Fruit Waste Potential for Single Cell Protein Production in Addis Ababa City, Ethiopia: A Review

Urban food waste presents a significant environmental challenge, but it also offers a promising opportunity for sustainable protein production. In Addis Ababa, it's estimated that around 70%-74% of municipal solid waste is biodegradable, with a large portion made up of fruit and vegetable residues; bananas, mangoes, avocados, and citrus fruits dominate these organic streams. These high-moisture, nutrient-rich materials are particularly well-suited for single-cell protein (SCP) production through microbial fermentation, positioning them as a climate-resilient alternative to conventional animal or plant-based proteins. Current research explores various aspects: substrate composition, effective pretreatment strategies, selecting optimal microbial strains, different fermentation approaches, and crucial safety issues such as nucleic acid content, allergenicity, and potential mycotoxin contamination. Globally, SCP yields range from 20 to 50 g/L, but translating these results to Addis Ababa is complicated by local variability in feedstock quality and seasonal availability. This means solutions must be tailored to the specific context. Scaling up SCP production isn't without hurdles. Major challenges include the heterogeneous nature of the feedstock, its high moisture content, limited cold-chain infrastructure, and noticeable gaps in technical expertise. Despite these challenges, there are tangible avenues for progress: establishing pilot-scale fermentation facilities, developing decentralized preprocessing and collection systems, and embedding these efforts within broader circular bio-economy frameworks. Together, these strategies could enhance local protein availability, reduce landfill contributions, and help curb greenhouse gas emissions. Still, several knowledge gaps remain particularly regarding Ethiopia-specific techno-economic analyses, process optimization for mixed fruit waste, and capacity-building in fermentation biotechnology. Addressing these gaps is essential for moving SCP production from the laboratory to a viable, city-wide solution. By integrating technological, regulatory, and industrial strategies, Addis Ababa can leverage fruit-waste valorization to address urban organic waste, strengthen nutritional security, and further Ethiopia's goals in advancing a circular bio-economy.