When Life Gives You Excrement, Make Fuel?
Via Ezra Klein, The New Scientist observes that “A kilogram of beef is responsible for more greenhouse gas emissions and other pollution than driving for 3 hours while leaving all the lights on back home.”
People tend not to understand this very well because the tendency is to use the term “carbon dioxide” as a shorthand for “greenhouse gasses.” But though CO2 is the most common greenhouse gas, it’s far from the most potent. And livestock create huge amounts of methane both from their farts (yes, really, this is a real problem) and from the decomposition of their manure. The good news, as the good people at the Danish Biogass Association were eager to explain to me yesterday, is that there’s a way to deal with the manure side of this. Methane, in addition to being terrible for the environment when released directly into the air, is also usable as fuel (”natural gas”) and when used as fuel it’s relatively clean-burning compared to coal or oil. What they do at biogas plants is basically gather up a huge stinking pile of shit which is submitted to anaerobic digestion. This leaves you with, on the one hand, some digested manure that can be used as an effective and non-emissions-producing fertilizer and on the other hand some methane gas you can use to heat homes or generate electricity.
The biogas itself involves some CO2 emissions, so this isn’t a perfectly green technology. But making the biogas is much cleaner than not making the biogas if we assume that the quantity of animal excrement produced is independent of the existence of the biogas facilities. In other words, if the demand for meat is determining the quantity of cow and pig shit, then biogas plants count as very clean. They sharply reduce the quantity of methane put into the air, and can substitute for other dirtier fuels like coal or oil. If biogas were to actually become such big business that people started raising pigs specifically for the purpose of turning their shit into home heating fuel, then that wouldn’t work ecologically at all.
Currently, though, biogas requires substantial subsidy (in the form of a feed-in tariff) to be viable. So the smart green move is to subsidize biogas production enough to clean up the excrement we have, but not so much as to encourage the creation of additional livestock. In principle, it would probably make sense to have some kind of tax on meat that could be used to raise revenue to defray the cost of biogas subsidies.
42 Responses to “When Life Gives You Excrement, Make Fuel?”
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October 9th, 2009 at 12:40 pm
Maybe someone can explain something to me. It seems like the greenhouse gases produced by food animals is a zero sum game. They turn plant matter which captures C02 into methane which releases CO2. Seems like the net increase in greenhouse gases is due to the fossil fuels to support the animals. Free range organic animals might be responsible for less greenhouse gas release, but that is because they require less fossil fuels to produce, not because they fart and poop less.
Am I missing some part of the cycle that is generating a net positive greenhouse gas release?
October 9th, 2009 at 12:43 pm
Matt, most of the methane from cows is due to belching, not flatulence. It comes from the bacterial breakdown of the grass in their stomachs. Although, admittedly, talking about cow farts is more amusing.
October 9th, 2009 at 12:50 pm
Greg —
A couple of things. First, I think that methane is a worse greenhouse gas per carbon atom than CO2 is; so if you vacuum a bunch of CO2 out of the air and convert it all to methane, you are making the climate change situation worse. Second, following up on BillS, the methane which you capture from the feces and burn to CO2 is, I think, zero-sum: CO2 goes through the food chain, becomes biogas methane, and is burned to get back to CO2. The CO2 portion which becomes methane in the form of flatulence and belches is negative-sum — you’ve taken a less-severe greenhouse gas and produced a more-severe one from it.
October 9th, 2009 at 12:51 pm
BillS is close. The excessive belching of feedlot cattle comes from the corn and soybeans they are fed. If they were fed only grass (their natural food) they would not belch as much.
And Greg is correct that Matt completely skips over the fact that a huge amount of fossil fuels are used in meat production.
The plant carbon to methane is not zero sum, however. Plants don’t take in methane. They take in carbon dioxide. When domestic livestock turn the carbon from plants into methane they are absolutely adding to net greenhouse gasses in the atmosphere. Efforts to capture the methane and turn it into CO2 would make the cycle zero sum.
October 9th, 2009 at 12:53 pm
Re: Free range organic animals might be responsible for less greenhouse gas release, but that is because they require less fossil fuels to produce, not because they fart and poop less.
