Refining the Greenhouse Gas Emission Accounting Boundary in Typical Papermaking Enterprises: A Techno-Economic Assessment of Mitigation Pathways

Abstract

The intricate interplay of biomass-derived carbon, purchased energy, and process-specific fugitive emissions renders the determination of an appropriate accounting boundary in the pulp and paper industry a nontrivial exercise, one that fundamentally conditions the perceived efficacy of subsequent decarbonization strategies. This study undertakes a systematic refinement of the emission accounting boundary for a representative integrated papermaking facility, moving beyond the conventional corporate-level or Scope 1/2 frameworks to incorporate a tiered, process-based delineation that distinguishes between energy conversion, chemical recovery, and end-of-pipe treatment stages. A hybrid life cycle inventory, combining on-site operational data with sector-specific emission factors, was constructed to quantify baseline emissions under the default boundary, revealing a possible underestimation of biogenic methane contributions from wastewater anaerobic treatment by approximately 12-18%, a gap that carries non-negligible implications for mitigation prioritization. Subsequently, three mitigation levers—black liquor gasification efficiency enhancement, anaerobic digestion with biogas upgrading, and integration of waste-heat-driven organic Rankine cycles—were evaluated individually and in combination, employing a discounted cash flow model coupled with sensitivity analyses on carbon pricing and energy tariff fluctuations.