Addressing nutrient depletion in Tanzanian sisal fiber production using life cycle assessment and circular economy principles, with bioenergy co-production

Nutrient depletion in Tanzanian sisal production has led to yield decreases over time. We use nutrient mass balances embedded within a life cycle assessment to quantify the extent of nutrient depletion for different production systems, and then used circular economy principles to identify potential cosubstrates from within the Tanzanian economy to anaerobically digest with sisal wastes. The biogas produced was then used to generate bioelectricity and the digestate residual can be used as a fertilizer to address the nutrient depletion. Life cycle assessment was used in a gate-to-gate assessment of the anaerobic digestion options with different cosubstrates. If no current beneficial use of the cosubstrate was assumed, then beef manure and marine fish processing waste were the best cosubstrates. If agricultural wastes were assumed to have a current beneficial use as fertilizer, then marine fish processing waste and human urine were the best cosubstrates. The largest reduction in environmental impacts resulted from bioelectricity replacing electricity from fossil fuels in the national electricity grid and improved onsite waste management practices. There is significant potential to revitalize Tanzanian sisal production by applying circular economy principles to sisal waste management to address soil nutrient depletion and co-produce bioenergy.