On the Kenyan shores of Lake Victoria, entrepreneur Dominic Kahumbu and his team are using rakes and their hands to remove water hyacinth.
It's an incredibly invasive plant, covering the surface of the water like a carpet, harming fish and helping mosquitos and bacteria thrive.
But where many see a pest, Kahumbu sees an opportunity.
"What we're doing out here on Lake Victoria is we are harvesting this... what everyone considers to be a real menace and a pest, an invasive species and it has many, many, negative connotations to it. But the actual fact is water hyacinth is a blessing in disguise."
And that's because, Kahumbu's company, Biogas International, is piloting a machine that converts water hyacinth into clean cooking fuel.
Kahumbu says two to three kilograms will provide fuel for a cooker making a meal of maize and beans over four hours.
"The gas is tapped from the center of the actual digester tube".
The project, in partnership with drugmaker AstraZeneca and the Institute for Sustainability Leadership at the University of Cambridge, has provided the "digesters" to 50 families in Kenya's western city Kisumu.
That's allowed residents like Tony Otieno to abandon his traditional stove, called a jiko.
It runs on charcoal, which Otieno says was costing him around 12 US dollars per sack.
"The gas has no smoke, it has no smell, then it is much faster than the jiko."
But at a cost of $650, Kahumbu acknowledges that they are not affordable for most families in the city.
"The elderly people who should be retiring, are choking themselves to death, which is criminal in this day and age, that we should allow such a thing when we have very, very … this is biogas, they should all have biogas."
He says the business needs capital investment and he's looking to the kinds of businesses that want to buy carbon credits to ensure his green fuel project can stay afloat.