Challenges and enabling mechanisms in sustainable biofuel supply chains: A comparative systematic review and global evidence synthesis of manufacturing and supply chain dynamics.

Abstract

Sustainable biofuel research contains a large number of proposed barriers and enabling mechanisms, yet it remains unclear whether reported enablers directly address the barriers with which they are associated and whether those relationships are supported beyond conceptual or model-based evidence. This systematic review synthesizes 104 peer-reviewed studies using a PRISMA-guided protocol, a fixed coding framework, system-domain and operational-level classification, a predefined barrier-enabler mechanism map, and evidence appraisal that separates conceptual alignment from enabler-specific support and causal identification. Across 272 study-barrier records, 188 (69.1%) exhibited direct alignment, but only 46 (16.9%) met the evidence-supported direct threshold. Environmental, land-use, and natural-resource trade-offs showed the weakest pattern, with 13 of 36 records directly aligned and only 2 evidence-supported. At the level of solution classes, only 45 of 185 study and enabler records moved beyond proposal or model testing. All stayed at levels supported by laboratory work or case studies. No enabler class reached pilot or field implementation. Moreover, 94 of the 104 studies lacked causal identification. Cross-biofuel patterns varied with feedstock structure, infrastructure, scale, policy conditions, and evidence maturity, while social dimensions were reported in only 22 studies. The findings show that the central gap in the biofuel literature is not a shortage of proposed solutions, but a scarcity of barrier-specific mechanisms supported beyond conceptual or model-based stages. Policy and managerial implications should therefore be treated as conditional priorities for targeted testing rather than as verified intervention effects.

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