Soil degradation, inadequate sanitation and lack of access to clean energy are important challenges facing African farmers and those living in rural areas.
According to the Bill and Melinda Gates Foundation, 40 percent of the world’s population lacks access to adequate sanitation facilities, a situation which contributes to around 700,000 children dying from diarrhea each year.
The use of solid fuels such as wood, crop waste, charcoal and coal for cooking and heating contributes to high levels of household air pollution, causing 4.3 million premature deaths every year according to the World Health Organization (WHO).
Recognizing the interrelationship between soil degradation, inadequate sanitation and clean energy, Rachael Nabunya Kisakye, project engineer at the Tusk Engineers Uganda, has developed a bio-latrine.
“The bio-latrine concept was inspired by the heavy burden borne by African women to bring food to the table when in fact they have a source of energy that is readily available but largely unexploited. The solution is the bio-latrine,” Kisakye says.
“A bio-latrine is an environmentally friendly toilet that is connected to a biogas digester that converts human excrement into a quality fertilizer that is safe to handle and can be used for agriculture. In the same process, combustible gas (biogas) is also produced and can be used for cooking, heating and lighting. This complete system addresses energy, sanitation, environment and agricultural production in a single cycle, and we are very proud of that,” Kisakye explains.
Her bio-latrine improves hygiene, community sanitation, living standards and the environment in general, through better waste management and the production of high-quality fertilizer and biogas.
Biogas digesters and bio-latrines are located in communal areas – community centers, schools, churches and hospitals – to ensure ready access. Single units are also set up in locations that serve 20 or more households, with each family contributing to the total monthly cost of running the bio-latrine.
“Each homestead is connected to the biogas digester through an electronic gas meter that relays information to a central processor for billing purposes,” Kisakye notes.
The bio-latrine is made from a combination of off-the-shelf products, including biogas digesters from India and China, as well as biogas lamps, pressure gauges and stoves from China.
With aspirations to develop a perfect digester, the company is planning further developments to enhance the performance of its bio-latrine.
“We plan to introduce an agitator to facilitate proper digestion and remove maximum biogas from the digester. We will also introduce a system that automatically circulates water from the slurry back to the mixing chamber. There are still many technical challenges to overcome before we come up with our ‘dream’ bio-latrine, but when we do we intend to protect our innovation,” Kisakye says, noting that the company is documenting all aspects of the bio-latrine’s design, operation and maintenance.
“If our innovation is copied at this stage, there are no guarantees of performance,” she warns.
“Innovation is about utilization of the available resources like technologies, manpower and machines to address our immediate challenges. It is not only about being new; it is also about having the capacity to address local challenges and making this world a better place to live in,” Kisakye observes.
The company is currently testing its technology within communities and has built and connected bio-latrines to more than 150 domestic biogas digesters and 40 institutional digesters ranging in size from 6 to 70 cubic meters of fixed dome design.
“We are currently working in Gulu in North Uganda, where we have connected a 50-cubic meter digester to 10 bio-latrine stances,” Kisakye says. “Our aim is to reach all of Uganda’s rural population.”
With a 45-cubic meter bio-digester, it is possible to generate 15 cubic meters of biogas in 24 hours. “The biogas stoves currently on the market consume 0.15 cubic meters of biogas per hour at maximum opening. That means the 45 cubic meter bio-latrine has an installed capacity of 100 appliance hours providing biogas to over 20 families,” Kisakye explains.
Having completed installation of its demonstration sites, Tusk Engineers is now looking to roll out a market awareness campaign across Uganda.
“Our campaign will focus in particular on Uganda’s off-grid market to ensure that our technology is widely adopted and used,” Kisakye adds.