Comparison of two methods to calculate GHG emission reductions in the production of bio-olefins

In this work, two different approaches of an attributional LCA are used to calculate the GHG emission reduction potential of a light olefins production process, where fossil feedstock is partly switched to biomass. In the first method (approach A), carbon uptake during biomass growth leads to a negative emissions or a GHG emission reduction and data from the current plant (steam cracker) is used. In the second method (approach B) the biogenic carbon is excluded from the modelling and average data of fossil emissions in the production of light olefins is used. A through discussion is provided indicating the advantages and drawbacks of each method. The results show that a similar saving of GHG emission, defined analogously to current European regulation for biofuels, is achieved (51%-52% vs. 58%, for A and B, respectively) when 25% of fossil feedstock substitution in the production of olefins.