Towards flexible large-scale, environmentally sustainable methanol and ammonia co-production using industrial symbiosis†

Abstract

As industries face increasing societal and governmental pressures to adopt sustainable practices, the methanol (MeOH) and ammonia (NH₃) sectors, significant contributors to greenhouse gas (GHG) emissions, are seeking innovative solutions to transition toward net-zero emissions. Here, we report on the use of industrial symbiosis (IS) as a transformative strategy to facilitate the cleaner co-production of MeOH and NH₃ by integrating green hydrogen (H₂) within a carbon capture and utilisation (CCUS) flowsheet. We examined the environmental assessment of various co-production pathways across a system boundary, which includes three (3) leading technologies – Steam Methane Reforming (SMR), Autothermal Reforming (ATR) and Gas Heated Reforming (GHR), considering both business-as-usual (BAU) and hybrid IS integration (Hyd). MeOH flowsheets utilised all three technologies, while NH₃ production employed SMR and ATR systems. This comprised six (6) BAU MeOH and NH₃ co-production schemes (GHR–SMR_BAU, SMR–SMR_BAU, ATR–SMR_BAU, GHR–ATR_BAU, SMR–ATR_BAU, ATR–ATR_BAU) and six (6) Hyd (GHR–SMR_Hyd, SMR–SMR_Hyd, ATR–SMR_Hyd, GHR–ATR_Hyd, SMR–ATR_Hyd, ATR–ATR_Hyd) cases, utilising cradle-to-gate life cycle assessments (LCA). Results show that IS-integrated flowsheets reduced GHG emissions by 12–28% compared to BAU operations, with GHG impacts improving in the order GHR–ATR_Hyd > ATR–ATR_Hyd > SMR–ATR_Hyd > GHR–SMR_BAU > ATR–SMR_BAU > SMR–SMR_BAU, in agreement with energy and resource efficiency results. Notably, the GHR–ATR_Hyd configuration outperformed all other cases, reducing natural gas consumption by 11% and heating requirements by 8.3%. Furthermore, sustainability results support IS as a pathway to environmental benefits-with ATR-based NH₃ operations achieving up to 31% improved impacts linked to both ecosystem quality and human health. Ultimately, our study underscores the critical role of IS in advancing resilient, low-carbon practices, promoting sustainable technologies for net-zero emissions and defossilisation, thereby supporting a transformative shift towards sustainable industrial operations.