Posted March 21st 2012 at 9:18 am by
in Waste Management Strategies in Coastal Nicaragua

Installing a Biodigester in the Wee Hours

In this post, Angela Hojnacki describes the process of installing a biodigester. Angela was the Teacher’s Assistant and trip leader for a class at MIT in which students traveled to Bluefields, Nicaragua to help develop new waste management strategies.

Installing a Biodigester in the Wee Hours

After two weeks of researching and planning several waste management strategies for the municipality of Bluefields, the “Biodigestors” team, stayed an extra week to implement a small-scale biodigester. A biodigester is machine that processes organic waste, like food and animal waste, into methane, a gas used for cooking. The ‘team’ is a subset of students from the D-Lab Waste class who studied biodigestion all semester and completed this project to earn grad credit. We built the biodigester in partnership with blueEnergy, an NGO based in Bluefields that implements wind and solar energy projects along the Caribbean coast of Nicaragua, and Colon, a local high school.

This demonstration project was a nice contrast to the heavy planning work we had done the previous week, and it would be a way for people living in Bluefields to see the concepts of biodigestion first-hand, after hearing our recommendations the week before.

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 9:00 p.m. on 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, and struggling to finish a 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 a Saturday, after seeing the rest of our classmates 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 school’s 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. However, after a few days of hard work in the sun, we realized how much work we still had left (and how much more there was to learn about digging in Bluefields’ very clayey soil).

We were working with a 33-foot long bag biodigester, which consists of two layers of a polyethelene plastic. The system includes 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 transfers the gas to the kitchen. Following the instructions used to build biodigesters by other D-Lab courses, we attempted to inflate the bag with car exhaust to expel any oxygen. To then seal the bag, we needed to fill it with water. Our only water source, however, was a nearby well, and daylight was fading quickly as we found ourselves passing buckets of water in an assembly line on 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.

Do you want to install a biodigester?  The MIT team used this installation guide.

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