In the Lab

• By Heida Diefenderfer
• Feb 01, 2002

New Process Enhances Use of Landfill Gas, Improves Air Quality

Columbus, N.J. -- Acrion Technologies Inc., a small business sponsored by the U.S. Department of Energy (DOE) offers a new approach in reducing pollution at municipal landfills where Americans deposit more than 100 million tons of garbage every year.

The garbage creates a major source of air emissions, expelling carbon dioxide (CO₂) and methane as it decomposes. Acrion will make it easier to capture the CO₂ before it escapes into the atmosphere and use the captured gases for commercial ventures, making such "landfill gas-to-energy" projects more environmentally and economically attractive.

Acrion, based in Cleveland, Ohio, received a small business innovation research grant from the DOE in 1998. With the federal backing, the company developed a process called "CO₂ Wash" which it initially tested at a New York site.

Now, with follow-on funding from the department's National Energy Technology Laboratory, the company has scaled up the process at the New Jersey EcoComplex, Acrion's first step to commercialize the innovation.

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 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 vaporized 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, from making dry ice to carbonating soft drinks. One option Acrion is examining is to pipe the CO₂ to Burlington County's R and 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 U.S. Environmental Protection Agency (EPA), every one million tons of waste deposited in landfills produces enough landfill gas to generate seven million kilowatt hours of electricity per year, enough for 700 homes. Using this gas for energy purposes, rather than expelling it into the atmosphere, is equivalent to removing more than 6,000 cars from the road, or planting 8,300 acres of trees.

A Treehugger's Dream

AUSTIN, Texas -- Researchers at The University of Texas at Austin report that cellulose recently discovered in a group of organisms may be a promising new resource for the industrial production of the substance and could eventually eliminate the need to harvest trees for wood or pulp.

The discovery of cellulose biosynthesis in nine species of cyanobacteria, or blue-green algae, also may be the source of the genetic material used for the formation of cellulose in present-day plants, such as trees and cotton.

The findings of the researchers -- David R. Nobles, Dr. Dwight K. Romanovicz and Dr. R. Malcolm Brown Jr. -- were published in the October 2001 issue of Plant Physiology.

Blue-green algae are among the most ancient of today's living organisms and have been in existence for more than 2.8 billion years. Fossils of forms that resemble cyanobacteria have been dated as far back as 3.5 billion years.

Cellulose is a biopolymer that plants use as the primary building block for their cell walls. Cellulose is important economically because it is the major source of such significant and useful plant products as wood, cotton and flax.

"Although cellulose biosynthesis among the cyanobacteria has been suggested previously, we present the first conclusive evidence, to our knowledge, of the presence of cellulose in these organisms," Nobles said.

Brown said an exciting future possibility based on this discovery could be industrial production of cellulose from cyanobacteria.

"If industrial production from this source were to be achieved," Brown said, "we might never need to harvest trees again for wood or pulp. In the future, we could possibly use cyanobacterial cellulose."

Brown said cyanobacteria inhabit vast, incredibly diverse environments ranging from freshwater lakes and ponds, to hypersaline water, to deserts where rainfall never has been recorded.

Cyanobacteria are common in the dry valleys of Antarctica and can live embedded in the surface of rocks. Some cyanobacteria do not require fresh water, nitrate-based fertilizer or even farmable land to grow and flourish.

From the standpoint of the evolutionary history of life, Brown said the discovery also "has shown that the cyanobacterial genes for cellulose production are closely related to those genes in land plants. This strongly suggests that the genetic code for the major building blocks for cellulose production of land plants came directly from the cyanobacteria."

The researchers reviewed databases developed from recent gene sequencing projects in their lab at The University of Texas at Austin and throughout the world looking for evidence of the presence of cellulose in diverse types of cyanobacteria. No previous research has demonstrated biosynthesis taking place in these types of microorganisms.

The researchers used microscopy and x-ray analysis to determine that cellulose was present in six strains of five genera of blue-green algae. Brown said colloidal gold can be coupled with an enzyme, cellubiohydrolase I as a tag. This enzyme specifically binds to cellulose as it begins to degrade in nature. Thus, it is possible to identify cellulose using this approach. Brown said gold labeling alone indicated the presence of cellulose in four additional strains.

"The genetic analysis suggests a close relationship between vascular plants and cyanobacterial cellulose synthases," Nobles said.

For more information, visit www.botany.utexas.edu/facstaff/facpages/mbrown/cyano/.

This article originally appeared in the February 2002 issue of Environmental Protection, Vol. 13, No. 2, p. 10.

This article originally appeared in the 02/01/2002 issue of Environmental Protection.