Energy Use and Alternative Energy Sources

Size of each trophic level is proportional to the energy acquired from the level below. Only about 10% of energy is transferred between trophic levels. Very inefficient!

What is Carbon?

• • • • • • Basis of all life forms (as we know them) Can derive ‘energy’ from carbon compounds to ‘do work’ Ex: energy (carbon) from food Ex: energy from fossil fuels (‘hydrocarbons’ CH) Law: Energy is never created nor destroyed, it can only be converted to different forms Ex: when we burn fossil fuels, we break the chemical bonds in hydrocarbons (CH) and release carbon in different forms that are greenhouse gases (CO2, CH4)

Central Questions

• • • • • What are the patterns of energy use around the globe and in the US?

What is the connection between energy use and carbon dioxide (CO2)?

What are the different sources of energy?

What are the pros and cons of each energy source?

Which sources are renewable and which are non-renewable?

Energy Demand

• • • Industrialized nations rely on vast quantities of energy to power their economies and produce goods and services. As populations increase and citizens demand better standards of living, global energy use will continue to rise Developing nations account for a growing share of total world demand

Increasing Demand for Energy

This projection assumes that current laws and policies remain unchanged. Many factors (economic growth rates, oil prices, and intensity of energy use) could alter these projections.

Global Energy Use

Fossil fuels (coal, oil, natural gas) Fossil fuels account for 80% global energy use Fossil fuels account for 86% US energy use

Energy Consumption in the United States

What human activity uses the most energy?

• • • • Industrial activity Residential and commercial consumption (heating, hot water heating, appliances) Generation of Electric Power Transportation

US primary energy source is oil (petroleum)

Consumption, Production, and Imports of Petroleum Products

Oil Production Predictions

Oil production might peak around 2010.

Our fossil fuel culture

• • Today most of the world's energy is derived from fossil fuels, which are non-renewable resources (available only in limited supply). In contrast, many alternative sources of energy are renewable resources consume them).

(their supplies are refreshed faster than humans – Examples: wind, solar, hydropower

Challenges in changing to renewable sources Changing to a new resource type involves: 1. Discovery (e.g. of new mineral deposit) and developing a new technology. 2. Altering systems that produce, process, and distribute these resources. – Ex: mining, processing, refining, and delivery represent billions of dollars in complex infrastructure Energy facilities typically operate for 30 - 50 years and cannot change overnight. Retiring them prematurely can be costly.

Example: off-shore oil drilling

• Supplies/personnel transported to/from platform • Sand removal/oil extraction • Oil tankers or pipelines to transport oil •Refining Offshore oil drilling platform, Gulf of Mexico

Thinking about supply

• • • • • Energy resources are central to human existence

When will we run out of oil?

Declining fossil fuel supply drives innovation Best oil deposits are exploited first, followed by lower quality sources as demand rises. As demand increases, supply decreases, the price rises: – reduces demand – incentive to develop lower-quality or costly sources, and improve technologies for obtaining more – spurs development of alternatives

Pump offering bio-based fuels, Santa Fe, New Mexico

Today, high oil prices are driving investments into fuel production from plant sources

Stock and flow of non-renewable sources • • • Stock field) - amount of material in a certain deposit or reservoir that can be recovered with today's technology (example: the total quantity of oil in a Flow - rate at which new material is added to the stock (inflow) or removed from the stock (outflow). Net flow rate whether the stock grows, shrinks, or remains constant.

- (inflow minus outflow) determines

Estimating Natural Gas Stock

Fossil Fuels

• • • • Coal, oil, natural gas Energy (carbon) stored in plant tissues by photosynthesis millions of years ago Ancient plants and animals died, were buried in sediments over time Earth's heat and compression from the weight of overlying sediment/rock eventually turned these deposits into coal, oil, and natural gas.

Coal

• • • • • The first fossil fuel exploited by humans A carbon-rich rock formed from buried plants in ancient forests or swamps. Plants are converted to peat —a loose, brown, organically rich soil As more rock layers press down on the buried deposits, geothermal energy heats the peat and reduces its oxygen and hydrogen content, converting it to coal As materials go through this process, known as thermal maturation , their energy content by weight increases.