Based on a talk I heard recently by an animal-husbandry scientist, free range organic cattle actually produce _more_ methane from digestion than corn-fed animals, because grass is harder to break down than grain.
Grass-fed animals of course produce a much lower _net_ impact on the environment than corn-fed (because as you say, it takes lots of fossil fuels to grow the corn), as well as their meat being healthier for you. However, with respect to the narrow question of methane production, free range raising is not advantageous.
October 9th, 2009 at 12:55 pm
Re: If they were fed only grass (their natural food) they would not belch as much.
I don’t think this is at all true, based on that talk I heard. However, this isn’t my field so I will need to get back to you with some citations.
October 9th, 2009 at 1:03 pm
Why not just put a tax on methane emissions? Then people could reduce their methane emissions either by not producing meat or by turning the manure into biogas.
October 9th, 2009 at 1:03 pm
See Harper, L.A., Denmead, O.T., Freney, J.R., and Byers, F.M. 1999. “Direct measurements of methane emissions from grazing and feedlot cattle”. Journal of Animal Science, 77(6): 1392-1401.
They found higher methane emissions from grazing cattle then from feedlot ones.
October 9th, 2009 at 1:05 pm
Nobel Prize in science to anyone who can figure out how to hook up politicians to some kind of breathalyzer apparatus to capture their brain farts.
October 9th, 2009 at 1:11 pm
There are a lot of these anaerobic digester projects in the works in New York. The state agency that provides the subsidies has been well funded despite the abysmal state budget situation, and Cornell University, long known for their electrical/mechanical engineering and agriculture programs has been a leader in R&D and implementation.
Non-trivial additional benefits of these projects are that some of the waste heat can be trapped and used to heat dairy farm barns or other buildings in some cases, and that disposing of the manure in this fashion prevents it from ending up in the water supply which is a big problem for some municipalities. Controls odor, too.
October 9th, 2009 at 1:11 pm
here’s an interesting article about this:
http://online.wsj.com/article/SB124527861144324987.html#articleTabs%3Darticle
October 9th, 2009 at 1:12 pm
Matt: “If biogas were to actually become such big business that people started raising pigs specifically for the purpose of turning their shit into home heating fuel, then that wouldn’t work ecologically at all. ”
That would be a very uneconomical way of producing fuel.
October 9th, 2009 at 1:13 pm
Normally I like the idea of taxing a polluting activity to reduce it, because it usually produces more efficient amelioration. However, in this particular case regulation would be better targeted. If we put a tax on meat, free-range producers will be affected as well as the feed-lot growers. Their costs are already higher, resulting in higher prices for their product, because it takes more land to grass-feed cows or let pigs root than it does to grow corn for them. But as pointed out, it takes significant fossil fuels to grow the corn, as tractor and truck fuel and fertilizer.
A regulation that feedlots must collect and biodigest the waste from their operations would place the cost burden on the worst sources of total GHG’s, reducing the price advantage “factory” farms have over more environmentally sound producers. It would also as a side-benefit reduce the other environmental impacts the waste produces — the stink, eutrophication of surface waters, and disease.
October 9th, 2009 at 1:16 pm
There are many farms in my state of residence that do this very thing. The manure is processed for energy and the inert material is recycled into bedding.
And yes it is cow burps, as they are front gut ruminants.
October 9th, 2009 at 1:17 pm
Hey Matt, can you please try to find out how much the Danes subsidize corn? Just curious. Thanks!
October 9th, 2009 at 1:22 pm
Besides being hilarious, this is a good subject for highlighting the need for accurate greenhouse gas emission taxes so that the market can work out all these weird dependencies.
October 9th, 2009 at 1:26 pm
don’t think this is at all true, based on that talk I heard. However, this isn’t my field so I will need to get back to you with some citations.
My bad. I stand corrected.
October 9th, 2009 at 1:30 pm
livestock create huge amounts of methane both from their farts (yes, really, this is a real problem) and from the decomposition of their manure
IANAclimatologist, but I’m not so sure. Where does the carbon in cow farts and decomposing cow manure come from? It comes from cow food, in other words plants. And where does the carbon in plants come from? Carbon dioxide! It’s the carbon cycle; atmospheric carbon and the carbon in living things are basically considered to be the same since they interchange freely.
