Agriculture Reference
In-Depth Information
the solutIon: RenewAble eneRgy
To avoid the serious negative consequences of fossil energy dependence, systems
that provide adequate amounts of economical, reliable, and sustainable renewable
energy must be developed and commercialized. A truly adequate and sustainable
energy system must be renewable and provide sufficient energy to meet demand.
Renewable energy must come from renewable sources, must not depend on non-
renewable inputs, and must have the potential for its production to be sustained in
perpetuity. Currently, most alternative energy relies to some extent (directly or indi-
rectly) on nonrenewable fossil energy. As a result, indices such as fossil energy ratio
and net energy are used to assess the relative sustainability of renewable energy
feedstock and fuel production practices and processes (Farrell et al., 2006).
When evaluating potential renewable energy sources, it must be considered that
the earth's only real source of renewable energy is solar energy, an energy source
humans have relied on as long as they have inhabited the earth. It is also the energy
that drives the climate and ecology that make the earth the place that it is. Fortunately,
it is a very large energy source (Crabtree and Lewis, 2007). In only a matter of min-
utes, the energy equivalent to that used by humans each year arrives from the sun at
the earth's surface.
Solar radiation is low intensity and widely distributed. These characteristics are
ideal for warming the earth and for the safety of plants and animals inhabiting the
planet. Wind, solar, hydro, and biomass energies are all solar radiation driven. Much
of the energy from these sources has traditionally been used at or near where it is
captured. Solar forms of energy are well suited for distributed, small-scale uses such
as pumping water for animals and for home heating of water. However, economically
capturing and making use of solar radiation for large-scale generation of heat, power,
and electricity has proven difficult. The challenge is to efficiently and effectively
convert solar energy into useful forms and to make that energy available in adequate
amounts when and where needed. Possibly the most difficult form of energy to pro-
vide is an energy-dense and transportable transportation fuel that can replace cur-
rently used gasoline and diesel fuel.
Because energy use is large, and increasing, it is unlikely that any single source
of renewable energy will replace fossil fuel. However, collectively solar, wind, hydro,
and biomass could provide all of the transportation fuel, electricity, heat, and power
for the world's industrial and domestic needs.
RenewAble bIoeneRgy
Green plants, through the chlorophyll molecule and the process of photosynthesis, cap-
ture and use the energy in sunlight to form carbohydrates from carbon dioxide and water.
The energy in these carbohydrates is in the form of reduced carbon or carbon-hydrogen
bonds. The solar energy captured in plant biomass provides energy and nutrition for the
animal kingdom. Biomass can also be used directly as a solid fuel or converted into
other forms, including liquid or gaseous fuels. These fuels are renewable bioenergy that
can be converted to heat, power, and electricity or used for transportation.
