Enhancing Switchgrass Drying Rate

Rapid drying to baling moisture reduces weather-related risks when harvesting perennial grasses to be used as biomass feedstocks. Drying switchgrass can be challenging due to large, dense swaths and unfavorable autumn drying conditions, so new methods to improve drying are needed. Two techniques to enhance switchgrass drying rate were investigated, which are intensive conditioning and wide-swath drying. Intensive conditioning involved rolls that crushed the stem along its length accompanied by differential roll speed to disrupt the waxy epidermis of the stem. Wide-swath drying involved a post-conditioning tedding operation that distributed the crop across most of the cut width. A mower-tractor-intensive conditioner-tedder combination was configured so that intensive conditioning, wide-swath drying, or both could be achieved in a single pass. Although not consistent across all trials, intensive conditioning and wide-swath drying were about equally effective at improving switchgrass drying rate compared to conventional conditioning alone. However, the combination of intensive conditioning followed by wide-swath drying consistently resulted in the most rapid drying rate. In eight separate trials, this combination produced switchgrass moisture contents well below 20% (w.b.) on the second or third day after cutting. An empirical model of switchgrass drying rate was developed, which can be used to predict switchgrass drying time based on weather conditions, conditioning level, and swath density.