This is not true when it comes to fossil fuels; the carbon in fossil fuels has been sequestered in the earth, but when burned it enters the atmosphere and increases concentration of greenhouse gases in the atmosphere.
This is why corn ethanol is supposed to be better for CO2 emissions; not because it doesn’t emit carbon, but because the carbon it emits was already atmospheric carbon to start with. It’s also why burning wood for heat is better for CO2 emissions than burning, e.g., natural gas.
Of course, quite a lot of fossil fuels are used by the meat-industrial complex.
October 9th, 2009 at 1:34 pm
Shoulda read the other comments first. Yes, methane is a ’stronger’ greenhouse gas than carbon dioxide, because it absorbs more heat. But on the other hand,
.
October 9th, 2009 at 1:37 pm
Michael Pollan (Omnivore’s Dilemma) claims that corn takes 1 calorie of fossil fuel for every 1 calorie of food a corn field produces. I’m assuming that sort of a lifecycle calculation though. That is, it is fuel for tractors + fuel to produce chemical fertilizer + fuel to truck the corn to the food processing plant + more.
If I remember right, cattle take three or four pounds of feed they eat for each pound of beef put on the table.
October 9th, 2009 at 1:51 pm
I think the feasability of this method (pigshit) to power a municipality was well established in the documentary on Bartertown. In the States it may have been called “Beyond Thunderdome.”
October 9th, 2009 at 2:04 pm
IT’S COW BURPS NOT FARTS! For some reason it really matters to me that people understand this.
October 9th, 2009 at 2:11 pm
why not use the CO2 produced in the shit de-shitification process to bubble up some seltzer? There’s gotta be a real pony of a marketing angle in there somewhere! Steamin’ Seltzer or something like that
October 9th, 2009 at 2:13 pm
Here’s an interesting discussion of the amount of feed it takes to raise a pound of beef. This comes from the Ag industry, so take it with a grain of salt.
October 9th, 2009 at 2:13 pm
I’m astonished that lots of angry commenters haven’t pointed out that Matt’s lack of familiarity with the methane content of cow burps demonstrates what an elitist dim bulb he is.
October 9th, 2009 at 2:13 pm
And if Bart Simpson ever grows up, he could get a job as a safety inspector at a hip green biomass plant. The very idea provides enough jokes and gags to write 20 or 30 episodes at least.
October 9th, 2009 at 2:14 pm
biogas, not biomass! D’oh!
October 9th, 2009 at 2:16 pm
More interesting facts, this time form USA Today. Producing one pound of beef emits 14.8 pounds of CO2 and is equivalent to driving about 20 miles.
October 9th, 2009 at 2:34 pm
May I point out that there’s a much easier was to obtain methane –from the ground as natural gas. Yes it’s a fossil fuel but still not wholly wicked. The US and Canada have loads and loads of it and it doesn’t need subsidies.
October 9th, 2009 at 2:41 pm
MY: If biogas were to actually become such big business that people started raising pigs specifically for the purpose of turning their shit into home heating fuel, then that wouldn’t work ecologically at all.
Barry @12: That would be a very uneconomical way of producing fuel.
It would indeed. There is no way this would happen. The value of the labor, fertilizer, and land needed to produce animal feed can be much more efficiently put to use producing plants that can be directly turned into fuel. People may like the taste of meat and thus be willing to pay for inefficient food, but nobody cares whether their homes are heated by canola oil or by pig shit.
A while ago I read about engineers who had figured out how to make an internal combustion engine that ran very efficiently on hazelnut oil. At this point, you might as well find a way to make an engine that runs on Monet watercolors and Fabergé eggs. The idea of growing pigs just to harvest their shit to make into methane lies somewhere between the hazelnut idea and the Monet/Fabergé idea.
