Biomedical Engineering Reference
In-Depth Information
Fig. 19.4 Advanced biofuel routes via sugar intermediate
herbaceous feedstocks such as corn stover or switchgrass. For catalytic conversion,
sulfur and alkaline earth metal concentrations can be a significant issue since these
compounds can be significant catalyst poisons.
Economics
The economics for conversion to advanced biofuels are much less developed than
they are for cellulosic ethanol primarily because the technology is in an earlier state
of development. Since the biomass deconstruction to intermediate sugars compo-
nent is essentially the same as it is for biochemical cellulosic ethanol, these costs are
well quantified. However, much less cost specificity exists for the advanced
biofuels production step. For the fermentative route, it is fair to say that this will
be a higher cost fermentation than ethanol fermentation since isoprenoid fermen-
tations are aerobic which are higher cost both from a capital and operating per-
spective than anaerobic ethanol fermentations. The final product, hydrocarbon
diesel fuel, has higher value than ethanol, so this cost/benefit ratio will determine
how the economics compare to cellulosic ethanol. For the catalytic upgrading route,
the challenge most likely will be the number of process steps required. Multiple
processing steps increase capital cost as well as operationally complexity. Since
fuel production like any commodity process requires high plant online time, simpler
processes will have the advantage.
Search WWH ::
Custom Search