Environmental Engineering Reference
In-Depth Information
Ethanol (ethyl alcohol or grain alcohol, CH
3
-CH
2
OH):
A clear, colorless flam-
mable oxygenated hydrocarbon with a boiling point of 173.5°F in the anhy-
drous state. However, it readily forms a binary azetrope with water, with a
boiling point of 172.67°F at a composition of 9557% by weight ethanol. It
is used in the United States as a gasoline octane enhancer and oxygenate
(maximum 10% concentration). Ethanol can be used in higher concentra-
tions (E85) in vehicles designed for its use. Ethanol is typically produced
chemically from ethylene or biologically from fermentation of various sug-
ars from carbohydrates found in agricultural crops and cellulosic residues
from crops or wood. The lower heating value, equal to 76,000 Btu per gal-
lon, is assumed for estimates in this text.
Ether:
A generic term applied to a group of organic chemical compounds composed
of carbon, hydrogen, and oxygen, characterized by an oxygen atom attached
to two carbon atoms (e.g., methyl tertiary-butyl ether).
Ethylene (C
2
H
4
):
An olefinic hydrocarbon recovered from refinery or petrochemical
processes which is gaseous at standard temperature and pressure. Ethylene
is used as petrochemical feedstock for many chemical applications and the
production of consumer goods.
Ethylene dichloride:
A colorless, oily liquid used as a solvent and fumigant for
organic synthesis and for ore flotation.
Evacuated tube:
In a solar thermal collector, an absorber tube, which is contained
in an evacuated glass cylinder, through which collector fluids flows.
Evaluation:
Examining how an organization's plans and actions have turned out and
adjusting them for the future.
Evaporation pond:
A containment pond (that preferably has an impermeable lining
of clay or synthetic material such as hypalon) to hold liquid waste and to
concentrate the waste through evaporation.
Evaporative cooler (“swamp cooler”):
An air conditioner that uses evaporation
from a centrally located pad; no refrigeration unit is involved.
Evapotranspiration (ET):
The combined evaporation from the soil surface and
transpiration from plants. Transpiration is the evaporation of water from
internal surfaces of living plant organics and its subsequent diffusion into
the atmosphere. Evaporation is the physical process by which liquid water
is converted to vapor.
Exothermic:
A chemical reaction that gives off heat.
Exotic species:
A species that is not native to an area and has been introduced inten-
tionally or unintentionally by humans; not all exotics become successfully
established.
Expenditure:
The incurrence of a liability to obtain an asset or service.
Externality:
A cost or benefit not accounted for in the price of goods and services;
often refers to the cost of pollution and other environmental impacts.
Extinction:
The termination of any lineage of organisms, from subspecies to spe-
cies and higher taxonomic categories from genera to phyla. Extinction can
be local, in which one or more populations of a species or other unit vanish
but others survive elsewhere, or total (global), in which all the populations
vanish.
