Waste- to-DME: Process Synthesis and Sustainability Evaluation

Abstract A macroscopic graphical targeting approach based on the C-H-O ternary diagram is proposed for the synthesis of waste-to-chemicals systems. Sustainability metrics are also considered to gain insight into the process efficiency and resource utilization. The process targets together with the sustainability metrics enable the screening, evaluation and comparison of various process routes. A case study for the conceptual design of a waste-to-DME facility is considered. The process includes waste gasification and DME synthesis. The DME production process has two main process targets, one based on the indirect synthesis route and the direct synthesis route, which require a syngas platform with compositions of H2/CO = 1 and H2/CO = 2 respectively. To achieve the syngas target required for the direct DME synthesis route, a mixture of H2O and CO2 or H2O and O2 is required as gasifying agents. A simplified input-output diagram of the overall waste-to-DME process was developed based on the process targets for the waste gasification and the direct DME synthesis process. The carbon efficiency, atom economy and global warming potential (GWP) is calculated. An additional source of hydrogen is required to achieve the syngas composition target for the indirect DME synthesis route (i.e. H2/CO = 2). Introducing methane (from landfill gas) to the process results in a substantially higher carbon efficiency.