The by-products of insect breeding accumulate. They could be fertilizer in a circular farming system.

Proteins from farmed insects such as mealworms, crickets and black soldier flies offer a solution to the growing challenge of sustainably feeding livestock: fast-growing and resource-efficient, these creatures quickly produce tons of protein, without the costly and damaging inputs required. to produce grain or grass for food.

But along the way, they also generate a massive amount of waste, releasing tons of crusty exoskeletons called “exuviae” and excreting a potent mix of feces and undigested food called “feces.”

Now, a group of researchers have written an opinion piece claiming that we’re missing a key trick as this six-legged cattle industry grows: we should be recycling this mountain of freely available trash into the soil to grow our cultures. By improving soil health and increasing nutrients, mixing insect waste into farmland soil could even limit the need for polluting chemical fertilizers and pesticides, they say.

write in Trends in plant science, researchers studied the available evidence to understand how insect waste interacts with plants and to infer the potential benefits it could bring to farms. In the first case, insect droppings are high in nitrogen, so it follows that adding this nutrient mix to the soil would provide a direct source of nutrients to plants, resulting in a “short-term nutrient boost”. accessible to plants”, explain the researchers. .

But incorporating this waste into the soil could also nourish plants in the longer term, through a series of complex and fascinating interactions with microorganisms. Adding insect byproducts to farmland is said to increase soil organic content, which fuels the growth of a rich cocktail of bacteria and others, many of which are beneficial to plants. For example, research shows that adding mealworm exuviae to the soil promotes the abundant growth of a class of particularly beneficial bacteria that take up residence in the roots of plants and, from there, help them to fight pathogens and pests. These bacteria also help plants by producing growth-promoting hormones and supplying them with nutrients such as iron and phosphorus.

There is also preliminary evidence to suggest that when these nutrient funnel bacteria receive a steady stream of insect waste, they can make plants more productive by helping them produce larger, more colorful flowers for increased pollination, which therefore increases yields.

Insect exuviae also contain a rich store of chitin, a polymer known to improve soil health and trigger intrinsic plant defenses against disease. Factories struggle to process this polymer in its raw form. But increasing insect organic matter in soil also supports a range of bacteria species that will readily break down chitin and unlock its ingredients for crops, underscoring the concurrent benefits that could come from enriching agricultural soils with insect waste.

The researchers warn that until we have more direct research, many questions remain unanswered, such as how much exuviae and insect droppings are needed to feed these microorganisms and keep them at needed levels. to support crops.

But the evidence available so far points promisingly to the ability of this emerging waste stream to stimulate microbial activity, and thus support plant growth, defenses and resilience, and possibly even re-start higher yields. Collectively, these benefits “may reduce the use of synthetic pesticides and fertilizers and thereby support sustainable agricultural production,” the researchers write.

In addition, the use of insect waste could move us towards a more circular agricultural system. One of the great appeals of using insects as food is that they can convert nutrients into protein very efficiently and are not fussy about what they eat, including agricultural and food waste. Insect farms could be supplied with waste, turn it into protein for livestock, and then their own waste could be recycled on cropland which again provides us with more food.

With the rapid increase in insect farming and the encouragement of favorable legislation in regions such as the European Union, it is likely that these crusty waste streams will only grow – and with them, the possibility of adopting the closed-loop systems that agriculture really needs, say the researchers.

“Insect-derived products represent a tremendous opportunity to improve crop productivity as part of circular agriculture.”

Barragán-Fonseca and. Al.”Insect droppings and exuviae to promote plant growth and health.” Trends in plant science. 2022.

Picture: Douglas Mills on Flickr