Energy

Energy gives us light, heats our homes, cooks our food, and fuels our economy. Today, energy comes largely from non-renewable fossil fuels, and our current rate of consumption has huge environmental impacts, particularly on global warming. Roughly 70% of global greenhouse gas emissions are directly related to fuel extraction, transportation, and power production. As concern over climate change grows, lower emission, renewable sources are being developed and utilized.   

Non-Renewable_Energy

Coal          Oil          Natural_Gas           Nuclear

Renewable

Biomass     Wood     Biofuel     Biogas     Hydroelectric

Solar         Wind      Geothermal

On_The_Horizon

Fuel_Cells

Waste_Heat_Recovery

Tidal_Power

Wave_Power

What_Can_Be_Done_
 

Non-Renewable Energy

Non-renewable sources make up the majority of the planet’s energy consumption. Nuclear energy contributes only 6.5% of the total, while fossil fuels account for over 80% of the world’s energy.

 
Fossil Fuels
Fossil fuels originate from ancient biomass (plant and animal), and have been altered through time and geologic processes to concentrate their carbon and methane content. Because the material has been isolated from the biosphere for hundreds of millions of years, its release into the atmosphere adds more greenhouse gases than can be absorbed.

Fossil fuel retrieval, processing and distribution accounts for 11.3% of the total of anthropogenic greenhouse gases.  It is estimated that the burning of fossil fuels releases 21.3 billion tons of carbon into the atmosphere every year. Roughly half this atmospheric carbon is absorbed through natural processes, known as “sinks” (forests and the ocean), but the remaining10.65 stays in the atmosphere, contributing greatly to the Greenhouse Effect.

Despite such concerns, fossil fuels remain the world’s primary source for fuel and energy, due to its high energy density relative to its mass, infrastructure that already exists for its extraction, refinement, and power production, and its cost relative to the investment in alternatives. 

Coal
Found on every continent, coal is the largest source of electricity worldwide. It is a readily combustible sedimentary rock formed by the oxidization and biodegradation of plant remains, often in former swamp ecosystems.

Extraction.  Aside from the energy and resources used to extract it from the ground, coal mining has numerous environmental impacts. These include:

• Acid mine drainage. Sulfuric acid is created when pyrite (iron sulfide, also known as “Fool’s Gold”) comes in contact with air and water. The mine tailings (the exposed and removed rock and soil) are made infertile, and leech acid into local waterways.
• Release of methane gas. A naturally occurring byproduct of decaying organic matter, methane gas, is a major greenhouse gas. It is found within and near coal seams and is released when the area is exposed to air.
• Creation and storage of coal slurry. Slurry is created when coal is processed at a coal preparation plant for transportation and use. This wastewater, also called blackwater, is stored behind a dam made from mine tailings. In addition to contaminating nearby water sources, the dam can breach, flooding local rivers and towns with highly toxic waste. 

Coal is found as seams throughout the earth’s crust. The depth of the seams, in addition to the geology of the area, determines what mining method is used. The most common are:

Surface Mining. This is an umbrella term for various types of coal mining that disrupts and often removes the area (usually referred to as the overburden) above the coal seam.  This involves:

• Open-pit utilizes a pit or borrow to remove the coal
• Strip mining removes the coal by stripping away the “overburden” in layers
•  Mountain top removal is used when seams extend down further into the ground. By the use of high-power explosives, miners remove rock and soil redepositing it to lower lying valleys, leveling the topography of a vast area. The EPA estimated the 724 miles of Appalachian streams were buried between 1985 and 2001.

Additional impacts include:

• Loss of habitat and biodiversity
• Waterway contamination from minerals and heavy metals in the tailings
• The introduction of invasive species from the reclamation efforts of mining companies once mining is complete

Underground Mining. Accounting for the majority of world coal production, it is removed by digging tunnels, stabilized by pillars. Cave-ins due to pillar instability and gas explosions from the combustible ready coal count for the hazardous conditions for miners. Between 1996 and 2008, there have been 406 coal mining fatalities in the United States.  The Chinese government reports nearly 6,000 deaths in 2005 alone. Life in the coal mine also has long term health impacts largely related to respiratory disease.

Power Production.  To produce energy, coal is generally pulverized and burned in a furnace attached to a boiler. Steam from the boiler turns turbines, generating electricity. 41% of power stations world wide are powered by coal, equaling roughly 10% of the anthropogenic greenhouse gas emissions. Coal is also a major contributor to acid rain, and its waste includes ash, arsenic, lead, mercury, and other heavy metals. Low levels of uranium and other radioactive isotopes can also be released into the environment, potentially leading to radioactive contamination.

Economics and Efficiency.  Coal is 75% less per unit of energy than natural gas and oil. It remains the most widely used source of fuel for the generation of electricity. However, coal fired power plants are notoriously inefficient, harnessing only 33% of the energy input. New technologies are being developed to try and improve efficiency, however none get above 60%.

