Comprehensive techno-economic and environmental assessment of sawdust–polypropylene co-pyrolysis adsorbent for Cu²⁺ adsorption at laboratory scale

Co-pyrolysis of sawdust and waste polypropylene represents an avenue for valorizing residual lignocellulosic biomass and non-recyclable plastic products. This investigation focuses on the adsorption of Cu 2+ ion by SPB-500, biochar prepared at a temperature of 500 °C. Factors considered in this study include adsorption kinetics, adsorption capacity, and adsorbent reusability. Moreover, economic costs, carbon footprints, and cost of carbon removal were analyzed in detail. The total cost involved in the entire project amounted to 6,978.57 THB (about 194.93 USD), resulting in an average cost of 64.62 THB per each data point (about 1.80 USD). Around 45% of the total costs corresponded to the purchase of equipment. When compared to other studies that use commercial carbons, SPB-500 proved more economical in terms of lower cost per experiment (about 64% reduction) and reduced costs of production ($8.83/kg) and the lack of any supplementary chemicals. The performance to price ratio of this study is estimated to be 14,330 mg USD⁻¹ which is better compared to those of other experiments conducted using commercial activated carbons. As for the carbon footprint of this research, it reached 16.03 kg CO₂-eq, with the highest contribution (58.2%) coming from the consumption of electricity. However, the monetary value of carbon emissions is relatively low 8.02 THB (0.22 USD), only 0.11% of all expenses. Despite its minor economic contribution (~ 0.11%), carbon cost was retained as a complementary metric for monetizing the greenhouse-gas externality rather than as a major determinant of experimental expenditure. Thus, energy consumption plays a major role in the carbon footprint, whereas its monetary value is relatively small.