First published June 2010, last updated August 2013
With the tide (thankfully) starting to turn against coal fired power generation, renewable energy is finding favor, as is electricity generated via the combustion of natural gas.
So, is natural gas green?
What is natural gas?
Natural gas consists mainly of methane and is often found associated with oil fields, coal seams and other fossil fuel deposits; but also may exist on its own in huge underground reservoirs.
Like oil, natural gas is often obtained through targeted drilling, however at times it’s a by-product of oil drilling. Not so long ago, gas associated with oil extraction was simply burned off (flaring), but now it’s increasingly captured for use.
In drilling operations where natural gas is targeted, hydraulic fracturing may also be employed once a well is sunk to the required depth to boost the flow of gas. The fracture is formed by pumping special fluid into the base of the well. This process is also known as “fracking”.
Natural gas processing
While natural gas will burn without refining; in order to make it suitable for residential, automotive and industrial use, it must be processed – and that in itself is an energy intensive task. However, the by-products of the process produces useful substances such as propane and butane.
Natural gas emissions
Natural gas is often referred to as the “cleanest” of the fossil fuels, including so-called “clean coal“. According to NaturalGas.org, the burning of natural gas emits almost 30 percent less carbon dioxide than oil, and just under 45 percent less carbon dioxide than coal.
However, this isn’t the full story – burning gas may create lower emissions, but the entire production process can be emissions intensive. A major issue is fugitive emissions from gas that escapes during extraction. In a medium case scenario, life-cycle emissions per joule of energy derived from fracked gas could potentially be similar to those derived from coal.
While the combustion of natural gas also results in lower levels of nitrogen oxides (which contribute to acid rain), sulfur, carbon monoxide, and virtually no particulate matter; it’s this lack of particulate matter compared to coal combustion that may mean a shift to gas could accelerate a rise in global average temperatures. Confused? I don’t blame you. Read more about this aspect here.
CNG (Compressed Natural Gas) and automobiles
CNG is becoming an increasingly popular alternate fuel for cars. NaturalGas.org says the EPA has found vehicles using compressed natural gas have reductions in carbon monoxide emissions of up to 97 percent, carbon dioxide emission reductions of 25 percent and nitrogen oxide emission reductions of up to 60 percent.
Natural gas environmental implications
Natural gas certainly sounds like a panacea for all society’s energy woes in some ways – but it is a fossil fuel and unlike solar power and like oil, it is a limited resource. As such, a massive switch to natural gas would see many of the problems associated with oil production still occur.
The fugitive emissions risk aside, extraction of natural gas can be an environmentally damaging process. The process of “fracking” involves toxic waste and can contaminate the ground water with the fluids and the gas itself. In some parts of the world, the amount of natural gas that has leaked into aquifers through nearby fracking activities is enough to burn – I’ve seen photos of people lighting their faucets.
Fracking operations can also draw heavily on groundwater and are believed to be connected with some earthquake incidents.
The hydraulic fluids themselves can be somewhat of a black box, with some in the industry refusing to reveal the components of the fluids involved. The documentary “Gasland” claims some fluids contain known carcinogens and heavy metals.
Gas produced from fracking operations is “wet” and needs to be separated from the water and fracking fluid when it comes to the surface and this wastewater can also be highly toxic.
In some countries, land owners may own the surface area of their properties, but not the resources that lay beneath. Some are forced to allow gas drilling operations on their property and there’s little recourse if the company involved doesn’t restore the land to what it was before. The same problems can occur on government or public land; as with all forms of mining.
As mentioned, another environmental issue is the methane itself. While methane does burn quite cleanly, it is a very potent greenhouse gas – around 60 times the Greenhouse Warming Potential (GWP) of carbon dioxide. Methane leaks from extraction and during transportation just add to an already greenhouse gas overburdened atmosphere.
A great deal of energy is required to process natural gas and while some by-products of that process are useful, others are just toxic waste, such as hydrogen sulfide and carbonyl sulphide
While natural gas may be “greener” than all other fossil fuels (and that is certainly debatable as more information becomes available), it’s certainly not green – it’s the lesser of the fossil fuel sourced energy evils.
Natural gas provides an interim source of energy while we wean ourselves off coal and oil and perhaps as a baseload source of energy when needed; but there’s a danger of natural gas being seen as a replacement for renewable energy for our future power needs.
Natural gas will not solve the climate change issue – it should be seen only as part of the solution and a stepping stone to even cleaner energy technology.