Plasma Gasification of Waste Creates Energy

This article was published by Newsletter, issue #51, .

In the related realms of ecological stewardship and human energy production, two of the critical questions are: How do we dispose of waste products in an environmentally responsible manner — such as recycling? How do we produce the energy demanded by our modern industrial culture, with minimal impact on the earth and its ecosystems? So far, mankind's track records in these two areas, have been abysmal. With landfills growing in size, number, and toxicity, it would appear that humans are intent upon turning our only home into a trash heap. Likewise, our burning of valuable fossil fuels is the primary cause of airborne pollutants and other sources of damage to the health of humans, animals, and plants worldwide. (In fact, future historians may look back upon our burning of these hydrocarbon resources as the single most significant mistake ever made by our race, because those resources may be critically needed by future generations in the construction of space colonies.) Other energy production methods have been similarly lamentable, such as our destruction of waterways and migratory fish through the damming of rivers.

Traditional waste-to-energy methods attempt to solve both of these major problems by incinerating garbage that would otherwise end up in a landfill, and using the heat to generate steam, which in turn powers steam turbines, thus generating electricity. However, this burning of trash also generate smoke as well as ash and other pollutants that still contain some of the most virulent chemicals found in the original trash. What is needed is a method that breaks down the trash into its constituents, at a molecular level, thereby converting toxic chemicals into their fundamental elements, all of which are harmless and can be reused for industrial applications.

Plasma gasification was invented by NASA during the 1950s, in order to create the temperatures encountered by spacecraft during reentry into Earth's atmosphere. The process involves utilizing an electrical arc to superheat a gas, turning it into plasma, which is hot enough to break down any material into its components — with temperatures up to 5,500 degrees C (9,900 degrees Fahrenheit). Plasma converters are now being used commercially for waste treatment, and produce elemental gas molecules and slag. The converter itself requires electricity, but the overall process can be net energy positive, when the proper waste materials are used as an input.

Plasma arc waste disposal has been employed in several countries. In the United States, the first plasma gasification plant will be developed by Geoplasma in St. Lucie County, Florida, and is planned to begin operations in 2009. It was originally intended to generate 60 milliwatts (MW) of electricity every year — enough to power 50,000 homes — as well as 550,000 kg (600 tons) of solid waste (slag). This translates into the disposal of 2.7 million kg (3,000 tons) of garbage per day. The county planned to not only add no further trash to their landfills, but also, within 18 years, to empty their existing landfill, which contains 3.9 million metric tons (4.3 million tons) of garbage collected since 1978. However, current projections are for the vaporization of 1,500 tons of garbage every day.

Detractors of waste gasification argue that it cannot be used to dispose of radioactive waste, and it does produce slag. Also, constructing just a single plant poses enormous technological and budgetary difficulties for even the largest of municipalities. Other concerns include the longevity of the liner used within each converter, being subjected to such intense levels of heat.

But this innovative new approach to energy production offers many advantages: the syngas (synthesis gas) it produces — once cleaned of all volatile compounds — can be burned cleanly. It effectively neutralizes a range of toxic chemicals, including dioxin, and dangerous biological material, including HIV-infected blood. It produces reusable metals, as well as the slag, which can be used for pavement materials, etc. A converter facility could be built right next to a landfill, minimizing transportation costs, and turning an environmentally unfriendly eyesore into a source of effectively free energy. Unlike traditional waste-to-energy schemes, gasification does not burn the waste and turn it into smoke.

Plasma arc waste disposal may emerge as the ultimate form of green energy — converting garbage and landfills into electricity and reusable chemicals.

Copyright © 2009 Michael J. Ross. All rights reserved.
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