New Technologies and Uses.  With concerns over global warming and the depletion of the world’s petroleum reserves, there have been efforts to increase coal’s versatility and reduce its carbon output. Two prominent adaptations include:

• Liquefaction (Coal-To-Liquids). By converting coal into a liquid form of fuel, it can be used as a substitute for petroleum. This alleviates concerns over oil prices and the political instability in oil rich nations. However, the process of liquefaction releases more CO2 than petroleum refinement, potentially increasing global greenhouse gas emissions.
• Gasification. This process breaks coal down into its basic compounds, usually by high temperature and pressure, producing a syngas (synthetic gas) made largely of carbon monoxide and hydrogen. It’s proponents claim that it burns cleaner and can be used with the more efficient gas turbines.
   

Clean Coal. To clean coal is to chemically “wash” it, and remove the sulfur dioxide. Such a process, which can include gasification, would increase thermal efficiency by power plants by only 10% and the sulfur would still be released as waste further down the line.

Oil
Petroleum is the most versatile of the fossil fuels. Pumped from the ground as crude oil, it is refined into multiple types of fuel and used in electrical power production and vehicle transportation.

Extraction and Transportation.  The most common method of petroleum extraction is by drilling a well into an oil field. Pumped largely by natural pressure, petroleum drilling has a relatively small footprint compared with other fossil fuel removal. The exception is underwater extraction that disturbs the marine environment, particularly when dredging is employed. Locating oil fields is also considerably invasive and often requires underground explosions.

Transportation, usually aboard a tanker ship, poses the greatest environmental threat. In addition to the amount of fuel necessary for shipping, transportation carries the risk of oil spills. Spilling anywhere from a few hundred tons to several hundred thousands of tons of crude oil, gasoline, diesel fuel, and waste oil, tanker accidents can severely disrupt marine ecosystems and blanket entire estuaries. In the Alaskan Exxon-Valdez spill in 1989, it is estimated that up to 500,000 seabirds, 1,000 sea otters, 12 river otters, 300 harbor seals, 250 bald eagles, and 22 orcas died immediately. The effects of oil spills are long term and it often takes ecosystems decades to fully recover.

Refinement.  Oil refineries, by use of heat, pressure, and chemicals, convert crude oil into multiple forms of fuel and industrial products such as lubricants, solvents, tar, and asphalt. On average U.S. refineries emit over 10,000 gallons a day of noxious waste into the land, air, and water. This waste includes:

• Particulate Matter
• Sulfur Oxides
• Carbon Monoxide
• Hydrocarbons
• Nitrogen Oxides
• Aldehydes
• Ammonia

For this reason, the U.S.  EPA estimates that 70 in 1 million residents within 30 miles of oil refineries have lifetime cancer risks due to toxic emissions.  The EPA also estimates that 90 million Americans live within 30 miles of a refinery.

Fuel for Power and Transport.  Petroleum’s amount and diversity of hydrocarbons allow it to be refined into multiple types of energy sources. By the amount refined from the world’s crude oil (the remaining percentages are used for industrial products), these fuels include:

• Gasoline 45%
• Distillate fuel oil (diesel fuel and home heating oil) 21%
• Kerosene-type jet fuel 9%
• Residual fuel oil or bunker fuel 5%
• Liquid petroleum gas (propane and butane) 4%
• Kerosene .5%

The vast majority petroleum based fuels are used in internal combustion engine. The emissions from transportation fuels is 14% of the global total for anthropogenic greenhouse gas emission. Due to cost of petroleum relative to coal and natural gas, only 1.6% of all US electrical generation comes from petroleum based fuels.  Heating oil, however, is widely used in areas where natural gas is not available. Home boiler systems average 80% energy efficiency.

Economics and the Theory of Peak Oil.  Since the Industrial Revolution petroleum has been a relatively abundant and inexpensive form of fuel. However, as oil prices and global temperatures continue to climb, that is changing. The theory of peak oil, also known as Hubbert peak theory for M. King Hubbert, argues that oil prices will continue to climb as reserves run out. The Energy Information Administration, an arm of the US Department of Energy, has data indicating that global production peaked in late 2006.

Because of these concerns, the petroleum industry is currently looking for alternatives to crude oil. Containing hydrocarbons capable of being isolated and converted to fuel, oil shale and tar sands are the two most popular alternatives. However, both require high energy inputs for extraction and the chemical conversion, making them a costly alternative to crude oil.

Natural Gas
Natural gas is used for power production, industrial heating processes and domestic uses such as for cooking ranges, ovens, clothes dryers, and heating and cooling systems. Consisting mainly of methane, natural gas is found both in oil fields and isolated in natural gas fields, where it is extracted much like petroleum. It is the most expensive fossil fuel, but its combustion releases significantly less greenhouse gasses per unit of energy than coal or petroleum, at a higher rate of efficiency. According to the US Department of Energy, natural gas furnaces are 75% more efficient than those run on liquefied petroleum gas or heating oil. It is also frequently used in combined cycle power generation that uses both a gas and steam turbine to utilize waste heat, increasing power production efficiency 85%.

