20 Louisiana Agriculture, Spring 2015 Conversion of Cottonwood and Switchgrass to Charcoal via Carbonization Process Sammy Sadaka, Hal Liechty, Matthew Pelkki and Michael Blazier Crop biomass can be co-fired with coal to produce energy. Co-firing has the potential to reduce carbon dioxide emissions from coal-fueled plants. Research has demonstrated that when co-firing is conducted with relatively low ratios of biomass to coal, there are significant reductions in both solid waste gener- ation and emissions. However, the nature and chemical com- position of raw biomass can lead to significant increases in infrastructure costs or reactor problems if co-firing is conducted with high ratios of biomass to coal. Moreover, high biomass-to- coal ratios may increase reactor corrosion and decrease effi- ciency. Consequently, co-firing using high proportions of raw biomass is a challenging process for heat and power production systems. Ameliorating raw biomass physiochemical properties and concentrating its energy density could increase acceptance of biomass for co-firing operations. Carbonization is a promising thermochemical process that can produce biomass with prop- erties comparable to coal and make biomass feedstocks more favorable for co-firing. Carbonization, which takes place in the absence of oxygen at temperatures of 750-930 degrees F, converts raw biomass into charcoal-like feedstock. During the carboniza- tion process, biomass chemical bonds break down, producing a charcoal-like material in addition to combustible gases and tar. Carbonization breaks down the complex substances in biomass into elemental carbon and chemical components. Cottonwood and switchgrass from LSU AgCenter and University of Arkansas research sites were used for a carbon- ization experiment. Woody biomass is more suitable than many other energy sources for co-firing because it contains fewer ash and alkali components. Switchgrass can also be co-fired with coal as a cleaner-burning energy alternative to low-grade coal. Biomass samples were carbonized in a carbonization reactor and placed in a muffle furnace at 750 degrees F for two hours. The weight loss of the sample was determined after allowing the sample to cool down. Physical, chemical and thermochemical characteristics of raw and carbonized biomass were measured. Feedstock volatile matter values were determined by heat- ing the feedstock under controlled conditions and measuring weight loss, excluding the weight of moisture. The initial volatile matter content was 78.0 percent for cottonwood and 73.9 percent for switchgrass. Generally, carbonization significantly reduced the volatile solids content of cottonwood to 25.3 percent and of switchgrass to 25.9 percent. Ash content and fixed-carbon con- tent increased significantly for the cottonwood and switchgrass samples. The ash content values increased from 1.8 percent to 5.8 percent for cottonwood and from 4.9 percent to 10.6 per- cent for switchgrass. Fixed carbon also showed similar trends, with a change in cottonwood from 20.2 percent to 68.6 percent. Switchgrass fixed carbon also increased from 21.2 percent to 63.4 percent. Carbonization drives off hemicellulose and cellulose from the biomass, leading to an overall reduction of the sample weight. This reduction led to the increases in ash and fixed-car- bon contents. Analyses were also performed on the raw and carbonized cottonwood and switchgrass samples to determine their carbon, hydrogen, oxygen and nitrogen contents. Carbon, hydrogen, oxygen and nitrogen for raw cottonwood and switchgrass were not significantly different from each other. The carbonization process increased carbon and nitrogen concentrations, but it decreased hydrogen and oxygen concentrations. Carbon concen- Carbonization is a promising thermochemical process that can produce biomass with properties comparable to coal and make biomass feedstocks more favorable for co-firing. Five-year-old cottonwood trees immediately before harvest as biofuel feedstock and switchgrass bales harvested for biofuel production at a study site in Archibald, Louisiana. Photo by Michael Blazier