The streets and marketplaces of Cameroon's economic capital Douala are strewn with fruit and vegetable debris of all sorts: banana peels, corncobs, coffee grounds, mashed sugarcane... you name it.

But one man's garbage is another's treasure, and the unsightly rubbish has become the raw material for Kemit Ecology, a startup that has developed a process for transforming the waste into fuel.

The company, launched in July 2014, sweeps the scraps off the streets and uses them to produce "organic charcoal" briquettes for cooking.

"It's an ecological solution. Collecting the rubbish cleans up the streets even before it is turned into fuel," said the startup's manager Mueller Tenkeu Nandou.

And "from the environmental standpoint, organic charcoal emits very little greenhouse gas and practically no smoke," asserted Tenkeu, who earned a master's in ecology, biodiversity and environment from the University of Douala in 2013 and now researches renewable energy there.

The briquettes aim at substituting for charcoal, for which demand is high and the environmental cost rising.

- Improve matters -

"Wood remains the main source of energy in Cameroonian kitchens," said environmentalist Didier Yimkoua . "Statistics are not official but it is thought that about 90 percent of all households use it to cook or smoke food."

Charcoal is also pressed into service for other household chores, like heating irons. Add to this thousands of traders who use it for braising or smoking fish and chicken and grilling plantains.

As of January, the Ministry of Waters and Forests had issued permits to private entrepreneurs to transform 1,500 tonnes of freshly chopped wood into charcoal.

So while not totally inoffensive, the "organic charcoal" could improve matters as it seems to emit two times less polluting gas than traditional charcoal, said Yimkoua.

Kemit Ecology estimates that the city of Douala alone consumes 90 tonnes of charcoal per month, much of it extracted from local mangrove trees which grow on an estuary in the Gulf of Guinea.

There lies the double attraction, says the little company. A smarter alternative would preserve the mangroves -- a precious ecological resource, which absorbs greenhouse gases and acts as a buffer against storms -- and also make money.

After Kemit Ecology collects the vegetable rubbish aboard a three-wheeled motorbike -- also saving cleanup expenses for some local merchants -- the company dries the raw material, then chars it in an oven.

The next step is to soak the matter in a mixture of water and a white clay called kaolin (used to make porcelain) to form briquettes.

These are then packed into 40-kilo (90-pound) bags to be sold.

- Surging demand -

Apart from the environmental benefits -- both ecological and aesthetic -- "organic charcoal" is cheaper than regular charcoal, according to Tenkeu.

One kilo (2.2 pounds) of charcoal costs an average of 91 euro cents ($1.02) in Douala, compared with 72 euro cents for a kilo of briquettes, he said.

And one kilo of briquettes is good for cooking up to five meals compared with the two meals that a kilo of wood coal can cook.

The project has won over cook Martielle Tchouffa, who has been trying out the "organic" briquettes. "I now prefer it, it's a very good charcoal. It's economical, doesn't smoke, heats well and cooks the food well."

At the moment Kemit Ecology produces one tonne of briquettes per month yet is reaching capacity with its order book bulging -- orders it cannot always fill, said Tenkeu.

He points to the young company's problems -- in getting a reliable energy source to bake the kaolin, and securing the funds to go to to the next level of development.

Yet they remain hopeful. If the technique catches on, he said, the cost of production will probably go down -- and Kemit may even become profitable .