Biomass Feasibility Project Final Report - Xcel Energy

Baled Agricultural Biomass
Preparing switchgrass or dried corn stover for storage may amount to little more than baling it at
a suitable moisture content and storing the bales until needed. Baled biomass can be stored in
a variety of ways: stacked and uncovered in a field, wrapped with plastic and left in a field,
stacked under a simple roofed structure or stacked in a large fully enclosed storage facilities.
Each of these techniques offers certain benefits and incurs certain costs. Generally speaking,
the more exposed the bales are to the elements, the lower their storage costs will be. But losses
to degradation can offset savings. At a minimum, bales stored in the open need some kind of
protection from water, like a tarp or plastic sleeve. Care should also be taken to protect the
bottoms of stacks from infiltration by soil and rocks. Storing baled biomass in sheds costs more,
but it preserves more of its original value.
(CVBP Interim Test Burn Emissions Report, 2003, Appendix G)
Woody Fuels
Figure IV-4: Storing Switchgrass Bales
Processing woody materials for storage is similar to processing them for combustion. They are
screened for contaminants, sorted by size (large chunks may be chopped up), and then sent to
the storage pile. Wood chips can be stored outside in a pile for up to a year before odors
become a problem, but piles that grow too high can combust spontaneously. Some facilities
spread new chips over the length of a pile to increase its heterogeneity and minimize variations
in fuel quality.
Identifying Effective Biomass Strategies: Page 47
Quantifying Minnesota’s Resources and Evaluating Future Opportunities