October 9th, 2009 at 2:57 pm
http://www.ganesha.co.uk/Articles/Biogas%20Technology%20in%20India.htm
“Currently, there are thought to be about 2.5 million household and community biogas plants installed around India (Dutta et al, 1997), though table 1 estimates that 12 million could be usefully employed. This essay will critically examine the drive to provide rural India with an ‘appropriate’ energy source, with particular reference to the rural poor. The potential benefits of biogas in a rural economy will be outlined, followed by the biological and biochemical foundations of methanogenesis, and the evolution of biogas technology. Case studies from different parts of India will be considered, from construction of biogas plants, to their long term functioning amongst the communities they are designed to serve.”
October 9th, 2009 at 3:19 pm
Can’t someone run a breeding program to create bacteria that cause cows to burp and fart carbon dioxide rather than methane. Either that or catheterize them and build gas flares that stick out of their bums.
October 9th, 2009 at 3:23 pm
Either that or catheterize them and build gas flares that stick out of their bums.
That’s one of the few research programs that people would enjoy writing grant applications for.
October 9th, 2009 at 3:40 pm
Of course, if we get to the point where we are running out of animal feces to turn into electricity from the meat markets, we will luckily be able to tap into an also unused resource: human shit.
Or does our stuff not produce methane?
October 9th, 2009 at 4:17 pm
One more thing to consider is that methane, although a stronger greenhouse gas, persists in the atmosphere for a considerably shorter time (a few years) than carbon dioxide (thousands of years*) after which it turns into carbon dioxide and water (it is essentially burned really slowly due to oxygen in the atmosphere).
I always thought if we could reduce our CO2 emissions enough, the CO2 product from the methane problem would essentially be solved, too. It just requires a little bit further reductions in CO2 than would be necessary with CO2 alone. Along with some additional burning of poop.
*Any particular CO2 molecule is captured in a carbon sink in a few years, but the net effect is an extra CO2 molecule in the atmosphere for thousands of years.
October 9th, 2009 at 4:21 pm
So … if we wind up using pig poop for power, who the hell gets to be Master and who gets to be Blaster?
I nominate Michelle Obama for the Tina Turner role …
October 9th, 2009 at 4:40 pm
Do we really, biologically need this much meat and fish? Making biogas is a second-order fix to a first-order problem of our own creation.
October 9th, 2009 at 7:36 pm
It’s very off-topic, but Matt’s line,
“So the smart green move is to subsidize biogas production enough to clean up the excrement we have, but not so much as to encourage the creation of additional livestock,”
is so reminiscent of Sam Spade’s need to
“make my play strong enough that it ties you up, but yet not make you mad enough to bump me off against your better judgment.”
Does The Maltese Falcon haunt his dreams as it does mine?
October 9th, 2009 at 7:50 pm
#20 mts:
True, but you/Pollan has got the units mixed up. How many calories are in those 3-4 lbs of feed versus calories in a pound of beef? It’s probably inefficient, but getting the units right would give us a better understanding.
And #29’s comment is missing the point. The point is to obtain energy WITHOUT digging up fossil fuels. Trapping excess methane from livestock increases the efficiency of what we’re already doing, without adding CO2 to the carbon cycle. Extracting natural gas, on the other hand, is adding that much more CO2.
Perhaps we should add some collector hoods to Alaska and Siberia and collect all that methane that’s going to come bubbling up in the summers. There’ve been a few news reports about large amounts of methane trapped under the tundra that will thaw out and add to the climate change problems.
October 10th, 2009 at 1:16 am
A coupla commenters have almost touched on this, but as you might suspect from Anandakos@13, this technology pits the benefits of free range grazing (health, animal welfare) against global warming reduction because it’s essentially impossible to do for free range animals.
October 10th, 2009 at 2:40 am
I read somewhere not too long ago that single pig farm located in one of those empty (two senators?) states like Wyoming or Montana produced more excrement in one year than was produced by all 12 million inhabitants of Los Angeles.
As far as I know, pig farms do not have sewer systems and waste treatments plants attached. That means there is a huge big pile of crap being formed out there near that pig farm and it’s growing larger every day. And I think if you applied some Law of Mathematics, maybe all of them, pig shit, from that one farm, will eventually cover the entire planet.
I don’t know. I think we burn shit for fuel. Sounds like a win, win. Oh, and put Tina Turner in charge of the program, and codename it -Thunderdome.
October 11th, 2009 at 11:25 am
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