Reimagining landfills as energy hubs: A new integrated approach for biomethane and green hydrogen production

Landfills have long been seen as a suboptimal waste management solution, yet innovative strategies can repurpose them as energy hubs. This study investigates an integrated valorization approach combining landfill gas (LFG) upgrading via Vacuum Pressure Swing Adsorption (VPSA), multi-stage reverse osmosis (RO) treatment of landfill leachate (LL), and green hydrogen (H2) production via electrolysis powered by renewable energy. The proposed approach has been partially validated at the Borgo Montello landfill (Latina, Italy) through the implementation of LFG upgrading, LL treatment, and photovoltaic (PV) modules installed along the basin slopes to promote energy self-sufficiency. The strategy was evaluated through site-specific mass and energy balance analyses, comparing four scenarios: A) representing the conventional approach with LFG used in combined heat and power (CHP) units and external LL management; B) featuring LFG upgrading to biomethane (bioCH4) and LL treatment via RO; C) an advanced model integrating H2 production from treated LL using a PV-powered electrolyzer; and D) which builds upon Scenario C but proposes an alternative pathway for bioCH4 valorization that eliminates the need for liquefaction. The mass balances indicated that the upgrading and liquefaction system achieved an 87 % (m/m) yield and 98 % purity in terms of methane, while the RO treatment displaced 68 % of water recovery and 99.9 % of contaminants rejection. Energy balances confirmed the viability of all configurations, with Scenario D delivering the highest energy surplus of +8938 MWh/year, followed by Scenario C (+5729 MWh/year), Scenario A (+5161 MWh/year), and Scenario B (+2418 MWh/year). Although Scenario A yields relatively high energy production, it provides limited resource valorization and circular economy benefits compared to the other scenarios, which integrate bioCH4 and H2 production within a more resource-efficient model. Overall, the results demonstrate that landfills can be repurposed into multi-functional energy hubs, contributing to circular economy goals, decarbonization, and resource recovery.