Vermont funds biomass projects

By Ryan C. Christiansen
Web exclusive posted August 8, 2008 at 9:14 a.m. CST

The Central Vermont Public Service utility recently approved $500,000 in renewable energy projects.

The Central Vermont Public Service utility awarded $15,000 to the Biomass Energy Resource Center in Montpelier, Vt., to study the potential use of pelletized digested or pre-digested manure solids for fuel in a cogeneration system to produce electricity and heat.

According to Adam Sherman, program manager for BERC, the center will research to see if any entity might be pelletizing cow manure for fertilizer and whether that pelletization process could be used to produce fuel for biomass energy production.

"We will be doing a technical assessment of the manure's chemical and physical properties to evaluate whether it is a decent boiler fuel," Sherman said. "We will be looking at the nutrients, calorific value, ash content, and mineral composition and then from there, we will be looking at-nationally and internationally-how many people are actually successfully using this material as a boiler fuel and what are their lessons learned? Are they pelletizing it or densifying it in other ways like briquettes or other shapes?"

Sherman said the study will look at whether 100 percent cow manure is ideal for pelletization or if a percentage of sawdust bedding might boost the value of the fuel. He said the researchers will also look at whether combining manure with wood waste or grass might benefit the fuel's performance. The study will compare pellets that are made from pre-digested manure solids with pellets made from the byproduct of an anaerobic digester that is fed cow manure.

Another project that received funding by the Central Vermont Public Service is the Lake Champlain Restoration Association in Bridport, Vt., which received $10,000 to study the feasibility of harvesting and transporting a nuisance aquatic weed from the lake and using it as biomass for an anaerobic digester. The biomass will be fed into a Cow Power Inc. anaerobic digester.

"The group is doing whatever it takes to improve the quality of the lake," said Chip Morgan, president of the lake association. "Right now, one of the biggest problems is these invasive weed species and in this particular area that we deal with-which is 50 miles or so worth of the southern part of Lake Champlain-Eurasian watermilfoil is the biggest problem, and so we have been concentrating on that for the last four or five years."

Commonly found in shallow bays and in bands along the shoreline, dense surface mats of Eurasian watermilfoil can make fishing, boating, and swimming virtually impossible. According to the Vermont Department of Environmental Conservation Water Quality Division, the non-native aquatic plant currently infests a number of Vermont lakes, including the state's largest, Lake Champlain. Eurasian watermilfoil grows and spreads rapidly within a lake and there is no known way to eradicate the plant. The nuisance weed competes for nutrients with more beneficial native aquatic plants and might contribute to stunted fish populations.

"It's a pretty big problem," Morgan said. "It's an invasive weed and it's growing. We do small-scale harvesting, but we're just doing enough to keep on top of it and to get access to members' docks and things like that. If we find that it can produce power, we will probably be interested in harvesting more."

Morgan said the lake association has a commercial harvester that uses a sickle to cut off the milfoil below the water's surface and then gathers the material on to a conveyor as it moves through the plant bed. The harvester doesn't remove the plant's roots during the process and only temporarily reduces the height of the plant's growth. When the harvester is full, a conveyor belt on shore is used to move the weeds into a dump truck. Currently, the weeds are dumped in piles and left to decompose and be used as compost by local farmers.

The lake association has been looking for something to do with the biomass for some time, Morgan said. "We have had a whole bunch of different ideas," he said, until someone in the group read a news article about using weeds to feed an anaerobic digester. The Central Vermont Public Service utility Cow Power program already uses anaerobic digesters to produce methane from cow manure to produce electricity and so the group approached CVPS with the idea. "There is [an anaerobic digester] that is fairly close to one of the major areas where we pull out weeds," Morgan said. "So we approached the CVPS organization and asked if they would be interested in trying to mix our weeds in with cow manure to see if we can make some power.

"We don't know what is going to be the best way to do it," he said. "I think we will be experimenting to see, ‘Is it better to put it in wet? Is it better to let it dry to a certain point? What will be the impact?'"

Eurasian watermilfoil stems can reach the surface in up to 20 feet of water. Morgan said in order to feed the weeds to the digester, they will need to be chopped up first or "they will just clog everything up," he said.

The lake association hopes to begin feeding weeds to the digester this year, Morgan said. However, the project might be delayed until next year, because the digester is currently offline and in need of repair. As well, typically begins harvesting the weeds in June and finishes the end of August or by early September.