Author’s Note: This is the ninth item in a series of articles that touch on the subject of sustainable practices in Costa Rica. There is a high degree of science, innovation and street smarts involved in sustainability; if you happen to know of a good sustainability tip, please feel free to share it with The Costa Rica Star.

A home located on the skirts of Mount Chirripo in the Southern Zone has one of the most sustainable kitchen operations in Costa Rica. A special biodigester unit just outside of the home of Dona Rosa Elizondo provides cooking fuel, herbs and vegetables, all thanks to a bunch of happy worms imported from California that increase the efficiency of the anaerobic digestion process.

According to an article by Diana Lucia Salas Viquez in El Financiero, there is also a pig involved in the process. The porcine excrement produced during the course of one day provides enough biogas for Ms. Elizondo’s family to cook all three meals. In case the pig’s bowel movements prove to be irregular, family members don’t have to go too far to look for fuel, as they are surrounded by dairy farms.

The residue from the biodigester is turned over to the worms and transferred to the family’s produce garden, where it functions as an excellent fertilizer for celery, lettuce, parsley, tomatoes, and other vegetables. This biodigester has been operational for 22 years, but the use of earthworms from California started about a decade ago. According to Raul Botero Botero, professor at EARTH University, using worms makes the anaerobic digestion process more efficient and greatly eliminates the odor issue that’s associated with biodigesters. This makes them more attractive to the squeamish.

In many rural areas such as where Ms. Elizondo’s family lives, wood stoves are predominant. The use of biodigesters in the last few years has greatly reduced the use of firewood as cooking fuel. Ms. Elizondo estimates that 75 percent of her household cooking is now fueled by biogas, and the source is plentiful. Excrement from cows, pigs, goats, and horses can be used. Human waste from septic tanks can also be used, as previously explained by an article in The Costa Rica Star that looked at a project from EARTH University, Ad Astra Rocket Company, and a young, smart indigenous Tico.

Vermicomposting

Not all the waste pumped into a biodigester is turned into fuel. The residue is taken care of by a bunch of worms from California that feed on it. The reaction between the slime excreted by these worms and the waste residue results in an organic fertilizer. Ms. Elizondo explains that the most important benefit of this fertilizer is that she knows exactly what her family is eating:

“With the produce from our garden we don’t consume the chemicals or artificial ingredients generally used in the cultivation of vegetables.”

According to Wikipedia, the organic matter produced by vermicomposting has been shown to contain reduced levels of contaminants and a higher saturation of nutrients.