Parthenium hysterophorus L. for second-generation biofuels: pretreatment, fermentation, and biorefinery approaches

Parthenium hysterophorus L. is a highly invasive weed that poses serious threats to agricultural productivity, biodiversity, and human and animal health. Conventional management approaches have achieved limited long-term success, prompting increasing interest in their utilisation as a renewable biomass resource. This review critically synthesises global research on P. hysterophorus, with a particular focus on its conversion into biofuels and value-added products within a sustainable biorefinery framework. Bibliometric analysis using VOSviewer reveals that existing research is strongly clustered around weed ecology and control strategies, whereas studies linking weed management with bioenergy and biomass valorisation remain comparatively fragmented. This review methodically analyses the physicochemical makeup of P. hysterophorus, then thoroughly examines physical, chemical, and biological pretreatments designed to enhance biomass accessibility and reduce harmful allelochemical effects. This analysis rigorously assesses key bioenergy pathways—including bioethanol, biogas, bio-oil, biochar, and platform chemicals—in terms of process efficiency, output yields, and technological readiness. Researchers emphasise anaerobic digestion and bioethanol production pathways, focusing on key hurdles like detoxification, operational stability, and large-scale implementation. Although recent progress confirms the viability of transforming P. hysterophorus into sustainable energy products, critical shortcomings persist in life cycle evaluations, economic feasibility studies, and combined approaches to weed control and biorefinery operations.