Insect waste could be a farmer’s treasure

When insects molt, their exuviae contain chitin, a hard polymer that also makes up the shell of crustaceans like shrimp. Microbes, such as Bacilli bacteria, help plants break down chitin into usable forms. And when insect exoskeletons break down, they stimulate the growth of bacilli and other microbes already present in the soil.

The researchers focused on the exuviae and droppings of crickets, mealworms and black soldier flies, said Katherine Barragán-Fonseca, a PhD student at Wageningen University and author of the paper.

While the new paper offers how this circular system might work in theory, researchers have begun conducting lab and field experiments to determine how it might work in practice. “It’s very exciting, but how much shit do I need?” said Dr. Ngumbi, by way of example.

After experimenting with different ratios of excrement and exuviae from different insects, Ms. Barragán-Fonseca finalized a powdered mixture. She then conducted experiments in which she mixed a few grams of it into the soil before planting mustard. She said she discovered that the mixture could increase plant reproduction by increasing the number of flowers, attracting even more pollinators. These results are unprecedented.

“It’s great to see the power these insects have,” said Ms. Barragán-Fonseca. “Garbage for someone can be treasure for other purposes.”

Insect farming is a growing industry, which means more insect waste will be produced. This waste used to be thrown away, but some companies are starting to sell it as fertilizer, Dr Dicke said. Although an insect’s droppings may seem negligible, they swell on an industrial scale; a Nebraska mealworm breeder produces about two pounds of feces for every pound of mealworms.

Recycling this waste would make insect farming – which is already more efficient than raising large livestock like cows and pigs – even more sustainable. “We are facing climate change, which brings a lot of stressors,” Dr Ngumbi said. “Anything that can increase plant productivity is always a plus.”