Processing.   While the natural gas burned for heat and energy (primarily propane and butane) is made mostly of methane, raw gas pumped out of the gas wells also has varying amounts of:

• Carbon dioxide
• Hydrogen sulfide
• Nitrogen
• Helium
• Water vapor
• Mercury (very small amounts)

At natural gas processing plants these other gases are removed. They are either isolated for industrial use, like sulfur, or released into the atmosphere.

Transportation. Because natural gas is very low density, transportation from the processing plant to the power plant, is a larger challenge. Overland pipelines have been the most economic option. While using the least amount of energy, pipeline construction and maintenance disrupt wildlife habitat. On lake or sea floors, where many natural gas reserves are located, dredging and construction stir up often toxic sediment, contaminating local marine ecosystems.

Only 15 countries have 73% of the natural gas reserves necessitating long distance transport.  For tanker transport to be economical, natural gas must be liquefied or compressed, and converted back at the pipeline or power plant. This process adds 20-40% more greenhouse gas to the life cycle emissions of natural gas, making it considerably less “clean.”  Liquefied natural gas (LNG) also requires refrigeration during transport to keep it in a liquid form, increasing its carbon footprint.

New Technologies and Uses.  Efforts are underway to use natural gas as a replacement, or augmentation, to petroleum to reduce overall greenhouse gases in the transportation sector. Fuels made and derived from include:

• Liquefied Natural Gas. Blended with petrodiesel, LNG has started (on a small scale) to be used as jet fuel.
• Compressed Natural Gas (CNG). Many cars are being converted to run on CNG, which is has fewer lifecycle emissions and is considered an alternative to gasoline. Many cities have converted their municipal buses to CNG.
• Hydrogen.  As one of the byproducts of processing natural gas, hydrogen is currently under consideration to power planes and automobiles. Either by conventional combustion or through the use of a fuel cell.

LNG and CNG have fewer lifecycle emissions when used for vehicles, as they do not need to be regasified.   Hydrogen’s lifecycle emissions are measured by the amount released in the extraction, processing, and transportation of natural gas.

Nuclear
Nuclear power is the production of energy through the splitting (fission) or bonding (fusion) of an atom’s nucleus. This releases a great amount of heat to produce steam and drive a turbine, creating energy. It produces cheap electricity due to low fuel costs, with no carbon emissions. According to the US Department of Energy, one ton of natural uranium can produce more than 40 million kilowatt-hours of electricity. By comparison, the same amount of electricity would require burning 16,000 tons of coal or 80,000 barrels of petroleum.

However, nuclear reactors have only a 33% thermal efficiency, a rate that is similar to coal fired power plants.  There are also environmental impacts associated with nuclear energy, which are listed below.  Currently, 15.7% of the world’s electricity comes from nuclear fission.  While touted as “carbon free”, nuclear fuel’s mining, enriching, transport, and processing of fuel and necessary for nuclear energy do emit greenhouse gases. The amount of emissions is dependent on the availability and quality of uranium. This fluctuation makes nuclear power produce between 20% -120% of the CO2 emissions for those of natural gas energy production.

Mining.  The fuel used in nuclear reactors is the isotopes uranium-235 and less commonly plutonium-239. While nuclear reactors exist around the world, uranium deposits are found in very few places. The two methods of extraction are:

• Open-pit mining. Uranium is frequently found in low concentrations, making volume intensive operations most common, specifically open pit mining. Utilizing a pit or borrow, open-pit mining often removes the soil and rock (usually referred to as the overburden) to access the uranium. It is very disruptive to wildlife habitat and commonly pollutes local waterways with sedimentation and toxic run-off.
• Underground Mining. If uranium is found deep beneath the surface, miners will dig extensive tunnels, stabilized by pillars to excavate it. Cave-ins, and high levels of radon gas are extremely hazardous to miners.

Both types of mining produce tailings and waste piles. They often contain high levels of radioisotopes and uranium ore that is not concentrated enough to be economically feasible to be processed in a uranium mill. Tailings and waste piles can leach radioactive material to the surrounding water and soil, possessing a significant threat to the heath of humans and nearby ecosystems. Once the uranium is mined, it is milled into a uniform power known as yellowcake.

Enriching Uranium and Transport.  Natural uranium does not contain enough of the fissionable isotope U-235 to sustain a nuclear chain reaction. Therefore, it must undergo an enrichment process to get the proper concentration. Depleted uranium is the byproduct of uranium-235, and 95% of it is stored as uranium hexafluoride.  It is generally held in steel cylinders in open air yards adjacent to enriching facilities. The US Department of Energy estimates that the United States currently stores 470,000 tons of uranium hexafluoride. Because of its toxicity, long half-life, and corrosive reaction to most metals, there is concern for it long term storage.

Because uranium is found in limited places and it’s processing requires several steps, uranium is transported at various stages, usually over great distances. All nuclear materials are radioactive, which make their transport a high risk for any potential accidents. The uranium is then made into fuel rods fitted for a specific reactor.

