MIT works with blueEnergy to develop biofuel solution for local school

By Angela Hojnacki -- After two weeks of MIT students researching and planning several waste management strategies for the municipality of Bluefields, a subset known as the “Biodigestors” team, stayed an extra week to implement a small-scale biodigestor in partnership with blueEnergy and Colon, a local high school. This demonstration project was a nice contrast to the heavy planning work we had done the following week, and it would be a way for the community to see the concepts of biodigestion first-hand, after hearing our recommendations for the slaughterhouse the week before.

The design.

A biodigester is a simple contraption that produces methane gas from organic wastes (in most cases, manure). The idea is that the gas from this biodigester will be used to cook in the school's kitchen where they are currently using three large sacks of charcoal every day. 

As ideal as it sounded, the prospect of building a working biodigester in a community that had only seen similar projects fail seemed ridiculous, especially at 9pm, during our last night in Bluefields. Our team, plus Casey and Kenia from blueEnergy, found ourselves in the dark, outside the local high school, drenched in water and cow manure, struggling to finish the biodigester we had started to build only five days earlier. With all of us at the end of our ropes, we contemplated how it was possible to ensure the sustainability of the project.

We began this “mini” project on Saturday, after seeing the rest of the DLab Waste team head back to Boston. Armed with whatever shovels and gardening tools we could find, we began to dig the trench With the help of George Bloomburg, an English teacher at the high school, and Vicente, the security guard, we had managed to remove two trees, clear the grass, measure out the trench, and break the ground by the end of the first day. After a few days of hard work in the sun, we realized how much work we still had to do (and how much more there was to learn about digging in Bluefields’ very clayey soil).

Smoothing the walls of the trench

The biodigester we built was a ten-meter long bag biodigester, which consists of two layers of a polyethelene plastic. The system consists of the bag (which is filled with water to seal the waste inlet and outlet), a gas outlet, a pressure release valve, a reservoir bag, and a typical propane stove that is adapted to use biogas. After finishing the trench, we laid the bag inside and began assembling the plumbing that will transfer the gas to the kitchen. Following the instructions used to build biodigesters by other DLab courses, we attempted to inflate the bag with car exhaust to expel any oxygen. To then seal the bag, we filled it with water; however, our only water source was a nearby well, and our daylight was fading quickly. Passing buckets of water in an assembly line, this is where we found ourselves the last night of the project.

After discussions that lasted most of the night, Alex and I decided to stay an extra day, and with that time, we were able to leave the biodigester and Bluefields knowing that it was in good hands with blueEnergy. Alex and I added the rest of the water needed to seal the biodigester, finished assembling the stove - with the help of Casey and the shop workers - and cleaned up the kitchen area at the school. Since our departure, we have kept in contact with blueEnergy, and our bag of poop is doing splendidly so far. While many biodigesters like these fail, we can only hope that our partnerships, regular communication and maintenance will ensure the success of this project, and hopefully the biogas production and utility will continue to convince others that this technology works.

Biodigester producing gas