Creating Ethanol from Trash
A new system for converting trash into ethanol and methanol could help reduce the amount of waste piling up in landfills while displacing a large fraction of the fossil fuels used to power vehicles in the United States.
The technology, developed originally by researchers at MIT and at Batelle Pacific Northwest National Labs (PNNL), in Richland, WA, doesn't incinerate refuse, so it doesn't produce the pollutants that have historically plagued efforts to convert waste into energy. Instead, the technology vaporizes organic materials to produce hydrogen and carbon monoxide, a mixture called synthesis gas, or syngas, that can be used to synthesize a wide variety of fuels and chemicals. The technology has been further developed and commercialized by a spinoff called Integrated Environmental Technologies (IET), also based in Richland, WA. In addition to processing municipal waste, the technology can be used to create ethanol out of agricultural biomass waste, providing a potentially less expensive way to make ethanol than current corn-based plants.
The new system makes syngas in two stages. In the first, waste is heated in a 1,200 °C chamber into which a small amount of oxygen is added--just enough to partially oxidize carbon and free hydrogen. In this stage, not all of the organic material is converted: some becomes a charcoal-like material. This char is then gasified when researchers pass it through arcs of plasma, using technology developed in the 1990s at MIT's Plasma Science and Fusion Center. The remaining inorganic materials, including toxic substances, are oxidized and incorporated into a pool of molten glass, made using PNNL technology. The molten glass hardens into a material that can be used for building roads or discarded as a safe material in landfills.
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