Researchers: Process removes sulfur from biogas

By Ryan C. Christiansen
Web exclusive posted Dec. 12, 2008 at 3:18 p.m. CST

Researchers at Cornell University in Ithaca, N.Y., have developed a process that uses mostly undigested manure along with some chemical fertilizers to scrub biogas produced from the anaerobic digestion of manure or sewage treatment plants and landfills. Dubbed SulfaMaster, the patented process pipes biogas through barrels containing the manure mix to remove hydrogen sulfide from the biogas. When the manure mix is spent, the sulfur can be returned to the soil.

"What is really good about our system is by repeated cycles, we can get up to 25 percent of the medium as pure sulfur. That's a very high loading rate. It just depends on how much of the hydrogen sulfide you have to take out," said Gary Harman, professor of plant biology at the New York State Agricultural Experiment Station in Geneva, N.Y., the developer of the technology. "All of this sulfur came from cows to begin with. We think what we can do-because there is nothing toxic in there-is that we can simply put it back with a liquid manure land-spreading operation. When the sulfur goes back on to the land it will, unless it is anaerobic, form sulfate, and that is where it was in the first place."

Harman said the SulfaMaster process is practical for smaller biogas production operations because most methods for removing hydrogen sulfide from biogas require expensive industrial-sized scrubbers. Herman and Terry Spittler, a retired analytical chemist from Cornell, own Terrenew LLC, a company that will license the technology from the Cornell Center for Technology Enterprise and Commercialization and will market the product from the Cornell Agriculture and Food Technology Park in Geneva, N.Y. The development of the SulfaMaster process was funded in part by the New York State Energy Research and Development Authority.

Harman said the SulfaMaster process is related to Terrenew's other product offerings, OilMaster and MetalMaster. The company first developed MetalMaster as a way to remove heavy metals from water. "We were looking then at a lot of stuff that says you can dump sewage sludge on the ground and it's not a problem if there is heavy metals and stuff in there, because it is all so tightly bound," he said. "And so we thought, ‘Why is that?' And then we started thinking about lignin chemistry. Well, if heavy metals are that tightly bound to the lignin, then it ought to be quite useful as a filter absorbent." The company developed the MetalMaster process which uses the lignin in tree bark to remove heavy metals from water.

However, livestock manure is also valuable as a filter absorbent, Harman said. Composts and municipal solid wastes have been shown to reduce the bioavailability of heavy metals when those products are added to contaminated soils or acid mine drainage waters, he said. As a result, Harman investigated whether and why manure might have value for this application. The lignin portion of plants is not digestible by ruminants such as dairy cows, he added, therefore dairy cows produce manure that's high in lignin. Harman developed the manure-based OilMaster product for Terrenew.

"It's sort of the backwards way we got into the whole concept," Harman said. He chuckled that he's becoming the George Washington Carver of manure.