How Goose Droppings and Black Soldier Flies Could Turn Waste Into Value

Goose sightings are difficult to overlook in spring. First, they pass overhead; then there is the evidence they leave on the ground. Parks, playing fields and other open areas can soon become coated in droppings.

The mess is unpleasant, foul-smelling and may even harm local ecosystems. Yet goose droppings could offer more than an unwelcome nuisance. Material that people normally avoid stepping in may have a practical use.

Scientists are now viewing goose waste differently and considering a straightforward question: rather than treating it solely as a problem, could it be converted into something valuable?

An unexpected ally in the insect world

To investigate this, researchers turned to an insect that already performs this sort of task.

The black soldier fly is recognised for processing organic waste. Its larvae consume discarded material and break it down while developing. As they do so, they transform the waste into reusable protein and nutrients.

A team led by Rassim Khelifa at Concordia University set out to establish whether these insects could process goose droppings.

“We wanted to see if the black soldier fly, a non-native species that is already industrially harvested widely, could be used to transform goose waste into valuable goods like protein and fertilizer,” said Khelifa. “The answer is yes; it can.”

Assessing waste processing and larval growth

The scientists first examined the quantity of waste left by geese in urban settings. They surveyed 11 locations in southern Quebec and Ontario.

Their findings revealed a direct relationship between goose numbers and the volume of droppings. Bigger flocks resulted in more contamination across public areas.

In laboratory trials, black soldier fly larvae received three different diets. The first was a standard research feed. The second blended that feed with goose faeces, while the third contained faeces only. Although the larvae survived on each diet, their performance varied noticeably.

Larvae given the mixed feed developed more quickly, had higher survival rates and processed the waste more efficiently. Those receiving only goose droppings nevertheless consumed over half of the available material, but their growth was slower and they became smaller adults.

These findings indicate that goose waste on its own can sustain the process, even though it is not the best diet.

The overlooked contribution of microbes

The researchers also investigated whether treating the droppings altered the outcome. They sterilised some samples with heat and pressure to eliminate bacteria, a method known as autoclaving.

Larvae fed the sterilised waste performed less well. They consumed less, developed more slowly and had shorter adult lifespans.

This suggests that the naturally occurring microbes in goose droppings may support insect development. It also demonstrates that bacteria, which are frequently regarded as harmful, may be beneficial under suitable conditions.

Converting waste into plant nutrition

The process extends beyond the insects themselves. Once the larvae have fed, they leave a material called frass. This nutrient-rich by-product can serve as fertiliser.

The team applied the frass to duckweed, a fast-growing small aquatic plant used for animal feed and water treatment.

The outcome was notable. Duckweed supplied with this fertiliser achieved 32 percent more yield than plants grown using a standard nutrient solution.

The plants also produced shorter roots, generally a sign that nutrients are readily available. Put simply, the frass enabled the duckweed to grow well without having to extend its roots in search of nourishment.

A cleaner cycle for urban areas

This method forms a cycle in which waste is made useful. Goose droppings feed insects, and the insects create material that supports plant growth. Rather than generating further waste, each stage adds value.

It could also provide practical advantages. Clearing droppings from parks would improve sanitation and lower the risk of environmental harm, including nutrient overload in water systems.

Meanwhile, the process yields protein with potential use in animal feed, alongside fertiliser that promotes plant growth.

Further work is needed before the approach can operate at large scale. Even so, the concept is straightforward and practical. It could offer city managers, farmers and remote communities an inexpensive means of managing waste that is usually overlooked.

Reconsidering what we discard

Goose droppings may never be welcome underfoot, but they need not have no value.

With appropriate tools and some imaginative thinking, even an unpleasant material can contribute to a functioning system.

Nature already operates through cycles, and this research illustrates how human systems might begin to mirror that model.

Rather than being the end point, waste can become the beginning of something new.

The full study was published in the Journal of Environmental Management.