You too can make gas from cactus and kitchen waste

A battle between villagers and cacti plantations that have covered swathes of land in Laikipia County has raged on for decades.

Over the years, few residents have known what to do with the invasive plant.

But things are changing as the thorny weed is now being turned into beverages, cosmetic and energy products.

Francis Merinyi, a programmes officer at the National Cohesion and Integration Commission, says the need to conserve the environment has seen him convert the plant into biogas, green energy.

His farm in Maikuran village in Laikipia North stands out as an innovation hub where fellow villagers have been flocking to learn on how to use the plant to make biogas for cooking.

“Since I started in May, I have received many residents willing to adopt this technique to save their animals from cactus,” he says, noting the use of the plant also helps to reduce the demand for wood fuel and charcoal burning in areas heavily invaded by the variety of cactus known as Oppuntia stricta.

He uses the plant to produce biogas rich in lignocellulose, the main raw material for the production of biofuels and biochemical.

The process involves anaerobic fermentation of cacti biomass where the entire plant is crushed using the ordinary chaff-cutter until it becomes a thick paste. The process is repeated three to four times to achieve desired results.

The paste is then diluted with water to make it less viscous before it is poured into a 250 litres tank to ferment. “After three weeks to a month, methane and other gases begin to form in a thermophilic process,” he explains, adding that it works best at a temperature of 370C.

The gas produced is a combination of methane, water vapour and sulphur, which is then collected and stored in a biogas tank.

OPENING DOORS

“Before the gas gets into the kitchen for use, I have it has to pass through a desulphuriser unit for purification.”
A wheelbarrow of cacti produces approximately 20kg of paste that he uses to make biogas that lasts for three to four hours of cooking.

“The gas produced is efficient and burns just like the normal cooking gas. It has no smoke or smell,” he explains, noting he spent Sh120,000 on the system. The making of the gas has helped him reduce the cost of using charcoal and firewood for cooking at his home.

Besides the biogas, he also produces liquid organic fertiliser from the fermented waste.

The project is opening doors for Merinyi since it has been picked by the Climate Innovation Cenre as a start-up business venture under their incubation programme with a potential funding and scale-up.

His idea is among 15 innovations participating in global Climate Launchpad programme.

Three of those that qualify at the national level will go to Scotland in November for the international competition.

Merinyi says the biogas system can utilise any other form of biomass including cow dung, kitchen waste and even hay.

“For now, my focus is to put into use the problematic cacti, the Omputia stricta that claims the lives of livestock. After that, I will focus on other species of cactus.”

National Environment and Management Authority (Nema) Laikipia director Fanuel Mosago says the agency supports the biogas system because it protects the environment and helps the pastoralists whose grazing land has been colonised by the cacti get clean energy.