Reduction of CO2 emissions through the co-combustion of lignite with biomass residues: Renewable and non-renewable CO2 per produced megajoule and fuel characterization

Abstract

Accumulation of unmanaged agricultural wastes is related to increased environmental concern, as they usually are left unexploited and/or burned uncontrolled in the fields. The reduction/utilization of these wastes by turning them into solid biofuels for energy production is a viable solution for addressing the related environmental issues. In this study, twelve alternative solid biofuels of biomass residues and lignite (sunflower husk - BSH, stem, disk florets and seeds biodiesel sunflower wastes -BSW, corn husk -HKC, corn stalk and husk -SHC) were mixed with lignite in several proportions and assessed by using energy content analysis, proximate analysis, and ultimate analysis. Empirical chemical formulas were also determined. Furthermore, it introduces a novel concept to separate and quantify the renewable CO2 emissions, from the non-renewable emissions resulting from biomass co-combustion with lignite (alternative solid composite biofuels). The renewable and non-renewable CO2 emissions were expressed per produced megajoule (MJ) and per kilogram (Kg). The non-renewable CO2 emissions per produced MJ of the blends were compared to lignite emissions. The results showed that blends with 70 wt%, 50 wt% and 30 wt% biomass in blend could reduce about 75 %, 57 % and 34 % the non-renewable CO2 emissions per produced MJ, respectively. The present work suggests that blends of agricultural residues with lignite not only could be used as alternative solid biofuels (with better combustion characteristics than lignite sample, e.g. better energy content, less ash content, less Sulphur content, and similar Nitrogen content), but also could help to reduce carbon emissions via the co-combustion process.