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Biomethane from Dairy Manure Could Power 1M Cars in the US

Cow power

Biomethane—natural gas made by upgrading biogas produced by the controlled decomposition of dairy manure or similar waste products—can serve as a cost-effective renewable substitute for natural gas, according to a study published earlier this year.

The study, Biomethane from Dairy Waste: A Sourcebook for the Production and Use of Renewable Natural Gas in California, surveys the most effective and economical technologies for producing biomethane, as well as specific applications and markets for the gas.

Project partners on the study, which was funded by the USDA, include Sustainable Conservation, Western United Dairymen, Institute for Environmental Management, Great Valley Center, CalStart and RCM Digesters.

The authors conclude that manure from about half the cows in California would provide enough biomethane to power all the natural gas vehicles currently operating in the state. Furthermore:

There are 8.5 million cows in the United States, each producing enough manure to potentially generate about 30 cubic feet of biomethane per day, which could replace significant amounts of natural gas at today’s prices. If used as vehicle fuel, biomethane could power a million cars.

The technologies for converting dairy manure to biomethane are already used at several landfills around the United States. Sweden has 20 plants producing biomethane and runs 2,300 buses on it. As natural gas prices continue to rise, biomethane fuel is becoming cost-competitive with natural gas and diesel, and is much cheaper than hydrogen.

Switching to biomethane improves air quality, reduces greenhouse gas emissions, improves water quality and strengthens rural economies.

Allen Dusault, Biofuels Project Manager for Sustainable Conservation

California has particularly good reasons for using biomethane. The state is home to more than 1.7 million dairy cows, with a technically feasible potential for producing about 18 billion cubic feet of methane a year, equivalent to over 150 million gallons of gasoline.

The San Joaquin Valley, where most of the cows reside, has some of the nation’s most polluted air. A dairy biomethane industry along Highway 99 could serve as the start for a renewable fuel highway.

Unlike ethanol and biodiesel, biomethane receives no direct government funding or incentives. To quickly achieve the full potential of biomethane, the federal and state governments must support development of the technology, markets, programmatic infrastructure and regulatory environment that will allow rapid use of this practical, domestic energy resource.

—Michael Marsh, CEO, Western United Dairymen

Stages and technologies in biomethane production. Click to enlarge.

The report deals with five major areas:

  • Producing biogas from dairy wastes with anaerobic digesters.

  • Upgrading biogas to fuel-grade biomethane by removing hydrogen sulfide, moisture, and carbon dioxide.

  • Using and distributing biogas and biomethane.

  • Meeting regulatory requirements and obtaining access to government incentives.

  • Determining the financial, economic, and business environment for the development of a biomethane industry.



Harvey D

I've read that USA and specially California have an important shortage of clean electrical power. Wouldn't it be simpler and more efficient to use methane gas from dairy wastes to produce electricity for the grid and close a few highly polluting Coal power generating units. This is already done for many years in many landfills around the country and adding dairy wastes may just make the existing process even more effective. Plug-in mostly electric vehicles are coming and more electricity will be required. Gas produced electricity is relatively clean and the technology is very mature. The electric power grid is everywhere and no new methane distribution system would be required. Why over complicate it. Lets go with the cleanest and easiest - PHEVs + electric vehicles.


Wouldn't it be more efficent to convert the grain directly into bio-fuel?
Plus, who needs more milk?
75% of the world population is allergic to the stuff anyway.


1 million clean cars and that much less methane warming our atmosphere. Sound like a great plan. The next plan is to make goverment believe that this is a good idea.


This is just some "if" senario. You can always use the Biomethane to bake apple pie or power a train. Biomethane is obviously more efficient for use at power station directly next to a digester. Compress methane as vehicle fuel waste too much energy, plus your mpg will go down, although you get cheaper gas bill.

And if the cow dung alone in USA can power 1 million cars, then the total Biomethane potential is massive, becuase we also have chicken, duck, lamb, zoo, and homo sapien.


I'm like a methane factory myself. If I could only figure out a classy way to harness the power of my...oh never mind. But seriously, I'm with Harvey on this one. Turn it into electricity and push for plug in hybrids.


While it's facinating to understand just how much bio energy is out there, to put it in perspective, replacing 150 million gallons of gas is the equivalent of less than one day's consumption in the US (we use about 200 million gallons of gas per day in the US right now). Still, if this were part of a more comprehensive biofuel generation infrastructure, it could be worth it.


