Many compost microbial communities have evolved to decompose lignocellulosic materials similar to those being considered for biofuel production.  Furthermore, these communities can tolerate a wide range of environmental conditions, offering great potential for enzymes that will tolerate harsh pretreatment conditions.  This study was designed to track changes in microbial and enzyme activity and community composition throughout the course of microbial colonization and decomposition of switchgrass.  Switchgrass was inoculated with finished green waste compost from a commercial facility.  Temperature was controlled to simulate a composting process with a fast ramp from 30oC to 54oC, 7 days of thermophilic levels at 54oC and a slow decrease back to 30oC over the course of 21 days.  Respiration was monitored on-line to track microbial activity and bioreactors were sampled at regular intervals for microbial community and enzyme analysis.  Carbon dioxide evolution rates (CER) peaked twice:  after one day of composting corresponding to initial consumption of sugars and again after eight days during the thermophilic phase. Comparison of 16S rRNA gene clone libraries from initial and final samples showed a significant increase in microbial diversity on the switchgrass.