Techno-economic potentials of integrating decentralised biomethane production systems into existing natural gas grids

Abstract

The search for sustainable low-carbon energies is on the rise in recent years due to erratic supplies and increasing prices and environmental impacts of widely utilised fossil fuels. Feasibility of cattle slurry-grass silage based biomethane (CSGSB) production as replacement for fossil natural gas is proven. However, high capital and feedstock mobilisation challenges impede national level CSGSB applications, hence the need to consider decentralised CSGSBs (DCSGSBs). The unknown techno-economic potentials of such DCSGSBs under the present economic conditions could however deter investors, thus were assessed using year 2022 bioresource and economic contexts of the rural districts of county Tipperary in Ireland as case study. First principle calculations were applied to simulate available cattle slurry and grass silage biomethane potentials, which were applied to evaluate the economics. Achieved DCSGSB plant capacities were 47.5–105 kt/a. Fixing biomethane price at the average natural gas price (€ 124.6/MWh) resulted in viable DCSGSBs. Profitability of plants ≤47.5 kt/a require grass silage prices ≤14 €/t, while plants ≥71.25 kt/a were viable even under harsh economic conditions (e.g. grass silage at 35–56 €/t). Hence, the DCSGSB is a viable alternative to natural gas for near-term applications, which when implemented could contribute to sustainable energy supplies and low-carbon economies.