A new technology that has arrived in rural villages in El Salvador makes it possible for small farming families to generate biogas with their feces and use it for cooking—something that at first sounded to them like science fiction and also a bit smelly.
In the countryside, composting latrines, which separate urine from feces to produce organic fertilizer, are very popular. But can they really produce gas for cooking?
“It seemed incredible to me,” Marisol Menjívar told IPS as she explained how her biodigester, which is part of a system that includes a toilet and a stove, was installed in the backyard of her house in the village of El Corozal, near Suchitoto, a municipality in the central Salvadoran department of Cuscatlán.
“When the first ones were installed here, I was excited to see that they had stoves hooked up, and I asked if I could have one too,” added Marisol, 48. Hers was installed in March.
El Corozal, population 200, is one of eight rural settlements that make up the Laura López Rural Water and Sanitation Association (Arall), a community organization responsible for providing water to 465 local families.
The families in the small villages, who are dedicated to the cultivation of corn and beans, had to flee the region during the country’s 1980-1992 civil war, due to the fighting.
After the armed conflict, they returned to rebuild their lives and work collectively to provide basic services, especially drinking water, as have many other community organizations, in the absence of government coverage.
In this Central American country of 6.7 million inhabitants, 78.4 percent of rural households have access to piped water, while 10.8 percent are supplied by wells and 10.7 percent by other means.
Simple Green Technology
The biodigester program in rural areas is being promoted by the Salvadoran Water Authority (Asa).
Since November 2022, the government agency has installed around 500 of these systems free of charge in several villages around the country.
The aim is to enable small farmers to produce sustainable energy, biogas at no cost, which boosts their income and living standards, while at the same time improving the environment.
The program provides each family with a kit that includes a biodigester, a biotoilet, and a small one-burner stove.
In El Corozal, five of these kits were installed by Asa in November 2022, to see if people would accept them or not. To date, 21 have been delivered, and there is a waiting list for more.
“With the first ones… set up, the idea was for people to see how they worked, because there was a lot of ignorance and even fear,” Arall’s president, Enrique Menjívar, told IPS.
In El Corozal, there are many families with the surname Menjívar, because of the tradition of close relatives putting down roots in the same place.
“Here we’re almost all related,” Enrique added.
The biodigester is a hermetically sealed polyethylene bag, 2.10 meters long, 1.15 meters wide, and 1.30 meters high, inside which bacteria decompose feces or other organic materials.
This process generates biogas, clean energy that is used to fuel the stoves.
The toilets are mounted on a 1-meter-high cement slab in latrines in the backyard. They are made of porcelain and have a handle on one side that opens and closes the stool inlet hole.
They also have a small hand pump, similar to the ones used to inflate bicycle tires, and when the handle is pushed, water is pumped from a bucket to flush the waste down the pipe.
The underground pipe carries the biomass by gravity to the biodigester, located about five meters away.
The system can also be fed with organic waste, by means of a tube with a hole at one end, which must be opened and closed.
Once it has been produced, the biogas is piped through a metal tube to the small stove mounted inside the house.
“I don’t even use matches, I just turn the knob and it lights up,” said Marisol, a homemaker and caregiver. Her husband Manuel Menjívar is a subsistence farmer, and they have a young daughter.
In El Corozal, biodigesters have been installed for families of four or five members, and the equipment generates 300 liters of biogas during the night, enough to use for two hours a day, according to the technical specifications of Coenergy, the company that imports and markets the devices.
But there are also kits that are used by two related families who live next to each other and share the equipment, which includes, in addition to the toilet, a larger biodigester and a two-burner stove.
With more sophisticated equipment, electricity could be generated from biogas produced from landfill waste or farm manure, although this is not yet being done in El Salvador.
Saving Money While Caring for the Environment
The families of El Corozal who have the new latrines and stoves are happy with the results.
What they value the most is saving money by cooking with gas produced by themselves, at no cost.
They used to cook on wood-burning stoves, in the case of food that took longer to make, or on liquefied gas stoves, at a cost of $13 per gas cylinder.
Marleni Menjívar, for example, used two cylinders a month, mainly because of the high level of consumption demanded by the family business of making artisanal cheeses, including a very popular local kind of cottage cheese.
Every day she has to cook 23 liters of whey, the liquid left after milk has been curdled. This consumes the biogas produced overnight.
For meals during the day Marleni still uses the liquefied gas stove, but now she only buys one cylinder a month instead of two, a savings of about $13 per month.
“These savings are important for families here in the countryside,” said Marleni, 28, the mother of a four-year-old girl. The rest of her family is made up of her brother and grandfather.
“We also save water,” she added.
The biotoilet requires only 1.2 liters of water per flush, less than conventional toilets.
In addition, the soils are protected from contamination by septic tank latrines, which are widely used in rural areas but are leaky and unhygienic.
The new technology avoids these problems.
The liquids resulting from the decomposition process flow through an underground pipe into a pit that functions as a filter, with several layers of gravel and sand. This prevents pollution of the soil and aquifers.
Also, as a by-product of the decomposition process, organic liquid fertilizer is produced for use on crops.
Checking on Site: Zero Stench
Due to a lack of information, people were initially concerned that if the biogas used in the stoves came from the decomposition of the family’s feces, it would probably stink.
And, worst of all, perhaps the food would also smell.
But little by little these doubts and fears faded away as families saw how the first devices worked.
“That was the first thing they asked, if the gas smelled bad, or if what we were cooking smelled bad,” said Marleni, remembering how the neighbors came to her house to check for themselves when she got the latrine and stove installed in December 2022.
“That was because of the little information that was available, but then we found that this was not the case, our doubts were cleared up and we saw there were no odors,” she added.
She said that, like almost everyone in the village, her family used to have a dry composting toilet, but it stank and generated cockroaches and flies.
“All that has been eliminated, the bathrooms are completely hygienic and clean, and we even had them tiled to make them look nicer,” Marleni said.
She remarked that hygiene is important to her, as her little girl can now go to the bathroom by herself, without worrying about cockroaches and flies.
By Edgardo Ayala – IPS / Globetrotter