Insights into integrated CO2 capture and utilization coupled with biomass oxidative pyrolysis

• Conversion of lignin to bio-oil, biochar and CO gas without CO 2 emissions. • Marble waste allowed efficient CO 2 capture and utilization. • Optimal marble to lignin mass ratio of 15. • Optimal CO 2 capture and utilization temperatures of 500 and 550 °C, respectively. • Maximum CO production of 0.030mol g -1 lignin without CO 2 emissions. Integrated carbon capture and utilization (ICCU) is a promising strategy for reducing CO 2 emissions, thus showing great potential in climate change mitigation. In this work, we have explored the combination of an ICCU strategy with the oxidative pyrolysis of lignin. Marble waste was used for CO 2 capture and utilization. Reverse water gas shift (RWGS) pathway was explored, using H 2 to convert the captured CO 2 to CO. It was first determined that marble allowed successfully capturing all CO 2 generated, also exhibiting a catalytic effect in the conversion of bio-oil. Then, the most important variables of the ICCU (Marble to Lignin (M/L) ratio (2.5–15), CO 2 capture temperature (400 °C − 550 °C) and CO 2 utilization temperature (500 °C − 650 °C)) were optimized. It was found that the M/L ratio required for avoiding CO 2 emissions in the CO 2 capture stage was 10, whereas a value of 15 was needed for avoiding emissions also in the CO 2 utilization stage. Optimal CO 2 capture temperature was 500 °C. Lower temperatures resulted in slower kinetics and higher ones in CaCO 3 decomposition, both cases leading to CO 2 releases. Regarding the CO 2 utilization temperature, at low values (500 °C), RWGS kinetics was slow, but no CO 2 emissions occurred. Above 550 °C, kinetics was faster, thus obtaining higher CO concentrations, but some CO 2 was released. In optimal conditions, total CO production was 0.030mol g -1 lignin , with zero CO 2 emissions associated. In essence, this work demonstrated that it was possible to implement a successful ICCU strategy using marble waste and avoiding active metal catalysts, thus making the process simpler and more sustainable.