"Wouldn't it be more efficent to convert the grain directly into bio-fuel?"

I like the idea of steaks as a by-product.


The one problem with biomethane from cow manure is collection. The only manure that can be efficiently collected is in feed lots or other concrete enclosures. You can have free range cattle, or you can have high biomethane output, but you can't have both.

However, if the price of grain goes up due to bioethanol/biodiesel production, you may see fewer cows anyway (or cows fed on increasingly unnatural foods).


Using the methane for electric power generation would not make it feasible to shut any coal-fired plants. The coal plants are used for base-load, and the much more valuable natural gas is used in plants that are only run during daytime peak hours. Plug-in hybrids would be charged at night, using coal and nuclear base-load electricity. Therefore, the bio-methane would be better used directly as a supplemental transportation fuel. It could also be burned in power plants, but in the small quantities discussed here, it would not change the cost of energy appreciably. Of course, the market will ultimately determine the best use. The main benefit, to my way of thinking, is the greenhouse-gas reduction achieved through removing the methane from the atmosphere.


That's why we should be using Salton Sea Algae to meet ALL of our fuel needs and eat the food grains directly.

$46 billion paid to USA in place of $150 billion paid to our "friends" in the middle east.


Sure there are problems and limitations with any green fuel, but we need to make the move away from fossil fuels and even baby steps are better than ignoring the problem. With enough alternatives maybe we can survive the changeover.


Could you also use this to heat your home? Or would that make your home smell like Pennsylvania?

Jesse Jenkins

Rexis writes: "And if the cow dung alone in USA can power 1 million cars, then the total Biomethane potential is massive, becuase we also have chicken, duck, lamb, zoo, and homo sapien."

I'd be careful with terms like 'massive potential.' The potential to power 1 million cars may sound like a big deal until you put it into perspective: there are almost 500 million internal combustion vehicles in the United States! While I'd love to see 1 million less of them using gas or diesel, lets not get carried away by thinking that this biomethane will make any kind of serious dent. 1 million cars is 2 tenths of one percent of our total vehicle fleet. I'd hardly call that massive...

On the same note, biomethane isnt going to make much of a difference in our electrical production either. Don't expect to see dozens of coal plants closing because of this. Maybe one or two...


Nope, your house wont smell like anything if you burn methane at home. Methane is naturally odourless, but most likely they will add some addictive into it to make it smelly so we can dectect leakage.

Well i dont think that we will have ANY coal plants close down at all. I think the point here is that we should go on by having lots of alternatives rather then depending on one particular resource(especially foreign resource). So be it biodiesel, biomethane, bioethanol, petroleum or Dr. Fusion in back to the future.

Depending a nation bloodline on foreign import is a very bad idea. Sending army to protect aka occupy a foreign land is a worse idea.


At 30 cubic feet per cow per day, 8.5 million cows supplies 255 million cubic feet of gas per day (assuming this is 100% methane).  The average gas-heated home uses about 50 thousand cubic feet per heating season (~50 million BTU), so each day's production is enough to heat 5100 homes for a year; the annual production is enough to meet the needs of 1.86 million homes.

Not too bad at all.

Now, the real smart thing would be to burn this gas (heck, all gas used for heating) in domestic cogenerators.  At 25% efficiency, this gas would produce 6.82 billion kilowatt-hours of electricity (plus 3 times that much as heat, enough to heat about 1.4 million homes).  Used in electric cars consuming 350 watt-hours per mile, it would be enough to drive 19.5 billion miles; if it was displacing gasoline at the rate of 35 miles per gallon, 556 million gallons of gasoline would be unneeded.

Sounds a lot better than 150 million gallons displaced, doesn't it?  And you're also heating 1.4 million homes.

Cogeneration and plug-in hybrid cars are the way to go.


Remember this was using methane production from only one state as an example.

While it's facinating to understand just how much bio energy is out there, to put it in perspective, replacing 150 million gallons of gas is the equivalent of less than one day's consumption in the US (we use about 200 million gallons of gas per day in the US right now). Still, if this were part of a more comprehensive biofuel generation infrastructure, it could be worth it.


Actually, we used 9,063,000 barrels of gasoline per day in 2004.  That's 381 million gallons per day.

