Stanley Chindikani Msiska

This chapter presents a comparative life cycle assessment (LCA) evaluating the environmental performance of intercropped mixed feedstock (IMF) biorefineries relative to monocrop single-feedstock systems in a representative sub-Saharan African context (Malawi). Six biorefinery scenarios (2.18 kt/yr capacity) were assessed, combining three product portfolios with two feedstock strategies. Scenarios S1–S3 represent monocrop systems producing (S1) electricity via combined heat and power, (S2) ethanol with electricity and biogas, and (S3) lactic acid with electricity and biogas. Scenarios S4–S6 replicate these configurations using IMF to capture agronomic and environmental synergies from intercropping. The LCA included all 18 ReCiPe 2016 midpoint categories. Results show that environmental impacts increase with product diversification due to the greater material and energy intensity of chemical synthesis and purification. For monocrop systems, global warming potential rises from 59.6 in S1 to 982.8 kg CO 2 -eq/t in S3, while fossil resource depletion and terrestrial ecotoxicity increase by more than 150% and 640%, respectively. Introducing IMFs consistently reduces impacts across all product portfolios. Relative to monocrop residues, IMF systems lower global warming potential by 61% (59.6 → 23.0 kg CO 2 -eq/t), fossil resource depletion by 15%, and terrestrial ecotoxicity by 22%, with additional reductions observed for ionizing radiation, freshwater eutrophication, and terrestrial acidification. These benefits stem from intercropping attributes such as biological nitrogen fixation, enhanced nutrient cycling, and reduced agrochemical inputs. However, lactic acid pathways remain environmentally intensive due to solvent, reagent, and thermal energy demands, indicating opportunities for process optimization. Overall, IMF biorefineries demonstrate strong potential for reducing environmental burdens while supporting soil health and sustainable rural industrialization.

Prussian blue (PB) and its analogues are promising cathode materials for sodium-ion batteries due to their open framework and favorable ion transport properties. However, their electrochemical performance is often limited by structural defects, poor crystallinity, and unstable cycling behavior. In this study, a synergistic strategy combining polyvinylpyrrolidone (PVP), sodium citrate (NC), and low-temperature synthesis is employed to regulate nucleation kinetics and crystallinity of PB particles. PB samples were synthesized via a co-precipitation method by varying sodium citrate content (0–7.35 g) and synthesis temperature (25 °C and 0 °C). The optimized sample, prepared with 7.35 g NC at 0 °C (NPB-3), exhibits enhanced crystallinity and improved electrochemical performance. Increasing NC content at 25 °C improves reversible specific capacity from 81 to 97 mAh g⁻¹ at 1 C, while low-temperature synthesis further enhances capacity retention from 68 to 76 mAh g⁻¹ after 150 cycles. The improved performance is attributed to the chelating effect of sodium citrate, which slows nucleation and reduces structural defects, and the low-temperature condition, which promotes controlled crystal growth and structural stability. This synergistic control of nucleation and crystallinity mitigates lattice degradation during cycling and enhances Na⁺ storage performance. The findings provide a simple and scalable approach for improving PB-based cathodes, contributing to the development of cost-effective and durable sodium-ion batteries.