Effect of harvest age on enzymatic hydrolysis of steam exploded hybrid poplar
Fast-growing poplar trees, developed by hybridization of normal poplar trees, which are then bred successively by grafting, have been widely noticed from the viewpoint of an important renewable resource. The objective of this study was to evaluate the effect of growth period on steam-explosion pretreatment (logR04.02, logR04.37) of hybrid poplar.
Hybrid poplar (Populus euramericana) was harvested after one year, four years and nine years of growth, ground and sieved. Pre-treatment of hybrid poplar was carried out in a batch pilot unit based on Masonite technology and equipped with a 1L reaction vessel designed to reach a maximum operating pressure of 40 kg/cm2. The severity of the treatment was designated by logR04.02 and logR04.37. After steam explosion, a residue was washed with distilled water 30 min at 60°, shaken, and then filtered. The water-insoluble material was extracted with methanol for 12 hours. The composition profile changes in lignin, cellulose, and hemicellulose after pretreatment, hydrolysis conversion efficiency were measured to evaluate growth period effectiveness.
The high content of cellulose in four years hybrid poplar and nine years hybrid poplar indicate that the two materials could both be a potential feedstock for bioethanol production. On the other hand, higher sugar yield was obtained at four years hybrid poplar.
Optimizing the harvest time to take advantage of the rapid growth of fast-growing woods may be one strategy for obtaining more suitable fast-growing wood material for enzymatic hydrolysis and subsequent bioethanol production.