Introduction to Environmental Science
Chapter 20: Conventional Energy Alternatives
Central Case: Sweden’s Search for Alternative Energy
• While Swedish citizens voted to shut down all nuclear plants in the wake
of Chernobyl, 55% now favor nuclear power as an alternative to
expanding fossil fuel use.
• 80% of Swedes support increasing research on renewable energy
Alternatives to fossil fuels
• Because fossil fuels are nonrenewable and will not last forever the
world’s economies must find alternatives.
• Most alternatives are costly and depend on undeveloped technologies.
• Three alternatives are the most developed and widely used:
• Nuclear power
• Biomass energy
• Hydroelectric power
Energy consumption in the U.S.
Nuclear energy is a non-renewable form of energy.
• Nuclear power currently contributes significantly to the energy we
consume and the electricity we produce.
• Nuclear power comes from uranium which must be mined and refined in
a long, involved process.
Consumers of nuclear power
Nuclear power has expanded 15-fold since 1970.
The process of generating nuclear energy from uranium
What is Nuclear energy?
• Nuclear energy is the energy that holds together protons and neutrons
within the nucleus of an atom
• We harness this energy by converting it to heat energy, which can then
be used to generate electricity.
• Each conversion process involves transforming isotopes of one element
into isotopes of other elements by the addition or loss of neutrons.
• This energy comes from the radioactive element uranium
• The nuclear fuel cycle enriches forms of uranium to make it into usable
• Electricity is generated by controlling fission in nuclear reactors.
Fission releases energy we can harness to generate electricity.
• In fission, the nuclei of large, heavy atoms such as uranium and
plutonium are bombarded with neutrons.
• In order for fission to begin, neutrons must be slowed down.
• All this takes place within the reactor core, and is the first step in the
electricity-generating process of a nuclear reactor.
Nuclear energy: Fission
Nuclear fission = energy is released by splitting apart uranium nuclei by
bombarding them with neutrons
This is the process used in nuclear reactors and weapons.
Breeder reactors make better use of fuel but raise safety concerns
• Using plutonium, breeder nuclear fission:
• Makes more fuel as it runs
• Generates more power
• Produces far less waste
• However, breeder fission raises the risk of explosive accidents.
• Plutonium can be used in nuclear weapons
• As a result, most breeder reactors have been shut down. There are none
in the US.
Nuclear Fusion Remains a Dream
Nuclear fusion = nuclei of lightweight elements are forced together
Currently, this process requires more energy than it produces, so is not
Fission Nuclear power grew fast, but ran into problems.
• As nuclear power was developed in the second half of the 20th century, it
showed great promise as a clean power source.
• Since then, the industry’s growth has stalled primarily because of cost
overruns, concerns over safety and environmental concerns.
• Nuclear power creates radioactive waste that must be entombed for
thousands of years before it becomes safe.
Waste will be stored in tunnels under Yucca Mountain.
o Truck Carrying
Nuclear Waste Cask
o Requirements for Shipping Containers for Nuclear Waste
Nuclear power plants have become a socially unacceptable way of
generating electricity in the USA
• In 1979, the partial meltdown at the Three Mile Island nuclear plant in
Pennsylvania released radiation into the environment, necessitating
evacuation of area residents and causing public alarm.
• This was followed by a more serious accident at Chernobyl, in the Ukrain
• Growth in nuclear generating capacity slowed to a crawl during the 1990s
and today, more than 100 of the world’s nuclear plants have been
decommissioned, leaving only 450 operational
o The Three Mile Island accident caused a partial meltdown.
o Fallout from Chernobyl was deposited across much of Western
Other Hazards of Nuclear Power
• Nuclear plants and shipments of nuclear waste are potential targets for
• Countries with nuclear power plants can develop atomic bombs from
waste products (ie. N. Korea & Iran).
Nuclear Energy delivers energy more cleanly than fossil fuels
• Despite the potential hazards, nuclear plants generate no air pollution
and no greenhouse gas emissions.
• It also generates more power per unit weight of material than burning
coal, or oil.
• It also fits nicely into our current power generating grid.
What is Biomass Energy?
• Biomass consists of those organic substances produced by recent
• Biomass can be used for energy in many diverse ways.
• Wood Biomass is commonly used in the developing world as a fuel
Upside of Biomass energy
• Biomass energy can be efficient in terms of both energy use and cost.
• Biomass tends to be the least expensive type of fuel for combustion in
power plants, and improved energy efficiency can lead to lower prices for
• It can be produced anywhere in the world, even in the developing world.
Downside of Biomass
• In terms of environmental impacts, biomass energy has a mixed record.
– Unsustainable wood harvesting can lead to deforestation, soil erosion,
– A larger issue is that the combustion of biomass does not reduce
emissions to the extent that other renewable energy sources do.
• Using corn for biomass takes it out of the food market, which drives up
prices at the supermarket and reduces exports to the developing world.
In hydroelectric power, moving water is used to turn turbines and
Hydroelectric Power Turbines
For nations with large amounts of flowing water (Brazil, Norway, Austria,
Canada…), hydropower has been key to their economic development.
Currently, 98% of U.S. rivers are dammed.
How does it work?
Water flowing through a dam spins turbines that turn generators to create
The upside of hydroelectric
• Hydroelectric power is widely used.
• Hydropower is renewable as long as rain still falls and fills rivers and
• Hydropower is cleaner than fossil fuels.
• Hydropower produces little to no air pollution.
The downside of hydroelectric
• The majority of the world’s rivers that offer excellent opportunities for
hydropower have already been dammed.
• In the United States, 98% of rivers appropriate for dam construction are
already dammed, and many of the remaining 2% are protected from dam
• Hydropower causes thermal pollution
• Dams disrupt the local ecology and economy of riverside areas.
• With increasing supply problems environmental impacts of fossil fuels,
many nations are pursuing alternative energy sources.
• The three most widely used alternatives so far are nuclear power,
biomass energy, and hydropower.
• High costs and public fears over safety have prompted some nations to
phase out nuclear power.
• Biomass sources can be carbon-neutral but are not all strictly renewable.
• Hydropower is renewable and pollution-free, but it is nearing its maximal
use and can involve substantial ecological impacts.