Water Usage.  Like all power plants using steam turbines, nuclear production uses vast amounts of water, nearly tens of thousands of gallons per minute.  While part of the water is used to produce steam, the majority is needed for cooling the reactor and the used fuel rods. This water carries away the waste heat, which amounts to two-thirds of the energy produced. It is routed to cooling towers where the water is released into the air as water vapor, or to a nearby body of water. Environmental concerns regarding the role of water in nuclear power production include.

• Even under normal circumstances, wastewater will contain some level of radioactivity and it may rise significantly in the event of an accident.
• The use and release of large amounts of warm water into exiting bodies of water effect animal and plant life. Altering the natural temperature, decreases the survival rate of fish larvae and other aquatic life passing through water near nuclear plants. For example, one Southern Californian power plant is estimated to have adversely affected 3.5 million fish in one year.
• Because nuclear plants use water for normal operations and rely on it to quell an emergency or accident, drought is a serious issue. In Europe, heat waves have caused reactors to shut down in France, Germany, and Spain due to lack of water.

Used Fuel and Other Waste.   Nuclear fuel rods are used for three operational cycles, about 6 years. In that time, they will use up 3% of their uranium. Once pulled from operation, they are placed in a cooling pond until they are cool enough to handle. All used fuel rods are transported in shipping casks designed to with stand 99% of any potential accidents.

Only Russia, India, France, England and soon Japan, reprocess spent fuel. Sometimes referred to as recycling, reprocessing fuel uses great amounts of energy and produces high-level radioactive liquid and sludge, which must be stored as waste. It is extremely expensive and is not allowed in the United States for fear of a security breach. Separated plutonium can be used in the construction of a weapon.

Reprocessing, however, does not eliminate the need for radioactive and high level waste to be isolated from the biosphere. Radioactivity has profound affects on any living organism it comes in contact with, including:

• Promotion of tumor growth such as cancer
• Surface burning
• Destruction of bone marrow
• Collapse of circulatory system
• Impaired or destroyed thyroid
• Genetic mutations

Nuclear energy production and reprocessing produce two types of waste:

1. Low Level Waste. This is any material that has even trace amounts of radioactivity, including the gas, liquid, or solid waste used in purifying a plant’s water. Gas and liquid can be filtered and processed enough that it can be released into the environment with limited radioactivity. Solid waste must be buried and left undisturbed for a number of years to allow its radioactivity to reduce.
2. High Level Waste. Usually spent nuclear fuel and the sludge from reprocessing fuel, high level waste requires extreme care and environmental seclusion. The only way for it to cease to be hazardous is through decay, and for certain isotopes, this takes up to 100,000 years. High level waste must be buried in impenetrable containers, immune to decay, leaking, or rupture. France, Japan, and the United State are scouting sites for “deep geologic repositories” were waste can be stored undisturbed, indefinitely. Currently, no such long-term storage exists. High level waste is stored in dry casks, where the waste is surrounded by inert gas in a sealed steal container, often above ground.

The average lifespan of a plant is 40 to 60 years. After that time, it is required to shut down and fully dismantle. Because of the low level waste throughout the plant, it must be safely isolated from the biosphere. Most often, this involved entombment, the complete encasing of the plant in concrete to allow for the radioactive material to fully decompose. According to the U.S. Nuclear Regulatory Commission, all the reactors currently in operation in the United States (103) will be at the end of their life cycle in 2033. 

Economics.   Nuclear fuel is the cheapest per unit of fuel of all the non-renewable sources. However, there are several costs and factors that alter the lifecycle price of nuclear power:

• High cost of power plant construction.
• Waste disposal. Many companies add a surcharge to the customer’s bills to cover the cost of waste disposal. However, because of the need for long term storage, the cost is likely to fall on national governments.
• Plant decommissioning., The   estimated cost  to fully decommission a power plant is $300 million. The US Nuclear Regulatory Commission requires companies to set aside money for this.

Cost of Potential Accidents and Toxic Leaks.  Nuclear power providers have insurance to cover immediate hazards and accidents. If the claim exceeds the amount insured, or it incident occurs far after the closure of a plant, the remaining cost falls to the government. For example, the U.S. Department of Energy is currently undertaking the clean up of contaminated soil and radioactive waste from nuclear fuel and energy production.

Public Debate.  In many countries, nuclear power has not been an easy sell. Arguments for nuclear power include:

• Inexpensive fuel cost
• Reduction in greenhouse gas emissions
• Reduction in dependency on foreign oil

Arguments against nuclear power include:

• Potential accidents with severe environmental consequence like the Chernobyl disaster
• Health risks by radioactivity on nearby communities
• Long term high level waste disposal
• Nuclear proliferation
• Waste used as weapons
• Security issues/terrorist targets
• Environmental impact of hot waste water
• Concerns over potential drought

 
Renewable

Renewable sources presently create nearly 12% of the world’s energy. Due to the shrinking reserves of fossil fuels, the raging debate over nuclear energy, and the rising concern over climate change this number is growing. More and more governments and individuals are investing in alternative sources for energy, and over 65 countries have goals and policies to increase their use of renewable sources. Internationally, the renewable energy sector accounts for 2.4 million jobs, has doubled its generating capacity since 2004.

