Human waste as fuel

Dried human waste could be the next big business opportunity in Sub-Saharan Africa as well as helping to flush out the problem of poor sanitation, according to a start-up in the coastal city of Mombasa.

Waste Enterprisers believes the "faecal sludge" found in pit latrines and septic tanks could be used as industrial fuel in place of imported coal and other biofuels. 

The company's CEO, Dr Ashley Muspratt, said that dried waste has been shown to burn at least as well as coffee husks and palm nut shells in tests. Unlike these more common biofuels, there is a plentiful local supply of sewage all year round. 

"I like to talk about what we're doing as replacing [sewage] treatment plants with factories. When you talk about factories you're talking about bringing in a raw material and putting out a value-added product," Dr Muspratt said. 

A pile of dried sludge in Kampala (Moritz Gold / SANDEC)

She also insists that the human waste does not smell when burnt since it is often combined with other types of fuel. If anything, it gives of a faint "organic chocolate" aroma, she said.

In order for the sewage to reach a combustible state, up to 95% of its liquid content must be removed through a process of filtering, pressing and drying. 

The company has been trying to compress this drying time using custom-built ventilated greenhouses at Mombasa's main waste treatment facility. The end product is a granular fuel that can be loaded into kilns or furnaces to generate heat. 

Waste Enterprisers set up shop in Mombasa last November with assistance from the Kenya Climate Innovation Center. It plans to build its first factory by the end of the year, pending the go-ahead from Mombasa County Government, and is eying expansion to other parts of the coastal region. 

Waste Enterprisers demonstrate one of their drying greenhouses (Kai Tabacek)

The firm has been in discussion with some of the cement producers around Mombasa, but Dr Muspratt believes there is also demand from a range of smaller industries. 

"Coal, which is the primary fuel used by the cement sector, is all imported from South Africa. Smaller industries are using firewood which they are under increasing pressure to eliminate because of deforestation," she said. 

It is a similar situation in Kampala in Uganda, which has a thriving industry dependent on firing clay products such as building and roofing materials. 

"We have spoken to industries and they are interested," according to Dr Charles Niwagaba, a senior lecturer at Uganda's Makerere University. "Some of them have told us that they travel 300-400 km [to Tanzania] … to buy coffee husks for their kilns, and yet we have a lot of faecal sludge … not just in Kampala but also in other towns." 

Sewage is dumped at Duombasie landfill in Accra, Ghana (Linda Strande / SANDEC)

While faecal sludge is already used as an industrial fuel in Europe and North America, the absence of functioning sewage systems in many African towns and cities presents a new set of challenges. 

Dr Niwagaba estimates that almost 90% of the population in Kampala use pit latrines and septic tanks to store their waste on site, but that less than a third of the waste produced is collected. 

The cost of having a latrine pumped or manually dug out places it beyond the means of a large segment of the urban population. Even when the waste is collected, it is often dumped close to settlements or released into the environment. 

Pit latrines at Old fadama slum in Accra, Ghana (Linda strande / SANDEC)

Dr Linda Strande, of the Swiss Federal Institute of Aquatic Science and Technology, believes this is one of the unforeseen consequences of UN Millennium Development Goals, which call for a halving of the proportion of people without access to basic sanitation by next year. 

"[We have moved] a long way away from open defecation and increased access to toilets a lot," Dr Strande said. "But one problem it has generated is that now people have built a lot of pit latrines or septic tanks in urban areas but they haven't considered what happens with the sludge when the systems have become full." 

By making faeces into a fuel, Waste Enterprisers believes they are creating a financial incentive to collect more sewage, thereby removing it from communities and the environment. 

"We have an incentive to get as much waste as we possibly can into the plant and so we'll be targeting these slum communities and doing everything we can to extract waste," said Dr Muspratt. 

"I think we have enormous potential to have a big impact and to have that impact among some of the poorest residents of the city," she added.

This article originally appeared in the Daily Nation on 21st April 2014