synga

takepart.com
Turning Trash Into Gas May Finally Be a Thing
People have been trying for decades to eliminate landfills and fight climate change by vaporizing garbage—with disappointing results. But that could be changing.

Excerpt:

Waste gasification could help transform the fight against climate change. How? For one, by reducing reliance on landfills, which are among the leading human-made sources of methane, a greenhouse gas that’s up to 84 times as potent as carbon dioxide over a 20-year period.

Gasification also could make a dent in global warming by reducing consumption of fossil fuels. Waste-derived syngas comes from previously used materials that would otherwise emit greenhouse gases through decay, rather than from hydrocarbons extracted solely for the purpose of burning. When that syngas and its byproducts are converted into energy, they release less CO2—again, theoretically—than coal or petroleum.

the EPA calculates that gasifying 100 tons of waste a day instead of landfilling it could translate to a reduction of up to 66,000 tons of CO2 a year—the equivalent of taking 14,000 cars off the road by using the trash of a medium-size suburb.

Three basic approaches emerged. With conventional gasification, trash was heated to between 1,450 degrees and 3,000 degrees in the presence of a small amount of air or pure oxygen. Another process, pyrolysis, used lower temperatures and no oxygen; the idea was to generate less ash and other toxic byproducts. Plasma arc gasification, trumpeted by Wired magazine and tested by the U.S. Air Force, deployed a high-voltage electric current to create temperatures typically ranging from 7,200 degrees to 12,600 degrees, with the aim of generating more energy and even fewer pollutants per unit of fuel.In trials with small amounts of carefully prepared feedstock, all these methods seemed promising. But attempts to scale up led to complications.