The breakdown for the world’s use of renewable energy is:

Biomass
Biomass is any biological material that can be used as fuel. Recently dead plant matter can be used directly for sources of heat or to generate a steam turbine. Furthermore, a plant’s cellulose, sugars, and oils can also be processed to produce liquid fuel and gas, generating electricity or powering vehicles. Even animal waste has enough original plant matter to be converted to an energy source.

Wood
Used by over two billion people to heat homes, cook and process food, wood is the most widely used biomass for energy production worldwide. In many developing countries, wood accounts for up 33% of the country’s total energy usage, and in sub-Saharan Africa, that number is up to 80%. If harvested and used to maximum efficiency, wood is the least expensive, most renewable, least emitting of nearly all the present energy sources. According to the Regional Wood Energy Development Programme in Asia, a UN subset organization, two frequent arguments against the use of wood fuel are:

• Increased Greenhouse Gas Emissions. Wood combustion releases carbon, particulate matter, and other greenhouse gasses into the atmosphere. When the there is an equal ratio between wood harvest and wood re-growth, these emissions are recaptured, producing a zero net gain in emissions.
• Photosynthesis absorbs the carbon, while the water cycle draws the nitrogen oxides back to the soil. It acts as a fertilizer, with wood’s solid waste, ash, also rich in potassium.

Deforestation. Recently the UN found that two thirds of wood used for fuel was harvested from non-forest areas, debunking the theory, that wood fuel was a major source of clearing of forest lands. In fact, it found that the number one reason for deforestation was clearing the land for agriculture and urban areas. The Regional Wood Energy Development Programme in Asia finds that wood use and harvesting leads farmers and landowners to plant and manage trees on their land.

Efficiency. Low efficient wood stoves (used to both heat homes and prepare food) not only have poor energy output per unit of material, but they also emit carbon monoxide, methane, and nitrogen oxides, through incomplete combustion (ie smoldering). Programs to promote efficient stoves in the third world, where wood remains a large source of energy, are sponsored by the UN.

The key to the effective use of wood as an affordable, carbon neutral source of fuel is efficiency and sustainable forestry. Because wood is a renewable resource, available virtually everywhere, it can be a localized fuel source, it has none of impacts and cost of extraction, processing, refining, and transportation, common with most other sources of fuel.

Biofuel
Biofuels are liquid or gas fuels derived from biomass. They are generally used with or to replace fossil fuels in vehicles, energy production, and heating homes. If made solely from biomass, they are both renewable and have the potential to emit no greenhouse gases when there is the proper balance between consumption and regeneration. Biofuels are derived from oils, alcohols, and the methane made through anaerobic decay. Plants from which biofuels most commonly come from include:

• Corn
• Switchgrass
• Hemp
• Sugarcane
• Oil palm

Vegetable Oil and Biodiesel.  Derived from the naturally occurring oils and fats found in most plants, vegetable oil was the original fuel of the diesel engine when it was unveiled at the 1900 World’s Fair. It can be pure plant oil, or used vegetable oil, sourced from restaurant fryers. Regardless of refinement level, it is too viscous to use in diesel engines without additional modifications. To remedy this, biodiesel has the glycerin (its thickening agent) removed, making it more accessible.

In some countries, like Germany, cars are manufactured to run on 100% biodiesel, but in the US, it is often combined with petrodiesel.  With little processing, straight biodiesel has the potential for being a local, low-carbon emission alternative to fossil fuels. It is also relatively safe, renewable, and biodegradable.

Ethanol.  Ethanol is the most used biofuel worldwide. It is made by the fermentation of a plant’s sugars and/or starches to produce combustible alcohols that are later distilled into fuels. In Brazil, cars are retooled to take 100% ethanol, while many countries, including the United States only use 10% ethanol in the standard gasoline sold. This is the most that manufacturers feel can be used in an unmodified engine. Car companies have begun developing fuel-flex vehicles that can run on pure petrogasoline and gas made from 85% ethanol, also known as E85. Ethanol’s energy output per volume unit is 34% of that of gasoline, potentially reducing fuel efficiency.

The burning and production of ethanol does emit varying degrees of greenhouse gases and pollutants.  The combustion of ethanol releases particulate matter and volatile organic compounds into the air that contribute to ozone creation and air pollution. According to the EPA, as much as 1,000 tons of VOCs are released annually from ethanol production plants. Unless, a proper balance is struck between use (emissions) and regeneration (absorption), the lifecycle (from well to wheel) of ethanol produces a significant amount of carbon dioxide. High input crops, such as corn, yield only a .3 increase of energy output for every unit of energy input. Ethanol made from sugar can has the highest energy input to output ratio, at a 1:8 ratio.  Often, fossil fuel supply ethanol’s energy input.

Research is currently being done to increase the energy output by using the cellulose in perennial grasses. Cellulosic ethanol has an 80% higher energy input/output rate than corn based ethanol. However, it is still far more expensive to produce, prohibiting its proliferation.

