Environmental footprints and implications of converting GHG species to value-added chemicals: a review

Abstract

Abstract This paper assesses various approaches that use captured greenhouse gases (GHG) as feedstocks for chemical synthesis. The analysis focuses mainly on the two most abundant anthropogenic GHG, such as carbon dioxide (CO2) and methane (CH4), as well, their conversion technologies to obtain methanol (MeOH), formic acid (FA) and dimethyl carbonate (DMC). These GHG conversions to chemicals technologies are compared with the conventional industrial methods based on fossil feedstocks. The essential information, such as the ranges of energy requirements, environmental footprint and economic production aspects, are summarised. According to the collected information and analysis, the conventional, non-GHG conversion methods are still more environmentally sustainable. Chemicals production technologies based on CO2, such as direct catalytic synthesis to obtain both MeOH and FA, as well as transesterification with MeOH to obtain DMC, are relatively good candidates for implementation on a large scale when a good source of co-reactants such as hydrogen, ethylene carbonate and urea will be provided. In turn, electrochemical methods to synthesise the target chemicals are less feasible due to energy consumption related to the concentration and purification stages of products being the main hotspots. Chemical synthesis based on captured CH4 is currently difficult to evaluate as too little information is available to draw a credible conclusion. However, it may be a trend in future. The limitations of GHG-based conversion for application are related to the capture and transport stages.