Reuse of rinse water to promote circular poultry farming
From algae culture medium to chicken feed enrichment
Rinse water from broiler houses is currently considered by law as slurry and must be spread on land by an approved company. Technically, it is water in which a limited amount of nitrogen and other nutrients are present.
Through this project, in collaboration with Radius Thomas More, Proefbedrijf Pluimveehouderij wants to investigate the possibilities of reusing rinse water more efficiently: by using it to cultivate microalgae. After all, algae have a high-quality nutritional value and are interesting to use in animal feed. Thus, we then want to investigate whether we can reintroduce the cultivated algae into the feed of broiler chickens.
A business analysis of this circular collaboration will provide more insight into the opportunities and bottlenecks for scaling up.
We were able to demonstrate that algae cultivation on rinse water from poultry houses is effectively possible. We converted present nutrients into valuable proteins and nutritional components for feed and food.
This circular farming model can reducenutrient emissions into the environment. Indeed, by using poultry house rinse water as a growth medium for algae, it is no longer applied as slurry on grassland and fields.
We conducted a feedtrial in broiler chickens with an already commercially available Chlorella powder. There was no significant difference in feed conversion, water-feed ratio, foot sole and heel lesions, gut health and digestion between the control feed and the algae feed.
The addition of the algae species Chlorella sorokiniana in chicken feed may act on the colour of abdominal fat and legs. This may be explained by the carotenoids present in the microalgae.
Addition of algae had a limited negative impact on litter quality with slightly increased breast fouling.
MOST IMPORTANT LESSONS LEARNED
A circular agricultural model with algae could contribute to a new earning model for poultry farmers: algae could form a new sales product for poultry farming or create new markets o.v. label or concept chickens.
Because the law currently considers rinse water as slurry, it is not allowed to use algae grown on that water in animal feed (including for farm animals). A realistic legal framework is still needed for this circular model.
High market prices for algae and by-products offer an opportunity for poultry farmers to cultivate algae profitably as a secondary activity on the farm. The algae will then not be used in animal feed, but in applications such as aquaculture and pet food.
In this project, the addition of the specific algae species Chlorella sorokiniana did not substantially improve the technical performance of broiler chickens. Further research with pellet feeds, lower doses, other algal species ... may provide new insights in that area.
WHAT DOES THE FUTURE HOLD?
The project has shown that algae cultivation on rinse water offers interesting circular opportunities. It is certainly an impetus for further research under the Flemish Protein Strategy.
Thanks to this research, we know that the specific algae species Chlorella sorokiniana (added to 5 and 10%) in chicken feed does not substantially improve the technical performance of broiler chickens. It would be valuable to conduct further research with pelleted feeds, lower doses, other algal species ... to gain additional insights for optimising technical performance.
The use of microalgae offers interesting opportunities to respond to the colour of meat and fat of chickens.
Furthermore, it is important to conduct additional pilot-scale tests with a limited number of algae to monitor and analyse the composition and safety of the cultivated algal biomass.
Finally, it is interesting to look at the possibilities of algae cultivationon the poultry farm itself. Cleaning sheds on a broiler farm happens about every eight weeks, which generates a relatively large amount of rinse water. It would also save on road transports with rinse water