Source: The Conversation – in French– By Rassim Khelifa, Assistant Professor, Department of Biology; Canada Research Chair Tier 2 in Global Change Biology, Concordia University
Canada geese are true gangsters. They are imposing, cheeky, and extremely adaptable, and they survive remarkably well in urban environments. Wherever they go, they leave their characteristic mark: cigar-shaped greenish droppings.
The population of Canada geese has experienced arapid expansion in many cities in North Americathanks to favorable urban environments — abundant food on lawns, safe nesting sites, and few predators — and the implementation of effective conservation measures over the past three decades.
Canada geese are certainly adorable, but when they gather in large numbers, they can become a nuisance. They damage crops and compete with other waterfowl. Their droppings, which are unpleasant to step on, carry pathogens that contaminate lawns and causethe ecological collapse of the bodies of water.
A Canada goose candefecate every 20 minutes. Now imagine the amount of fecal matter produced each day by hundreds, or even thousands, of these birds in a city. Yet, almost no effort has been made to explore the potential beneficial uses of this waste.
According to the findings of our researchpublished in theJournal of Environmental Management, the droppings of barnacle geese could be used to create a source of protein serving both as animal feed and fertilizer, thanks to the contribution of a recycling champion found in nature: the black soldier fly.
Producing poultry food from Canada goose droppings
Black soldier fly larvae are known for their remarkable ability to consume and decompose organic waste, particularlyanimal-origin waste from agricultural holdings. However, they have never yet been tested on Canada goose droppings.
As part of our study, we fed black soldier fly larvae with three different diets: a standard nutrient-rich mix composed of corn, wheat, and alfalfa (control mix), a combination of this feed mix with goose droppings, and finally a diet composed exclusively of droppings.
We also introduced another variable by sterilizing part of the excrement, to help us determine whether the microorganisms present in the feces have an impact on digestion.
The results were surprising: the insect was able to complete its entire life cycle by feeding exclusively on excrement. In fact, it managed to ingest a little more than half of it. Its body size and lifespan were reduced as a result, but this did not pose a problem since it fulfilled its function.
The larvae grew faster and reached a higher body weight when the excrement was not sterilized, suggesting that the microbes present in the droppings somehow promote the development of the insects. It is worth noting that the larvae that consumed the mixture of excrement and nutrient-rich food developed even better than those fed only with nutrient-rich food, and they reached a similar physical condition at the adult stage.
These results seem to indicate that black soldier fly larvae and goose droppings could be used to feed a large-scale organic waste treatment system. The goose droppings could be collected from parks and green spaces in the city, then transported to a facility where the larvae could be raised by consuming this waste.
The larvae could then serve as a source of protein for poultry feed and aquaculture, according to a circular waste management approach focused on “suprarecycling.”
Nutrient-rich fertilizer
The digestion process of the larvae also produces a residue, the frass. The frass of black soldier flies haswere testedwithin the framework ofseveral studies, mainly on terrestrial crops, where they haveimproved plant growth and crop yield.
We have decided to study the potential of guano produced from the droppings of Canada geese — as fertilizer for duckweed, a fast-growing aquatic plant with high protein content used for animal feed, biofuel production, and wastewater treatment.
As part of this experiment, we tested three different potential fertilizers for duckweed. The first (the control) was an ideal solution containing the nutrients necessary for the plant’s growth. The second consisted of untreated Canada goose droppings, and the third of feces resulting from the digestion of Canada goose droppings by black soldier fly larvae.
When the droppings were applied, the growth of the duckweed was 30% higher than that of the duckweed fertilized with the control fertilizer. We also observed that the roots of duckweed grown in droppings from goose excrement were smaller than those grown in untreated waste, which is a typical reaction to an environment richer in nutrients, where they are easily accessible by the roots.
Sustainable circular economy
There are already industrial waste treatment installations making use of insects.Entosystem, a Quebec company that produces insect proteins intended for the feeding of farm and domestic animals, uses black soldier fly larvae to transform food and organic waste into proteins and fertilizers.
In Nova Scotia, the biotechnology company Oberland Agrisciencealso uses black soldier fly larvae and employs technologies such as AI and robotics to transform organic waste into animal feed and soil products.NRGene, in Saskatchewan, is a research and demonstration center that also conducts tests with the black soldier fly with the aim of optimizing the large-scale conversion of waste into proteins.
Similar systems could be used to valorize goose droppings thanks to the black soldier fly, rather than transporting this waste to the usual dumps or landfill sites.
This method allows waste to be transformed into resources of great use for the agri-food industry: larvae can be used as feed for poultry or in aquaculture, while the droppings can be used as organic fertilizer for various crops.
Thanks to this environmentally respectful approach, a conflict situation related to the presence of wildlife in urban areas becomes an opportunity to seize. It helps to establish acircular economydurable where waste isreused, recycled or transformed into a new resource.
Rassim Khelifa benefits from funding from the NSERC CRC Level 2 program (CRC-2022-00134) and an NSERC Discovery Grant (RGPIN-2024-04564). Rassim Khelifa is a member of the Quebec Center for Biodiversity Sciences and the Canadian Society for Ecology and Evolution.
Carlos Antonio Lopez Manzano benefits from funding from the Fonds de recherche du Québec – Nature et technologies (FRQNT) through the merit scholarship for foreign students (PBEEE). Member of the Quebec Center for Biodiversity Sciences (CQSBD) and Aquatic Resources Quebec (RAQ).
–ref. We have found a way to convert goose droppings into poultry feed and fertilizer –https://theconversation.com/we-have-found-a-way-to-convert-canada-goose-droppings-into-poultry-feed-and-fertilizer-282098