**Background:** The growing global population and increasing demand for healthy food have led to a significant rise in food waste (FW) generation, causing severe environmental and economic impacts. Food waste represents a loss of resources such as labor, water, energy, and land. By 2050, an estimated 68% of the world's population will reside in urban areas, placing immense pressure on food production systems. The concepts of 'circular economy' and 'bioeconomy' are central to addressing this challenge, aiming to keep products, materials, and resources in the economy for as long as possible while minimizing waste. This review explores the potential of converting FW into animal feed as a sustainable solution that addresses waste management, food security, and environmental preservation.
**Methods:** This is a narrative review that synthesizes existing literature on the characteristics and types of FW, its nutritive attributes, and various advanced treatment methods for converting FW into animal feed. The review covers processing techniques including solar drying, spray drying, dehydration, freeze drying, microwave drying, and silage production. It also examines the use of FW as feed for different animal categories (poultry, fish, cattle, and swine) and discusses meat quality outcomes, energy consumption for feed production, and safety policies.
**Key Results:** The review reports that the nutritional value of FW or loss per day is approximately 1200–1500 food calories. Carbohydrates make up around 30–60% of FW, proteins range from 5–10%, and fats make up 10–40%. One tonne of dry FW could be used instead of the same amount of maize grain to meet an animal's protein needs. The black soldier fly (Hermetia illucens) mature larva has 40–45% protein in biomass and up to 35% fat by dry weight, demonstrating its usefulness as animal feed. The energy needed to make feed from FW is 18.30 MJ/kg, which is 1.8 MJ/kg less than the energy needed to make feed from corn (20.10 MJ/kg). Regarding meat quality, studies found that feeding FW had no impact on 16 of 18 pork quality measures (e.g., juiciness, dressing percentage, meat colour, flavour, overall palatability). Pigs with a substitution rate of 50% had a growth rate that was 13% slower. The review presents data on household food waste across 22 countries, ranging from 50 kg/capita (Netherlands) to 189 kg/capita (Nigeria). The World Wildlife Fund estimates that by-products from food production and processing make approximately 30% of the feed given to animals globally. In the US, 14.7 MTs of food waste remain that could be utilized as animal feed. Currently, only 3 million tons of manufacturing food losses are recovered as animal feed out of the 102.5 million tons of FW produced in the EU each year.
**Clinical Implications:** While this review does not present original clinical data, it has significant implications for veterinary and agricultural practice. The use of FW as animal feed can reduce livestock production costs (feed accounts for approximately 80% of total pork production costs globally) and decrease environmental burdens associated with FW disposal, including greenhouse gas emissions, eutrophication, and acidification. However, the review emphasizes critical safety concerns: untreated FW may contain pathogens, as demonstrated by the 2001 foot-and-mouth disease outbreak in the UK caused by feeding uncooked FW to pigs. Appropriate heat treatments (prolonged heating to temperatures above 70°C for more than 30 minutes) can make recovered feeds safe. The review calls for systematic nutrient analysis, quantitative assessment of resource and environmental benefits, stakeholder engagement, and economic analyses to support the development of effective policies for incorporating FW-derived feeds into modern animal production systems.