I came across a tidbit in a recent RAND technical report, Near-Term Opportunities for Integrating Biomass into the U.S. Electricity Supply. While the focus of the bulk of the 187-page report, commissioned by the US Department of Energy, is biomass, RAND makes an intriguing, all-too-brief comparison with carbon capture and sequestration.
Its conclusion is that wood biomass, if sourced locally, is less costly than CCS – at least for the first 5 percent of reduced fossil fuel input!. Here’s the nub of the report’s CCS assessment:
“Biomass cofiring is an alternative… [to CCS]. In CCS, the CO2 is captured from the flue gas and compressed for pipeline transport and permanent storage (NETL, 2010)…. [The] current estimated cost per ton abated for subcritical PC plants employing CCS, $94 per metric ton CO2e (NETL, 2010). We see that, for our three supply scenarios, our most likely cost of abating GHGs never rises above this estimate…. This result implies that, in a carbon-constrained world, cofiring would be an attractive option for reducing GHG emissions when compared with CCS at today’s costs. This result holds for the relatively expensive biomass–pellets transported over long distances, except at the high end of the cost estimates. Although the cost per ton of reducing GHG emissions is more attractive with cofiring than with CCS, the total number of tons of GHG emissions avoided is relatively small. Systems for CCS typically remove 80 to 90 percent of CO2 from flue-gas streams, reducing lifecycle GHG emissions by a similar percentage…. [C]ofiring subbituminous coal and wood chips at 10 percent results in GHG reductions of 8.7 percent because so much of the electricity is still generated by coal.”
For those interested in deeper details on cofiring, check out the 70-plus page report by clicking here. Regrettably, however, RAND makes no further mention of CCS, leading to more questions than answers.
- Topping that list, as my colleague Christopher Short pointed out in our discussions of this report: why is CCS the bad guy here, posited as a high cost alternative? Any number of low-carbon technologies can make electricity, most of which are more expensive than co-firing a small amount of biomass with coal, but none of which address the compelling need to find a fix for greenhouse gas emissions from the installed base of fossil-fuelled power plants.
- The findings are surprising given that some have claimed that biomass would lead to little—if any—net reductions of emissions over its lifecycle. If so, RAND’s exercise may ultimately be a moot point. In this camp is Resources For the Future’s Roger Sedjo, who has written that this conflict is in part due to varying time lines being assessed. In the long run, he argues, “biomass carbon is a zero sum game.” But for short periods and individual sites, he writes, the question is more complex.
- The study’s conclusions are predicated on the coal substitute being “locally sourced wood biomass.” The study gives detailed cost comparison metrics about biomass costs and transportation’s factor. All the same, the cost question opens a Pandora’s box of follow on questions one of which is what about the majority of markets where supplies of woody biomass are scant or distant? That’s especially a concern for populated, built-up areas where power demand is typically greatest and biomass transport would be most costly.
Finally, however carbon-neutral or cost-effective it may, decarbonizing coal based energy systems through co-firing with biomass ultimately still requires the development of CCS to abate all the emissions. A less well known expectation is that to meet the stabilisation target of 450ppm of CO2-eq, CCS with biomass co-firing is a technology requirement for many of the energy-climate models used to explore mitigation pathways.