(23c) An Overview of Storage-Related Changes Occurring in Cellulosic Biomass Under Commercially Relevant Conditions

The U.S. Department of Energy Bioenergy Technologies Office (DOE-BETO) is committed to the development of sustainable, nationwide, commercial biofuel production to displace petroleum-derived fuels and increase domestic energy production. Reliable biomass supply systems are necessary to realize this vision. Research at Idaho National Laboratory (INL) focuses on improvements to supply chain logistics operations that enable efficient conversion processes. Biomass variability associated with storage—moisture content, composition, and conversion yield—challenges industrial scale biomass utilization. Moisture exposure during harvesting and storing biomass results in varying extents of physical and chemical degradation. Research indicates that aerobic biological activity leads to internal heating (> 65°C), dry matter loss (DML >20%), and moisture migration in bulk and baled stored cellulosic biomass. This presentation provides examples of physical and chemical degradation occurring as a result of biodegradation and moisture migration in storage. Commercial scale (>20 Mg dry matter) baled and bulk corn stover, cobs, and switchgrass were monitored for moisture changes, dry matter losses, and compositional changes to identify when and where material changes occurred during outdoor storage. Results from multiple storage studies show common trends of internal heating, moisture migration, and carbohydrate losses. The timing and spatial locations of these events are dependent on the initial moisture contents and physical storage formats of the materials. Rates and extents of carbohydrate losses are proportional to the initial moisture contents but measurements in the field are made difficult by non-uniform moisture distributions, varying material density, and inability to control for environmental conditions during storage. These physical, chemical, and biological phenomena have parallels in the composting industry—perhaps a model for worst-case scenarios of biomass storage. Comparisons will be made between composting environments and biodegradation in storage that will be useful in measuring, predicting, and controlling bio-deterioration in commercial scale storage systems.