Green Portfolio

The current portfolio of renewable generation for the Company’s “Think Green” Program is derived from three major fuel sources: wind power, landfill gas generation plants, and low impact hydroelectric facilities. The mix changes annually.

Wind Power

Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth’s surface, and rotation of the earth. Wind flow patterns are modified by the earth’s terrain, bodies of water, and vegetation. Humans use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity.
The terms wind energy or wind power describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity.
So how do wind turbines make electricity? Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.

Landfill Gas Generation

Every day, millions of tons of refuse is delivered to landfill sites throughout the country. As a result of the natural process of bacterial decomposition of organic material contained in landfills, methane gas is created. Several factors influence the quantity and quality of gas that a landfill generates. The important factors determining the components of this gas include the type of the waste buried in the landfill, and the length of time it has been buried, the types of organic compounds in the waste, and surrounding climate. Both temperature and moisture level influence quantity and quality of the methane gas.

There are significant environmental advantages to collecting and burning landfill gas. This process will reduce emissions of organic compounds that would otherwise be released from the landfill. In fact, in 1996 the EPA began to require certain landfills above a specified size to collect landfill gas and burn the gas. A “large” landfill is a term of art defined as having a design capacity of at least 2.5 million metric tons and 2.5 million cubic meters. Typically, landfills meet this requirement by burning the gas in a flare or by utilizing the gas as an energy source to generate electricity.

Landfill gas is considered a medium Btu gas, with a heating value of 350 to 600 Btu per cubic foot. This is approximately one-half of the Btu level of natural gas. Landfill gas is an extremely reliable source of energy because it is generated 24 hours a day, 365 days a year. In using the gas from landfills to produce energy, we can significantly reduce the emission of methane from these sites and avoid the need to use fossil fuels to generate electricity.

Utilizing the methane gas created by a landfill is an effective means of reducing overall greenhouse gas emissions. The key to these projects is that they utilize an otherwise wasted fuel source, and displaces the use of other fuel sources such as fossil fuels and nuclear energy. This displacement of fossil fuels is an environmental benefit, the magnitude of which would depend on the actual amount of electricity generated or the landfill gas used.

Landfill gas energy projects involve collecting and combusting landfill gas. The process of combustion destroys organic compounds. During the combustion, these organic compounds chemically react with oxygen in the pressure of heat, breaking apart to form water vapor, carbon dioxide, and other, less volatile, compounds. Combusting the gas in a reciprocating engine, gas turbine, or boiler to generate energy also reduces pollution associated with the extraction and use of fossil fuels to produce the same amount of energy.

According to E.P.A. estimates, if a 3 MW landfill gas electricity project starts up at a landfill with previously uncontrolled landfill gas, the project would have a direct methane reduction of approximately 6000 tons per year. (125,000 tons of carbon dioxide equivalents and a fossil fuel displacement of approximately 700 tons of methane per year (15,000 tons of CO2 each year). The combined emissions reduction of 6,700 tons of methane per year (140,000 tons of CO2 per year) would be equivalent to any of the following annual environmental benefits for 2007:

  • Removing emissions equivalent to 28,000 cars
  • Planting 38,000 acres of forest
  • Offsetting the use of 630 railroad cars of coal

Hydro-Electric Power

Hydroelectric power is the oldest form of renewable energy. Hydroelectric power or “hydro power” as it is called involves the electricity generated by the force of moving water as it flows through a turbine. The water is flowing from a higher elevation to a lower elevation.

These turbines are connected to electrical generators, which produce the power. Hydro systems are typically very efficient, approaching 90%, and involve no emissions during the generation process. There are no smokestacks and therefore there are no emissions from this form electric generation. The energy generated is essentially derived from the sun, and therefore is inherently renewable. Energy from the sun causes evaporation from the lakes and oceans and it returns to the earth by precipitation.

Hydro-electric power plants capture the energy released by water falling through a vertical distance, and transform this energy into useful electricity. The rotation of the water turbines is transferred to a generator which produces electricity. The volume of the water and the distance of the vertical drop are critical factors in determining the quantity of electricity generated.

Hydro-electric Power has a long history in comparison to other forms of electric generation. There are reports that hydro-generated energy was used to power a clock, built in approximately 250 BC. Water-driven power has been used in grain and saw mills, as well as a host of other applications. The first reported use of moving water to produce electricity was a waterwheel on the Fox River in Wisconsin in 1882. This event took place only two years after Thomas Edison invented the incandescent light bulb. The first of many hydro electric power plants at Niagara Falls was completed shortly thereafter. At the time it was viewed as one of the marvels of modern technology. In 1901, Buffalo, New York, hosted the Pan American Exposition and people from all over the world visited the city. At night, to the amazement of all, many buildings were fully illuminated. People were in awe of the technology and Buffalo was referred to as the “City of Light”. This was all energized, of course, by the hydro facilities at nearby Niagara Falls.

Hydro Power grew in importance throughout the twentieth century but the country’s voracious appetite for energy forced planners to turn to other generation types since suitable hydro generation is strictly limited to sites with the necessary resources. This resulted in the construction of many fossil fuel fired plants.


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