Environmental Engineering Reference
In-Depth Information
FIGure 28.2
A living sound barrier wall planted with
S. miyabeana
adjacent to a highway.
and Briggs 2003; Dimitriou and Aronsson 2005; Kuzovkina and Quigley 2005; Volk et al.
2006). Planting shrub willow fields adjacent to wastewater treatment facilities captures multiple
environmental benefits because the removal of excess nitrogen and phosphorus from wastewater
stimulates willow growth and increases yield of biomass that can be used for bioenergy (Aronsson
and Perttu 2001). Shrub willow plantations are particularly well suited for the uptake and removal
of cadmium from soil (Dimitriou et al. 2006). As a result, sewage sludge may be applied to willow
plantings with less chance for long-term accumulation of cadmium in the soil (Labrecque and
Teodorescu 2001; Dimitriou et al. 2006). Willow plantations also represent a viable system for the
restoration of contaminated urban brownfield sites when they are used in a final polishing phase
to remove low levels of organic or heavy metal contaminants and restore the quality of highly
disturbed soils (French et al. 2006).
Initially studied as a source of pulpwood, the oil shortages in the late 1970s accelerated the
development of perennial woody crops for the domestic production of feedstock for renewable
energy. Fast-growing shrub willow was among those perennial crops studied for its fast growth
rate and potential for high yields with relatively low inputs on marginal agricultural land
(Anderson et al. 1983; McElroy and Dawson 1986; Gullberg 1993). Many of the original willow
varieties that were tested in Europe were obtained from the National Willow Collection of the
United Kingdom, which was maintained and managed by Kenneth Stott (Newsholme 1992; Stott
1992). Primary among those evaluated by pioneering researchers in northern Europe were
Salix
“Aquatica Gigantea” and
S. dasyclados
Wimm (McElroy and Dawson 1986; Pohjonen 1987; Stott
1991). Varieties selected for basket-making, including genotypes of
S. viminalis
and
S. triandra
,
were also included in early trials. Cultivation of willow crops for energy first gained a foothold in
commercial markets in Sweden, where it is grown on approximately 13,000 ha and is used as fuel
for district heating plants and for combined heat and power (Verwijst 2001). Breeding programs
aimed at improving the yield and sustainability of willow bioenergy crops were established
in Sweden, England, and Canada (Eriksson et al. 1984; Zsuffa 1990; Lindegaard and Barker
1997; Larsson 1998), which all resulted in the release of improved germplasm that is grown
commercially for bioenergy today.
