Environmental Engineering Reference
In-Depth Information
perimenting with E85, which is 85 percent gasoline mixed with 15 percent ethanol. Ethanol can be made from
corn, soy, or plant waste material.
Advantages and Disadvantages of Biodiesel
Advantages
Disadvantages
Increased NO
x
emissions and increased photochemical
smog.
Reduced CO and CO
2
emissions.
Reduced hydrocarbon emissions.
Higher cost than regular diesel.
Better gas mileage.
Low net-energy yield for soybean crops.
Has the potential to be renewable if the source for
the biodiesel is renewable.
Loss and degradation of biodiversity due to land being
used for increased crop production.
Sources such as algae and oil palms offer high
net-energy yield.
May compete with growing food for land use and raise
food prices.
Sources from other crops offer moderate net-en-
ergy yield.
Advantages and Disadvantages of Ethanol
Advantages
Disadvantages
Reduced CO emissions.
Low net-energy yield with some crops.
Some reduction in CO
2
emissions if sugarcane is
used.
Increased NO
x
emissions and increased photochemic-
al smog.
Can be mixed with gasoline and sold as E85 or as
pure ethanol.
May compete with growing food for land use and raise
food prices.
Potentially renewable. Higher cost than regular diesel.
High net-energy yield for bagasse and switchgrass. Higher CO
2
emissions using corn.
Another new fuel used to power vehicles is the hydrogen fuel cell, which coverts hydrogen into energy. There
are various ways to access the hydrogen and convert it into useable form. One such way is electrolysis, where
electricity is passed through water, separating the hydrogen and oxygen. The by-product of hydrogen fuels
cells is water.
Mass Transit
The goal of public transportation is to move large numbers of people in one vehicle. When asked about mass
transit, most people think of buses, subways, and light rail. Other forms include air, trains, and ships. People in
Japan, Europe, and a few places in the United States, including the San Francisco Bay area and New York City,
frequently take into account the accessibility of mass transit when evaluating where to live and work. Rider-
ship in Japan is close to 50 percent, with the percentage of riders even higher in Tokyo. In a 2006 survey, 5 per-
cent of the U.S. population used mass transit, while 20 percent had easy access to mass transit. Public trans-
portation is more likely to be used by people living in cities with a population greater than 100,000. For ex-
ample, ridership in New York City is over 50 percent; Washington, D.C., at 39 percent; Chicago at 25 percent;
and Los Angeles at 11 percent. In the five years of 2006 to 2010, the use of mass transit increased in the United
States partly in response to increases in gasoline prices, incentives of employers to increase the use of mass
transit, expansion of some mass transit systems, and the idea of being more "green."
