Optimal design of a sector-coupled renewable methanol production amid political goals and expected conflicts: Costs vs. land use

Abstract

Methanol is an important bulk chemical which can be produced from renewable resources with the currently available technologies and doing so has a high potential for greenhouse gas (GHG) emission reductions for the chemical sector. Reaching the targets for climate change mitigation and biodiversity protection will require designing not only renewable, but also land-efficient chemical production systems. However, under the current economic imperative of cost minimization, the efficient use of land is often not considered during production system design and compromise solutions are left undiscovered, the potential of land-use intensifying technologies stays unknown and the impact of their exclusion, e.g. due to political reasons, is not quantified. This study addresses these issues for renewable production of methanol through the biogas- and power-to-methanol production pathways, which are considered concurrently with processes allowing intensified land use (agrivoltaics, wheat straw anaerobic digestion, heat pumps, wind turbines, etc.) in a previously unexplored technological scope. The designs, as well as the effect of coupling with other production systems (residential heat, electricity, and food) as a strategy to reduce the total annualized costs (TAC) and direct land use, are investigated using the FluxMax approach, an optimization-based design methodology. It simultaneously accounts for the, often neglected, dynamics of renewable energy harvesting, waste-heat utilization and biomass production under the fluctuating renewable resource and product-demand conditions of an example location in Saxony-Anhalt, Germany. Reductions of the TAC of 19 %, direct land use of 9 % and GHG emissions of 12 % for the production system by coupling all four of these products were determined. Furthermore, Pareto fronts were constructed to quantify the trade-off between the conflicting objectives of minimizing TAC and direct land use, demonstrating that land use can be reduced by up to 10 % with minimal extra costs among the available technologies. Political conflicts and goals, which may influence the deployment of the considered technologies, are discussed from a political science perspective and highlight the need for further interdisciplinary collaboration.