Valorisation of Agroforestry Waste for Optimised Biole Formulation Through Diversified Inputs for Nutrient Recovery ^†

Closing nutrient loops is central to the circular economy in agriculture. This study evaluated whether diversifying local agroindustrial inputs can upgrade the nutritional quality and production efficiency of biol, a liquid digestate widely used as a biofertiliser in the Andean highlands of Ecuador. Three formulations were prepared in a 37 °C tubular biodigester under a randomised complete block design: T1 (cattle manure), T2 (cattle manure + panela, yeast and whey) and T3 (cattle manure + molasses, milk, ash and alfalfa). The physicochemical parameters were quantified by applying the analytical procedures in the national regulations for organic amendments and and were subsequently assessed through a parametric statistical test to determine significant differences among treatments. The optimised T3 mixture raised nitrogen, phosphorus and potassium to 0.20%, 0.30% and 0.55%, respectively, delivering 4–15-fold gains over the control and simultaneously boosting calcium and magnesium. Organic matter reached 48.8%, almost 50% higher than in T1. Fermentation time fell from 30 days (T1) to 14 days (T3) while maintaining a 178 L yield and 92.4% overall efficiency. These results show that strategic co-digestion of manure with sugar- and protein-rich residues accelerates microbial activity, concentrates macro- and micronutrients and shortens reactor residence time without additional energy demand. By converting heterogeneous organic waste streams into a high value liquid fertiliser, the approach offers a practical, low-carbon pathway to return nutrients to soils, reduce dependence on synthetic inputs and strengthen circular bioeconomy strategies in smallholder production systems. This valorisation pathway directly operationalises Sustainable Development Goals (SDG) 12 (Responsible Consumption and Production) by diverting agroforestry residues from disposal and recovering almost all of their nutrient content in a biofertiliser, thereby reducing synthetic fertiliser demand. Simultaneously, it advances SDG 11 (Sustainable Cities and Communities) by mitigating peri-urban waste loads, lowering life-cycle CO₂-equivalent emissions, and strengthening circular nutrient flows between processing hubs and surrounding smallholder farms. The process thus provides a replicable, low-carbon model for resilient food systems at the urban–rural interface.