Agricultural residues, such as corn cobs, are one of the first promising cellulosic materials to be fermented and thermochemically processed into fuel in the emerging bio-based economy. Few studies have been conducted on the deterioration of cellulosic feedstock in storage. This study measured the loss of corn cob dry matter, as measured by carbon dioxide evolution, under various storage conditions (temperature and moisture content) for 21 days. High moisture content and temperature conditions (35% w.b. and 30°C) resulted in almost 3% dry matter loss in 21 days, as opposed to negligible losses at drier conditions (15% w.b.). There was a significant interaction between the effects of moisture content and temperature on dry matter loss. These data provide a first approach to understanding the material loss due to microbial activity, thus helping to identify storage strategies to maximize the conservation of cellulosic feedstock.