Strengthening circular economy in Sub-Saharan agriculture through intercropped mixed feedstock biorefineries: A techno-economic and life cycle assessment approach

• Intercropped-mixed-feedstock biorefineries (IMFB) boost circular economy (CE). • IMFB integrating solid waste for fertilizer (SWF) (S3-S4) increases efficiency. • IMFB with SWF (S4) attain higher returns (43.59%) than S1-S3 (40.44%-42.76%). • S4 reduces environmental impacts by 9.54%. • IMFB reduce reliance on external inputs by regenerating nutrients from waste. Biorefineries utilizing mixed agricultural residues from intercropping systems, such as maize and pigeon peas, offer a promising avenue for advancing the circular economy (CE) in sub-Saharan African (SSA) agriculture. This study evaluates the CE potential of intercropped mixed feedstock (IMF) biorefineries that co-valorize maize stover (MS) and pigeon pea stalks and leaves (PPSL), compared to conventional single-feedstock (SF) systems. Four scenarios were assessed: S1 (SF without recovery of biorefinery waste-based fertilizer, RBWF), S2 (IMF without RBWF), S3 (SF with RBWF), and S4 (IMF with RBWF). The evaluation focuses on value addition, biofertilizer regeneration, and pollution reduction. Economic performance was analyzed using net present value (NPV), annual profits (AP), and internal rate of return (IRR) through process simulations and techno-economic modeling. Environmental impacts were quantified via life cycle analysis across 18 midpoint categories, including global warming potential (GWP), terrestrial acidification (TA), and fossil resource depletion (FRD). Among all scenarios, S4 demonstrated the highest CE performance, combining superior economic returns with the lowest environmental impacts. Notably, S4 achieved an IRR of 51.61%, surpassing S1, S2, and S3 by 28%, 21%, and 4%, respectively. S4 also recorded the lowest TA at 2.93 kg SO₂ eq/ton of feedstock which is 11%, 8%, and 2% lower than S1, S2, and S3, respectively. These findings underscore the benefits of diversified biorefinery feedstocks and the regeneration of farming inputs (e.g., RBWF) in strengthening circular economy integration and sustainability. However, realizing this potential at scale requires supportive policies, targeted investments, and active stakeholder engagement.