Commercially viable cellulosic ethanol plants has proven devilishly difficult to bring to fruition. The primary outlier from the list of efforts that have shut down over the past few years is POET/DSM’s Project Liberty (earlier post). In an editorial in the journal Biofuels, Bioproducts and Biorefining, two POET team members set out some of the lessons they learned during the four-year startup period.

1. Biomass collection. POET/DSM has shown that large-scale commercial corn stover collection is possible and that farmers are willing to participate. Further, POET/DSM, in collaboration with USDA and NLAE (National Laboratory for Agriculture and The Environment, Ames IA) conducted research that concluded with specification of stover harvest guidelines. The guidelines took into consideration prevention of wind and water induced soil erosion, maintaining proper SOC (Soil Organic Carbon) and sustain or improve chemical and physical properties associated with soil growth. The research results were shared with participating farmers and the recommended harvest guidelines are followed during the biomass collection.

2. Interdependence of unit operations. Among the bigger challenges for Project LIBERTY startup, the authors said, were the scale of the operation and the integration of multiple units of operation. For example, the Solid Fuel Boiler (SFB) is designed to operate on filter cake; however, if pretreatment is not running then there is no filter cake to run SFB. As in the case of biomass collection, integration with the co-located starch plant was crucial in this initial period, in this case i.e. enabling ‘borrowing’ of steam from the starch plant.

3. New operation areas. The larger challenges of starting up the plant were associated with new areas of operation such as netwrap (the material used to bale corn stover) removal. Not only had it required proprietary equipment for removing netwrap, it required correct operation of pretreatment in order to avoid costly downtime resulting from melted residual netwrap clogging pipes.

   Pretreatment was another challenge, with the biggest lesson being that stover does not behave like a wood chips. It took the POET/DSM team two years to optimize the original design and another two years to introduce and perfect the new POET-designed pretreatment.

4. Saccharification and Fermentation. Saccharification and fermentation were not a major source of problems during the startup process, although the team gleaned some valuable lessons there as well.

The last and most probably the most important lesson was that it takes money and determination to commercialize a new technology. Liberty starting bill was 275 M$ and without significant resources as well as help from the DOE this undertaking would not be possible. However, as a retraction of large and established companies shows, financial resources are not sufficient. Besides capital, a determination and commitment to the agriculture and environment was the main enabling factor in Liberty start up. Without the determination of Jeff Broin and his counterpart at DSM, Feike Sijbesma, the commercialization of cellulosic ethanol would not be possible and they deserve the largest credit for bringing this technology to life.

—Slupska and Bushong

Resources

• Slupska, M., & Bushong, D. (2019) “Lessons from Commercialization of Cellulosic Ethanol - A POET Perspective.” Biofuels, Bioproducts and Biorefining, 13(4), 857–859. doi: 10.1002/bbb.2033