Slow Pyrolysis of Deoiled Canola Meal: Product Yields and Characterization

Canola meal is a byproduct of the biodiesel industry and abundantly available in Canada. Slow pyrolysis of deoiled canola meal was performed over the temperature range 300-700 degrees C to study the potential applications of the pyrolysis products as fuels and sources of value-added products. The biochar yield decreased with increasing pyrolysis temperature, but the yield of gas products showed the reverse trend. The bio-oil yield increased up to a pyrolysis temperature of 500 degrees C and then decreased. The carbon and nitrogen contents of biochars were in the ranges 66-81 and 6-9 wt %, respectively. Van Krevelen's diagram showed that a higher pyrolysis temperature formed a highly condensed aromatic structure for biochars. Alkaline elements had the largest concentration in the ash present in biochar, followed by P and Fe. Biochars showed a basic pH range, and their electrical conductivity decreased with increasing pyrolysis temperature. A higher heating value of 29.8 MJ/kg was observed for biochar produced at 400 degrees C. The energy recoveries by biochars and bio-oils were 42-65% and 15-32%, respectively. The bio-oil yield was in the range of 10-24 wt %. Bio-oil produced at a pyrolysis temperature of 400 degrees C had a higher heating value (30.8 MJ/kg) than bio-oils produced at other temperatures. The concentration of phenolic compounds in bio-oil increased with increasing pyrolysis temperature. The same trend was observed for nitrogen compounds produced at temperatures up to 500 degrees C. The total acid number for bio-oils was in the range of 96-21 mg of KOH/g. The largest heating value for gas products (14.9 MJ/m(3)) was observed at a pyrolysis temperature of 500 degrees C.