Interview of Prof. Nickolas Themelis with NBC reporter working on MSW gasification project
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Interview of Prof. Nickolas Themelis with NBC reporter working on MSW gasification project
Municipal (MSW) and other solid wastes contain carbon and hydrogen which, when reacted with oxygen. produce heat.
This can be done
1) by controlled combustion of the wastes and using the heat of combustion for generating electricity or for heating.
2) By gasification, whereby partial combustion plus external heating (electricity or fossil fuel) are used to produce a “syngas”, consisting of carbon monoxide and hydrogen plus carbon dioxide. The syngas is then combusted in a gas engine to produce electricity; or it can be used to produce a liquid fuel, which is then combusted in an engine to produce mechanical or electrical energy.
MSW is the worst possible fuel used by humanity. The simplest way to recover the chemical energy in MSW is by direct combustion of the solid wastes. Gasification, followed by combustion of the syngas, is a more complex process and requires a higher capital expenditure but has the potential for higher energy efficiency.
So far, after 60 years of development, direct combustion is the only means of recovering the chemical energy of MSW: About 300 million tons of MSW are combusted in such plants in over fifty nations.
In the last 25 years, the Earth Engineering Center of Columbia University has investigated dozens of waste-to-energy processes. We believe that gasification has a place in the recovery of energy from wastes but the feedstock should not be the typical U.S. MSW which has a very low calorific value (10 MJ/kg) but source separated mixed plastic wastes (calorific value: 30 MJ/kg).
