Reduced life cycle climate impact from manure through catalytic methane conversion and carbon dioxide removal

Agri-food systems constitute around one-third of global greenhouse gas (GHG) emissions, with roughly half consisting of non-CO ₂ GHGs, mainly methane (CH ₄ ) and nitrous oxide (N ₂ O). Methods and technologies to mitigate non-CO ₂ GHGs are currently limited, which is a reason for agriculture being categorised as a hard-to-abate sector. This study examines mitigation of GHG emissions from manure storage headspace through oxidisation of CH ₄ emissions at low concentrations using a thermal catalytic process with and without subsequent CO ₂ capture and storage (CCS). The technology is studied using a combination of process modelling and life cycle assessment at four CH ₄ concentrations: 300, 1000, 3000 and 10000 ppmv. The primary energy demand and net climate effect were evaluated, reaching a net climate effect of + 0.10, -0.77, -0.91 and − 0.97 g CO ₂ -eq emitted/g CO ₂ mitigated, respectively. The wide range of results is mainly influenced by the process energy demand being strongly correlated to the CH ₄ concentration. The sensitivity analysis shows that a net negative climate effect can also be achieved at 300 ppmv with access to low emission energy sources. Coupling CCS worsens the net climate effect of the system at all studied CH ₄ concentrations, mainly due to the additional energy demand for CO ₂ separation.