The Composting of Water Hyacinth: A Life Cycle Assessment Perspective

Abstract

Water hyacinth is an invasive species that causes eutrophication in lentic waters. While mechanical removal is effective, it generates hazardous waste with biological contamination risk. Composting is a safe waste treatment option, inhibiting seeds and yielding agriculturally suitable compost. Life cycle assessment evaluated the environmental impacts of six composting piles using eight different by-products (potato peel, cattle manure, wood chip, rice straw, potato leftovers, olive pomace and biochar), all formulations containing water hyacinth. The worst environmental performances were the M2 pile (water hyacinth + olive pomace + cattle manure + potato leftovers) which achieved the highest AP (47.33 kg SO2 eq.) and EP (10.56 kg PO4³− eq.), while M3 (water hyacinth + olive pomace + rice straw + potato leftovers) had the highest GWP (816.51 kg CO2 eq.) and OLD (2.99E-11 kg R11 eq.). The biological composting process contributed the most to the overall increase in the impact categories for all piles due to air emissions (CH4 and N2O). M3 and M5 (water hyacinth + wood chip) had the worst performance in fossil fuel consumption due to distances travelled from by-products and energy use in the maintenance of composting piles. Concerning packaging, Big Bags with polypropylene had a greater impact than polyethylene bags (50 kg capacity). Evaluating the potential avoidance of mineral fertilisers, M3 compost showed potential for reducing TSP fertiliser production by 46%. Overall, M4, which incorporated a mixture of water hyacinth, olive pomace, wood chips and biochar, was the most favourable option from an environmental point of view.