The harmless soldier fighting mounds of harmful waste

10/06/2024

In early 2023, Abidjan, Côte d'Ivoire's bustling metropolis, found itself at a critical juncture. The city, home to six million souls and growing annually by 187 000 more, was generating a staggering 2 500 tonnes of organic waste daily. City officials strained to manage this burgeoning waste problem.

The problem was easy to see. Outside the city’s markets, towering heaps of pineapples remnants, watermelons skins, rotted tomatoes, bananas peels and old lettuce leaves sat decomposing under the sun, omitting foul odours and attracting rodents.

“The district authorities reached out to us,” says Isabel Albinelli, a Bioeconomy Specialist of the Food and Agriculture Organization of the United Nations (FAO). “We noticed that there was a significant opportunity for valorising organic waste.”

At the same time that the city grappled with this organic waste problem, urban and peri-urban farmers were depending on imported fertilizers which were growing more expensive by the month. This, in turn, had caused food prices to rise. The task was to find a way to mitigate the food waste while enhancing local agricultural resilience.

The solution was an FAO project called Circular bioeconomy in Abidjan: from Food Waste to the Fork or BioDAF. The project sought not only to address the problem in the District of Abidjan, but to offer a model for other cities grappling with similar issues of waste management, food security and economic empowerment.

The key to it all was a not-so-tiny insect called Hermetia illucens or the Black Soldier Fly. The creatures, which are abundant throughout the Western Hemisphere, look more like a wasp than a common fly. When they take to the air, they make a loud buzzing which even Albinelli admits, “can sound rather alarming”. But in fact, they are harmless creatures, who lay thousands of eggs and whose larvae consume prodigious amounts of organic waste.

The idea was to get the flies to mate, give their offspring tons of garbage to eat, then dry the larvae to use as either feed for livestock or powdered food for fish farms. The project received a grant from FAO’s incubator and intrapreneurship ELEVATE programme. ELEVATE funds novel projects that provide workable solutions to critical agricultural challenges.

The project began with a series of kick off workshops designed to refine the ideas of the BioDAF team. The ELEVATE team “helped us in thinking out of the box and in making our project successful,” says Albinelli. “They were there to find solutions when challenges arose that we hadn’t thought of.”

The logistics of mating Black Soldier Flies is no simple matter. The first thing the project needed to do was build a “love shack” for the mating flies. They created an enclosure about the size of a one-car garage with plenty of plants and fabric soaked in water for them to drink. They also placed small bits of wood where the flies could lay their eggs in the hundreds of thousands.

“It’s weird to work with them and think that such tiny insects could have such a great impact, simply by carrying out their natural tasks,” muses Albinelli.

Once the eggs are laid and the larvae hatched, they are placed in pools made from concrete filled with rotting fruits and vegetables that have been put through a mulcher. To achieve the greatest effect, the vast hordes of larvae have to be churned into the organic garbage by hand. And while that might not be the most appealing activity in the world, the benefits in terms of waste mitigation and fertilizer development are well worth the effort.

After 14 days, the larvae have grown by up to 10 000 times their size as eggs. At this point, they are separated from their excrement – which is used as fertilizer – and dried. The dried larvae are then used as animal feed. 

The FAO team in Côte d'Ivoire worked with government officials, the Institute of Circular Economy of Abidjan and local startup BioANI to train local farmers, particularly women, in how to harvest the flies and develop the fertilizer and feed. The big worry for the team was whether local farmers would buy into the idea of feeding dead black fly maggots to their animals or using their waste as fertilizer. “We were expecting behavioural barriers from farmers, as these organic fertilizers are actually the frass of some larvae eating waste,” said Albinelli. “But actually, the fertilizer is so effective, cheap and locally available that more and more farmers are buying it.”

In fact, the project was so successful, that they couldn’t keep up with local demand. And for good reason. The larvae and the organic fertilizer were sold at about half the price of imported fertilizers and worked just as well. As a result, this year the project seeks to expand to several more markets in the Abidjan area.

In addition, it hopes to provide not only animal feed and fertilizer but also food to supply tilapia fish value chain. Côte d'Ivoire, being a great consumer of this fish, has expressed interest in utilizing the larvae of soldier flies for fish meal, which is notably costly.

“This project exemplifies a unique combination of solutions that are at the heart of what agricultural innovation should be,” said Vincent Martin, FAO Director of the Office of Innovation. “It tackles real needs -- sustainable waste management, the cultivation of local agricultural resources and the economic empowerment necessary for bolstering food security. That is what real innovation looks like in the field.”

The ELEVATE programme run out of FAO’s Office of Innovation is currently working with another eight projects to fuel innovation in agricultural contexts.

Related links

Learn more

• Publication: Circular bioeconomy in Abidjan: from food waste to the fork
• Website: FAO Office of Innovation
• Website: FAO country profile: Côte d’Ivoire