Environmental Engineering Reference
In-Depth Information
direct-fired and gasified willow biomass produced approximately 40-50 times more electricity per
unit of fossil fuel input energy than the U.S. grid average, as shown in Table 11.8. For comparison
purposes, building-integrated photovoltaic (BIPV) and wind energy systems are included in the
table (Keoleian and Lewis 2003; Schleisner 2000).
11.3.2.2 mixed Wood Waste
A similar LCA of biomass co-fired electricity compared a pulverized coal power plant to 5 and
15% biomass co-fire facilities (Mann and Spath 2001; see Figure 11.23). The LCA boundaries
included surface coal mining operations, power plant capital equipment production, transport of
biomass and coal, upstream grid electricity production, and displacement credits for avoiding the
assumed typical fate of the biomass feedstock. The model considered biomass from various sources,
including urban wood waste, mill waste, construction residue, and industrial wood residue. The
physical properties of this mixed feedstock were defined similarly to those of the willow studied by
Keoleian and Volk (2005), except that the energy content was approximately 8% lower, by mass, and
the ash content was approximately 50% higher. Higher ash content can increase solid waste genera-
tion, although solid waste is not discussed in this chapter.
taBle 11.8
ner for various electricity Production systems
ner
(electricity out/fossil energy in)
electricity source
Coal only (pulverized coal)
0.313
10% Blend co-fire
0.341
(9.5% wood waste, 0.5% willow, 90% coal)
10% Willow co-fire
0.342
(10% willow, 90% coal)
U.S. grid average
0.257
Gasified willow
12.9
(100% willow gasified)
Direct-fired willow
9.9
(100% willow combusted)
BIPV
4.3
Wind
30.3
Source:
Keoleian, G.A. and Volk, T.A.,
Crit Plant Sci Rev,
24, 385-406, 2005.
250
Coal
200
5% Co-fire
15% Co-fire
150
100
50
0
Biomass
transportation
Water treatment
at power
plant
Lime
production
Limestone
production
Lime and
limestone
transportation
Coal
transportation
Coal mining
FIGure 11.23
Energy inputs per MWh of electricity output for various life-cycle activities. (From Mann,
M.K. and Spath, P.L.,
Clean Prod Processes
, 3, 81-91, 2001.)
