The idea of turning trash into usable energy has been around for decades. Concerns about energy security and warming, as well as the rising cost of disposing of global waste, have prompted gasification, a method used in the past to dispose of hazardous waste such as medical waste, to potentially be used to for household garbage.
Gasification and plasmagasification both involve heating waste at high temperatures in a closed combustion chamber. The process takes place in the near absence of oxygen, and instead of burning the organic components of the waste, they are converted into a syngas (synthesized gas) of carbon monoxide and hydrogen. This gas is filtered so that the chemical components can be "cleaned" to remove toxic molecules and gases, and then burned to produce energy, or converted into fuels such as biogas, ethanol, or synthetic diesel. After this process, dust, filters and cleaned chemicals are left behind, which can then be disposed of and sent to a landfill or discharged into the sewer.
In the past, waste was treated by burning it in an incinerator to create steam that drove a turbine, which drove a generator to produce electricity. In comparison, gasification produces more energy than burning a given amount of waste. And even more energy can be generated if ultra-high-temperature arc plasma is added to the syngas.
Plasma gasification evaporates waste at higher temperatures, vaporizing more organic waste at temperatures of up to 10,000 degrees Celsius, compared with 1,600 degrees Celsius for normal gasification. Another advantage of plasma gasification is that the high temperatures don't turn the waste into a fine ash, but rather a glassy solid that could theoretically be used as filler in the construction industry.
Pilot plants for the gasification of waste technology have been established in the United States, Canada, France, the United Kingdom and Portugal, most of which use plasma gasification technology. Two commercial plasma waste gasification plants have been established in Japan. But these pilot gasification plants have focused on treating household waste rather than generating energy from it.
But IST Energy still thinks the pilot gasification plants are too small. Its closed, non-plasma "green energy" system (GEM), for example, can process three tons of municipal waste per day, releasing gas that could generate enough energy to power a building housing 500 people.
Despite a growing number of pilot waste-to-energy plants around the world, not everyone is welcoming the environmentalists' "ideal". Opponents argue that the process of gasifying waste is not clean, that it is not environmentally friendly in terms of energy consumption and pollution emissions, and that it could "fan the flames" of a wasteful society.
Toxic emissions can be generated when organic materials are heated at high temperatures during the gasification process. Others say chlorine gas, which is produced during the gasification process, could cause additional problems in the high temperatures and lack of oxygen of plasma gasification.
Early explorations of waste gasification were often environmentally and financially ruinous, and the method has been vilified, including a toxic gas leak at a commercial waste gasification plant in Karlsruhe, Germany. The plant was temporarily shut down in 2000 and officially closed in 2004.
Opponents also argue that gasification still produces carbon dioxide. Neil Tangri of the Global Alliance for Incinerator Alternatives says gasification plants are nothing more than a gilded edge to incinerators. He said, "There's an intermediate process of waste gasification yes, but the end result is still combustion."
Another green "proof" question about waste gasification is how efficient the pilot plants are at generating energy and minimizing greenhouse gas emissions compared with other waste treatment methods.
A recent study by the Tellus Institute, an independent think tank in Boston, concluded that landfills with methane recapture systems emit 2.5 times less carbon dioxide than burning gasification mixtures, even though gasifying each ton of waste produces five times more energy per ton than landfilling.
In short, it will take some time to achieve the full effect of getting rid of waste, and for now it seems that waste gasification is not a panacea for waste disposal and energy problems, and only time will reveal the answer.