From Ecopedia

Overview

Introduced in nineteenth century, bicycles (otherwise known as bikes or cycles) are human-powered, pedal-driven, single-tracked two- to three-wheeler vehicles used for transportation purposes. Being an environment-friendly vehicle, a bicycle is highly efficient in both mechanical as well as biological terms. On an average, the energy spent in bike riding almost equals the energy required in walking.^[1]

Bicycles are typically made of aluminum, steel, and plastic parts, though carbon fiber is also an upcoming material for lightweight racing bicycles. Depending on the type of riding environment and use, bicycles can be constructed differently for purposes of mountain or off-road riding, racing, cruising, and commuting.

Environmental Benefits

Energy Efficiency

Bicycles are considered to be extremely energy efficient, as bicycles demand only 35 calories of energy (energy used per passenger-mile) as against 1,860 spent in car driving.^[2]

As the bicycles are powered by food-fueled humans, energy consumption compared to machine-powered vehicles is extremely less. In fact, compared to walking, bicycles are considered to be five times more efficient in terms of energy consumption.^[3]

Unlike automobiles, which run on fossil fuels, bicycles are powered by humans, which gain their energy from renewable energy sources such as food.^[4] Moreover increased bicycle riding could reduce the use of global warming causing automobiles, which are heavy in emissions of greenhouse gases.

Carbon Dioxide Reduction

Bicycle riding is considered to be the quickest and most efficient way to minimize environmentally-hazardous carbon dioxide (CO2) emissions.^[5]

Environment-conscious people all over the world are promoting increased bicycle use as the bicycles are regarded as an efficient means to curb air pollution, especially in highly-polluted urban areas.

As bicycles occupy little space, require no gasoline and turn out no harmful waste, many environmental hazards such atmospheric pollution, global warming and smog could be easily averted.^[6]

Besides controlling carbon emissions, bicycles also effectively check the emissions of other environmentally-harmful pollutants such as nitrogen oxide (NOx), which causes atmospheric contamination.^[7]

References

1. ↑ http://en.wikipedia.org/wiki/Bicycle
2. ↑ http://www.treehugger.com/files/2006/07/world_most_ener.php
3. ↑ http://www.exploratorium.edu/cycling/humanpower1.html
4. ↑ http://www.exploratorium.edu/cycling/humanpower1.html
5. ↑ http://www.alternative-energy-news.info/bicycle-environmental-hero/
6. ↑ http://bicycling.suite101.com/article.cfm/cycling_and_the_environment
7. ↑ http://www.environment.ucf.edu/bikepath/