How company turns human waste into animal feed, fertiliser 

After driving for about 20km up a dirt road from the Mombasa Road junction, we arrive in Kinanie, Machakos County. This quiet area is perched on rocky hills, large irrigated vegetable farms and dusty tracks.

It has a distinctive aura of new development, with a smattering of newly-built homes and roads under construction. While it is sparsely inhabited, evidence shows the population is growing.

This is the home of Sanergy. The firm located about 43km southeast of Nairobi, converts human and other organic waste into animal feed and organic fertiliser using the circular model of economy.

There’s frenzied activity in the compound — forklifts moving different loads, dozens of workmen in the thick of the action and trucks driving in and out. There’s also the consistent buzz coming from greenhouse-like structures.

By turning waste into insect-based animal protein and organic fertiliser, the company provides solutions in four fundamental aspects of the economy: Urban sanitation, energy, food security and job creation.

But how does this model work? What are the cost implications? Is it sustainable?

Mr Michael Lwoyelo, the managing director of Sanergy, explains that the process begins with providing about 4,000 portable toilets to residents of Nairobi’s low-income informal housing settlements such as Mukuru Kwa Njenga.

“We then collect the waste and transfer it to our factory for processing into different products,” the mechanical engineer adds.

In city neighbourhoods such as Mukuru, Kibera and Mathare, basic sanitation infrastructure coverage is as low as 30 per cent, sometimes lower. As such, portable toilets are a godsend — they eliminate one of the social menaces among locals.

To entities like Sanergy, it’s a convenient and cheaper way of getting their raw material — faeces. By using handcarts, the company can penetrate the farthest reaches of slums, thus creating job for youth.

At 6pm every day, the offloading bay at the factory is humming with activity. About 200 tonnes of organic waste arrive here daily. 

“This is a mixture of human waste collected from our toilets in the city and green waste from markets, hotels and restaurants.

“This is also an assortment of waste from fruit and vegetable processing factories in the Nairobi metropolitan area,” Mr Lwoyelo explains.

In the next few hours, this waste will be sorted, mixed and shredded to make it even for processing. It’s then loaded onto 50-metre racks using a special pulley system ready for production.

But it’s the company’s use of black soldier flies (BSF) technology to break down this waste that’s most fascinating.

This makes the factory’s processes a classical convergence of engineering and insect biology in waste management and manufacturing.

Mr Lwoyelo says: “The larvae of the BSF are fed on the solid waste for about two weeks. They extract nutrients from the waste for their growth while breaking it down. After 15 days, the larvae are ready for harvesting.”

This process takes place in specially designed structures where temperature and humidity are controlled.

So efficient are the flies that every day they consume about 150 tonnes of waste. At the end of the period, they will have broken down this mass completely, leaving only what looks like black earth.

“It’s this residue that we use to manufacture organic fertiliser. The rest is used to make briquettes,” the manager adds.

Some of these high-value briquettes are sold and others used internally to power factory functions. Sanergy has a specially designed kiln where briquettes are burned to generate steam that operates the air conditioning system at the production nurseries.

For many Kenyan manufacturers today, energy constitutes one of the biggest expenses, a situation only aggravated by its rising cost. This has forced some large-scale consumers of energy to either diversify their sources or to look for cheaper means to power their operations.

For firms seeking cheaper and readily available energy options, briquettes come in handy. Various estimates show that briquettes are four times cheaper than hydropower and almost as efficient.

Meanwhile, at Sanergy, the harvested larvae go to the manufacture of animal feeds, where they are “washed, treated and dried to about 10 per cent moisture content before being packaged for sale”.

Manufacturers of animal feeds are the biggest point of sale for BSF larvae, which they mix with other ingredients to produce highly nutritious feeds for chickens, pigs and fish. 

Incidentally, the only other animal protein available in Kenya is omena. In a country that’s food-insecure, using omena for animal feeds at the expense of humans is often a question of logic. 

“Black soldier flies, therefore, come in as an efficient and sustainable source of insect-based animal protein,” Mr Lwoyelo argues. 

During the process, five per cent of the larvae grow into pupae and later adult flies to maintain the colony, he says.

These flies are transferred to Kilifi County, where they lay eggs before the cycle begins afresh.

Climate control

But why the coastal county? “Kilifi is warmer and more humid than Nairobi, which makes it suitable for their breeding. The temperature in this county is 30° Celsius, which can be constant.”

To replicate these conditions in Nairobi is an expensive undertaking that requires a lot of energy for climate control.

For a company anchored on the tenet of minimal energy use, Lwoyelo says, any cheaper alternative is a no-brainer.

‘‘When the flies lay eggs, we transport them from Kilifi to the factory by road every day to introduce them to the cycle,’’ he adds.

Mr Lwoyelo speaks with an overspill of enthusiasm about this business model. His excitement, though, is neither exaggerated nor misplaced. Sanergy’s operations are at the core of Kenya’s economic blueprints of the Big Four Agenda (manufacturing and agriculture) and Vision 2030.

In 2016, Sanergy scaled beyond sanitation to waste management to become a fully fledged manufacturing company.

‘‘We needed to get the right recipes for our products. To do that, we had to have a mix of different waste forms, which allows us to maximise our points of value from every tonne of waste.’’

“From a Vision 2030 perspective, we’re tackling the economic and social pillars by creating jobs and advancing sustainable ways of managing waste respectively,” Mr Lwoyelo notes 

“Our farmers have been trained to use chemical fertilisers. After using them without replenishing organic elements in the soil, the soil is degraded, affecting yields,’’ observes Mr Lwoyelo. He argues that using organic fertiliser boosts soil fertility and produce by up to 30 per cent.

For 120 years, successive regimes have invested billions of shillings in sanitation infrastructure in the city.

Traditionally, waste management has followed a sequential approach of make-use-dispose. This approach, though, is fast becoming expensive and inadequate. 

Nairobi’s population is growing exponentially by the year, stretching the city’s installed capacity to effectively manage its waste. Consequently, some of this waste ends up in dumping sites, polluting the environment. 

The government’s Sh20 billion to expand the sanitation infrastructure in the city has, therefore, been a drop in the ocean. 

At the current rate, experts argue that it would take 150 years to attain universal sanitation coverage in the city county alone, even longer across the rest of the country.

Meanwhile, the population boom continues. But nowhere else is this growth steeper than in informal settlements.

It’s estimated that 60 per cent of residents in Nairobi live in low-scale neighbourhoods where housing is inadequate and access to basic services such as sanitation is a nightmare. Kenya is at a tipping point.

To sustainably manage waste in Nairobi and other urban centres in Kenya, Mr Lwoyelo says, the circular economy model is no longer an option but the imperative.

‘‘By collecting, recycling and converting waste into end products, you lower the net cost of waste management while making the process profitable as well,’’ he says.

Why, then, has uptake been low? The expert argues that the circular economy approach in waste management requires manufacturing expertise and diverse players.

"It introduces [among other players] scientists such as entomologists (insect biologists) and agronomists and energy management engineers.’’

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