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The increasing cost and environmental impacts of chemical fertilizers have driven interest in sustainable alternatives like brewery sludge, a nutrient-rich organic byproduct of the brewing industry. In Ethiopia, where soil fertility degradation is widespread and brewery waste is often underutilized, the potential of this resource remains largely unexplored. This systematic review assessed the agronomic effectiveness, soil health impact, and environmental safety of brewery sludge used as a soil amendment in Ethiopia. Following PRISMA 2020 guidelines, 10 peer-reviewed studies from Ethiopia were synthesized using a qualitative approach; no meta-analysis was performed due to heterogeneity in study design. The findings reveal that brewery sludge application at rates of 10–15 t ha⁻1 consistently improved crop yields, particularly maize, wheat, sorghum, and potato, often exceeding the performance of recommended chemical fertilizers. Additionally, sludge application enhanced key soil properties, including total nitrogen, available phosphorus, potassium, organic carbon, and cation exchange capacity, while maintaining heavy metal concentrations within international safety limits in most cases. However, studies applying lower sludge rates (< 1 t ha⁻1) showed limited agronomic benefits. Despite these promising outcomes, data on long-term environmental risks, heavy metal accumulation, greenhouse gas emissions, and microbial dynamics remain limited. Therefore, this review highlights brewery sludge as a viable component of circular nutrient management strategies, with significant potential to improve soil health and crop productivity. Future research should focus on optimizing application protocols, ensuring safety and exploring large-scale feasibility for sustainable agricultural development in Ethiopia and similar contexts.
Assefa et al. (Mon,) studied this question.