food carbon

July 23, 2009 at 1:42 pm | | science@home

This is sorta old news, but I found this paper again. What are the best diet choices to minimize your carbon (and entropy) footprint? Many say that buying local goods is essential, to minimize transportation. This is true, but the type of food is far more important in reducing greenhouse gases (GHG).

Or, as the authors state: “Shifting less than one day per week’s worth of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable-based diet achieves more GHG reduction than buying all locally sourced food.”


Bottom line: cows produce a lot of GHG. It is obvious that growing meat is less efficient than plants (animals must be fed plants, and they are inefficient at converting plant matter into meat. Every extra rung of a food latter loses energy). What is not as obvious is that cows produce a lot of methane, which is a more potent GHG than carbon dioxide.

Red meat produces the most CO2 equivalents per calorie, more than twice dairy or fruits and vegetables. Another reason to go veg… and buy local!


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  1. If I recall when that paper first made the rounds, it was claimed that the benefits of buying local ( in terms of transportation costs) would be cancelled out if the person who walked to the market to buy food exclusively ate beef.

    Comment by Joel — July 23, 2009 #

  2. Actually, locally grown food may not be as carbon efficient as you think:

    Comment by azmanam — July 23, 2009 #

  3. well, i quoted from the paper the authors’ actual claim.

    Comment by sam — July 23, 2009 #

  4. It’s surprising to see fruits and veggies are higher carbon than cereals and oils. I wonder if the study factored packaging and processing into their data.

    Comment by jordan — July 27, 2009 #

  5. I can’t see how growing water-intense crops like lettuce, oranges, and spinach in the desert (i.e. local California)can be less carbon intensive than growing it in a wetter climate.

    Eating local makes sense in the Midwest and the Plains. I don’t think it makes much sense in the desert…

    Comment by charles — August 4, 2009 #

  6. as with all things (including this statement), there are many exceptions to any rule.

    with all else being equal, local produce is better. but the savings from transportation may be canceled out in any particular situation, like needing to transport more water.

    we need numbers!

    Comment by sam — August 4, 2009 #

  7. In my limited understanding it seems to me that this conclusion is not valid for all circumstances of meat production when the complexity of the full system is considered.

    Organic matter, produced by primary processes driven by energy from the sun, incorporates carbon from carbon dioxide in the air. Herbiovores of all scales may consume this plant material. In all of them, the cellulose is broken down by protozoa in an anaerobic environment, whether in the rumen of a ruminant or the gut of a termite, all producing GHG’s. The methane produced in this anaerobic degradation process is a more potent GHG than carbon dioxide but it’s atmospheric half-life is also a log less than carbon dioxide. If instead of being consumed by a herbivore the plant dies and the plant matter falls onto an aerated soil, the degradation process is aerobic, the cellulases being produced by fungi in the presence of oxygen and the carbon is released as carbon dioxide. If the soil is waterlogged, such as in marshes and rice paddies, the process is anaerobic, bacteria break down the cellulose and the carbon is released as methane. The bottom line is that this is a cycle, however man intervenes in it.

    The other component of this is that ruminants prosper on lower quality feed than can monogastrics such as poultry and fish, being closer to humans in their food quality needs. In a sense, one can see this in their relative conversion efficiencies, fish and poultry being considerably more efficient converters than ruminants. The species evolved in different ecosystems on different feedstuffs. Under some circumstances, taking the ruminant out of the production system has unintended consequences, such as making the management of nitrogen pollution more difficult. My understanding is that for this reason the National Academies of Science panel working on updating alternative agriculture will recommend incorporating livestock back into midwest farm production systems.

    So if the farmers are making rational use of their resources then ruminants are being grazed where human-food producing plants cannot be raised, hence consuming lower “quality” feedstuffs, and thus the GHG results of humans consuming grass-fed ruminants would be a wash, providing the primary production originated in a native grassland ecosystem. Has anyone evaluated meat production capacity under sustainable circumstances?

    Comment by jon — August 23, 2009 #

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