Studies on microwave vacuum drying of round Bambusa tulda

Bamboo is one of the important ligno-cellulosic materials available as an alternative to timber. For quality products from round bamboo, drying is an important processing step. Most bamboo species show a propensity to develop defects during drying. In this study, Bambusa tulda bamboo specimens were taken from three heights: top, middle and bottom. Three treatments involved air drying for one, two and three weeks, respectively, followed by microwave vacuum drying (MWVD). A fourth treatment consisted of only the bottom portion of the culms and was dried in MWVD without air drying. A fifth treatment consisted of drying of bamboo (from all three portions top, middle and bottom) in a conventional kiln until defects started to arise, followed by MWVD. The drying rate, variability in final MC%, and the occurrence of defects was evaluated for all the treatments. The results suggest that MWVD is 9–10 times faster than conventional kiln drying. The drying behaviour of the top, middle and bottom portions of the culms differed. Defects were more frequent in the top portion compared to the middle and bottom. Combination drying (kiln drying until defects start to show followed by MWVD) resulted in the least number of defects.