Environmental Engineering Reference
In-Depth Information
Energy crops:
Crops grown specifically for their fuel value. They include food
crops such as corn and sugarcane and non-food crops such as poplar trees
and switchgrass. Currently, low-energy crops are under development: short-
rotation woody crops, which are fast-growing hardwood trees harvested in
5 to 8 years, and herbaceous energy crops, such as perennial grasses, which
are harvested annually after taking 2 to 3 years to reach full productivity.
Energy efficiency:
A ratio of service provided to energy input (e.g., lumens to watts
in the case of light bulbs). Services provided can include buildings-sector
end uses such as lighting, refrigeration, and heating; industrial processes; or
vehicle transportation. Unlike conservation, which involves some reduction
of service, energy efficiency provides energy reductions without sacrifice
of service.
Energy source:
Any substance or natural phenomenon that can be consumed or
transformed to supply heat or power. Examples include petroleum, coal,
natural gas, nuclear, biomass, electricity, wind, sunlight, geothermal, water
movement, and hydrogen in fuel cells.
Enhanced geothermal systems (EGSs):
Engineered reservoirs that can extract eco-
nomical amounts of heat from geothermal resources; rock fracturing, water
injection, and water circulation technologies to sweep heat from the unpro-
ductive areas of existing geothermal fields or new fields lacking sufficient
production capacity.
Enthalpy:
A thermodynamic property of a substance, defined as the sum of its inter-
nal energy plus the pressure of the substance times its volume, divided by
the mechanical equivalent of heat; the total heat content of air; the sum of
enthalpies of dry air and water vapor per unit weight of dry air; measured
in Btu per pound (or calories per kilogram).
Environment:
The sum total of all biological, chemical, and physical factors to
which organisms are exposed.
Environmental health (abiotic aspects):
The composition, structure, and func-
tioning of soil, water, air, and other abiotic features comparable with his-
toric conditions, including the natural abiotic processes that shape the
environment.
Environmental Impact Statement:
A document created from a study of the
expected environmental effects of a new development or installation.
Environmental restoration:
Although usually described as “cleanup,” this function
encompasses a wide range of activities, such as stabilizing contaminated
soil; treating groundwater; decommissioning process buildings, nuclear
reactors, chemical separations plants, and many other facilities; and exhum-
ing sludge and buried drums of waste.
Environmental restrictions:
In reference to coal accessibility, land-use restrictions
that constrain, postpone, or prohibit mining in order to protect environmen-
tal resources of an area—for example, surface- or ground water quality, air
quality affected by mining, or plants or animals or their habitats.
Ethane (C
2
H
6
):
A straight-chain saturated (paraffinic) hydrocarbon extracted pre-
dominately from the natural gas stream, which is gaseous at standard tem-
perature and pressure. It is a colorless gas that boils at a temperate of -127°F.