My point is that it's much better to promote a program which displaces 556 million gallons AND heats 1.4 million homes than one which displaces only 150 million gallons and heats nothing.


150 million gallons of gas equivalent from all dairy cows in California, that's 16% of the US dairy cow population (9 million), it only has about 1.5% of the US cattle population (96 million).

But it's the pig and especially chicken manure that are legitimate problems in their own right. Any process that can eliminate these health and environmental concerns has value even if it does nothing but make some money for the people who manage the plant. ISTR that someone got promising rates of methane production by mixing it with cow manure.


Pig manure can be pressure cooked into crude oil that can be refined normally at a cost of about $13 a barrel and most of the energy required for the process comes from the methane byproduct.


Schwa, that sounds like thermal depolymerization.  None of the feedstocks listed in CWT's press kit resemble pig manure (or any conventional biomass stream) at all; they all incorporate lots of grease, fat, plastic or the like.

Perhaps you'd like to point us to your supporting data?  Oh, and while you're at it, could you compare net energy yields from the two options?

Shirley E

We're ignoring a fair amount of expense and energy (for powering pumps, etc.) that would be required to collect and transport all this gas to locations where it would be ultimately used. Don't forget this is a widely dispersed resource. In most cases, cattle farms tend to be significant distances from large population centers. To make such a large scale system we'd need an installed pipeline system going to every cow/pig/chicken farm. Thousands, perhaps millions of miles of new pipeline. And this would all have to be pressurized to make the gas flow, metered, tracked and paid for, and does the gas have to be scrubbed or filtered?, etc.

It seems to me a much more efficient use of this energy resource is to find ways of using it locally. Agriculture is very energy intensive. I know a lot of farms that collect methane today use it to produce their own electricity and heating, etc. Many are nearly self-sufficient as a result.

An alternative, where there was more methane produced than they could use on the farm itself, would be to convert to electricity and sell back to the grid. Here you're looking at some of the same transport issues as selling the gas, but one advantage is that all farms are already electrified and don't need an entirely new piping infrastructure. And many of the transactional details are already established.

Another alternative: one of the objections we keep hearing against biofuels like ethanol is how much energy is required to produce it. What if the cattle rancher put a compressed natural gas station at the roadside and sold his biomethane to his neighbors, who were growing switchgrass or some other biofuel crop? How difficult would it be to use a CNG tractor? The resulting biofuel that the second farmer produced could also be used locally, in other vehicles. Such as in the cattle rancher's car. :)

I think one of our future needs is going to have to be figuring out solutions that get away from long distance transport of everything, in favor of more local production and consumption.


Pig Manure Converted to Crude Oil

The reference to $13 a barrel may be a bit off, that's what was estimated for a larger scale production facility in a radio interview.


Hey, that's great!  I'd quibble about the terminology ("thermochemical conversion" and "thermal depolymerization" appear to be more or less the same thing) but being able to produce oil from non-fatty organic stuff is progress.

Let's see, this mentions a hog population of about 60 million (doesn't say if this is a snapshot or annual production), and the Nat. Geo. article states a figure of 21 gallons per pig.  The product of these two figures is 1.26 billion gallons (per year?); perhaps 2% of diesel consumption, but progress.

The one thing I would do with this is try to use solar energy for the heat input in the conversion process.  If you can sell the methane as a product instead of using it for process heat, you've got one more revenue stream.

Shirley:  Bio-gas is usually mixed with carbon dioxide and sometimes other gases like hydrogen sulfide.  Scrubbing of some sort (like the CO2 Wash process) will be required if it's going to be stored at high pressure (CO2 will condense out and cause problems) or sold via pipeline.  Farms which are near gas lines could sell their product to wider markets, and it's fetching a mighty good price these days!  A farm producing 5000 barrels of bio-oil and 2500 barrels-equivalent of methane would be able to sell the methane for more than $140,000 if they got a price of $10/million BTU; today's natural gas prices are considerably higher.  (The oil, which definitely qualifies as "light sweet", would probably command in excess of $65/bbl; that's another $325,000 a year.)  This looks like it could be a big profit center.

Waste into gold.  This is the kind of thing I love to see.


only catch those methane bugs hate antibiotics. thus reduced production.


only catch those methane bugs hate antibiotics. thus reduced production.

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