Natural gas supports green efforts
It’s true that natural gas is a fossil fuel, and as a fossil fuel its combustion involves the release of carbon dioxide, a "greenhouse gas" which is believed by most scientists to contribute to global climate change. Yet natural gas also can play a major role in the reduction of global greenhouse gas emissions. How is this possible?
Replacement for Heavier Emitters
Natural gas is increasingly being chosen to replace other fossil fuels which produce much higher levels of greenhouse gas emissions. It is generally estimated that combustion of natural gas reduces these emissions by 25% to 50%, depending on the previous fuel characteristics and the combustion technology used. There’s no dispute that replacing a coal-fired boiler with a natural gas equivalent amount of generation will reduce not only carbon emissions, but will virtually eliminate sulfur dioxide and particulate emissions and greatly reduce nitrogen oxides.
Renewable energy sources for electric generation are important tools for reducing greenhouse gases. But for them to be practical, they need a backup that will operate when they can’t. Solar and wind are just two examples of promising renewable technologies that can’t be relied upon 24 hours a day, 365 days a year. Natural gas can. In its backup role, it makes it practical to use the renewable approaches for electric generation.
Enabling New Technologies
Many newer technologies use natural gas more efficiently than ever. Examples include condensing boilers or furnaces that wring that last amount of energy from the fuel. Another example is combined-cycle generating plants. These use natural gas-fired turbines to spin generators, then use the turbine exhaust to generate steam to spin an additional steam turbine-generator, boosting the plant efficiency to well over 50%.
Natural gas is the natural choice also for combined heat and power (CHP) systems for industry, which supply both site electric energy and steam or hot water for plant processes, or even to supply absorption cooling. A CHP plant can achieve a total energy utilization of over 75%, compared with 50% or less with separate electric and thermal systems. Thus they work to extract more energy from fuel combustion and help reduce emissions.
Another area where natural gas can reduce greenhouse gas emissions is in replacing combustion of gasoline or diesel fuel in motor vehicles. Millions of vehicles around the world have moved to using natural gas as a primary motor fuel. This also has the effect of reducing total greenhouse gas emissions.
Existing Pathway for Renewable Gas Fuels
The existing natural gas distribution network is also the logical mechanism for gas fuels produced in renewable forms. Example might be fuels developed from biogas from municipal landfill gas or digester gas products from wastewater treatment plants, agricultural wastes, or wastes from food processing industries. All of these streams can be upgraded to be interchangeable with pipeline natural gas, thus can be efficiently transported from the point of production to the end user. Therefore, not only does natural gas support other renewable technologies, but the industry collection and distribution structure simplifies getting green fuels to market. Many U.S. and Canadian utilities are studying this possibility.
A Strong and Steady Bridge
The time may come when most of our energy comes from renewable sources. It is obvious we’re not there yet. Clean and abundant natural gas, wisely used, can be depended upon until that full-renewable future is here.
This article originally appeared in the Gas Technology Summer 2016 issue.