Biogas
Biogas is produced by the decomposition of biomass. Largely made of methane, it is either trapped or produced by fermentation. Biogas is burned to power an electrical generator, and creates energy with few carbon emissions. Biogas can be used for:

• Electrical Production
• Space and Water Heating
• Compressed and used to power fuel-flex and fuel cell vehicles

Because biogas is derived from animal waste, landfills, and material from energy crops, it has the advantage of sequestering harmful methane gas. It burns with a high level of efficiency can be a local source for energy.

Animal Waste.   While animal waste has been used as a source of heat in some cultures for thousands of years, many countries have begun converting it into fuel. Animal waste produces 19% the world’s methane, and methane makes up 20% of the world’s greenhouse gases.  Largely though the process of decomposition and fermentation, this methane is trapped and used to power a electrical generator. It creates electricity with significantly fewer carbon emission per unit of energy than any other hydrocarbon.

The initial cost of converting waste into energy remains high, but there are many programs either working or underway in China, the United States, and other European and Asian countries. In addition to being a low-carbon, methane sequestering, renewable energy source, animal waste can be produced locally, eliminating the cost and impacts of extraction, processing, refining, and transportation common with most other sources of fuel.

Hydroelectric
Generating over 60% of the world’s renewable energy, hydroelectric power uses to the force of water to generate electricity. Rivers and streams are dammed, with some water released through steep and narrow channels called penstocks, accelerating its power. The water then spins a turbine, generating electricity. The force of the water, and ultimately its amount of potential energy, is dependant and the slope and size of the penstock, and the volume of the reservoir pressing up against the dam. Smaller rivers can be redirected into pipelines that plunge down extremely steep elevations.

Hydroelectric production is tailored to the size and geological surroundings of a river, and its output is easily manipulated to fluctuate according to current power needs. Because of its versatility and simple concept, it can range vastly in size, and electrical generation. While the initial cost of construction is high, the operating cost is minimal due to largely automated systems, and an ever plenty, free generating source, water. 

Environmental Impacts.  Power generated from hydroelectric plants utilizes a free, renewable resource, and produces neither air pollutants nor greenhouse gas emissions. Nevertheless, hydroelectric, specifically large hydro projects, have significant environmental impacts. These impacts include:

1. Habitat Destruction. Hydroelectric power requires damming rivers and consequently flooding upstream areas. In addition to drowning entire ecosystems, the abrupt change from river habitat to a lake environment severely disrupts surviving plant and animal life, including many endangered species. Another consequence is the forced relocation of human communities. The largest hydroelectric dam in the world, the Three Gorges Dam in China, has and is expected to
- Displace nearly 7 million residents by 2020
- Degrade water quality due to flooding older industrial cities without the proper clean up
- Increase soil erosion due to deforestation near the reservoir’s edge
- Threatens the survival of the endangered Siberian Crane and the Yangtze river dolphin, the Baiji, while also disrupting Yangtze sturgeon

2. River Ecology. In addition to flooded areas, the river’s ecology, both upstream and down is effected by hydroelectric dams. Large dams can alter the environment so greatly that the population of many species such as birds, river otters, fish, can severely decline. Some of the specific ecological impacts include:
- Sediment build up in the reservoir, changing the mineral content, visibility and even temperature of the water
- Change in water temperature due to drawing from cold water at the bottom of a reservoir or water warmed by the turbines
- Affects the mobility of aquatic life including migrating fish populations, restricting them from spawning upstream.

3. Greenhouse Gas Emissions from Aerobic Plant Decay. While the generation of power may not emit greenhouse gases, the dammed reservoirs do. Frequently, when areas are flooded for hydroelectric plants, they are not cleared of trees and other plant matter. These decay in an anaerobic environment and releasing large amounts of methane and carbon dioxide. Additionally, the fluctuation of water levels cause more decay as plants colonize the water’s edge and are later drowned once waters rise due to season shifts in rainfall. The emissions of artificially flooded areas, particularly in warmer, tropical environments, emissions can at times be greater than power plants running on fossil fuels. 
 

Solar
Solar power is the conversion of energy from the sun into heat and electricity. Harnessing the sun’s energy is one of humanity’s first efforts to control an energy source. Today, solar power production ranges from high to low tech, personal to industrial, and local to regional. Use of solar technology is limited by the unpredictability and amount of scattered and direct sunlight. For this reason, solar is not appropriate as the exclusive source of energy in all parts of the world, and it requires advanced electrical storage capabilities. In its power production, solar systems emit neither air pollution nor greenhouse gases, however, the production of conversion and storage devises due have environmental impacts.

Solar Thermal.   Solar thermal technology converts solar energy into heat. On the simplest, home level, solar thermal collectors are used to heat swimming pools and water heaters. The most common type of collector is a flat plate that absorbs heat through its black surface. It transfers heat to either water or air. The National Renewable Energy Laboratory estimates that 50% of the hot water used in the U.S. for both commercial and residential could be supplied by solar thermal heating systems.  For more information, visit   Solar Thermal Systems.

