What are the main environmental impacts of shale gas extraction?
The main environmental impacts cited in relation to shale gas extraction include water contamination and water extraction, greenhouse gas emissions, and impacts on landscapes and local communities.
Given the use of chemicals in fracking fluids, water contamination, or pollution of water supplies from leaking methane, have been raised as concerns.
In the US, there is some anecdotal evidence of water polluted by methane; but, as yet, it is unclear if this results from natural causes, or from shale gas extraction.
In the UK, the risk of water supply contamination from fracking is deemed relatively low, according to the latest Royal Society and Royal Academy of Engineering assessment, given the distance between aquifers (typically within 300 metres of the surface) and the depth at which fracking occurs (usually at depths of two or more kilometres).
Even if contaminants could reach water supplies through fractures, certain pressure conditions are required to enable them to flow – and are unlikely to be met. Experts suggest water contamination is more likely to result from spillages on the ground, or cracks in wells allowing leakage – risks faced by all oil and gas extraction. Preventative action can include ensuring strong and well-cased wells (so called ‘well-integrity’), alongside careful review and allocation of permits by the relevant regulatory body where fluids with pollutants are to be pumped into rock formations that store groundwater.
Shale gas extraction may also require greater water abstraction, given its need for larger volumes of water than those required for conventional gas extraction. Whilst this is likely to constitute a fairly modest amount at a national level, water extraction could have a more significant impact on supplies at a local level. Both water extraction and waste water disposal require permits or a licence from the Environment Agency and can be monitored accordingly.
A number of environmental groups raise concerns that shale gas extraction could undermine the UK’s climate change commitments if it replaces the use of cleaner, renewable technologies. While shale gas releases less greenhouse gas emissions when combusted than coal, some leakage of powerful greenhouse gases like methane is possible when shale gas is extracted, and so careful monitoring and checks are required.
Finally, concerns have been raised regarding the impact of shale gas on communities and landscapes, in terms of potential noise impacts, damage to the natural environment and space required for drilling sites.
Typically, shale gas sites require several acres for infrastructure, including containment ponds, storage tanks and compressor stations, for example. Population densities and environmental protection may mean that shale gas extraction is not socially or environmentally feasible in some areas.
