Circular strategy for sustainable furfural production: A multi-scale investigation on upcycling furfural residue into adsorbent for CO2 capture

Waste furfural residue is converted into high-performance CO 2 adsorbent. • The adsorbent delivers 4.78 mmol/g CO 2 uptake with 99% cyclic stability. • The integrated system cuts CO 2 emissions while generating extra adsorbent output. • Techno-economic and life cycle analyses evaluate adsorbent use for flue gas CO 2 adsorption. Agricultural residues such as corn stover and oat husks are promising renewable feedstocks for the sustainable and cost-effective production of furfural, which is a widely recognized platform chemical derived from biomass. However, the production of furfural produces large amounts of furfural residue (FR). Its lower carbon and higher ash content relative to the original biomass pose significant disposal challenges. In this study, we propose a strategy that upcycles FR into porous carbon adsorbents and apply them in the furfural production system to simultaneously address the low-value utilization of FR and the flue-gas treatment challenges in furfural plants. Hydrothermal pretreatment combined with synergistic activation using potassium oxalate monohydrate and urea was employed to produce porous carbon materials. A post-combustion CO 2 capture system incorporating the porous carbon into a furfural plant was established, and the process was evaluated through techno-economic analysis (TEA) and life cycle assessment (LCA). The results indicate that the CO 2 adsorption capacity reached 4.78 mmol/g at 0 °C with 99% capacity retention after 10 cycles. TEA and LCA further showed that, compared with the conventional process, the system produces an additional 221 kg of adsorbent per ton of furfural and reduces CO 2 emissions by 5180 kg. Compared with the conventional system, the integrated system with flue gas CO 2 adsorption reduced both global warming potential and primary energy demand. In addition, the integrated system exhibits improved environmental performance. The global warming potential (GWP) decreases from 2.61 kg CO 2 -eq to a significantly negative value in the integrated system, indicating net CO 2 capture benefits enabled by the introduction of the flue gas adsorption unit. The acidification potential (AP) is also reduced compared with the conventional system, suggesting lower emissions of acidifying gases such as SO 2 and NO x . Overall, this work demonstrates a feasible circular strategy for sustainable furfural production by upcycling FR into porous carbon adsorbents for flue-gas CO 2 capture, supported by a multi-scale evaluation integrating material performance, process simulation, and life-cycle impacts. Download: Download high-res image (124KB) Download: Download full-size image