We could be generating huge amounts of power from sewage. The process is fairly simple — just ferment sewage to produce a fuel called biogas. Biogas is almost entirely methane, and so is natural gas, so the two are essential interchangeable. The potential to produce biogas is almost entirely overlooked by most countries — except Sweden.
In Sweden, 25% of all energy use is derived from biomass. In Linköping, Sweden’s fifth biggest city, all the buses and garbage trucks run on biogas. The also have a biogas powered train line and some private taxis run on biogas.
Last year, the Swedish government converted more than 700,000 liters of ‘confiscated alcohol’ into biofuel, which otherwise are poured down the drain by the customs officials, as a standard procedure. “Amanda,” thought to be the world’s first biogas train, started chugging along the southeast coast of Sweden in 2005.
You can find biogas being sold at gas stations around Sweden. Cars using biogas created a stir when they began to be rolled out on a large scale at the start of the decade. The tailpipe emissions are virtually odorless, the fuel is cheaper than gasoline and diesel, and the idea of recovering energy from toilet waste appealed to green-minded Swedes.
In Stockholm, 25% of city buses run on biogas or ethanol.
A comprehensive book about of biogas is the Complete Biogas Handbook. It’s technical but full of information on this fuel. See also the book, Reusing the Resource, which is all about treating sewage as resource, not a waste product.
For more on biogas in Sweden, see this article in The Guardian
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Many large landfills and sewage treatment plants in the US (large being a relative term) capture and combust their biogas in engines. Reciprocating engines are the most efficient use of a gas power supply (turbines would be more efficient), but due to some impurities in biogas, it requires recips and sometimes a bunch of maintenance. In Washington State, the largest landfill powers electric generators and both Seattle’s large sewage treatment plants have similar units.
I love the idea of getting the fuel distributed to mobile sources of air pollution. Now that more of the bus and taxi fleets are running natural gas-fired units, it would be realtively easy to convert to biogas!
Yes, mobile fuel sources are much more valuable than electric generation. Let’s copy Sweeden.
Interesting. I have not looked into biogas lately, but I think that there are (were) issues with scaleup, with anaerobic fermentation. I wonder what kind of subsidies does the Swedish government provide this industry…
I have a suggestion for the title of the article:
“Biogas: Producing Ultra-Efficient Fuel From Sewage” does not reflect what the article is about. IMO, fuels by themselves cannot be termed as efficient, it is the conversion processes that are efficient or otherwise. For example, efficiency of burning natural gas in a fuel in SOFC (solid oxide fuel cell) is higher than that in a conventional gas turbine. Here, the natural gas by itself is not “ultra-efficient”, it is just clean burning (low SOx emissions, low particulates).
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Ok,regards from Uruguay South America.