The energy contained in plasma waste is found in its chemical bonds. Plasma gasification technology has been developed over decades, and with this technology the energy in the waste can be extracted. The process is theoretically simple: when an electric current is passed through a gas (usually ordinary air) in a closed container, an electric arc is created and an ultra-high-temperature plasma, or ionized gas, is produced, which can reach temperatures of up to 7,000 degrees Celsius, even hotter than the surface of the sun. This process is known as "lightning" when it occurs in nature, so plasma vaporization is literally artificial lightning that occurs in a container.
The extremely high temperature of the plasma breaks the molecular bonds of any waste in the container, converting organic material into syngas (a mixture of carbon monoxide and hydrogen) and other material into a glass-like slag. The syngas can be used as fuel in turbines to generate electricity, or to produce ethanol, methanol and biodiesel; the slag can be processed into building materials.
In the past, gasification has struggled to compete on cost with traditional municipal waste disposal methods. But maturing technology has made the method less expensive, while energy prices have climbed. Now "the two curves have intersected -- it's becoming cheaper to send waste to a plasma plant than to pile it into a mountain of garbage," said Luis Zirceo, director of the Georgia Institute of Technology's Plasma Institute.
Early in the summer of 2009, waste management giant Waste Management began working with InEnTec to put InEnTec's plasma gasification equipment into commercial use. They are building large-scale pilot plants in three U.S. states - Florida, Louisiana and California - each with a capacity to process more than 1,000 tons of waste per day.
Plasma is not perfect. Although the toxic heavy metals implicit in the vitreous slag have passed the EPA's leachable standards (Japan and France have been using the stuff as a building material for many years), communities are skeptical about building such a plant. Syngas power generation has a smaller carbon footprint than coal-fired power generation. Zirceo describes how "treating 1 ton of waste with plasma is equivalent to reducing the amount of carbon dioxide emitted into the atmosphere by 2 tons." But the method still increases net greenhouse gas emissions.
While things can't be perfect, the U.S. Environmental Protection Agency has calculated that if all U.S. municipal solid waste were treated with plasma and electricity were generated, it would provide 5 percent to 8 percent of the nation's total electricity needs -- the equivalent of about 25 nuclear power plants or all the hydroelectric power plants currently in operation.
At present, foreign plasma arc waste melting technology in the melting of medical waste, municipal waste (with the best scale of this technology can be 1000 tons of municipal waste per day, power generation of 20 megawatts), incineration of fly ash and other fields have entered the practical application stage. It is expected that by 2020, the U.S. waste production will reach 1 million tons per day. Therefore the use of plasma technology to recover some of the energy from the waste will become increasingly important.