Bioenergy, Geothermal, Hydropower

Landfill Waste and Manure Produce Fast Gas in New Mexico

Professors at New Mexico State University (NMSU) have developed a two-phase process to convert landfill waste and manure into methane gas, which can be used as a renewable source of fuel for electric power plants.

LAS CRUCES, New Mexico 2002-02-22 [] NMSU Civil Engineers Zorhab Samani and Adrian Hanson developed the process, which can digest paper and other waste products to generate high-quality natural gas leaving only usable compost. Methane from landfills is produced slowly and is often burned off to prevent the odor from effecting neighbors. A more productive method for disposing of the methane is to use it as a fuel to produce electricity at on-site power plants. The new method, which the men say may be commercially viable in two years, can turn the waste into usable gas in a fraction of the time nature does the same thing. The research to speed up the decomposition process to produce Renewable Energy has been under way at NMSU for six years using various types of bacteria. Cellulase bacteria, which breaks down grass in the stomachs of cows also breaks down paper and other materials in the methane production process. The “two-phase bio-fermentation process,” uses two separate containers to break down the waste. First, solid waste is mixed with cattle manure and placed in the first container. Water is applied through a sprinkler system, then circulated through the container while bacteria convert solids in the waste to volatile fatty acids. Once the desired concentration of acids has been leached into it, the water is piped into the second container, where a different type of bacteria turn the acids into methane, Semani said. Converting the acids to methane takes less than a day and results in a gas with a 70 to 80 percent concentration of methane, with the remainder being carbon dioxide. The gas can be used locally or transported for use in gas-fired electric power plants. Many waste treatment facilities extract methane from waste and use it to provide at least part of the fuel for their electric generators using a single-phase anaerobic process that is less efficient and uses a slurry composed of 80 percent water. The two-phase process is cleaner, doesn’t use as much water and produces a higher concentration of methane according to Semani. Use of the manure in a methane production process could provide a market for waste from dairies and feed lots. Samani is researching combining manure and other waste materials to produce energy. With the help of a $50,000 grant from the U.S. Department of Agriculture and the New Mexico Cooperative Extension Service, he is researching combining cow manure and cotton gin waste in the two-stage process.