Oxi-Loc - Sustainable and exemplary treatment of residual gas emissions from landfills in the aftercare phase using the example of the old landfill Loccum

The greenhouse gases methane (55-60 %) and carbon dioxide (40-45 %) make up the majority of landfill gas. Conventionally, the gas from capped landfills is collected with an active or passive gas collection system and either used for energy in a CHP plant or burned in a high-temperature flare. However, as a landfill ages, the amount of gas produced and the methane content decrease. Thus, further efficient gas collection, methane removal and energy recovery with conventional processes are no longer technically and economically feasible. This is the case at the old Nienburg/Rehburg-Loccum landfill.

In cooperation with Betrieb Abfallwirtschaft Nienburg (BAWN), the Oxi-Loc research project aims to demonstrate and implement in practice an external biofilter or methane oxidation filter to prove sufficient methane oxidation of the residual gas from old landfills using old plant components of landfill leachate treatment. This will provide necessary supplements to the technologies for optimised collection of landfill gases in municipal landfills and the technologies for aerobic stabilisation of municipal landfills. Furthermore, old structural components of landfill leachate treatment are used as models and thus further resources are conserved. The Oxi-Loc demonstration project aims to show that residual gases from landfills can be treated in the aftercare phase with the help of methane oxidation filters, so that their climate-impacting components can be sufficiently reduced and, in addition, municipal material cycles can be closed.

To achieve the aim of the research, in the first phase of the project, experimental filters with the necessary measurement and control technology as well as suitable filter material (including screen oversize from composting, vegetable charcoal, etc.) are to be set up on a laboratory scale at the site of the old Loccum landfill. The laboratory tests will first determine the operating and control parameters of the test filters. In the second phase of the project, the functioning and technical feasibility of the experimental filters for methane oxidation will be demonstrated and verified. For this purpose, an existing landfill leachate tank will be upgraded to a landfill residual gas treatment plant as a demonstration plant. In the final third project phase, the project will be evaluated in terms of its climate balance using material flow and energy balances. Furthermore, the demonstration plant will be transferred to licensed regular operation and an economic feasibility study will be carried out to determine the investment and operating costs for a model transfer to other old landfill sites with similar boundary conditions.

In Lower Saxony, numerous old landfills are in the aftercare phase. Their comparability to the old landfill Loccum is not only given with regard to gas development, but also in terms of size, history or sealing standard. The operators concerned will have to deal with the treatment of the decreasing gas quantity and quality. The question remains how sufficient methane oxidation can be demonstrated, or what technical effort will follow to achieve the goal of release from aftercare. The experience gained from the project should provide a high information value for all operators of landfill facilities, regardless of whether they are already in the aftercare phase or still in the disposal phase.

The Oxi-Loc project is funded by the state government with more than 400,000 euros. BAWN will receive 200,000 euros for practical implementation and field research on the new procedure. The rest of the funding will go to the ISAH for scientific support.