In response to your online news article on “Report suggests Weald shale oil viable”, I write to comment on some potential risks from hydraulic fracturing.
In the US, chemicals added to fracking fluids have included zirconium, chromium, antimony and titanium salts to enhance the effectiveness of gelling agents, together with benzyne, toluene, and ethanol, some of which are known carcinogens.
People working or living near wells were exposed to air emissions comprising harmful volatile organic compounds where waste fluid was left in open air pits to evaporate, and to dust with high levels of respirable crystalline silica during the fracturing process. Chemicals within the fracturing fluid affected the skin, eyes and other sensory organs together with the nervous system, immune system, kidneys and cardiovascular system, whilst airborne chemicals affected the brain, liver, and the endocrine system of glands including reproductive elements.
In the UK, while there is no generic list of approved chemicals for use in hydraulic fracturing, the Environment Agency has set out that the only additives permitted should be polyacrylamide, hydrochloric acid and a biocide.
Nonetheless, the process has raised environmental and human health concerns including: seismic activity resulting in loss of water resources, release of fugitive gas emissions, and damage to property; surface contamination from spills of fluids from storage tanks; contamination of groundwater by gas or dissolved minerals moving through other rocks into aquifers; leaks from production wells into neighbouring rock formations and aquifers; freshwater depletion; risks to air quality from escaping methane; the migration of hydraulic fracturing chemicals to the surface; and the mishandling of waste and wastewater.
While shale gas is cleaner than coal, as it does not contain sulphur and emits 50% less carbon dioxide, fugitive emissions can seriously undermine any carbon benefits from its use due to the high global warming potential of methane; as little as 4–5% leakage will cancel out the gain. These fugitive emissions, together with other emissions in the region, may together form ozone or other photochemical oxidants which may have adverse effects on human and animal health and may damage vegetation.
When fracturing is completed and the well is de-pressurised, between 25% and 75% of the injected fluid flows back into the well and returns to the surface over a period of weeks or months. This returning spent flow-back fluid is toxic and non-biodegradable, is often saline and has a high mineral content, including high levels of sodium, potassium, magnesium, zinc, lead, chloride, bromide, iron, and naturally occurring radioactive minerals since shale tends to contain more uranium than other types of rock. Most of the remaining volume of injected fluid is retained in the ground whilst some may return to the surface via other pathways where it may poison grazing livestock. Hydraulic fracturing for shale gas in the countryside poses a risk to cattle, sheep and food safety, and in the US there have been links between fracturing operations and farm animals suffering from reproductive and neurological problems, respiratory failure, deformity, and stillbirths.
Micro-organisms, including bacteria, can exist in deep shale formations need to be removed for health and safety reasons, and the toxicity of fracking wastewater means that it requires treatment prior to its careful disposal. But, if the treatment process includes the use of chlorine-based disinfectants, these may combine with bromide and dissolved organic matter within the wastewater to produce trihalomethanes many of which are considered to be carcinogenic.
So, given all of the above, perhaps our dash for gas should slow down?
Robert Jackson, firstname.lastname@example.org