http://www.mindfully.org/Air/2002/Incineration-RepackagedJul02.htmPYROLYSIS AND GASIFICATION
Two other technologies being promoted as clean alternatives to typical trash incinerators are pyrolysis and gasification. Pyrolysis is a thermal destruction process that burns waste in the absence of oxygen. A plasma arc is often used to generate the heat at high temperatures. This process produces a mixture of gases, liquids and solids, some of which will include toxic chemicals depending on the make-up of the original waste mixtures. With household trash, the emissions and solid residuals can be expected to include heavy metals, dioxins, and other contaminants typically found when household trash is burned.
Gasification is a similar thermal destruction process, only in this case small amounts of oxygen are present during the heating process, which also occurs at high temperatures. In this process, often called "starved-air gasification," a gaseous mixture is produced that will again include toxic chemicals depending on the make-up of the original waste mixture. If household trash is gasified, emissions will again include heavy metals, dioxins, and other contaminants.
Both of these technologies are considered to be in the developmental stage with regard to their application to household trash. As a practical matter, the health and environmental concerns that these processes raise seem no different than if the waste were burned in a traditional incinerator. With both of these systems, toxic gases are formed during the treatment process that are similar to those found during the combustion of household trash in a traditional incinerator and are released out a stack. Some—but not all—of these emissions may be captured by pollution control equipment. With pyrolysis, solid residue remaining after the treatment may contain toxic chemicals similar to those found in ash from traditional incineration.
http://www.sierraclubcalifornia.org/alchemyofgarbage.shtmlTHE NEW ALCHEMY OF GARBAGE
By Bill Magavern
No one likes trash landfills. They often smell bad, attract pests, and leak toxins into the environment. To reduce the need for such unwanted facilities, Sierra Club has long supported waste reduction, reuse, materials recovery and composting, and has opposed trash incineration because of its adverse effects on our air, water and health.
Now some companies and government officials are once again touting technological solutions to California’s solid waste problems. These advocates claim that what they call “conversion technologies” can keep our garbage out of landfills and turn it into useful products. Clearly, anyone who could turn trash into gold would become as popular as medieval alchemists. But, as Californians Against Waste puts it, “Conversion Technologies (CT) is an unfortunate euphemism that refers to an unconstructively broad spectrum of real and theoretical waste management technologies that range from relatively benign organics composting-like facilities to environmentally dangerous and economically dubious incinerator-like facilities that ‘cook’ garbage at temperatures up to 7,000ƒ F and have been found to produce dioxins, one of the most carcinogenic substances known to humankind.”
Indeed, controversy has surrounded the high-heat technologies, like gasification, pyrolysis and plasma arc, because of concerns that their emissions will pose the same kind of health threats as those created by solid waste incinerators, including the emission of toxins that cause cancer and reproductive and developmental damage. For this reason, community groups have opposed a number of facilities that would “cook” garbage and convert it into saleable commodities like electricity and liquid transportation fuels. Recycling advocates have also expressed concerns that development of large, expensive trash-cooking facilities would detract from ongoing efforts to reduce, reuse, and recycle (the “3Rs”) more of California’s solid waste.
Sierra Club California has kept an open mind to the possibility that new technologies could reduce the need for landfills, but we insist that these technologies not emit poison into our air or water and not interfere with the 3Rs. During the three-plus years that the issue has been debated in the Legislature, our mantra has been “show us the emissions data.” Without credible, verifiable real-world data on the effect that gasification and pyrolysis facilities have on our air and water, we can not support any policies that would favor or subsidize such plants. Although the companies selling the products have often promised that such evidence was imminently forthcoming, they have yet to actually present it.
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