The environmental case for using natural gas as a bridge to a renewable energy future can be summarized as follows. First, natural gas pollutes more than renewable energy but less than oil or coal. Second, the supply of gas has limits, but for at least the next few decades, gas can generate far more electricity than all the renewable energy technologies combined. Third, due to its immediate availability, natural gas can displace many more tons of coal now and in the near future than renewable energy can.
Natural gas pollutes more than renewable energy, but it offers clear environmental advantages over other fuels, especially coal.
Natural Gas and "Conventional" Pollution
All energy technologies, renewable energy not excepted, affect the environment.26 Natural gas pollutes more than renewable energy, but it offers clear environmental advantages over other fuels, especially coal. (See Table 3.) Unlike burning coal or oil, gas combustion releases almost no sulfur which, in the form of airborne sulfur dioxide (SO2), contributes to acid rain and harms human health.27 Coal and oil plants beget masses of solid waste-up to 590 tons per day-while gas plants create none. Natural gas plants also release less waste heat, due to their higher efficiency.
The most significant conventional pollutants released by gas combustion are oxides of nitrogen (NOX) formed by heating air around the point of combustion. Harmful to human health itself, NOX combines with airborne hydrocarbons to form ozone, a pervasive urban scourge. NOX emissions are a precursor of airborne particulate pollution, which causes over 50,000 deaths per year in the United States.28 For example, NOX is responsible for up to one-third of total particulate matter in Los Angeles.29 NOX also contributes to acid rain. Because of their low NOX emissions, some renewable energy technologies can make a greater immediate impact on environmental problems than natural gas plants. Advanced gas combustion technologies also reduce NOX emissions significantly, although the majority of plants in service now use older technologies.