Landfill gas loading ramp-up strategies: Acclimatization optimization and long-term oxidation capacity of methane...

Methane (CH₄) emissions from landfills represent a challenge in global climate mitigation efforts. Methane oxidation biosystems (MOB) offer a low-cost solution for addressing residual and fugitive CH₄ emissions, yet the role of the acclimatization phase has not received enough attention in the technical literature. Here we optimize the acclimatization of compost-based MOBs through controlled landfill gas (LFG) ramp-up strategies. Four identical laboratory-scale columns were subjected to distinct flow increase patterns: exponential, linear, first-order-like, and constant inlet loading. The results showed that exponential and linear strategies accelerated the attainment of 100% CH₄ removal faster than the constant-flow system. Additionally, the axial gas concentration profile revealed that ramp-up strategies influenced the depth required for complete oxidation. Notably, exponential ramp-up led to full CH₄ removal within the first 50 mm of the methane oxidation layer (MOL) when actively aerated, suggesting the potential to significantly reduce its thickness in field systems. An additional 175-day column test, designed to estimate the maximum methane oxidation capacity under increasing loadings, confirmed the benefits of gradual acclimatization. By assuming that the oxidation rate follows the Michaelis-Menten model, the system achieved sustained removal efficiencies (>90%) and reached a maximum oxidation rate (V_max) of 3811 g_CH4·m^-3·d^-1 and a K_m of 12 g_CH4·m^-3. These findings highlight the importance of ramp-up strategies in designing efficient and more compact MOBs that can quickly attain design loadings.