Getting more from carbon dioxide
12 Dec 2001
Acrion Technologies Inc., a small business sponsored by the US Department of Energy, is showcasing a method this week that could offer a major advancement in reducing pollution at municipal landfills where Americans deposit more than 100 million tons of household rubbish every year.
The rubbish creates a major source of air emissions, expelling carbon dioxide (CO2) and methane as it decomposes. At an open house at the New Jersey EcoComplex, Acrion is demonstrating how its innovation, dubbed the CO2 Wash, will make it easier to capture CO2 before it escapes into the atmosphere and to use the captured gases for commercial ventures, making such 'landfill gas-to-energy' projects more environmentally and economically attractive.
Since it began operating this summer, the system has been processing gases captured from decomposing waste at the Burlington County landfill. After moisture is removed, the gases are compressed and fed into the bottom of the unit's three-story high column. As the gases drift upward, refrigeration at the top of the column condenses the CO2 into liquid form. A portion of the liquid CO2 washes down the column, cleansing volatile organic contaminants from the gas.
Clean, high-grade fuel gas exits the top and can be used directly in turbines, boilers or fuel cells to generate electricity. Methane produced from Acrion's CO2 Wash is reportedly two-to-three times cleaner than required by fuel cells, which can convert the hydrogen-rich gas into electricity without using combustion. The landfill gas could also be further processed into methanol or upgraded to pipeline specifications, depending on local market needs.
The small stream of contaminant-laden CO2 that is used to wash out impurities in the landfill gas is vaporised and burned in a flare to destroy the volatile organic compounds. The CO2 not used for the wash is drawn off as a 99.99 percent pure liquid CO2 stream that can be used in a variety of commercial applications.
One option Acrion is examining is to pipe the CO2 to Burlington County's R&D Greenhouse and Resource Recovery Complex, where 'Jersey Fresh' tomatoes and other plants would benefit from the CO2-enriched environment. Acrion is also providing samples of the pure liquid CO2 to distributors and consumers for analysis and testing in commercial applications.
Acrion's innovation is expected to add to the growing interest in using landfill gas as a renewable energy resource. Current federal law requires many landfills to collect the gas and dispose of it in one of two ways: either flare the gas, or install a 'landfill gas-to-energy' system.
According to the US Environmental Protection Agency, every one million tons of waste deposited in landfills produces enough landfill gas to generate seven million kilowatt hours of electricity per year, which is said to be enough for 700 homes. Using this gas for energy purposes, rather than expelling it into the atmosphere, is reportedly the equivalent to removing more than 6,000 cars from the road, or planting 8,300 acres of trees.
