The Power of Poo

Farmers generate energy, save money and help the environment, with a little help from some dung.

This cow's poo helps keep the lights on. [Credit: Monica Heger]
By | Posted October 8, 2008
Posted in: Environment, Featured, Life Science
Tags: , ,

I saw the monstrous blue tank before I saw the New Hope View sign. Even though the tank was set back from the road, it stuck out like a sore thumb nestled among the bucolic hillsides. As I turned into the driveway, I couldn’t help but wonder if other passersby knew what it held—three million gallons of liquefied cow dung.

New Hope View Dairy Farm is one of 15 farms in New York State generating electricity from an ever-plentiful, if rather unlikely source: cow manure. At New Hope View in Homer, New York the 1,000 dairy cows produce enough poo to power the entire farm.

This process of converting manure to electricity—called anaerobic digestion—is being done on farms throughout the United States and is becoming more widespread as energy costs soar.

Wisconsin leads the pack with 20 farms producing biogas, the gas captured from the poo, about 60 percent of which is methane. A utility company in Vermont offers its customers the option of buying cow-power, and some California dairy farms just signed a contract with Pacific Gas & Electric.

The benefits are multifold for farmers. Anaerobic digesters don’t just turn manure into electricity; they also create, as a byproduct, a nutrient rich, odor-free fertilizer as well as a solid that farmers can use for compost or cow bedding. Plus, there are environmental benefits. Manure emits methane, a greenhouse gas with 20 times the heat trapping potential as carbon dioxide. Capturing the methane to use for electricity prevents it from entering the atmosphere. The neighbors are also appreciative, as anaerobic digestion greatly reduces the stinky smell.

“It’s cleaning the environment and tapping an untapped resource,” says Trevor Head, owner of New Hope View Dairy Farm.

Anaerobic digestion also offers farmers an added source of income—they can save money on electricity, cow bedding or compost, and possibly make extra money by selling leftover electricity or solids.

In order to make money, though, you have to spend money. And the biggest hurdle to overcome is price. Initial capital investment, which can be over $1 million, is often a disincentive, and the eventual payback can take years. Another problem is maintenance. Dairy farmers are in the business of making milk, not electricity. Operating an anaerobic digestion system is time away from their main job.

***

Head and I tromp across the field to get a better look at his digester, where the process of converting manure to electricity begins. Standing next to the cow barn, he points to a long white dome popping out of the ground in front of the gargantuan blue tank holding the liquid poo. That’s the digester. It is a long, cylindrical, airtight, underground tank kept at 100 degrees Fahrenheit—the same temperature as a cow’s stomach.

He collects manure from the cows and loads it into the digester. Bacteria, which come free of charge with the cow pies, go to work breaking down the dung. “The digester is a living, breathing organism, just like a cow,” he says.

There are two types of bacteria in a cow’s stomach that get passed out with poop. The first one breaks the poo down into acids. The second type breaks the acids down into a gas. Besides the 60 percent that is methane, the rest of the gas is mainly carbon dioxide, with trace amounts of hydrogen sulfide and ammonia.

Head says the manure takes about three weeks to fully break down. As it breaks down, it moves along the length of the digester. It goes in one end and comes out the other, just like in a cow. Standing in such close proximity to the digester, I’m not disappointed that the poop and its accompanying odor is kept underground.

An underground PVC pipe carries the biogas to a microturbine in the utility room. Head and I walk toward the utility room where the loud whirring of the microturbine can be heard long before setting foot inside.

The biogas from the manure has two main tasks. The first is to heat the water that keeps the digester at 100 degrees Fahrenheit. Secondly, it powers the microturbine, which generates electricity for the farm. If more biogas than is needed to continuously power Head’s 70-kilowatt microturbine is generated, the remainder is burned off.

Head points about 30 feet away from the utility room to a long pole that looks a bit like an oversized tiki torch. Every so often a billow of steam drifts out the top. It is the extra biogas being burned off.

“It’s a balancing act,” Head says. Ideally, you wouldn’t have any leftover gas. Or the leftover gas could be used for other things—Head wouldn’t mind if he could use it to heat his house, for instance. But that would require a very long pipe to channel the gas to his house a mile away. Selling electricity back to the grid is even more complicated and requires a purer biogas and cooperation from the local utility company.

Next page »

Related Posts


comments

All comments are moderated, your comment will not appear on the site until it has been approved.

  1. This is a really great article! But, I have a question. I recently went to a lecture on energy and the environment given by an economist, of all people. But, there was a scientific discussion about the amount of greenhouse gases produced by methane. I don’t remember the specifics, but essentially many people brought up the point that methane has a higher concentration of greenhouse gases per molecule than say carbon dioxide. One, is this accurate? Two, is less methane required for to generate heat/power than other forms of energy so that the higher concentration of carbon dioxide per molecule is essentially canceled out because less methane is needed?
    Thanks!

    Stephanie Heger, October 9, 2008 at 3:47 pm
  2. Methane is a more potent greenhouse gas than carbon dioxide–about 20 times more potent. This just means that one molecule of methane traps more heat than one molecule of carbon dioxide.

    By using the biogas from the cows to make energy, you are preventing that methane from entering the atmosphere.

    When you use methane as energy, you are essentially breaking the bonds that hold it together, which creates the heat used as energy. So the end product is no longer methane. One of the byproducts is carbon dioxide. However, you are still emitting less greenhouse gases because you are preventing the methane itself from entering the atmosphere.

    Does that make sense?

    Monica, October 10, 2008 at 12:20 pm
  3. Enlightening article…thanks for explaining the system and process in layman’s terms and for the humorous personal interjections. Such a fresh approach – a serious global concern addressed responsibly without the gloom and doom undertones many writers feel compelled to burdon the reader with. Question: What are the chances that human poo will also find a niche in natural energy production?

    Kay Hunt, October 13, 2008 at 9:48 am
  4. Anaerobic digestion is a very promising technology indeed — some big dairies are generating power from the methane produced and selling it back to the electric grid. (NY Times, Sept. 24, 2008)

    Problem is, it isn’t really cost-effective for smaller dairy farms, which although a dwindling portion of the total in the U.S., still produce half our milk.

    Michigan State University researchers aim to develop scalable, modular technology to digest manure and use the methane to generate electricity — and use the liquid and solid byproducts for additional biofuel, fertilizer, animal bedding, feed and even building materials.

    The story, linked to a wealth of background, can be read at: http://news.msu.edu/story/5695/

    Mark Fellows, October 17, 2008 at 12:17 pm
  5. I think this is a great article. It points out the multiple benefits of biogas production.

    Michel, October 20, 2008 at 12:26 am
  6. OH MY GOD ITS LARRY! THE COW THAT COMFOTS ME WHEN PPL MAKE FUN OF ME FOR SHITTING MYSELF AND LICKING WINDOWS!!!!!!!!!!!!!!!!

    lil_miss_geekiness, December 29, 2008 at 1:24 am
  7. im doing homework right now on poo power but im from the u.k and im only in
    year 7 / eighth grade and out off all of the sites i have been on this make the most sense!
    thank you i can finally finish my homework !
    xx

    megan hethear, March 9, 2010 at 1:03 pm
  8. hi im from the u.k and im only in year 7 / 8th grade ! im doing my homework on
    poo power and out of all of the websites i have been on this one makes the most sense !
    thank you sooo much now i can finally finish my homework !
    xx

    megan hethear, March 9, 2010 at 1:05 pm
post your comment