CO2e emissions of renewable methanol from forestry residues and conventional natural gas-based methanol: a comparative analysis

Abstract

A comparative analysis of CO₂e emissions of renewable methanol produced from forestry residues (FR) and conventional methanol produced from natural gas (NG) is undertaken to assess which production pathway yields lower emissions. Pathways examined include steam methane reforming (SMR) of NG feedstocks, with and without carbon capture and storage (CCS), and steam or steam-O₂ gasification of FR feedstocks with alternative syngas conditioning methods, including external H₂ produced from electrolysis or NG SMR with and without CCS. Pathways are assessed across a range of carbon intensity of electricity (CI_elec) scenarios. Assessment of production emissions incorporates land-use emissions, including direct land-use change (DLUC) and soil organic carbon (SOC) while post-production assessment considers methanol end-use as a fuel or chemical product. Findings show that NG pathway production emissions are driven by scope 1 and fugitive emissions. However, methanol production from FR pathways offers significant emissions reductions compared to NG pathways, particularly when using steam gasification with CO₂ removal only or steam-O₂ gasification with external H₂ supplied from NG SMR with CCS. However, using electrolysis-based H₂ requires a low CI_elec to improve emissions relative to NG + CCS pathway and other FR pathways. Land-use and fugitive emissions can critically affect certain pathway comparisons, especially under moderate CI_elec. Methanol use as a fuel leads to unavoidable emissions while use as a chemical product can achieve carbon storage through FR pathways, provided that secondary processing demands are relatively low and CI_elec is moderate to low. Ultimately, renewable methanol has the potential to provide substantial climate change mitigation benefits, but its effectiveness depends on the syngas conditioning method, CCS implementation, and CI_elec. Consideration of these factors is critical to realization of environmental benefits.