Codensification of Eucommia ulmoides Oliver stem with pyrolysis oil and char for solid biofuel: An optimization and characterization study

This paper presents the results regarding the parametric optimization and characterizations on codensification of Eucommia ulmoides Oliver stem using biochar and bio-oil as additives. The results reveal that the relative importance of different parameters contributing to the pellet physical stability follows the order of: particle size > bio-oil content > biochar content > pressure > bio-oil type, and smaller particles size (0.1-0.3 mm) is critical for the formation of durable pellets. The biochar functioned as the fuel promoter and improved the higher heating value and energy density, however, caused poor physical stability by secondary size reduction during densification. The apple tree branch pyrolysis oil acted as an effective binder, improved the surface morphology and enabled strong interlocking of the particles, therefore, enhanced the physical stability. Above all, codensification of Eucommia ulmoides Oliver stem with biochar and bio oil generated pellets with excellent physical stability and moisture resistance. The pellets also showed better fuel characteristics than the Eucommia ulmoides Oliver stem pellets, and the cost is significantly lower than the char pellets. With comprehensiveness, these results can guide the future industrial implementation of codensification technology for the production of clean, sustainable, and efficient fuel with low cost.