Sustainable upcycling across the agricultural value chain: A scoping review of by-product generation and valorisation pathways

Introduction : Agriculture generates substantial volumes of by-products during crop production and post-harvest processing. Many of these by-products remain underutilised despite their potential to be converted into value-added products such as foods, biochemicals, materials, soil amendments, bioactive compounds, and energy. The evidence on agricultural by-products, their stages of origin, and the technological routes by which they are generated has been compiled in this scoping review. Objective : To map and synthesise global evidence on how agricultural by-products are generated across value chain stages and upcycled through diverse valorisation pathways. Methodology : A systematic literature review was conducted in four electronic bibliographic databases: PubMed, ProQuest, Scopus, Web of Science. A predetermined extraction framework was used to chart the data, which were then narratively synthesised using stage-wise and pathway-wise categorisation. From eligible studies, data were extracted, summarised, and collated to develop probable frameworks. Results: Most residues originated from the post-harvest and processing phases, which together accounted for 88% of the reported by-products. The literature was dominated by studies on rice, maize, wheat, coffee, sugarcane, banana, and a variety of horticultural and plantation crops. Food and ingredient development, animal feed, biochemicals and bioactives, materials and bioproducts, soil amendments, and bioenergy were identified as the main valorisation pathways. Cascading multi-pathway strategies were frequently reported. Conclusion : A variety of underutilised biomass streams with significant potential for circular applications are represented by agricultural by-products. More opportunities were identified at the post-harvest and processing stages, alongside a growing technological emphasis on high-value biochemical and food-based routes. The scope of future work should focus on developing integrated biorefinery approaches, increasing research on underrepresented crops, and improving reporting consistency.