Effect of soil on fast pyrolysis products from pine (Pinus taeda) biomass

Detrital soil contamination during wood harvesting cannot be avoided without a further cleaning step. The objective of the current study was to determine the effect of Piedmont soil on pinewood pyrolysis products. Ash content was varied at 0.56%, 1.16%, 2.77%, 4.40%, 6.87%, 8.35%, and 15.52% by adding soil to woodchips to mimic the highly soilcontaminated biomass that can be found in biorefineries. This study found that bio-oil yield decreased from 47.1% to 26.3% with an increase in ash content from 0.56% to 15.52%. However, the oxygen content of the bio-oil decreased and the carbon content increased, which led to an increase in heating value from 22.5 to 24.9 MJ kg^-1. Inorganics in the soil aided in the catalytic cracking and dehydration reactions for bio-oil formation. A slight increase in the total acid number (106 to 117 mg KOH g^-1) and water content (20.72% to 24.99%) was observed with more soil inclusion in the pyrolysis. The effect of soil on biochar O/C and H/C ratios was minimal even though the heating value decreased with an increase in soil content. This study showed that soil (4%wt to 7%wt) in the biomass assisted in deoxygenating the bio-oil and lowered the total mass yield while keeping the total energy yield almost constant.