Biomass Feedstock Storage for Quantity and Quality Preservation - Engineering and Science of Biomass Feedstock Production and Provision - page 167

from an animal feed standpoint. However, that may not be true for biochemical
processing of the feedstock. Moreover, the relatively long-term storage, a part of
ensilage, may not be desirable from the overall supply chain standpoint.
Steel bins/silos or concrete bins are currently being used for grain storage, and
they can potentially be used to store biomass feedstock. A demonstration plant
setup by Genera Energy ( http://www.generaenergy.com/ ) at Verona, Tennessee,
USA, uses silos to store ground switchgrass before transportation. Storage in bins
of containers, though, would necessitate grinding, chopping, or pelletization of bio-
mass. This may lead to additional costs in the overall supply chain. The handling
and conveying of feedstock however is significantly more efficient. The applicabil-
ity of this method on a large scale appears to be limited at this stage.

7.3 Plant Material Properties Relevant to Storage

The important engineering properties of biomass feedstock were discussed in Chap. 2 .
Here, the properties important and relevant from a storage standpoint are high-
lighted and the methods used to measure those properties are described.

7.3.1 Moisture Content

Gravimetric moisture analysis, by oven drying at 103 °C, results in volatile organic
compound losses and consequently overestimates moisture content. Karl Fisher
titration is a method in which an iodine-based titrant and methanol react to produce
iodide but only in the presence of water. The presence of iodide alters the electric
potential of the solution. In a voltametric Karl Fischer titration, a solution consisting
of methanol and the sample is titrated with incremental known volumes of iodide-
based titrant until an equilibrium voltage is reached. Voltage is measured by an
electrode immersed in the solution. Thiex and Van Erem [ 9 ] demonstrated that Karl
Fisher titration, where the methanol titrant is maintained at boiling point (60 °C),
can be used for accurate moisture content measurement in forages and without
homogenizing the sample.

7.3.2 Cutting Force and Shear Force

Measurements of cutting and shearing forces, and mathematical relationships pre-
dicting changes in these forces in response to storage conditions, can allow predict-
ing the pretreatment requirements and costs. Pretreatment consists of mechanical
and possibly chemical and biochemical methods of breaking down the cellulose-
hemicellulose-lignin complex. If, for example, a storage system was optimized to
decrease cutting forces in biomass segments, it would result in reduced milling cost