Annie Fabian Abel Chimphango

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.

Ultrasound-assisted extraction (UAE) enhances extraction rates while preserving the structural integrity and functionality of thermosensitive compounds, such as polyphenols and anthocyanins. Additionally, deep eutectic solvents (DES) are emerging green alternatives to organic solvents, like methanol, for polyphenols and anthocyanins extraction. However, from a green engineering perspective, optimisation of ultrasound-assisted deep eutectic solvent (UA-DES) extraction conditions is necessary to enhance yield and extraction efficiency beyond the conventional methods, because DES type and concentration, temperature, time, and solid-to-liquid ratio can significantly influence the extraction process. In this study, the three-level Box-Behnken experimental design was applied to optimise UA-DES processing time, DES (choline chloride and lactic acid) concentration, and liquid-to-solid ratio for extracting polyphenols and anthocyanins from starch-extracted sweet potato peels (SSPP). The UA-DES extraction efficiencies for total phenolic content (TPC) and total anthocyanin content (TAC) were compared to those of ultrasound-assisted methanol (UA-methanol). In both extractions, ultrasound-assisted water (UA-water) extraction was used as a control. The yield was calculated based on neochlorogenic acid. At the optimal extraction conditions (22.5% v/v water/ DES, 20 mL/g liquid: solid ratio, and 10 min processing time), the UA-DES yield, TPC, and TAC were about 75 µg/g dw, 10.54 mg gallic acid equivalent (GAE)/g dw, and 17.83 g/g dw, respectively, compared to 40.24 µg/g dw, 7.90 mg GAE/g dw, and 13.78 g/g dw for UA-methanol. Therefore, UA-DES is a potentially efficient green method for integration in the starch production process to obtain high-value-added products from SSPP. However, a comprehensive sustainability analysis is necessary for scale-up production.

Mango waste valorisation in integrated biorefineries supports circular bioeconomies, sustainable development goals, and climate change mitigation by diverting waste from landfills for value addition. The biorefinery concept potentially supports full valorisation, product diversification, cleaner energy provision, and proper waste management in mango processing facilities. Preferred biorefinery options for commercialisation depend on sustainability attributes (social-economic benefits and acceptance, economic competitiveness, and environmental performance). However, sustainability assessments are often limited to technical and economic feasibility and/or environmental impacts. The study combined the Life Cycle Sustainability Assessment, Jobs and Economic Development Impact Assessment model, and Multicriteria-Decision Analysis approaches for a holistic sustainability assessment of six simulated commercial integrated mango waste biorefineries (MWBs) co-producing bioproducts, and combined heat and power (CHP). The MWBs are annexed to a dried mango chips processing facility processing 27.8 tonnes/hr of mangoes, generating 5.56 and 6.94 tonnes/hr of peels and seeds, respectively, and 50 tonnes/hr of wastewater. Scenario 1 (S1) produces CHP, S2 co-produces CHP and pectin, S3 includes polyphenols, and S4 produces bioethanol to S2, whereas S5 co-produces polyphenols, pectin, bioethanol, and CHP, and S6 co-produces bioethanol and CHP. Notably, system-wide socio-economic benefits (job creation and value-addition to GDP) increase with the recovery of more bioproducts ( pectin and polyphenols ) . However, selecting sustainable biorefinery pathways depends on preferred sustainability metrics for the stakeholders’ developmental goals instead of the trade-off between environmental and economic benefits. Therefore, the results from this study would inform investment and policy decisions regarding the social benefits and MWB’s acceptance, which complement the economic competitiveness and environmental performance.