Co-pyrolysis of Melocanna baccifera and Royal Poinciana: Integrated product characterization and synergistic effects on aqueous and organic phases

Abstract

The increasing demand for sustainable energy and resource recovery underscores the need to explore underutilized lignocellulosic biomass. This study is driven by the motivation to harness such renewable resources through pyrolytic valorization, aiming to optimize the yields of aqueous phase and characteristics of biochar, biphasic liquid products, and gaseous outputs under both individual and co-fed feedstock conditions. The feedstocks selected for the pyrolysis experiments are: i) pure RP (Royal Poinciana pod) biomass and ii) 1:1 (mass ratio) mixture of MB (Melocanna baccifera) and RP, referred to as RM. The experiments were conducted in a semi-batch reactor over a temperature range of 450 °C to 600 °C. In this study, the co-pyrolysis of RP and MB was carried out to assess the synergistic interactions between the feedstocks, which led to enhancements in product yields and resulted in significant improvements in the physicochemical characteristics of biochar, liquid fractions, and the energy content of the gaseous phases. In the aqueous phase, the highest yields were observed at 450 °C, 10.5 % for RP and 11.2 % for the RM blend, where the increase in yield for RM is attributed to the synergistic effect of co-pyrolysis with MB biomass. The aqueous phases RM were enriched with ionic species such as acids and electronegative compounds, as verified by FTIR, with ¹H NMR confirming higher area percentages. GC–MS analysis of the organic phase at this optimal condition indicated a phenolic content decreased to 32.62 % upon co-feeding due to thermal degradation, demethoxylation, and condensation to non-volatile compounds. The biochar demonstrated high heating values of 26.58 MJ kg⁻¹ (RP) and 28.41 MJ kg⁻¹ for RM at 600 °C, suggesting that it can be used as a solid fuel. The gaseous products notable increase in methane and hydrogen, and a decrease in CO₂ observed as a result of synergistic interactions of feedstocks. This co-feeding strategy enhanced the overall quality of the solid, organic, aqueous, and gaseous products, thereby broadening their potential applications across energy production, material development, and green chemical industries.