by Marion Nestle
Jul 21 2009

Use manure as a biofuel?

Here’s another USDA report well worth a look.  This one looks at the use of manure in the United States.  Interesting statistics: about 5% of cropland is fertilized with manure, and about half of that goes on cornfields.  So the obvious question seems to be that if there’s all that manure around, why not use it to produce biofuels?

Why does this seem like a bad idea to me?  It makes about as much sense to use manure as corn for biofuel.   Wouldn’t it be better to use all that CAFO (Confined Animal Feeding Operations) effluent to fertilize the other 95% of cropland?  Wouldn’t composting animal waste and using it on crops instead of chemical fertilizers be more sustainable and solve a lot of problems?  Or am I missing something here?

  • At first glance, it does make perfect sense. I too wonder why more is not used this way? I know a lot of smaller operations (i.e. Straus Dairies in NCal) using the manure for both generating electricity and fertilizer.

    I am sure there are some issues, and I am not sure I would want to be the one known as the “manure king” heading the charge, but certainly sounds like a good use of stimulus spending.

  • I imagine it might be prohibitively expensive to ship manure effluent from CAFOs, which tend to be in the middle of barren nowhere, to major agricultural regions – especially when the alternative is dry, super concentrated synthetic fertilizer.

    I really hate the idea of CAFOs, and myself would be happy to eat less, more expensive meat to see them disappear, but biofuel is probably a pretty elegant technological fix for what it’s worth. Plant biofuels have really been impeded by 1) the inability of microbes to break down heterogenous mixes of local plant debris 2) the expense of shipping in homogenous plant debris from large non-point sources (e.g. corn fields) and 3) the inability of microbes to break down cellulose well. Manure gets around all of these plus is nutrient rich. Plus, I think there may already be commercial operations generating energy from manure waste…

  • Lachlan McDavid

    The problem with fertilizing crops with manure from CAFOs is that it’s very often contaminated (even more so than normal manure). You could cook the manure sufficiently to kill microbes like e. coli and salmonella, but can we really guarantee that *all* the manure would be disinfected properly? Given CAFOs’ pollution record, I’d be skeptical, and even a small amount of infected manure could contaminate a lot of crops—it seems to happen to spinach all the time.

    Even if we did disinfect the crops of all microbes, what about prions? Carleton Gajdusek thought prions could conceivably infect plant crops if they were fertilized with the manure of prion-infected animals, and if any animals are infected with prion diseases I’d say it’s the ones in CAFOs. Gajdusek may very well have been wrong, but I’d rather not take the risk.

  • Good point,

    Some of the recent E. coli outbreaks were due to raw, uncomposted manure being spread (illegally) on field crops.

  • susanne

    if what was coming out of CAFOs was actually “manure,” it would be great to use as fertilizer or compost. but it is not just manure. it is contaminated with all the junk they feed the cattle–antibiotics, pesticies, hormones, and antibiotic-resistant bacteria.

    in order to use manure from animals, they need to be raised in a more sustainable and healthy way.

  • We no longer grow our crops and our animals on the same piece of land.

    Wendell Berry, in The Unsettling of America, wrote that industrial agriculture has taken “a solution and divide[d] it neatly into two problems.”

    Matt made a good point that shipping costs would make using CAFO fertilizer prohibitive. Animals used to defecate directly into the soil. Now the animals are hundreds of miles away from the nearest cropland.

    And Lachlan’s comment drives the nail into the coffin. The whole system is a danger to our health.

  • John Senner

    Over here in Arkansas, the places that produce a lot of manure (mostly chicken) are in areas that don’t have a lot of crop land. They spread as much as they can on the crop land, but you can’t over do it without getting into stream pollution.

    All the good flat crop land that could take the the manure without generating much runoff is way on the other side of the state. Probably cheaper to burn it for fuel than to burn the fuel needed to get it to the crop land.

  • sachi

    I think there has been alot of problems with what exactly is in the manure of animals raised in these huge feedlots and factory farms, it could be contaminated with god knows what, they aren’t raised on grass anymore. Servings of anti-biotics or heavy metals anyone?