One-third of all food produced is wasted each year, resulting in a massive loss of resources. By the end of 2023, an estimated 2.5 billion tonnes of food were lost or wasted worldwide, with approximately 40% of food intended for human consumption ending up as waste. Improperly managed, food waste poses severe environmental and public health risks and contributes significantly to greenhouse gas emissions. This review aims to provide a comprehensive overview of typical sources of food waste—including fruits, vegetables, and grains—and the bioactive compounds they contain, such as dietary fibre, protein, vitamins, minerals, polyphenols, and prebiotics. It explores potential applications and practical methods for harnessing these bioactive substances to convert food scraps into valuable products, supporting a circular economy approach. This review follows PRISMA guidelines, analyzing over 240 publications from 2020 to 2024, focusing on food waste valorization, bioactive compounds, and their applications in fruit, vegetable, and grain wastes. Food waste contains valuable biological elements often in higher concentrations than in rejected market products. Various extraction techniques—including conventional methods (maceration, Soxhlet) and novel technologies (supercritical fluid extraction, ultrasound-assisted extraction, enzyme-assisted extraction)—can be used to recover bioactive compounds. These compounds demonstrate significant health-promoting properties, including antioxidant, anti-inflammatory, antimicrobial, anticancer, and cardioprotective effects. Industries can repurpose this waste for functional foods, nutraceuticals, cosmetics, animal feed, bioplastics, and bioenergy production. Sustainable valorization of fruit, vegetable, and grain wastes into valuable products that leverage their bioactive compounds offers substantial economic and environmental benefits. This approach addresses food security challenges, reduces landfill waste, lowers greenhouse gas emissions, and creates new revenue streams, aligning with multiple Sustainable Development Goals (SDGs 2, 3, 7, 8, 9, 12, and 13). However, challenges remain regarding extraction costs, scalability of novel technologies, and product stabilization. Further research is needed to optimize extraction processes and enhance the commercial viability of food waste-derived products.
Worku et al. (Sat,) studied this question.