Coal

• • • Brown coal (lignite) – younger coal, low energy content, (more needed relative to higher-grade coals in order to generate the same amount of power) Sub-bituminous coal and bituminous coal - dark black, most important coal grade for energy production Anthracite coals - gray, very high energy content. Most accessible reserves in the US have been exhausted.

Environmental Impacts of Coal Mining

• Underground mines – Hazardous – Mine collapse – Coal dust and methane gas (commonly found with coal) raise risk of explosions.

– Worldwide, several thousand miners on average die each year in coal mining-related accidents.

Environmental Impacts of Coal Mining

Strip mines – removing soils and overburden to extract shallow coal – leave permanent scars on the landscape. – mountaintop removal coal seams : land is clear-cut and leveled to expose

Environmental Impacts of Coal Mining

• Acid drainage (underground and strip mines) – Coal contains sulfur, – when rain or groundwater comes in contact with coal, it produces sulfuric acid.

– can pollute surrounding areas long after the mines are shut down.

– Many underground mines are below the water table and flood often; contaminated water flows out of mines, lowering the pH of lakes, rivers, and streams and leaching toxic heavy metals from the ground.

– Major source of pollution in WV and PA

Environmental Impacts of Coal Combustion

• • • • produces significant amounts of atmospheric pollution and greenhouse gas emissions sulfate and nitrogen emissions contribute to acid deposition, regional haze, and smog. produces mercury technologies to ‘clean’ coal and re-capture carbon lost to atmosphere under development, but currently expensive

Oil and Natural Gas

• • • from ancient sea beds marine organisms die, settle to the seafloor in anaerobic environments (no oxygen) where they are preserved, buried by sediments and heated to form hydrocarbons Hydrocarbons – organic compounds consisting of carbon and hydrogen atoms

1. Drilling

Predicting the location, type, and quality of hydrocarbon systems is critical oil and gas development.

2. Processing

• • • Oil Refineries distill crude oil to produce different fuels about 1/2 barrel of oil (42 gallons) converted to gasoline. also yields kerosene, jet fuel, diesel fuel, home heating oil, and lubricants in varying proportions • • Natural Gas may require processing to remove undesirable gases and other impurities.

In some cases this process can yield useful byproducts, such as sulfur, which is sold and used to generate fertilizer and for a wide range of other industrial purposes.

• • • • • • •

3. Environmental Effects

drilling pads, access roads disturbs ecosystems contamination of aquifers from drilling Offshore drilling can cause spills, leaks that pollute ocean waters Transporting oil and gas subject to spills. Oil produces lower levels of CO2, sulfur dioxide, nitrogen oxide, and mercury than coal Natural gas combustion emits lower amounts of nitrogen oxide and CO2 and virtually no sulfur dioxide or mercury.

Drilling has moved into environmentally sensitive regions, public lands that are home to rare and endangered species

Nuclear Power

• • • generates 6% total global energy consumption produced by enhancing the radioactive decay of fissile materials —elements whose atoms can be split, releases energy. 0.7 % of natural uranium consists of the isotope uranium-235 - radioactive, fissile and is the most widely-used fuel in standard nuclear reactors.

Nuclear Power

• • • • • companies mine uranium ore and, by uranium enrichment , increase the concentration of U-235 to 4% Enriched uranium formed into fuel rods, placed inside a nuclear reactor and bombarded by neutrons. U-235 atoms split into two or more smaller atoms releases large amounts of energy also releases excess neutrons, which split other U 235 atoms, causing a nuclear fission chain reaction .

