Environmental Engineering Reference
In-Depth Information
1.7
Energy losses along the photosynthetic, respiratory, and
harvesting pathways in a temperate grain field.
Similarly, very different efficiencies result when tracing
the fate of solar radiation incident in a temperate grain
field: no more than 0.1% of solar irradiance may be con-
verted into chemical energy in grain, but the photosyn-
thesis is actually energized with only about 10% of all
incident radiation owing to a sequence of large prefixa-
tion losses (fig. 1.7): redefinition of inputs boosts the ef-
ficiency by 1 OM. And why should all residual phytomass
(roots, shoots) be excluded from efficiency calculations
when it provides excellent livestock feeds as well as irre-
placeable ecosystem services after its return to the soil?
Photosynthetic efficiency can be at least doubled by
counting this phytomass. In any case, higher photosyn-
thetic efficiency may actually be counterproductive if the
grain is fed to cattle whose inefficient metabolism pro-
duces fatty meat, the consumption of which promotes
obesity and cardiovascular mortality. Clearly, worship-
ping higher energy efficiency as an abstraction is a du-
bious faith.
The primary analytical tools used in this topic (in addi-
tion to the measures already noted) make matters even
more complicated because they have no universally
