Using black soldier flies to improve sanitation

Grown up larvae before it is dried and milled into powder to make a protein concentrate used for animal and fish feed. PHOTO | FILE | NATION MEDIA GROUP

What you need to know:

  • Scientists have created a simple method of recycling human waste into animal feed and fertiliser — using a fly.
  • The researchers collect the waste from the school, where they have constructed special toilets that separates urine from stool, and take it to the research centre at the university, where it is transformed into animal feed and organic fertiliser.

Researchers at Meru University of Science and Technology (MUST) have invented what is billed as a solution to the problem of poor sanitation in congested urban and rural areas. It is also expected to contribute to efforts to attain food security.

The scientists have created a simple method of recycling human waste into animal feed and fertiliser — using a fly. The project, dubbed Bio Resource Based Sanitation, is already in the piloting stage at Kunene Primary School, just opposite the university in Nchiru, Tigania West Sub-County.

The university is undertaking the project in collaboration with Aston University in the United Kingdom under the Newton Utafiti Fund, which builds research and innovation partnerships.

Trials started in September last year with a modest funding of about Sh4 million, with the project bringing together four departments at the university — Microbiology, Mechanical, Civil Engineering and Business.


The researchers collect the waste from the school, where they have constructed special toilets that separates urine from stool, and take it to the research centre at the university, where it is transformed into animal feed and organic fertiliser.

Listening to Joy Irungu, the lead researcher who is the brain behind the project, explain the process, one wonders why sanitation should remain a problem after commercialisation of this invention. Her colleagues from the other departments are Dominic Kiogora, Dr Guyo Huka, John Njeru and Sarah Wandili.

But Ms Irungu, a civil engineering lecturer, first explains how they breed the black soldier fly, the main agent of her invention. “We enclose the flies [in] a net, where they lay eggs which hatch into larvae. Before they get to pupae stage, they need to eat a lot and this is when we introduce them to the waste,” she says.

The scientist says as the larvae feed on human, kitchen waste or even cow dung, they grow into pupae ready to become grown flies. After consuming the waste, what remains is a black substance.

Ms Joy Irungu (left) shows larvae at the research centre during the launch of the project. PHOTO | GITONGA MARETE

This process takes about 10 days and at the optimum larvae stage, the scientists kill the insects by dipping them into hot water. They then dry and mill them into powder to produce animal or fish feed concentrate rich in proteins that is mixed with other feeds.

Before the product is packaged, it is taken through testing at the laboratory to ensure it is fit for animal consumption. The dried larvae may also be fed to chicken just like they eat them from decaying matter when they free-range. Some larvae are allowed to grow into flies, completing the cycle.

“The larvae contain high levels of protein at 60 per cent even more than omena (40 per cent), and when it is added to other types of feeds, it is very nutritious. The black substance is organic fertiliser which is a good soil conditioner,” says Ms Irungu, adding that urine is also used to make another type of fertiliser.

She says her invention was inspired by health challenges resulting from poor sanitation, which is a major cause of waterborne diseases. She conceived the idea while studying for her PhD. She developed an interest in effective sanitation technologies for informal and peri-urban settlements.

While the project addresses three of the government’s Big Four agenda items — manufacturing, healthcare and food security — the current high rates of urbanisation call for smart technologies to be put in use to solve some of the problems facing the population, Ms Irungu argues.

“By using this simple process, we have addressed health problems arising from poor sanitation, which is a global crisis and at the same time manufacture animal feed and fertiliser,” she adds.

Ms Irungu graduated in 2001 from Egerton University with a bachelor of science in agricultural engineering before obtaining a master’s in environmental engineering and management from Jomo Kenyatta University of Agriculture (JKUAT) in 2010.

The scientist, who has completed her PhD studies in sanitary engineering at the UNESCO-IHE Institute for Water Education (Netherlands) and is set to graduate in December, is so passionate about human waste management that she views flash toilets as a waste of resources.


“When you go to the toilet, your waste is about 300 grammes, but you use about five litres of water to flush it, amounting to 9.5 litres of waste which is even more complicated to recycle. You can imagine how much water we waste with flush toilets. It is also easier to manage the solid human waste than when it is mixed with water,” says Ms Irungu, whose thesis was based on biogas production from human waste.

One of the challenges she has faced so far is the acceptability of the project, because most people have a negative attitude towards human waste. The larvae at the centre have a daily capacity to process three tonnes of waste yet they are currently getting only 200 kilograms.

“Some people say they cannot stand the sight of stool being collected but what they don’t know is that by digging pit latrines and depositing it there, it creates more problems,” she says.

While the pits get full and have to be emptied manually, which is unhygienic, more have to be dug, taking unnecessary space. Besides, human waste in the pit latrines contaminates groundwater and produces high levels of carbon dioxide and methane gases, which when released to the atmosphere contribute to global warming, Ms Irungu explains.


The project has, however, received praise from members of the community, especially at Kunene Primary School, where the management says they had a problem with pit latrines.

“It came at the right time when we were about to dig more latrines after the ones we had filled up. But we did not have enough space since most of our land is occupied by classrooms. It was a godsend,” said Julius Kathurima, the school board of management chairman.

At the commercial level, the university intends to take up the project first as a community social responsibility activity, where they will build the toilets in schools or shopping centres and engage the youth, women and people living with disabilities to run them, vice-chancellor Prof Romanus Odhiambo said.

“They will have an income by charging people in need of the toilet facilities and we will be collecting the waste for processing,” said Prof Odhiambo.


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