Environmental Engineering Reference
In-Depth Information
Biomass pellets are popular in applications such as gasification, flash pyrolysis, biofuels, and
syngas production. However, as with other harvest and logistics considerations, the high costs
associated with pelletizing and briquetting could be a serious constraint on increasing cellulosic
biofuels production (Lam et al. 2007). Increasing energy efficiency and reducing operational cost are
current challenges that need to be addressed. To create highly efficient biomass-to-energy chains,
biomass torrefaction in combination with densification could be a promising step to overcome
logistics economics in large-scale green energy solutions (e.g., Bergman 2005). Torrefaction is a
roasting process that drives off volatiles and hemicellulose at temperatures between 200 and 300°C,
resulting in a much more energy-dense product that is easily pelletized (see Table 7.1). Although
the costs and energy losses associated with combining these two processes are considerable, the
savings potential, especially for long-range transport, are also considerable (Uslu et al. 2009).
7.6.2 B alE c omprESSion
Although most hay bales are consumed on the farm where they were produced, some square hay
bales are currently densified for transport overseas. This densification is expensive, but it is justified
because of the high demand for quality hay in Middle Eastern countries. To increase bale density
and, therefore, reduce handling cost, bale compression technology has been tested with several
biomass feedstocks and appears to have considerable potential (Brownell et al. 2009). The bulk
density of normal hay bales is approximately 160 kg/m 3 , but a bale compressor can densify the
bale to 2-3 times of this density (Steffen Systems 2009). However, the cost of bale compression is
approximately $27 per wet Mg (Miles 2008) and, therefore, is currently only applied to international
hay shipping industries with high value markets. Some large square bales of hay are dense enough
to be transported at legal truck limits (truck capacity is limited by weight not volume), but loading
and unloading of the bales is often time-consuming. These issues need to be addressed and cost
efficiencies achieved if biomass energy feedstocks are to compete successfully with low-cost fossil
fuels like coal and natural gas.
7.7 suPPly chaIn and loGIstIcs manaGement
To achieve system-level efficiencies and economies of scale, the individual unit operations described
above need to be knit together into integrated systems. One such approach is the uniform format,
solid feedstock supply strategy of Hess et al. (2009). This approach would process diverse biomass
feedstocks as close to the harvest locations as possible. Local processing allows the biomass supplier
to produce a uniform particle size, consistent flowability, and a consistent moisture content. With
these and other related characteristics rationalized and homogenized, downstream transport and
logistics operators can manage a diverse range of biomass feedstocks with common equipment
and efficient operations. In addition to these coordinated technical systems, there is also a need for
coordinated business systems.
Biomass supply chains are generally composed of many interconnected business units that per-
form a range of different activities. They include landowners and contractors who manage ground
preparation and planting of a mix of species in the field and forest. There are also biorefineries and
other clients that may range from harvesting, handling, and managing logistics of to producers of
chemicals and liquid fuels that, in turn, serve different customers. Various other entrepreneurs are
also involved in harvesting, handling, processing, storing, and line-haul transporting biomass for
use at biomass energy facilities. The interaction of these businesses at a strategic network and rela-
tionship level constitute supply chain management.
A biomass supply chain performs two important physical functions: production and logistics.
The production function produces and collects raw biomass and converts raw biomass (such as
woody biomass and agricultural wastes) into processed biomass (such as woodchips and pellets)
Search WWH ::




Custom Search