Basic petrochemicals from natural gas, coal and biomass: energy use and CO2 emissions

Abstract

While high-value basic petrochemicals (HVCs) are mostly produced through conventional naphtha and ethane-based process routes, it is also possible to produce them through coal and biomass-based routes. In this paper, we compared these routes in terms of energy use and CO2 emissions per ton of HVCs. (The term ton and abbreviation t should be read in this paper as a metric ton or 1000 kg.) Within the cradle-to-grave system boundary, we found the following: • The total energy use of the conventional routes is the lowest (about 60 GJ/t HVCs, of which 50GJ is the calorific value of HVCs) whereas that of the methane-based routes is 30% higher, and that of the coal and biomass-based routes is about 60–150% higher. • The total CO2 emissions of conventional and methane-based routes are about 4–5 tons CO2/t HVCs whereas those from the biomass-based routes range from 2 tons CO2/t HVCs (a maize-based ethanol related route) to 4 tons CO2 avoided per ton HVCs (a lignocellulosic biomass-based Fischer–Tropsch route). Avoided CO2 emissions are due to electricity co-generation. The total CO2 emissions of coalbased routes are by far the highest (8–11 tons CO2/t HVCs). An exception is a coal-based route with CO2 capture and sequestration features, for which CO2 emissions are similar to those of the conventional routes. It is technically possible to add CO2 capture and sequestration features to any of the routes mentioned above. Given the large differences shown above, more research into energy efficiency improvement of coal and biomass-based routes is recommended. However, the total energy use of biomass and coal-based routes is unlikely to match that of the conventional state-of-the-art routes any time soon.