Concentrated Solar Thermal Power Plants.   Concentrated thermal systems utilize the sun’s energy to create steam to power a turbine and generate energy with zero greenhouse gas emissions.  With the use of a series of large scale mirrors and other curved reflective materials, the sun’s energy is transferred as heat to oil located in receiver tubes. It can be employed directly to heat water and generate electricity or be stored for later use. Storage allows the plant to generate electricity at night and on overcast days.

For maximum efficiency, concentrated solar thermal (CST) systems require a hot, arid location, as well as a large area of land. This excludes solar thermal for small, local use and may impact wildlife habitat. Currently, there are only a handful of plants around the world. One of the largest plants is located in the Mojave Desert in California. It can generate enough electricity to supply electricity for up to 75,000 homes with an 18% efficiency rate.

Photovoltaics.  Also called a solar cell, a photovoltaic cell converts light into energy through a process known as the photoelectric effect. Photovoltaics are versatile enough to power a single wristwatch or to fuel a solar power station. The world’s largest solar power plant built by the Australian company, Solar Systems, in Victoria, provides power for up to 45,000 homes.

Their versatility makes them attractive for home use to add supplemental power. Most home power systems use batteries to store the electricity. Often connected to the regional electrical grids, homeowner can sell excess electricity or purchase power when they are experiencing a shortfall. Growing 48% every two years since 2002, photovoltaic production is the world’s fastest growing energy source.
The four major commercial types of photovoltaic cells are:

• Multicrystalline silicon
• Monocrystaline silicon
• Ribbon silicon
• Thin-film cadmium telluride

While solar technologies produce no pollution while generating electricity, their production requires the use of lead and mercury. They also use large amount of energy to manipulate their base substances by extreme heat and pressure. Cadmium, in thin film photovolaics, can be toxic to aquatic life, particularly when it builds up in the food chain. 

Recent improvements in efficiency have increase the ratio between energy input for production to energy output. Currently, it takes between 1.5 and 3.5 years for crystalline silicon cells to “payback” its energy usage, and 1-3 years for thin-film cadmium systems to replay theirs.  This constitutes a 90% reduction in greenhouse gas emissions over the lifecycle of photovoltaic versus conventional fossil fuel energy sources.  The lifetime expectancy of photovoltaics are between 25 and 50 years.  For more information, visit   Photovoltaics.

On the Horizon.  As photovoltaic technology develops, its use expands. New concepts include:

• Building integrated systems where photovoltaics are a part of a building’s structure, allowing it to generate some of its own electricity
• Utilizing photovoltaics as auxiliary power for hybrid cars and aircraft

Wind
Wind is converted to electricity by the use of tall wind turbines equipped with blades. Propelling the blades, wind powers the turbine and generates electricity.  Wind energy creates neither air pollution, nor greenhouse gases. The manufacture of wind turbines does use energy in addition to steel, concrete, and aluminum. Tracking the performance of their turbines since 1999, the Danish manufacturer, Vestas, claim that the energy used in production and transport, is “repaid” after 9 months of operation. Wind turbines are 80% recyclable and have a 20-25 year life expectancy.  Wind does not use water to generate electricity, like nearly every other fuel used for electrical generation.

Wind Farms.  To generate electricity for large populations, dozens of wind turbines are connected to the electrical grid. Wind farms require large amounts of open space, not only for the turbines but to avoid any impediment to wind flow. The location must have a near constant flow of wind 10 mph or more. The Horse Hollow Wind Energy Farm in Texas is the largest wind farm in the world. It has 421 turbines and supplies electricity to 230,000 homes per year.

Because of the intermittent nature of wind, some wind plants need to be supplemented by other available means of power, such as a solar energy plant, or a conventional fossil fuel power plant. This can decrease the overall savings in air pollution and greenhouse gas emissions associated with wind power production. Furthermore, wind turbines threaten wildlife, particularly birds and bats. In a report published by the California Energy Commission, the Altamont Pass wind farm kills between 1,766 and 4,721 annually.  However, according to the British Royal Society for the Protection of Birds, appropriately placed wind turbines do not significantly threaten birdlife, particularly compared to the impacts of climate change.

Small Scale Wind Power.  Wind power systems are available for home, business, and farm use. Generally utilizing one generator connected to a battery, these systems can prove emission-free local electricity. They are particularly useful in rural areas, often replacing or supplementing the use of a diesel generator. A single large turbine, rising high above surrounding buildings can be used in urban or suburban areas to power as much as 1,000 local homes and businesses.  For more information, visit    Wind Power.

Geothermal
Geothermal power harnesses the heat trapped inside the earth’s crust to create thermal heat and electricity. Water and steam are the principal conduits drawing the heat up. Water only circulates near the surface in less than 10% of the Earth’s land area,  in the remaining areas water must be injected down into the earth. This method, known as “hot dry rock”, uses the steam coming back up to power turbines for electricity.

