Air Pollution Implications of Sugarcane Bioethanol Blending: A Critical Review of Global and Indian Evidence With Reference to E20 Policy

India's National Biofuel Policy mandates 20% ethanol blending (E20) in petrol by 2025, with sugarcane as the primary feedstock. Despite extensive global bioethanol lifecycle assessment (LCA) literature, the full multi-pollutant environmental implications spanning GHGs, PM2.5, PM10, NOX, CO, SOX, and VOCs remain poorly characterized in domestic policy. This paper synthesizes peer-reviewed evidence across global bioethanol LCA, the Brazilian benchmark, Indian-specific analyses, vehicular emission science, and biofuel health risk literature. The review concludes that E20's environmental credibility requires structural reforms in field burning, distillery emission controls, and regionally differentiated procurement.