|SHINNERS, KEVIN - University Of Wisconsin|
|WEPNER, AARON - University Of Wisconsin|
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2010
Publication Date: 1/15/2011
Citation: Shinners, K.J., Wepner, A.D., Muck, R.E., Weimer, P.J. 2011. Aerobic and anaerobic storage of single-pass, chopped corn stover. BioEnergy Research. 4:61-75.
Interpretive Summary: Corn stover (the stalk, leaves, cob and husk) is potentially an attractive source of biomass to produce ethanol. However, a major issue is how to store this material until can be used at a bioethanol plant. The problem is that stover often contains enough moisture at harvest so that it is susceptible to spoilage. In this study, we compared several ways to store corn stover: uncovered pile, a covered pile that still permitted access to air, a sealed 9-foot diameter bag silo, and a ventilated bag. The uncovered piles had the largest losses, averaging 22%. The best preservation occurred in the seal bag silos where oxygen was kept out; losses averaged 1%. Losses in the other two storage systems were intermediate. These results will be beneficial to producers and planners of stover-based bioethanol plants and indicate that oxygen-free storage systems have the most promise for minimizing storage losses.
Technical Abstract: Corn stover has great potential as a biomass feedstock due its widespread availability. However, storage characteristics of moist corn stover harvested from single-pass harvesters have not been well quantified. In 2007, whole-plant corn stover at 19.1 to 40.3 % (w.b.) moisture content was stored for 237 days in aerobic piles, one covered and one uncovered, as well an anaerobic silo bag. In 2008, two stover materials – whole-plant and cob/husk from 31.7 to 58.1% (w.b.) moisture – were stored for 183 or 204 days in covered and uncovered aerobic piles, ventilated bags, or anaerobic silo bags. Stover stored in uncovered piles was rehydrated by precipitation, which increased biological activity resulting in DM losses from 8.2% to 39.1% with an average of 21.5%. Stover in covered piles was successfully conserved when the average moisture was less than 25% (w.b.) with DM losses of 3.3%. Stover above 36% (w.b.) moisture and piled under a plastic cover had DM losses from 6.4% to 20.2% with an average of 11.9%. Localized heating lead to temperatures where spontaneous combustion might be a concern (i.e. > 70°C) occurred in the aerobic piles when moisture was above 45% (w.b.). Ambient air blown through a center tube in the ventilated storage bag dried stover near the tube to an average of 24.2% (w.b.), but the remainder of the bag averaged 46.8% (w.b.) at removal. Loss of DM ranged from 7.4% to 22.0% with an average of 11.8% with this storage method. Stover was most successfully conserved in the bags where anaerobic conditions were maintained. Under anaerobic conditions DM losses ranged from 0.2% to 0.9%. When anaerobic conditions were not maintained in the silo bag DM losses averaged 6.1% of DM. Anaerobic storage is the best solution for conserving the value of moist corn stover.