Hydrogen production strategies in pulp and papermaking environment- a review on processes, challenges and economics

As the world seeks to transition to a lower-carbon and sustainable energy future, H2 is gaining attention as a renewable fuel in the energy landscape. Policymakers, industry stakeholders, and researchers are actively working to unfold the full potential of H2 as a renewable fuel. H2 production from the pulp and papermaking resources is an emerging area of interest that aligns with the growing demand for clean and sustainable energy sources. Pulp and paper mills (PPM) generate various by-products, viz., waste biomass, prehydrolysis liquor, black liquor, lignin, lime mud, wastepaper, wastewater, effluent treatment sludge, etc., which can be utilised for H2 production through different physicochemical and biological methods. Dark/photo fermentation, enzymatic hydrolysis, electrolysis, gasification, sub/supercritical hydrothermal treatment, saccharification, photocatalysis, etc., are some processes that have been sustainably implemented for H2 production from the aforementioned PPM-based by-products. However, integrating H2 production into existing PPM operations requires careful consideration of technical and economic aspects to ensure viability and sustainability. Hence, this article, in a first attempt of its kind, provides an overview of H2 production strategies in the PPM environment, highlighting process fundamentals, existing scenarios, technical aspects, mechanistic pathways, case studies and cost analysis, along with possible associated operational and economic challenges. It also provides an overview of PPM operations, highlighting the point of origin of the above-mentioned by-products, making this article helpful for non-papermakers. Adopting a comprehensive action plan for H2 generation from PPM-based by-products can be an excellent initiative to achieve the goals of global energy sustainability.