• • Operators control rate of fission using control rods and moderators that absorb excess neutrons and by adjusting the reactor temperature, which affects the reaction rate. Energy generated in the reactor heats water, steam, or other fluid, which is used to produce steam that drives electric turbines

Problems with Nuclear Power

US >100 nuclear power reactors, but no new reactors ordered since 1978 – Shoreham plant closed 1989 without ever generating electric power Major concern is safety – Nuclear accidents: • Three Mile Island, 1979 • Chernobyl, 1986; estimated ~4000 eventual deaths, many more times that in health problems – Can cause radiation exposure, causes cancer

Problems with Nuclear Power Storage of radioactive waste • • • • Spent fuel rods remain highly radioactive for thousands of years Delay of nuclear waste storage facility, Yucca Mountain, NV Concerns that waste will not be isolated from the environment Many nuclear plants store waste onsite Main tunnel shaft descends >5 miles into Yucca Mountain.

Problems with Nuclear Power

3. Facilitates development of nuclear weapons – Technology that enriches uranium to 4% U-235 can be used to enrich uranium to 90% U-235 or higher – Used to make nuclear weapons.

– Nuclear power produces plutonium, also used in weapons

Renewable Energy Sources

Biomass Energy

• • • • Most is low-tech in developing countries (includes wood-burning stoves) Inefficient and high impact (produces air pollution) Burning plants and plant-derived material (agricultural crops and wastes, trees, forestry wastes), animal wastes and municipal solid waste.

Newer, more efficient, cleaner biomass technologies . . .

Biomass

• • Ethanol fermented from corn and other crops Used as a gasoline additive (~10%) • • Biodiesel From vegetable oil, soybeans, or other crops can be used in place of diesel (and is cleaner) • • • • Problems: requires a lot of energy to make!

requires fuel to make fertilizer, run farm machines, transport fuel no significant net energy savings over gasoline and diesel growing corn is water-intensive and removes significant levels of nutrients from soil Heavy reliance on these sources could divert crops from the food supply

Cellulosic Ethanol

• • • • Cellulose – indigestible plant material Carbon-rich (produces more energy than same amount of corn) Cellulose is tough and must be broken down before it can be fermented Examples: switchgrass, corn stalks

Hydropower and Ocean Energy • • • • • generates about 17% of world electricity power of flowing water used to generate electricity River dams, placing turbines ocean areas with significant tides and currents Low pollution emissions

Limited future : only a few good sites available for development (Africa, Asia, and Latin America) Falling water flows through pipes ( penstocks electricity ), then turns turbine blades, spins generator, produces Negative environmental impacts of dams: – Kill plants, displacing animals – Alter river flow, stream beds, river banks; – Modify water temperature, oxygen and nutrients – Reduce transport of nutrients and sediments below dams – Block migration of fish

Wind Energy

• • • • • • Wind turbines directly harness wind power and convert it to electricity. generates < 0.5% world's electricity supply but high growth potential best locations are areas with consistently high winds where large turbines can be situated can be located on land and in shallow offshore waters LI Offshore Wind Power Project

Wind Energy

• • • • Pros and cons Do not produce air pollutants or greenhouse gases May impact birds and bats Can be visually disruptive Others . . .

Geothermal Energy

• • • • Energy companies can drill a mile or more to tap underground reserves of steam/hot water, drives electric turbines to generate electricity renewable because it draws from unlimited heat of the Earth's interior virtually no atmospheric pollutants or greenhouse gas emissions. US resources are located west of the Mississippi River

U.S. geothermal resources (est. temperature at 6 km depth) Unreliable for eastern US because high electricity demand and the local geology does not provide sufficiently high subsurface temperatures.

Solar Energy

Photovoltaic (PV) systems - sunlight hits PV cells, material produces electrons creating an electric current.

- can be used in wide range of climates and latitudes - residential systems are now common - needs improvement with efficiency Solar concentrating systems -focus sunlight with mirrors to heat a liquid that boils water, creating steam to turn a turbine that generates electricity – best for power plants in areas with strong sunlight and clear skies

Hydrogen Power Fuel of the Future?

• • • • Hydrogen stripped from fossil fuels (CH) or by splitting water (H20) using electricity or heat Costs: process uses lots of electricity or fuel energy; deriving H from fossil fuels emits CO2 Benefits: portable, storable, can be used in highly efficient combustion engines or fuel cells, low emissions. hydrogen fuel cells to power cars

Necessity is the mother of invention.