Life cycle assessment of the catalytic production of ethyl levulinate derived from Colombian residual lignocellulosic biomasss

Abstract

Valorization of agro-industrial wastes into valuable products is an alternative to boost the economic and social development of those regions where agricultural practices are unsustainable. Herein, upgrading of Colombian rice straw (RS) to ethyl levulinate (EL) was considered as an alternative fulfill the aforecited goal. To do so, a technical and environmental analysis were carried out. Process design was performed using Aspen Plus v12. Life Cycle Assessment (LCA) methodology was used to estimate the environmental impacts using ILCD 2011 midpoint + impact assessment method. The product system was a cradle-to-gate approach, including the cultivation stage and the biorefinery process using dilute acid hydrolysis. Said stage encompasses: (i) RS pretreatment; (ii) levulinic acid (LA) purification; and (iii) EL production. Concerning the technical analysis, the overall yield obtained was 0.115 kg EL/kg RS with a total energy consumption of 37kWh/kg of EL produced. Energy consumption was associated with high-water requirements needed to hydrolyze RS. Regarding the environmental impact, carbon footprint was 5.3 kg CO2-eq/kg EL, mainly ascribed to the use of steam derived from fossil fuels even with the CO2 capture from the paddy rice culture. Alternative scenario for reducing the overall environmental impacts was assessed. For this purpose, both low pressure steam (LPS) and medium pressure steam (MPS) generation from solid hydrolyzed residue was implemented as well as an increase in paddy rice yield from 4.97 to 5.7 ton/ha. Steam generation reduce carbon footprint by 11 % since steam from fossil fuels is avoided, as well as a reduction of 8 % in photochemical ozone formation, 9.7 % in acidification, and 12.5 % in ozone depletion. Furthermore, a comparison among RS combustion and diesel-EL blends combustion were performed to determine the environmental feasibility on the use of EL for energy purposes.