Vol. 38, No. 18

1-31-2007
By: Adam King

Manure makeover

If tossing manure and grease into a big plastic bag sounds like a dirty job — it is. But researchers Jay Martin and Stephanie Lansing don’t mind.

They hope their research in Costa Rica will help the environment and lead to increased energy output.

The researchers’ goal is to figure out how much grease to add to a manure-water mixture in the bag, also known as a biodigester, so they can create enough methane gas to power a generator for up to eight hours.

Right now the process, in which microorganisms turn the waste to methane, high-quality liquid nitrogen fertilizer and clean water, can only produce two hours worth of electricity at a mid-sized farm. Farmers in rural areas with no electricity also pipe the gas directly to their kitchens for cooking, and they use the fertilizer on their crops.

By capturing methane, the biodigesters contribute to the elimination of greenhouse gases, which studies have shown are a major contributor to global warming. That’s what motivates the research duo — being able to take waste and turn it into a resource.

“In ecological engineering, we try to design sustainable systems to help the environment and help people at the same time,” said Martin, an Ecological Engineering associate professor. “That’s what makes these digesters so appealing is they’re simple to use and manage.”

Digesters have been around for literally thousands of years in China, but Martin and Lansing’s research, a collaboration with five other professors from Ohio State and Earth University in Costa Rica, is about finding ways to broaden the reach of the simple system.

“There are 5 million digesters being used throughout the world at the household level, but there’s been a real lack of experimental research on these systems,” said Lansing, a doctoral student in the College of Food, Agricultural and Environmental Sciences.

Digesters in the United States are seen only on large farming operations, are technologically advanced and can cost an average of $1.5 million. The digesters on small Costa Rican farms cost about $150 and work well because of the tropical climate, which helps activate the microorganisms.

Lansing and Martin are researching ways to make the digesters work on mid-sized farms in the United States, especially areas that experience severe cold. They expect to test burying the units underground to maintain warmth or using a portion of the methane gas to heat the digesters.

These farms are only deriving two-plus hours of electricity from a 40-kilowatt generator powered by the methane. Smaller farms are using the methane for six or seven hours of cooking time, which helps conserve the use of propane or firewood, but doesn’t cut down on electricity usage.

The researchers believe kitchen grease will improve the process.

“What we’re hoping to do is by using grease and fats of animal and vegetable origin, basically cafeteria waste, we can get six to eight hours of electricity,” said Lansing, who is moving to Costa Rica for a year in March to continue her work.

If Martin and Lansing can figure out how to make the digesters work in the U.S., farmers here won’t have to pay others to collect and remove waste or have the waste pool in a lagoon, where odor is an issue (digesters, in fact, remove the odor). That saves farmers time and money in an industry where margins are razor thin.

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