Geothermal energy is accessible nearly everywhere, but particularly in “hot spots” where the crust is thin enough to allow for access. These areas are usually near volcanoes, tectonic plate boundaries, and are seismically active. Such availability makes geothermal an option for a localized heat and energy source. It can range in size to accommodate the needs of the nearby population, whether it’s a city or small village.  Types of application include:

Direct Use. The oldest and most direct way of using geothermal heat, it pumps water underground to supply hot water for hot springs, growing crops, and drying lumber, fruit, and vegetables. Direct use can also be employed to heat buildings. In Reykjavik, Iceland, 95% of homes and businesses are heated through the circulation of hot water pumped directly from the ground.62

Ground-Source Heat Pumps. A highly efficient method of heating and cooling homes, ground-source heat pumps use the constant 50 degree temperature 5-10 feet below the surface. Through buried pipes, air is warmed underground then spread circulated throughout the building in the winter. In the summer, hot air is drawn away from the house and is cooled by the use of antifreeze liquid underground, and is then re-circulated. According to the EPA, ground-source heat pumps are 72% more efficient than conventional electric heating and air conditioning systems.

Power Production. Geothermal heat can be converted into electricity by using hot water or steam to power turbines. Less that 1% of the energy in the US is powered by geothermal sources. California supplies about 4% of it's power from its 33 geothermal power plants.
 
While geothermal is a widely available, renewable resource, it is not free of greenhouse gas emissions. Steam from underground carries with it trace amounts of nitrous oxide, hydrogen sulfide, sulfur dioxide, particulate matter, and carbon dioxide. According to the US Department of Energy, these amounts are negligible, and with improved technology, these gases can be re-injected into the earth.
 

On The Horizon

Fuel Cells
While not a fuel, isolated hydrogen is an energy carrier that can provide power either by combustion similar to gasoline in cars, or in conjunction with a fuel-cell. The latter combines hydrogen with oxygen to create energy, while only emitting water vapor. Because it is renewable and releases neither pollution nor greenhouse gases, hydrogen is seen as a potential alternative to fossil fuels in vehicles and in industry.

Because isolated hydrogen does not exist, it must be separated from other compounds. The two most common methods of hydrogen production are:

Steam Reforming. This is the least expensive method and accounts for roughly 95% of hydrogen produced in the US. It is separated from methane found in natural gas. Both the process of separation and the use of natural gas, a fossil fuel, emit greenhouse gases.

Electrolysis. This process splits hydrogen from water, emitting only oxygen. However it is costly and also requires energy.

Hydrogen powered vehicles are currently being developed, with hopes of reducing the market price, making them economically viable.

Waste Heat Recovery
Power stations in the US lose two thirds of the energy it produces as waste heat. Utilizing this heat, either for thermal related uses such as space heating and hot water or to power turbines to generates additional electricity, could reduce fossil fuel consumption by nearly 50%.  It would also raise a plant’s efficiency from 38% to 95%, according to the Washington-based Environmental and Energy Study Institute.

Companies like Recycled Energy Development seek to fit industrial smokestacks, not just power plant stacks, with boilers. These boilers heat a network of water filled tubes that produce steam and power turbines that generate electricity.  One such boiler was fitted to the stacks of a steel plant. In 2004 it generated nearly the same amount of electricity as was generated by all the grid-connected solar collectors around the world. Today, both Holland and Denmark generate almost 50% of their energy from waste heat.

Tidal Power
While utilizing the power of tides and the ocean has been around for thousands of years, it is seen as a potential source of sustainable energy.  Tidal power utilizes the movement of water and tides, usually at the mouth of a bay or estuary, to power a turbine, generating electricity. Tidal power has the advantages of being a free and renewable resource, producing zero emissions, and is more predictable than wind and solar power. Tidal power generation can affect the salinity, sediment, and aquatic life of a tidal zone. The three types of tidal power generation are:

1. Tidal turbines that generate electricity much like wind farms 60-100 feet below the surface of the water
2. Barrage turbines that stretch over the opening of a tidal estuaryTidal fences that act like linked turnstiles.

Cost and developing technology has made electrical generation from tidal power limited to a few locations in Europe, Asia, and the United States. However, there are many proposed sites for new construction in hopes of creating a low-carbon, local power source.

Wave Power

Wave power is generally located in temperate zones with high wave action. There is a variety of different ways to generate electricity. Some examples include:

- Offshore Systems. Some of these systems utilize buoys, capturing the waves’ bobbing motion to power a pump that generates electricity.

- Onshore Systems. Operating at the shoreline, these systems harness the energy in breaking waves.

Wave power is behind tidal power in development and popularity. However, many new power generators are planned in places such as Northern California, Portugal, Scotland, and England.

What Can Be Done?

• Move from central power distribution to local power distribution.
• Conserve energy through better building envelope design, practices and  equipment efficiencies.
• Government tax and credit stimulus for home and business solar panel installation.
• Property tax incentives for efficient building envelopes and solar design.
• Tax incentives for alternative energy development.
• Carbon penalties and tradable credits on a global scale.
• Install waste heat recovery systems on power plant and industrial exhaust stacks.
• Tax incentives to encourage replacement of older equipment with higher efficiency units.