Solar energy footprint of ethylene processes

In conclusion, the fossil based processes give a better return on the emergy invested in the short term but are very emergy inefficient and represent large environmental loadings. Therefore, the biomass based processes should be favored for long term sustainability. These consume only about 40% of biosphere resources per kg of ethylene compared to the fossil based processes. The ultimate choice depends on whether only ethylene is required or other olefins also; the switchgrass ethanol dehydration process produces ethylene with the best emergy efficiency. If other olefins are also required, the pine chips MTO represents the best specific emergy value for the whole pool of products. Still lower ethylene specific emergy could be achieved by replacing switchgrass by an uncultivated forest biomass for the production of the bioethanol required in the dehydration process.