(462g) Preconcentration of Methane By Vacuum-Temperature Swing Adsorption for Removal from Air

The continual increase in atmospheric concentrations of greenhouse gases is a substantial driver of global warming and climate change. The intergovernmental panel on climate change (IPCC) in its sixth assessment report clearly highlighted the significant contributions of non-CO₂ greenhouses such as methane (CH₄) on global warming and their role in meeting climate neutrality by 2050. While the atmospheric concentrations of CO₂ have increased by about 50% since preindustrial times, the CH₄ concentrations in the atmosphere, although much lower than CO₂, have more than doubled (~2 ppm vs 722 ppb) during the same period. Particularly, agriculture activities related to dairy cattle, manure, etc., are the dominant global source of anthropogenic methane emissions. Since the emissions at these sources are mostly in confined areas, the CH₄ concentrations found are higher than in the air, typically around 10 – 1000 ppm. With over 25 times more global warming potency (due to its high radiative efficiency) compared to CO₂ over a 100-year horizon, removing CH₄ from the atmosphere or other diluted sources is very beneficial and presents an opportunity of slowing down climate change. Unlike CO₂ which has to be separated from air, CH₄ is reactive and can be removed by converting it to CO₂ or other products. However, the ultra-dilute concentrations of CH₄ in the air make it extremely challenging to directly remove CH₄ in the conversion process. To tackle this challenge, one option can be focusing only on mitigating CH₄ emissions with increased concentrations at agricultural sources or the other route is to preconcentrate CH₄ in the air from ppm to % levels to facilitate the conversion. The latter option further accounts for the removal of historical CH₄ emissions.

This study considers the second option where the feasibility of preconcentrating CH₄ in the air or from very dilute sources to a few % levels is examined using vacuum-temperature swing adsorption processes before CH₄ conversion. The proposed concept involves the simultaneous enrichment of CH₄ and CO₂ from air, which can be easily integrated with direct air capture (DAC) systems downstream. The process design methodology used herein is based on detailed process simulations and optimizations with an emphasis on minimizing energy consumption and maximizing the productivity of the process. The details of the process and the adsorbents along with the optimized results will be presented at the meeting.