(267c) Characterization of Biochar, the by-Product of Energy Production From Biomass Via Thermochemical Processes

Ellen M. Knapp and Justinus A. Satrio

Chemical Engineering Department, Villanova University, PA 19085

Biochar is the solid product obtained through thermochemically processing biomass, namely through fast pyrolysis, slow pyrolysis, and gasification.  The use of biochar has been shown to hold great potentials to aid in the sequestration of carbon dioxide and to act as a soil restoring agent. The thermochemical processes for energy production from biomass that stores carbon as biochar can be considered carbon negative due to high recalcitrant property of biochar. As a soil restoring agent, biochar has been shown to improve the quality of soils by increasing microbial activity, lowering soil acidity and density, and improving nutrient and water retention.  It has also been shown that during thermochemical processing of biomass, a significant portion of mineral nutrients contained in the original biomass are recovered in biochar. 

It is believed that all biochars are not created equal and will have different physical and chemical properties depending on their biomass origins and the thermochemical processing used for producing the biochars. The purpose of this study is to  evaluate the effects of biomass precursors and process conditions of thermochemical processes on the chemical and physical properties of the produced biochars. For this study,  biochars are synthesized by fast pyrolysis and slow pyrolysis processing of selected biomass materials using a small tubular reactor furnace at selected process conditions. A variety of biomass materials, commonly available in the state of Pennsylvania, particularly in the region where Villanova University is situated,  are used for the study, which include wheat straw, switch grass, woodchips  and spent mushroom substrate (SMS). The last material, SMS, is the waste product from mushroom growing industries and is produced in very large quantities in Chester County, which is known as the “mushroom growing capital of the world.”  Currently, Chester County accounts for approximately 37% of the mushroom production in the U.S.A. Biochar produced from various biomass materials by various process conditions will be analyzed for their physical and chemical characteristics/ properties.  Analysis will include proximate analysis, elemental analysis, heating value, surface area/porosity, and composition of mineral matters. Focus will be placed on the comparison of the chars formed from each biomass precursor at different process conditions. In particular, emphasis will be placed on comparing the characteristics of SMS char versus wheat straw char. SMS is a derivative of wheat straw that has been combined with various manures and grains. The comparison of chars produced from these two biomass precursors in particular will provide insight into the effects of additional materials added to the straws in the SMS  on the properties of chars.