Life Cycle assessment of biorefinery technology producing activated carbon and levulinic acid

Abstract

Life Cycle Assessment (LCA) is applied to eco-design the H3PO4-assisted hydrothermal carbonization (HTC) process converting biomass residue into high-value products. The main innovation of the process relies on the combination of the H3PO4-assisted HTC with the activation treatment of the obtained hydrochar, resulting in activated carbon that is then functionalized. In addition, the liquid phase obtained from HTC is eventually purified to extract levulinic acid. Under average conditions at the laboratory scale (reference), the LCA showed that electricity consumption is the main contributor (45–70%) to impacts on climate change, photochemical ozone formation, acidification, freshwater eutrophication, freshwater ecotoxicity and fossil resources use. Pyridine, the main chemical used in the functionalization stage, contributes to impacts on human toxicity and on marine eutrophication respectively by 77.3% and 47.3%. Building on these results, two further scenarios were studied, one considering the maximum capacity of each equipment and another one assuming the potential improvements once the process will be upscaled. The scenarios were validated in a series of laboratory scale tests. Depending on the environmental impact category chosen, the results showed a reduction potential of 30–65% as compared to the reference scenario. These findings confirm the added value of LCA in the ecodesign of technologies and pave the way to further improvements of the technology itself but also of the LCA methodology used for the assessment.