Sanivation, a start-up company in Kenya is turning human waste into a usable fuel source for cooking and heating.

The start-up tested its product for several years after finally commercially treating human waste into sun’s heat to create environmentally friendly fuel source. First, they installed, lightweight sit-down toilets in people’s homes for nothing upfront, but they charged a monthly fee of (about $7) to take away the waste twice a week. After taking away the waste they neutralized the pathogens and combine that with carbonized agricultural residues, after grinding the mixture eventually becomes charcoal briquettes.

In developing countries, the “International Energy Agency” estimates that about 2.5 billion people cook with biomass: charcoal from the forest, agricultural waste, animal dung, and other sources. But burning these type of charcoal for cooking food or for another purpose can kill 4.3 million people a year, because of the pollution that it caused.

Woods says sanivation’s sun-treated poop fuel briquettes can burn two times longer than normal charcoal, yet release about one-third of the carbon monoxide and particulate matter emissions. Each metric ton of the briquettes saves about 88 trees yet they are less in cost if compared to charcoal.

The process starts with fecal waste that the company collects from latrines and ends with a fuel briquette.

The first stage is treatment. Sanivation applies heat to sanitize the waste—waiting in a container—and remove any harmful pathogens.

A glass and steel parabolic disk with an area of about 5 m² acts like a solar concentrator. When the sun’s rays hit the disk, it reflects the light and focuses it on the glass side of an approximately 13- by the 13-centimeter receiver containing the waste. The waste starts warming up to about 60° C—the other sides of the receiver prevent the heat from escaping because they are insulators: cement or fiberglass.

The trick to the treatment is that once poop gets hot enough, pathogens disappear. One estimate says this happens after waste is heated to 60° C for one hour. Woods says many researchers are working on finding the lowest possible temperature and time to sanitize waste, but for now, Sanivation errs on the side of caution and goes to 60° C for three hours.

The company is trying to expand themselves in other parts of Kenya that have poor sanitation.