Creating Ethanol from Trash
Researchers find a way to make liquid fuels from waste cheaply and without the pollution produced by earlier methods.
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.
The next step is a catalyst-based process for converting syngas into equal parts ethanol and methanol. Ethanol is now widely used as a fuel additive, and it can also be used as a substitute for gasoline in some vehicles. Methanol is important for producing biodiesel and is currently made from methane in natural gas.
There is enough municipal and industrial waste produced in the United States for the system to replace as much as a quarter of the gasoline used in this country, says Daniel Cohn, a cofounder of IET and a senior research scientist at the Plasma Science and Fusion Center.
According to Jeff Surma, another cofounder and the CEO and president of IET, the multistage system makes it possible to produce fuels from waste at competitive costs. The economics look even better when including the fact that cities and manufacturers will pay to have waste removed, he says. This makes possible costs of between 10 and 95 cents per gallon of fuel, depending on the size of IET’s system and how much it is paid to take waste. IET is currently in talks with a major Midwest utility and several municipalities interested in employing its technology, Surma says.
But George Sterzinger, executive director of the Renewable Energy Policy Project, an advocacy group in Washington, D.C., cautions that IET shouldn’t rely too much on being paid for its feedstock. It will face stiff competition from landfills, which have an economic stake in keeping the waste to themselves, he says.
At this stage, multiple new approaches for transforming waste into biofuels are being explored, and the winner is not yet clear. IET’s success will depend in large part on how it scales up its technology and develops a complete system, from getting the waste in the first place to distributing the fuel that it makes.