energy paths in the ecosphere

ENERGY PATHS in the ECOSPHERE

TREN 1F90Sustainability,

Environment and Tourism

ENERGY

• What is it?

What is it?

BASIC DEFINITIONS AND LAWS

ENERGY

• Defined as:

THE CAPACITY TO DO WORK

ENERGY

POTENTIAL ENERGY:• Stored energy in all its forms• When released, it can do work

Examples:• Coal, oil, gas• Foodstuffs

• Rivers and streams above sea level

ENERGY

KINETIC ENERGY:• Energy in motion

• Energy possessed by moving objects

Examples:• Falling leaf

• Diving kingfisher• Waterfall

• POTENTIAL ENERGY

ENERGY

• KINETIC ENERGY

↕ INTERCONVERTIBLE ↕

Laws of Thermodynamics

All energy follows basic laws of thermodynamics, central to the

understanding of ecological processes and environmental issues.

Laws of Thermodynamics

FIRST LAW:Energy can be neither created nor destroyed – it can only change form.

Laws of Thermodynamics

SECOND LAW:During transformations,

energy goes from a concentrated form to a less concentrated form.

Less concentrated energy is dissipated in the form of heat.

Laws of Thermodynamics

HEATis the inevitable

byproductof energy

transformations

Laws of Thermodynamics

HEATCOAL

↓Burned to generate electricity

↓Transmission of electricity

through wires↓

Lighting of bulb filament↓

Light energy

Laws of Thermodynamics

HEAT• May be defined

as the kinetic energy associated with the random motion of atoms and molecules

Laws of Thermodynamics

HEAT• Useful in

concentrated form (e.g., internal combustion engine), but generally dissipated to the environment in a dilute form

ENERGY CONCEPTS

ENERGY QUALITY• The ability of a given form of energy to

perform useful work• Also called energy density• High quality energy sources are

concentrated (large energy content per unit of measure)

ENERGY CONCEPTS

ENERGY QUALITY:

All energy sources are degraded in quality with use, to a less useful form (heat)

ENERGY CONCEPTS

ENERGY QUALITY:

All energy sources are degraded in quality with use, to a less useful form (heat)

↓

Wise energy use requires careful matching of energy source with needs

ENERGY CONCEPTS

Matching of energy source with needs:

Use low quality energy for low-grade needs• E.g., passive solar radiation for heating living spaces

Use high quality energy for high-grade needs• E.g., electricity to weld steel in industrial arc-welding

ENERGY DENSITY / QUALITY

• VERY HIGH

• HIGH

• MODERATE

• LOW

• Electricity, nuclear fission

• Natural gas, gasoline, coal, concentrated sunlight

• Geothermal, biomass, tar sands, oil shale

• Wind, ambient heat

ENERGY EFFICIENCY

• The ratio of useful energy output to the total energy input.

ENERGY EFFICIENCY

Internal combustion engine in car

Energy in 1 litre of gas: 6500 kcal

Energy output from engineconsuming 1 litre of gas 1300 kcal

Energy efficiency: 1300 = 0.20 = 20% 6500

ENERGY EFFICIENCY

Incandescent light bulb

Every light bulb consuming 100 w of electricity radiates 5 w of visible light energy and 95 w of heat

↓ Incandescent light bulbs are about 95%

efficient as heaters, but only 5% efficient as light sources!

NET ENERGY

Total energy available in a given source

minus

the energy used to find, concentrate, and deliver energy to the user

NET ENERGYTar sand oil extraction process

Tar sands mined in open pits;Hot water and steam used to liberate oil

↓ Energy costs of extraction may be

up to 80-90% of energy recovered↓

Net value of extracted oil is only 10-20% of the oil’s true energy content

NET ENERGY

Food productionin industrial nations

High yield agriculture requires large energy subsidy (fossil fuels for machinery and fertilizer production)

↓ Though total crop yields per hectare

increased, the ratio of food energy produced to fuel energy used actually decreased through the mid- to late 20th century

Ethanol fuel production

• Ethanol (a renewable alternative fuel) is produced primarily from corn

• Corn ethanol requires fossil fuel inputs for production (industrial agriculture)

• Net efficiency of ethanol was quite low prior to 1990s-> research shows it takes more fossil fuel energy to produce than the energy it yields

• Artificially high price of corn due to fuel use causes increased global food costs and contributes to famine and food shortages

Ethanol fuel production

• nitrogen fertilizers• irrigation pumps• gas + diesel fuels• machinery (including

energy costs of manufacture)

• drying of harvested corn• seeds (includes all inputs

required to produce the seeds)

• phosphorus fertilizers• herbicides

- Pimental et al. (1990) in Carrol et al: Agroecology

Main fossil fuel inputs in US corn production are:

Ethanol fuel production

• Efficiency may have improved in past 20 years:

1991: 24%1998: 36%2001: 67%

• Shapouri (2004): attributed to technological advances in farming and manufacturing

Source: Shapouri, Hosein. 2004. The 2001 net energy balance of corn-ethanol. www.usda.gov/oce/reports/energy/net_energy_balance.pdf

Ethanol fuel production

• Results vigorously disputed by some authorities

“About 30 percent more fossil energy is required to produce a gallon of ethanol than you actually get out in ethanol”

– David Pimental, 2006, cited in Ratigan, Dylan: Ethanol as gas replacement: Hope or hype? MSNBC On The Money, 23 May 2006 (http://www.msnbc.msn.com/id/12934470/ )

Hope or hype? MSNBC On The Money, 23 May 2006 (http://www.msnbc.msn.com/id/12934470/ )

Ethanol fuel production

• Ethanol subsidies called ‘catastrophically idiotic’ (Drum, 2012)

• Corn ethanol “worse than gasoline" for environment• Corporate handout gave $0.45/gallon to ethanol

producers and fuel blenders; cost taxpayers $6 billion in 2011

• Subsidy expired at end of 2011• Replaced by revised 2007 Renewable Fuel Standard

legislation, under the Energy Independence and Security Act (EISA)

Ethanol fuel production

• RFS program: U.S. govt. mandates that >37% of the 2011-12 corn crop be converted to fuel ethanol and blended with the gasoline that powers U.S. cars

• Profits go to agribusiness (corn production) and big oil (fuel blenders). 10% of farms (largest) collected 74 per cent of all subsidies between 1995 and 2010.

• upshot: ethanol subsidies didn't go away after all; they are just hidden a bit better!

- Drum, Kevin. 2012. Ethanol Subsidies: Not Gone, Just Hidden a Little Better. Mother Jones