Environmental Engineering Reference
In-Depth Information
given their evolving nature and associated uncertainties, including weather and yield risk previously
discussed (Coyle et al. 2008, 2010).
7.8.2 p
roduct
f
actorS
Several characteristics of biomass product have a direct bearing on the cost of logistics, notasly the
density and the physical form of biomass.
7.8.2.1 density
Density refers to the weight-to-space ratio of the product. An item that is lightweight in relation to
the space it occupies, as in the case of biomass, has low density. Transportation providers generally
consider how much weight they can fit into their vehicles when establishing their prices because
they quote their prices in dollars and cents per unit weight. On high-density items, these providers
can afford to charge a low price per metric ton, while ensuring acceptable revenue, because they can
fit more weight into their vehicle (Coyle et al. 2008, 2010). Hence, the low bulk density characteristic
of biomass means less mass of material can be transported in any given trip, resulting in higher
costs of transportation. Increasing bulk densities by processing the biomass into the previously
described chips, bundles, pellets or bales, and/or increasing load size per trip by, for example, using
larger transport vehicles, can help to reduce transportation costs (Allen et al. 1998; Frisk et al. 2010).
7.8.2.2 Physical Form
The physical form of biomass also affects transportation, material handling, and storage
requirements and, thus, total logistics cost incurred. Storage requirements vary depending on the
type of biomass. Typically, storage facilities can store nonprocessed and processed biomass, albeit
separate capacity will be required. For example, although nonprocessed forest biomass such as tree
tops, branches, and slashes can be stored on any surface, woodchips have to be protected against rain
and must be stored on a hard (e.g., concrete) surface. Similar distinctions apply to transportation and
handling requirements. For example, types of trucks used to carry nonprocessed forest biomass are
different from those used to carry forest biomass that has been chipped or bundled. Chip vans are
typically used for landing-to-market hauling of chipped forest biomass, whereas bundled biomass
is transported using log trucks (Sokhansanj and Fenton 2006; Eksioglu et al. 2009). Examples of
biomass transportation options are summarized in Table 7.2.
7.8.3 S
patial
f
actorS
Spatial factors, or the location of fixed points in the logistics system in terms of demand and supply
points, are particularly important factors that affect transportation cost because these costs tend
to increase with distance (Coyle et al. 2008, 2010). Biomass supply sources are geographically
dispersed, and transportation infrastructure networks serving between those source locations and a
biorefinery may be limited. Adding these spatial factors to the product factors discussed earlier, one
can appreciate the underlying challenges in managing biomass feedstock logistics.
The spatial factors also influence the question of whether an intermediate storage depot or
satellite preprocessing facility will be used in the logistics system. Whether biomass products
should be taken directly to the biorefinery or to intermediate storage/preprocessing locations
before being delivered to the biorefinery depends on a range of factors and involves tradeoffs. If
preprocessing generates co-products or byproducts such as animal feed or nutrient streams that
should be redistributed to the source farms, a distributed satellite infrastructure may well make
sense (Carolan et al. 2007). Because each satellite facility has a specified total capacity, available
capacity will affect logistics costs associated with duration of biomass storage, transport planning
and arrangements, and biomass processing possibilities. Where storage capacity is limited, small,
