I am not really sure why. Enzymes do indeed have a potential ecological (and public health) burden, especially if they involve recombinant processes, e.g. synthetic biology. For example, there is the possibility of gene flow to native species. How such burden is weighted will drive the characterization factors in the LCA. Whether these are correct will be debatable. I am not sure you will get a scientific consensus on what is "normal" for most environmental matters.

Thank you very much for your time. i need to get a bit further into this issue. Your opinion is much appreciated

We (colleagues and myself) have encountered the same issue, both for the enzyme cocktail you mention (data from the US LCI database) and for the Cellic CTec2 enzyme cocktail. For Cellic CTec2 we obtained the life cycle data from the manufacturer, and have reported these in Liptow et al. (2013). The lion share of the impact can be explained by the significant use of fossil energy in the production of the enzyme product.

We have used the data for enzyme production (both Celluclast and Cellic CTec2) also in studies on a new ethanol production process from spruce wood chips and wheat straw (Janssen et al., 2014; Janssen et al., 2016). In both cases, the enzyme production and use is by far the largest contributor to the environmental impacts we assessed (except for eutrophication in the case of straw due to fertilizer use).

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Thank you so much!!  In the meantime, i run again and again the model with various input ranges (sensitivity - like) so i confirmed the large impact of enzyme use, and by some literature around i also conclude, it is the energy input, to its great extent fossils, that cause the high impact (electricity for pumps, heating up,) but also the CO2 emitted by the enzymes, if i am not wrong. Great for sending me your work!  Thank you again.

We have a paper in the working which shows how to eliminate the problem of the high environmental impact of the enzymes, Pål Börjesons group did the LCA. There is an report on the f3 website on it www.f3centre.se

I was not aware of your report, Ola. 

In the paper on the LCA of ethanol from wood chips that I referred to in my earlier post we also did an analysis of on-site enzyme production (based on data and process description from an NREL report (Humbird et al, 2011)) which resulted in an overall reduction in GWP of about 60%. Note that recycling of enzyme (produced off-site) with a rate of 25% lowers the GWP of the process by approx. 20% (shown for the cases of wood chips and wheat straw).

Thank you for this interesting discussion. While dealing with my 'enzyme problem' i crossed this paper (attached) that studies exactly what you mentioned Ola and Matty, onsite enzymes production, to reduce costs in the first place and render biobased ethanol really sustainable. 

 Dear Prof Wallberg, would you indicate which report on the f3 website you talk about? There are so many reports that it will take some time to identify which one for the information i am looking for.