This is a big deal! Bioenergy coupled with CCS has the potential to be net carbon-negative, where the feedstock crops act as biological CO2 collectors, and the energy production+CCS system acts as a pump injecting that CO2 into permanent storage in geologically stable formations. In such a system, the more fuel or electricity you produce, the more net removal of CO2 from the atmosphere you get- a very refreshing role reversal for the energy sector! Ethanol facilities are good candidates for these technologies: for every 2 atoms of C from the original starchy feedstock that are converted to ethanol, one molecule of CO2 is produced, and the resulting relatively pure CO2 stream can be collected and pumped away without any complicated gas separation operations.
The rub to all this, however, is that CCS is both energy intensive and expensive. Right now the technology’s boosters like to point out that there’s a shortage of industrial CO2 relative to demand, and that CO2 has great value for beverage manufacturers and for enhanced oil&gas recovery. However, if and when CCS starts to become a more widespread technology those markets will almost certainly quickly saturate against the staggering total volume of emissions that could be captured. Most estimates suggest that widespread CCS will only be economically feasible at carbon prices on the order of $50-100/ton CO2 eq, putting this technology towards the high end of the carbon abatement cost spectrum.
I haven’t seen much personally in the way of lifecycle assessment (LCA) studies for any such system in the literature yet. I wonder how it looks in a modern ethanol production facility that already reduces emissions on the order of 50% compared to a gasoline baseline? Where are these plants getting the energy for CO2 compression/liquefaction from? And to the extent that CO2 geological storage is at the moment exclusively associated with enhanced oil & gas recovery, should LCA practitioners be discounting system GHG benefits to reflect the additional fossil fuel extraction that the technology facilitates? I suspect there’s much more research needed to fully explore the potential lifecycle benefits of these technologies.