Evaluation of the potential of pelletized enzyme-treated Ginkgo leaf residues for use as a solid fuel

Converting biowaste to solid fuel pellets is an efficient and environmental-friendly way for forestry residues utilization. Here, we investigated the effect of enzyme treatment on the quality and combustion characteristics of Ginkgo leaf residues (GLRs) pellets. The results indicated that compared with the untreated control sample (T1), the GLRs treated with 100 (T2) and 200 mg/g (T3) concentrations of cellulase enzyme were coarser and cracked with enhanced specific surface area. GLRs heating value increased from 17.8 to 18.9 and 19.3 MJ/kg for T2 and T3, respectively. Increase in pellet durability (from 73.4 to 80.8%) and hardness (from 0.8 to 1.3) as compared to T1 pellets. The energy consumption of all pellets kept in a low range of 15.1-16.1 J. The kinetics analysis found that the activation energy of T3 pellet decreased from 45.5 to 34.2 kJ/mol in the first order reaction model and from 95.8 to 77.8 kJ/mol in the 3D diffusion model compared to T1. Further, molecular dynamics simulation suggested the enzyme treatment was effective in disorganizing the crystalline cellulose chains, which not only improved the extraction efficiency of bioactive components in Ginkgo leaves, but also promoted the acquisition of high-quality GLRs for manufacturing solid fuel pellets.