Agriculture Reference
In-Depth Information
ultimate impact of high grain prices on food has yet to be seen. Almost certainly,
feed prices three times their historical levels will elevate food prices. The demand
created for biomass feedstock to produce energy will no doubt increase feedstock
cost. This will negatively affect current consumers of feedstock, those that use it for
food, feed, and fiber. Changes in supply-demand dynamics will cause at least short-
term disruptions that will create winners and losers.
w
a t e r
Water is essential for biological life. Although the Earth's surface is largely covered
with water, most contains levels of dissolved salts that make it generally unusable
by plants and animals. Growing the plants to produce the large quantities (billion
or more dry tons) of biomass feedstock that will be necessary to produce sufficient
quantities of biofuels will require large amounts of water. In addition, conversion
of biomass feedstock to liquid fuel and products may require additional significant
amounts of water.
Water is a finite natural resource that exists in a constant quantity on the earth.
But, is that quantity sufficient? The global supply of water is estimated to be
1,386,000,000 cubic kilometers or 206 billion liters for each of the world's nearly
6.7 billion humans. Unfortunately, 97% of this water contains excessive dissolved
solids and without treatment is unusable by most plants and animals. This leaves 5
billion liters of freshwater per person. Of that, over two thirds is frozen in ice caps
and glaciers and not readily available. That still leaves about 1.6 billion liters of fresh
surface and groundwater for each person on the planet. Assuming that per capita
usage of freshwater is 2 million liters per year (an estimate for personal, agricultural,
and industrial use in industrialized countries), human needs would require only one
eighth of 1% of the freshwater available.
If desalinated, seawater could easily provide all water needs. The major obstacle
is the energy required to remove the dissolved solids. The minimum energy to desal-
inate seawater is about 0.66 kcal/L. That is true regardless of the technology used.
Therefore, it would take 2 million L * 0.66 kcal/L = 1.32 million kcal (5544 million
J) to desalinate the water needed by one person in an industrial lifestyle. That equals
the energy in about 70 gallons of ethanol.
This suggests that there is plenty of water; unfortunately, it is not well distributed,
and therein lies the problem (see Chapter 19). In many cases, local water supplies are
simply insufficient. In other situations, the water is not effectively or efficiently used.
The challenge then is to engineer systems for the sustainable use of a water resource
that is sufficient in overall quantity but is lacking in quality and distribution. This
challenge must be met to reduce human misery, to enhance the environment, and to
eliminate a major cause of strife.
L
a n D
u
s e
C
h a n g e
There are concerns that cropping changes to produce bioenergy feedstocks in one
location will result is land use changes in other locations, changes that could result
in significant oxidation of carbon in the existing vegetation and in the soil, with a
