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The Switch: Biogas
In the final installment of our energy series, The Switch, we'll talk about generating energy from waste. Biogas, otherwise known as methane, comes from three major waste sources: cow manure, landfills and waste water (which is a nicer way to refer to sewage). Each of these kinds of organic waste produces methane as it decomposes. Through the use of a digester, it's possible to capture this gas and use it to generate heat and electricity. Landfills and dairy farms in Oregon have started using digesters to generate their own power and, in some cases, additional energy to sell back to the electrical grid.
Methane is also a greenhouse gas. So capturing it as a power source has the added benefit of keeping it from further polluting the atmosphere. Federal and state tax incentives mean more and more businesses and municipalities will be likely to consider biogas as an energy source in the next few years.
Do you work on a dairy farm, at a landfill or a water treatment facility? Do you currently use biogas as a power source? Are you considering it? What do you see as the advantages and drawbacks?
GUESTS:
- Dan Hurley: Senior engineer associate for Lane County Public Works Waste Management Division
- Mark Kendall: Senior policy analyst for renewable resources in the Oregon Department of Energy
- Bill Eddie: Director of origination and procurement at Bonneville Environmental Foundation
Tagged as: the switch
Photo credit: Ecosan / Flickr / Creative Commons
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In the THU DEC 11 2008 OREGONIAN you can find an article about a digester project involving Three Mile Canyon Farms, NW Natural Gas, and Bonneville Power. It is staggering that this type of project is not already commonplace. Just in terms of water supply protection it makes sense. I lived next to a dairy farm near Banks and waste and water was one of the owner's ongoing curses.
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We have to be careful that providing financial incentives does not make a bad situation worse. In two of these cases - livestock and landfills - we have a bad situation that could be made better by minimizing the generation of gas in preference to using the gas that is generated. The last thing we want to do is have the incentives lead to the creation of more gas.
In one sense, using livestock manure to generate energy is like strapping a windmill to your SUV to generate power. You put a lot of energy into the system, and get little out. With livestock, huge amounts of energy and fertilizer goes into growing the food for the cattle. Much of that energy comes out of cattle in the form of methane directly from their guts - something that the manure digesters cannot capture. According to EPA, close to 3/4 of the methane from livestock comes from their guts, and only about 25% comes from the manure. In addition, huge amounts of greenhouse gases are generated directly from growing the corn and soy to feed cattle, and from the nitrogen fertilizers (released as nitrous oxide - a very potent greenhouse gas).
With landfills too, capture of methane by the landfill is not complete, and if only a small amount of methane escapes the landfill, it negates all of the energy captured from the landfill gas that is captured. This doesn't mean that you shouldn't capture and use landfill gas, but it does mean that you should not purposefully put organic materials into landfills in order to capture the gas.
Peter Spendelow, Ph.D.
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Source of the EPA numbers:
http://www.epa.gov/methane/sources.html
EPA numbers show that livestock are the largest sources of human-generated methane in the United States if you combine the "enteric fermentation" (methane from the guts) at 115 Tg CO2 equiv.with manure at 39.1 Tg CO2 equiv. Landfills produce 131.2 Tg CO2, so both are very large sources.
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Is there a substantial difference between cattle and livestock in general? And are these beasts problematic only when they are industrialised?
Here we have free range chickens and goats and are growing non GMO, non-patated organic soy.
Is it the animals or the practices of industrialisation where a few very rich owners who never step on the farmland reap profits at cost to the earth and food quality?
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In reply to Zaph Mann's question, the issue of methane directly produced by animals in their guts ("enteric fermentation") is comment to cattle, goats, sheep, and all the other ruminant mammals, but I don't think it is a problem with other mammals. I think the amount of methane produced by cattle and goats is not that different between factory farmed animals and animals raised in less-crowded conditions, but I don't have data on that. On the other hand, methane releases from manure are a problem when you have high concentrations of animals of any kind in factory farms and you have wet manure that gets stored temporarily in large lagoons. They are not a problem where animals are not crowded and you don't have the manure lagoons that go anaerobic and produce methane.
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I'd be curious to know if it would be technically feasible to create small scale "digesters" or fermenters that could be used by local communities or even individual households to make usable methane or alcohol from common yard debris, or even better, invasive plants like Himalayan Blackberry, English Ivy or Reed Canary Grass, etc. That could help to "finance" eradication efforts & would reduce household energy expenses.
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This is a very smart idea. I use goats, but they take a lot of fencing in.
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I applaud the efforts of the dairy industry to help reduce greenhouse gasses and create more energy alternatives. While I understand that cattle contribute to methane levels, I find it hard to believe that so many people are focused soley on the issues of cow burbs and gas.
We have so many other areas to consider where people contribute to the levels of green house gas and other polution. I believe that concentrating our efforts on some of these other areas will impact our environment more. Changing our habits as consumers and how society disposes of waste is hugely important.
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I know that other countries such as Japan and Sweden have used incinerators to dispose of solid wastes for decades. The emissions are filtered through lime scrubbers and other filters to have virtually no tracable emission levels. This technology could be adapted used for reducing the impacts of burning solid waste.
This will also reduce the mass of the waste by 80%. Incinerators are also used for generating energy (like a steam generator). Maybe there are options for generating engergy from fecal waste at multiple stages of the operation.
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Methane is 20 times more potent than CO2 over a 100 years period. It's about 70 times more potent over a 20 year period. The next 20 years are more critical than most of us know.
Keeping compostables out of the landfill and composting them makes more sense than sending them to landfills to capture a percentage of the methane (20-40%). . Dealing with problems at the source is always a better solution than sending them downstream. . Of course that means taking personal responsibility for our own mess.
Compost will capture and store the carbon in the soil and has many other upstream benefits for the environment. Improved soil tilth, better water retention, less need for fertilizers , pesticides, and herbicides. All and all an improve local foodshed. -
The Senator thinks we should be taxed across the board. No, tax the people that make the most money, including large corporations. The corporations are not moving to other states, thats a rediculous comment, they are going out of business, which has nothing to do with our taxes. The middle and lower class citizens are barely getting bye these days, its smarter to go after the people that make the most money, period.
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Comments are now closed.
I am an engineer working on a project to upgrade a combined cycle power plant in California. The plant burns the methane produced from sewage digesters, in a sewage treatment plant. This is an easy way to generate green energy. The technology for combined cycle power plants is well developed. The gas turbine is essentially a jet engine. The heat generated from the jet engine is used to heat up steam to generate more energy in a standard steam turbine. This technology is very well developed on both large and small scale.
Converting methane to power and CO2 is a good bet, because methane is a horrible green house gas, much worse than CO2. By converting it we generate power with something that was waste in the past.
Sewage treatment plants and landfills can be used to generate electricity that otherwise would be burnt in flares, or released to the atmosphere.
We should increase the electric power we produce with the green technologies we currently have fully developed instead of waiting for the magic bullet technology to solve our greenhouse gas problem.