Orange peels bioashes from thermal treatment for adsorption of methyl orange: Experimental investigation and Life Cycle Assessment

Waste generation and water pollution are two major concerns that impact the environment due to their potential damage to the ecosystem and human health. Although biochar made from agricultural waste (including orange peel waste) has been receiving increased attention due to its absorbent capacity in water treatment, little is known about the bioahes produced from orange peel waste, including their characterization, application and performance in wastewater treatment, and environmental impacts related to production. This paper presents the production of bioashes from oxygen-limited thermal treatment of orange peel waste, the utilization of these materials as an adsorbent of methyl orange, and the Life Cycle Assessment (LCA) to present the environmental impacts related to production and application. Despite the low yield (10.1 %), high activation energy for ash formation (149.8 kJ.mol-1), non-porous nature, low specific surface area (<5.0 m².g-1), and low surface charge, the functional groups present on the surface promote dye adsorption, resulting in 0.10 mg of Methyl Orange per gram of adsorbent. The LCA revealed that electricity consumption is the hotspot for the production of bioashes. The potential direct emissions of C2H4, C2H6, C2H2, and CH4 due to the decomposition of biomass in the process are a point of attention because it can generate significant impacts in the photochemical oxidant formation and climate change categories. The findings indicate that bioashes can be useful for wastewater treatment and a way to reduce waste, and that LCA should be more considered in this kind of research to unveil the possible environmental impacts.