Feasibility of phytoremediation/pyrolysis/adsorption framework for valorization of water hyacinth: Life cycle assessment, techno-economics, and sustainability pillars

Abstract

While several studies have employed phytoremediation to treat surfactant-laden kitchen wastewater (SLKWW), there exists a research gap in addressing the profitability, sustainability, and environmental effects related to spent plant valorization. This work utilizes water hyacinth for SLKWW phytoremediation, followed by managing the exhausted aquatic macrophyte by either direct disposal into landfills (Scenario#1), or pyrolysis to generate biochar used as an adsorbent for post-treatment (Scenario#2). The best scenario was selected based on the techno-financial study, life cycle analysis (LCA) impact categories, and sustainable development goals (SDGs) achieved. The phytotechnology was operated under 23 ± 2 °C, light:dark cycle of 18:6 h:h, 65 ± 5 % relative humidity, plant density (1.0–4.0 kg m⁻²), pH (3–11), and retention time (4–14 d), getting maximum surfactant removal efficiency = 97.45 ± 4.62 %. The exhausted plant biomass was pyrolyzed at 500 °C for 120 min to produce biochar used as an adsorbent for effluent treatment, achieving 91.39 ± 4.43 % surfactant removal at adsorbent dosage = 8.9 g L⁻¹, pH = 4.3, and time = 135 min. The techno-economic investigation demonstrated that Scenario#2 was the desired pathway with enhanced financial performance (net present value = 12.5 US$, internal rate of return = 8.2 %, and payback period = 7.1 years), and superior LCA environmental benefits related to human health and carbon credit. The study outcomes comply with SDG_3 “protect human health from landfill leachate”, SDG_6 “surfactant-laden kitchen wastewater treatment”, SDG_7 “exhausted plant pyrolysis”, and SDG_12 “recycling of plant residues”. Further studies should focus on the sustainable management of the exhausted adsorbent after SLKWW post-treatment to avoid the risk of secondary pollution.