Animal feed is the greatest value option for effectively making use of food waste, and is likely to bring livestock productivity benefits too, according to a study by researchers in China and the US.
Despite increased awareness of food waste, it remains a problem on the rise. Scientists set out to review the existing evidence on using such waste to feed livestock.
Food waste as an alternative feed offers numerous advantages over other recycling options, they said, as it allows for the replacement of conventional feed ingredients such as soy and corn, with cascading positive environmental effects. They also found that in more than three quarters of studies to date, animals fed food waste performed optimally or increased productivity, with the remainder showing decreased performance.
“To meet the growing demand for animal-sourced food while mitigating the climate and resource burdens of the agri-food systems, doing business-as-usual is not acceptable,” the research team wrote in the journal Resources, Conservation and Recycling.
“Leveraging animals to optimize the safe and productive re-use of food waste biomass can be a viable, practical, and impactful option to support sustainable productivity.”
Can old practice be revived?
Feeding livestock food waste has a long history, though is rare in modern food systems, due to their demands for precision, uncertainties about supply and lack of supporting policies, among other barriers. In Europe, the use of food waste as animal feed is banned, due to fears around disease transmission, and in the study, this was reflected in only small amounts of European research available for review.
While there is growing interest in using food waste in large-scale aquaculture, this hasn’t so much been the case in terrestrial livestock farming. But “with pressing climate and sustainability challenges, there is heightened interest in reviving the old wisdom to tackle the new problems,” the researchers noted.
As well as analysing effects on animal performance across 102 studies, the researchers also looked at the different methods used to process food waste into suitable alternative feed products, aimed at removing impurities and ensuring feed safety. Thermal treatments were most common, with enzymatic digestion and fermentation using microbes also seen. They noted, however, that some waste sources such as fresh citrus waste was fed directly to animals without necessary treatment.
“Field-based evidence is abundant and shows that feeding properly treated food waste is safe for animals with minimal public health risk,” the scientists stressed, suggesting that risk-reducing strategies and good management practices, combined with regulatory and technical control mechanisms offer a route forward that can bring producers peace of mind.
Nutrition is central focus
Safety is unlikely to be the only possible roadblock to widespread adoption. If food waste is to become a mainstream animal feed once more, ensuring proper nutrient balance is key, the researchers said, with some studies demonstrating low nutrient availability, low protein and fibre and imbalanced fats and carbohydrates.
“To maintain optimal production and minimize potential loss when incorporating food waste into livestock diets, it is essential to balance the supply of major nutrients from all feed ingredients in the diet to meet animal production requirements,” they added.
“As food waste materials are diverse and the nutritional attributes vary, accurate and rapid nutrient analysis is key for successful adoption and implementation.”
