingested is emitted (a biological impossibility!), there’d be 2.9 pounds of carbon fixed for every pound emitted! Beef cattle are carbon negative!

Someone (perhaps Todd Becker?) asked me what happens to methane in the atmosphere. A good question, and one I wasn't completely sure about. So I went looking and found the following at this site:
"In the lower part of the atmosphere, below about 10-12 km (the troposphere), the key cycles are mediated above all by the presence of what are called OH radicals — colloquially known as the atmospheric detergent. All hydrocarbon chemical species that are emitted can be eventually broken down (or oxidized) by these radicals to CO2 and H2O, and methane is no exception. An average molecule of CH4 lasts around eight to nine years before it gets oxidized. This is a long time compared to most atmospheric chemicals but is fast enough so that there can be significant year-to-year variability."

21 comments:

  1. Hi Peter,

    Your memory is correct - I'm the one who asked the question about methane. Thanks for the informative answer.

    I very much enjoyed your talk and meeting you at AHS!

    Todd

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  2. This is great. Are there any scientific papers or published articles (besides this one) that you can link me to so I can properly site this info?

    Also, does this only apply to GRASS-FED as grains are annuals and not perennials?

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    Replies
    1. I'll try to post some of the references.

      Grass fed is going to be less than grain fed, but the majority of a steer's life is spent on grass so the difference will not be as great as frequently stated.

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  3. Just got this comment on a share I did on Facebook .. anybody care to answer?

    "What about all the air the cow breaths throughout its entire life cycle and all the CO2 it therefore exhales? Does that not count as carbon? Sorry but I don't think there is a way to raise cattle that is "carbon negative"."

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    Replies
    1. There is 0.04% CO2 in the atmosphere. The additional CO2 a cow respires comes from metabolic processes. She isn't creating new carbon. It is coming from the products of microbial fermentation of feed she's ingested - either directly or after she's absorbed them.

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  4. This is a really interesting analysis. On the face of things it is a statement of the blindingly obvious, but it is also contrary to popular widely held beliefs on the question. The case you present, however, has a much wider appeal beyond those who can understand the technicalities, language and assumptions you use and make. How about a simple, make no assumptions whatever, version for that wider audience? It will attract huge interest.

    Meanwhile, I look forward to viewing your presentation when it is available.

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  5. Peter,

    Very interesting info. I think many people who hear the media hyperbole regarding cattle and CO2 are ignorant to the concept of "cycles" in nature.

    Regarding sustainability - Currently beef from CAFOs is the main supply for most of the US. I know you have blogged on this before, but do you think that it will be possible to create a forage based meat supply that does not rely upon CAFOs? Is it a feasible change given increasing population? I would love this to happen, but have a hard time getting my mind around it.

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  6. I learn so much from this blog. Thank you.

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  7. Thanks for speaking at AHS12! It was great to meet you, and in addition to enjoying your blog, I have forwarded your blog to my farming/ranching father.

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  8. Methane is highly problematic - in the atmosphere, as well as nearer the ground: it also contributes to ground-level ozone, which is a human health hazard. It interacts with many chemicals once it's "up there," and it's effect to cause warming is 6x that of CO2 due to all of its interactions. So the methane is a big problem.

    However, speaking of methane, did you know that rice paddies produce an enormous amount of methane? Seriously.

    So while there are ways to handle cow methane (feed them grass, no corn *ever*, & supplement instead with canola, for example, which they can eat fine, and it interacts in their bodies to produce less methane) - as well as responsible managed pasturing, which the ARS part of the USDA itself found increases the ability of the land to hold carbon - what is the solution for rice paddies?

    The next time a veg*n gives you a hard time about sustainability, ask them squarely what their solution for the rice paddy methane problem is. Rice agriculture is responsible for 13% of the world's methane emissions; cattle at best 18%. Both of these problems have to be solved - we have ways forward on cattle, but nothing much yet on rice.

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  9. Thanks for speaking at AHS.I really enjoyed and content is useful.

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  10. I just stumbled upon your blog and wanted to say that i have really enjoyed reading your blog posts.

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  11. Pete,

    Excellent. Try this for more data on cattle and methane - http://www.tochallengethethinking.co.uk/186-2/ and view "Climate Change - the answer is bullocks" As you well know there is no simple one liner on climate change (other than possibly zero fossil fuels!!) - but this in c 60 mins covers a lot of ground in challenging "wisdom". It can be viewed in 10 min chunks.
    Dave Stanley.

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  12. I couldn't make it to the speech, but thanks for uploading!
    @"Unknown" Wow, crazy stats, never thought of that!

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  13. I sent your articles links to all my contacts and they all love it including me.useful reference

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  14. How about grass? Do they give off methane too? If grains have methane and fed as <a href="http://www.topstock.com.au/index.php?page=rangeland-grazing-supplementation>livestock supplements</a> then a great number of cattle would be really helpful.

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  16. The methane/co2 'concerns' are based on a supposed 'scientific consensus' ( an oxymoron ) as popularized by a UN bureaucracy angling to tax the planet on energy use - essentially Prometheus' gift of fire. I'm sure you won't take my word for that, but a look around at climategate.com should show you that physicists are harassed for fighting politicized 'post normal science'....and that one should think there is more an allegation of consensus than agreement between those pushing manmade climate change and those who think it all a load of unverifiable nonsense. Which is not to be cavalier about what is happening to our water supply : an essential lost in representations about pollution that ignore ozone and the nitrogen cycle.

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