Landfills might seem like the last place on earth one might consider as a resource for renewable energy, but with the right technology, trash can be turned into ethanol and methanol in a cost-effective, efficient manner with minimal environmental impact. Landfill material has been turned in energy in the past through incineration, but while this strategy can produce usable energy, it generates significant pollution in the process.
An article in Technology Review highlights a new system originally developed by researchers at MIT and at Batelle Pacific Northwest National Labs and commercialized by an enterprise called Integrated Environmental Technologies (IET) which instead uses extremely hot temperatures to vaporize trash, thus subtracting harmful emissions from the equation. This process, called plasma-based waste processing, yields a gas called "syngas" composed of hydrogen and carbon monoxide. IET's proprietary system has been dubbed "Plasma Enhanced Melter." According to the Tech Review piece:
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.
The company intends to use the Plasma Enhanced Melter across a number of applications and to scale it to the point of offering distributed power generation. IET sees a potential economic advantage in the fact that numerous companies will pay to have waste removed directly from their facilities, and a commercial viability advantage in the fact that the system's low emissions make it likely to pass air quality permitting inspections.
So far, IET has sold commercial systems to companies in the US, Japan, Taiwan and Malaysia. It's doesn't seem clear yet whether the concept will take widely, but it does appear that through a combination of intensive scientific research and a tenacious, detailed business approach, IET will become a reliable case study for how we can close the loop on our waste stream and reintroduce it as a power supply.









