As we count down to the 4th International Conference on Carbon Dioxide Removal in Milano, we are hosting a series of discussions on the research that will be shaping our sessions this June! 
While CO2​ dominates the climate conversation, methane removal from dilute sources like dairy farms is absolutely critical for slowing near-term warming. 
This study explores a novel process chain that enriches highly dilute methane before converting and storing it, providing a much more energy-efficient and feasible pathway for non-CO2​mitigation! 
Full Abstract: Evaluating the techno-economic feasibility of methane abatement from dilute and atmospheric sources
Authors: Sai Gokul Subraveti, Kian Karimi, Sairam Sirigina, Shareq Mohd Nazir, Matteo Gazzani, Simon Roussanaly, Rahul Anantharaman
While greenhouse gas (GHG) mitigation efforts have predominantly focused on CO2​, other GHGs like methane are emerging as major contributors to global warming. The IPCC sixth assessment report highlights mitigating non-CO2​GHGs is essential to achieving climate neutrality by 2050. Atmospheric methane levels have more than doubled since preindustrial times, driven by rising anthropogenic emissions from hard-to-abate sectors such as agriculture, dairy farms, coal mining, wetlands, etc. Agriculture alone accounts for over 40% of global CH4​ emissions, with source-level concentrations typically around 10-1000 ppm. With CH4​ global warming potential being approximately 80 times that of CO2​ over a 20-year period and more than 25 times over a 100-year horizon, mitigating CH4​ from these dilute sources presents a compelling opportunity to slow near-term warming. However, technological solutions for methane mitigation from dilute sources are still largely conceptual, with limited understanding of their process-level feasibility.
One promising approach for mitigating CH4​ emissions from dilute sources involves converting CH4​ into CO2​, followed by the capture of CO2​ for geological storage. However, highly dilute CH4​ concentrations make direct conversion at the source very expensive and challenging. Instead, CH4​ at these sources can be enriched to moderate concentrations via separation before converting into CO2​. For instance, we evaluated the process feasibility of CH4​ enrichment using an adsorption process and the results showed that the moderate concentrations (5-30%) of enriched CH4​, along with high-purity CO2​, are co-produced during enrichment, indicating a strong potential for feasible downstream CH4​ conversion and storage.
This study investigates the techno-economic feasibility of abating CH4​ emissions particularly from air and dairy farms by evaluating the entire process chain from source capture to geological storage. Specifically, the proposed process route first enriches CH4​ to moderate levels using vacuum temperature swing adsorption, and then converts the enriched CH4​ to CO2​, along with CO2​ separation, which is co-produced in both enrichment and conversion steps. Two different CH4​concentrations, i.e., 25 ppm (open barns) and 100 ppm (semi-closed barns), representative of dairy farms, are considered. An integrated techno-economic optimization tool encompassing process models of different process steps along with the cost model is first developed. Both energy and costs are chosen as KPIs. Using this framework, the proposed route is evaluated and compared to a case of direct CH4​ conversion into CO2​, followed by direct air CO2​ capture. The preliminary process analysis revealed that the overall energy demand for 25 ppm feed CH4​ concentration is ~8 MJ/CO2​eq., combining energy demand from enrichment, conversion, and downstream CO2​ separation and conditioning. At the conference, we will present the optimal energy and cost performances of the proposed route.
Given methane’s high warming potential, should we invest more heavily in capturing dilute non-CO₂ gases despite the intense energy demands of enrichment?