Building Biogas Digesters in Nicaragua

In a rural patch of Nicaragua they worked, spending their days constructing biogas digesters for local families, spending their nights on cots in a local school house.

Before the group of five McCormick students went down to Nicaragua for spring break in March 2009 as part of a Engineers for a Sustainable World trip, they didn't know what to expect. But after the week was through, they didn't want to leave.

The student group, which mobilizes engineers and student engineers through education, training, and practical action, had met with an NGO called Green Empowerment, which connected them with local Nicaraguan group Asofenix, which develops projects using renewable energy technologies. Asofenix was doing work in two villages — Bramadero and Potreritos — installing a solar water pumping system and biogas digesters for the locals, and asked if the ESW students could help with grant writing and installation. The group agreed, and after submitting four or five grants and received one from the Thanksgiving Fund. They used the money to purchase supplies for biogas digesters and to travel to Nicaragua over spring break.

"From start to finish the whole experience was awesome," says Ellen Abrams, a mechanical engineering junior. "It was really exciting for me. It's what I want to do with my life, so it was a great introduction into this sort of service."

Biogas digesters are low-tech devices that convert animal manure into biogas, which has a high methane concentration that can be used for cooking, heating, or lighting. Besides the devices' inherent environmental benefit — methane is 21 times more potent than carbon dioxide for trapping heat — they provide a way for Nicaraguans to solve several problems at once. Deforestation has left the land in the area dry, and the little wood that's left burns continuously in home stoves, affecting the respiratory health of women and children. Biogas digesters reduce deforestation while providing cleaner air for those who work in the home.

But to install biodigesters, students first had to get their supplies through customs — "We had these huge bags and we tried to explain what they were," says Andrew Dai, an electrical engineering senior — and take long drive through the mountainous Nicaraguan roads.

Four flat tires later they arrived in the village. They met with volunteers from the NGOs and got to work.

"They sent us a diagram before we went, and the villagers knew how to make the concrete tank, so we went from there," Dai says.

"It's an art the way they put the tanks together," Abrams says.

The digesters themselves look like giant cylinders topped off with tarps. They work like this: you mix cow manure with water to make a slurry, then pour it in an opening at the top of the tank. As the tank fills up, it forms a water seal, which keeps the oxygen out. Anaerobic bacteria then grow and produce methane, which is pumped out of the tank and into a reservoir in the house, which feeds directly to the stove.

To create the digesters for the chosen families — the ones who needed it the most and who would most likely take care of it — the students worked from sun up to sun down.

"I really liked doing manual labor outside all day," Abrams says. "By sundown we were exhausted. We took bucket showers, ate, and then passed out."

Since Asofenix had already developed a relationship with the community — they helped create a community charged with overseeing and maintaining the devices — the locals welcomed ESW: the kids played games, the adults offered food.

"I took Spanish in high school, so I tried to talk to one guy who helped us," Dai says. "He told me to go sit in the shade, and I didn't know what he said, so I said something really stupid."

"The food they cooked for us was unreal," Abrams says. "They originally brought volunteers huge plates of food, but no one could finish them, so they arranged it buffet style, even though that is not part of their culture."

After a week the group had installed several biogas digesters. When they got home, they decided that future projects would involve the same community. This spring break, they hope to install wind turbines for homes not connected to the electricity grid.

"The second day we were there, we settled into a routine and said, we could do this for a while," Dai says. "We're anxious to go back."