3.1. Cell wall chemical structures before and after pretreatments
The cell wall chemical composition of aspen was very different from the other three poplars (Table 1). Aspen had a high glucan content of 45.6% and low lignin content of approximately 20%. The other three poplar samples had similar yet lower glucan content of approximately 40%. The lignin content was approximately 23% for NE222 and DN5 and greater than 25% for NM6