Our lab is involved in different aspects of industrial ecology, which is the integration an entire industrial process to maximize resource use, minimize waste generation and maximize its re-use. Indeed, we study the impact of biomass processing and logistics prior to its conversion. We also study the environmental impact of the technologies we develop and how they compare to other technologies from a life cycle perspective.
One area of cellulosic ethanol research and development that has not received enough attention is the impact of harvesting time and post-harvest storage and processing on the yield of sugars from cellulosic feedstocks such as switchgrass. There is a rich body of literature on pretreatment of different cellulosic feedstocks; however, there is limited research on how the postharvest handling and storage of these feedstocks influences sugars yields. The biomass conversion lab is interested in generating a matrix of feedstocks based on different pre-processing and logistics options and testing the effect of these options on sugar yields following pretreatment and saccharification steps.
During the conversion of biomass to ethanol, the pretreatment step is critical to allow cellulose to be accessible for hydrolysis and to reduce the polymerization degree of cellulose. This step is the bottleneck of the process (Lynd, Laser et al. 2008) : it can be energy consuming, degrade biomass and produces fermentation inhibitors(U.S. Department of Energy 2006). It also raises safety and environmental concerns in the case when high quantities of acid or catalyst are used. We are working on assessing the environmental impacts of the process and its energetic efficiency, using heat integration and life cycle assessment. In addition, we are interested in the influence of different pretreatments methods on the overall performance of the process. The pretreatment techniques that are considered are: Sodium hydroxide pretreatment, dilute acid pretreatment, CO2/H2O pretreatment, AFEX pretreatment and steam explosion.
The overall process should be considered in order to be able to compare the impacts of the pretreatment step to the total impact of the process. We use Belsim flowsheeting software model and a Matlab LCA interface developed in the LENI laboratory (École Polytechnique Fédérale de Lausanne, Switzerland or EPFL) in order to assess environmental impacts. The results will enable to compare the environmental impacts of the different pretreatment methods.