Researchers look into manure-based energy

Tony Parra

Nothing goes to waste. Not even waste goes to waste. Not anymore, at least.
Researchers at New Mexico State University are investigating a more efficient method of creating electric energy out of manure. NMSU civil engineers Z.A. Samani and Adrian Hanson have been working on enhancing the two-phase bio-fermentation process, which would be used mainly by dairies.
Construction on a full-scale digester system began in February according to the NMSU Website. Sierra Vista Growers of La Mesa, which is about 15 miles south of Las Cruces, will use the digester after it’s completed. The projected time of completion is 2006.
“It’s a pilot plant,” NMSU Dairy Extension Specialist Hilary Sullivan said about the digester system. “It’s for a dairy with only about 100 cows. It’s more feasible for generating energy for a dairy, not for selling to electric companies.”
The two-phase bio-formentation process entails the use of two separate containers, according to a press release from NMSU.
The press release states that solid waste is mixed with cattle manure and placed into one container then water is applied through a sprinkler system and circulated through the container while bacteria converts solids in the waste-volatile fatty acids.
Once the desired concentration of acids has been leached into the water, it is piped into a second container, where a different type of bacteria forms the acid into methane, according to Samani in a press release.
“We project that with the 31,000 tons of solid organic waste we collect each year, just from commercial sources and from our parks department, we would generate 93 billion BTUs of energy a year,” Samani said in the press release.
The process is still some time off for Portales, according to the researchers. Sullivan said if Portales had a central digester system, the cost for dairies to transport manure to the digester system would be greater than the worth of the energy created.
“Most recently dairies in Chino, Calif. shipped it to a central digester system,” Sullivan said. “There was not enough land for the amount of manure they had. It made more sense for them to ship it to a centralized digester system, because they had to ship it out anyway.”
However, water is one of the most important elements of the process, and the eastern plains of New Mexico do not have an abundance of water. Sullivan said some dairies use a flush system for manure removal and this type of manure would be ideal for creating energy because it contains a good amount of water.
However, Sullivan said many dairies in Portales use a dry-scraping method which does not use enough water for the manure to produce energy.
“That is why Mr. Samani is researching a way to generate electricity with less water through the pilot plant,” Sullivan said. “Dairies use recycled water to move manure in the flush dairies.”
Sullivan said the digesters would be a more viable option for individual dairies than commercial use. She said more than likely, not enough electricity would be generated to sell to electric companies.