make PE->h2/synfuel/gas conversion route costs even more consistent

[robertpietzcker]

This commit #1881
already improves the consistency between the different conversion routes, but I think further harmonization would be useful.

I don't say they all have to be totally aligned, but it would be great that there are similar directions of cost changes, and that the magnitude is roughly similar - I highlighted in yellow the parts that I find implausible.

so some basic principles that come to mind are:

• coal is a lot more difficult to move around and process than gas -> more expensive
• biomass is even more difficult to process (drying, inconsistent quality, ...) -> even more expensive
• adding CCS to processes around syngas/h2 production should likely have roughly comparable cost increases, as the gas treatment processes should be similar

[robertpietzcker]

@lecfab @fschreyer

[robertpietzcker]

Fabrice found this 2014 report by ECN with an interesting comparison of costs for coal/bio->gas/liquids/electricity

https://www.biosng.com/fileadmin/biosng/user/documents/reports/The_Economy_of_Large_Scale_Biomass_to_Bio-Methane.pdf

quite surprising how close the values are to each other - maximum of 30%+