Bioproducts and biofuels production from pyrolysis might benefit from recycling CO2 within the process instead of using conventional inert gases such as N2. In this study switchgrass (Panicum virgatum L.) was pyrolyzed within CO2 and N2 environments at 300, 400, and 500 °C for 2.5 min in a labscale fixed-bed reactor of 25 g/batch capacity. Chars, liquids, and noncondensable gases were monitored and characterized and yields were compared. A significantly lower liquid yield was observed at 300 °C–CO2 in comparison to a 300 °C–N2 environment, which was reflected with the char volatile content being higher under 300 °C–CO2 and within the elemental composition of the solid and liquid products. Carbon dioxide also showed an effect at 500 °C, where liquid and gas yields significantly reduced and increased, respectively. At 400 °C–CO2, CO concentrations were lower and CO2 was higher compared to the levels at 400 °C–N2, while at 500 °C–CO2, CO concentrations were higher, CO2 was lower, and CH4 was lower compared to levels at 500 °C–N2. At 500 °C, a significant ash content reduction with respect to original biomass was observed only in the CO2 environment, suggesting that CO2 may effect inorganic content and subsequently the feedstock conversions since some feedstock inorganic elements are known to play a catalyst role along these reactions. Additional tests were conducted by following regular 500 °C tests with a char air quench. This resulted in a char specific surface increase of about 20 times; CO2 and N2 initial environments confounded.

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In a perspective of biomass value addition, biomass char, a thermochemical product, long time considered as a residue, is now getting attention and may represent a vector in the sustainability of the whole biomass sector. Some char types were shown to have great potential as a solid fuel or precursor for further transformations as well as having attributes for storage and transportation. Other types showed potential as a soil carbon sequestration technique and soil amendment enhancing biomass yields. Depending on several factors, but mostly on biomass and production conditions, biomass char physico-chemical characteristics may vary tremendously. Therefore, in order to be used in accordance for specific utilizations, its characteristics must be carefully understood and controlled. In this study, chars with varying properties were produced in a custom-made lab-scale fixed bed reactor. Along these experiments, various biomass chars were produced under CO 2 and N 2 for temperatures of 300 and 500 °C. Char was produced from switchgrass (Panicum virgatum L.) an energy crop grown in Canada. It was then characterized for ultimate and proximate analysis as well as for calorific value. In addition, specific surface was characterized by Brunauer-Emmett-Teller (BET) technique. Char organic content composition was verified by Soxhlet extractions using dichloromethane and extracts were analysed by GC-MS.

In a perspective of biomass value addition, biomass char, a thermochemical product, long time considered as a residue, is now getting attention and may represent a vector in the sustainability of the whole biomass sector. Some char types were shown to have great potential as a solid fuel or precursor for further transformations as well as having attributes for storage and transportation. Other types showed potential as a soil carbon sequestration technique and soil amendment enhancing biomass yields. Depending on several factors, but mostly on biomass and production conditions, biomass char physico-chemical characteristics may vary tremendously. Therefore, in order to be used in accordance for specific utilizations, its characteristics must be carefully understood and controlled. In this study, chars with varying properties were produced in a custom-made lab-scale fixed bed reactor. Along these experiments, various biomass chars were produced under CO 2 and N 2 for temperatures of 300 and 500 °C. Char was produced from switchgrass (Panicum virgatum L.) an energy crop grown in Canada. It was then characterized for ultimate and proximate analysis as well as for calorific value. In addition, specific surface was characterized by Brunauer-Emmett-Teller (BET) technique. Char organic content composition was verified by Soxhlet extractions using dichloromethane and extracts were analysed by GC-MS.