Energy From Trash

I already discussed a potential breakthrough in creating energy from sewage; here’s a concrete means of creating energy from trash that can make landfills obsolete. From CNET:

Columbia University researchers assert that tech breakthroughs in recent years now make sending trash to landfills a waste of energy.

While recycling and energy recovery from plastics is on the rise, about 86 percent of used plastics are still sent to landfills. It’s a big waste considering its energy potential, according to the 33-page report, “Energy and Economic Value of Non-recycled Plastics and Municipal Solid Wastes that are Currently Landfilled in Fifty States” (PDF).

The study, co-authored by researchers at the university’s Earth Engineering Center, determined that if the U.S. took all the non-recycled plastic currently sent to U.S. landfills each year and instead sent that trash to a waste-to-energy (WTE) power plant, it would produce enough electricity for 5.2 million U.S. homes annually.

If that plastic was separated by type, enough petroleum-based plastics could be recovered and sent to a pyrolysis conversion facility, a plant that converts non-recycled plastics into fuel oil, to produce 3.6 billion gallons of oil. That’s enough to power 6 million cars for a year…

The energy potential is even greater when you expand beyond plastic.

“Hypothetically, if 100 percent of the landfilled municipal solid wastes were diverted from landfills to new waste-to-energy power plants, they would reduce coal consumption by 108 million tons and produce 162 million MWh of electricity, enough to power 16.2 million households for one year,” said the report.

The report’s assertion that the tech for this is already available is evident.

The article doesn’t explain what WTE power plants do exactly, so I went to my trusty Wikipedia. It looks like mainly they, uh, incinerate trash. Incinerating all of our trash sounds environmentally problematic, but it’s actually better in terms of greenhouse gas emission than using landfills, according to Wikipedia (based on a 2003 Columbia SEAS paper):

In thermal WtE technologies, nearly all of the carbon content in the waste is emitted as carbon dioxide (CO₂) to the atmosphere (when including final combustion of the products from pyrolysis and gasification). Municipal solid waste (MSW) contain approximately the same mass fraction of carbon as CO₂ itself (27%), so treatment of 1 metric ton (1.1 short tons) of MSW produce approximately 1 metric ton (1.1 short tons) of CO₂.

In the event that the waste was landfilled, 1 metric ton (1.1 short tons) of MSW would produce approximately 62 cubic metres (2,200 cu ft) methane via the anaerobic decomposition of the biodegradable part of the waste. This amount of methane has more than twice the global warming potential than the 1 metric ton (1.1 short tons) of CO₂, which would have been produced by combustion. In some countries, large amounts of landfill gas are collected, but still the global warming potential of the landfill gas emitted to atmosphere in e.g. the US in 1999 was approximately 32 % higher than the amount of CO₂ that would have been emitted by combustion.

Well, there you go. Maybe incinerating trash for energy isn’t as bad as it sounds. We’d better leave some to fuel our DeLoreans in 4 years though…