Expert Scientific Panel on Unconventional Oil and Gas report

Chapter 6: The environmental and societal challenges

Introduction

6.1 The extraction of unconventional oil & gas is ultimately an industrial process and, as with most, if not all, industrial processes, there will be some environmental impacts. There are a number of areas where the environment in the vicinity of operations may be impacted by unconventional oil & gas operations, including the surface and subsurface water environment, the air environment and the geological environment around wells. Globally, extraction and use of unconventional hydrocarbons may impact on the atmospheric greenhouse gas balance.

6.2 Additionally, as with any industrial development, there may be both positive and negative social impacts associated with the unconventional hydrocarbon industry. The social and public health impact of development is dependent on the demographics and economics of the area in which it is being developed.

6.3 This chapter reviews a suite of potential problems. However, it should be noted that the existence of a potential problem does not mean that it will occur. There are numerous regulations and assessments in place to reduce, or eliminate, adverse occurrences.

6.4 In the case of societal impacts, early and continued consultation should aim to minimise adverse impacts and maximise local enhancement (see chapter 8 for more details).

6.5 In this Chapter, the Expert Scientific Panel has reviewed the following main environmental challenges associated with unconventional oil & gas operations:

• Impacts on the water environment;
  (i) Water usage and associated pressures;
  (ii) Management of hydraulic fracturing fluids;
  (iii) Management of wastewater.
• Naturally Occurring Radioactive Materials ( NORM);
• Seismic activity;
• Noise from site activity and increased traffic;
• Light pollution;
• Landscaping and visual impact;
• Air emissions and air quality;
  (i) Direct Air Emissions
  (ii) Indirect changes to air quality
  (iii) Compatibility with Scottish Government greenhouse gas ( GHG) reduction targets;
• Baseline characterisation, post production remediation issues and reinstatement of assets.

6.6 The descriptions of these environmental challenges should be read in conjunction with Chapter 7, which outlines the regulatory system in place to mitigate these challenges.

6.7 Additionally, the Expert Scientific Panel has considered the following societal challenges (adapted from the Australian Council of Learned Academies, Cook et al (2013)):

• population growth and a changed demographic profile;
• upwards and downwards pressures on property values;
• concerns about community health, safety and wellbeing.

Impacts on the water environment

6.8 Unconventional hydrocarbon extraction can both produce and consume water. In considering the environmental challenges of unconventional hydrocarbon extraction to water quality and resource integrity, the following are key areas of focus ( AEA, 2012a):

• borehole drilling;
• upstream acquisition of water;
• chemical mixing of the fracturing fluid;
• injection of the fluid into the formation;
• the production and management of flowback and produced water; and
• the ultimate treatment and disposal of produced and hydraulic fracturing wastewater.
• 6.9 If inappropriately controlled, unconventional gas operations can impact groundwater and surface water quality, with key impacts being:
• aquifer cross-contamination due to poor borehole construction;
• pollution from unplanned release of gas, drilling fluid or fracturing fluid into other parts of the water environment;
• surface spills from storage tanks and lagoons, from fluids and chemicals used in drilling and fracturing or of produced or flowback waters;
• pollution from unauthorised disposal of liquid or solid waste containing potentially polluting substances;
• abstraction of quantities of water that could lead to an unacceptable impact on the environment; and
• contamination that could arise from the construction and removal of infrastructure, including that which could link between different boreholes across the drilling area.

Water usage and associated pressures

6.10 The water requirements for shale gas and coal bed methane operations vary significantly due to the fundamentally different ways in which these processes are undertaken. Coal bed methane extraction involves essentially a dewatering process, whereas shale gas operations require water for the hydraulic fracturing process. This results in some similar, and some divergent, environmental impacts.

6.11 Sourcing of water is an important factor to consider. In Scotland, the vast majority of water is normally supplied from surface sources, although the industry may still wish to abstract groundwater for logistical reasons.

6.12 There are a number of potential environmental impacts associated with surface water and groundwater abstraction. If not subject to control, there could be impacts on river flows, groundwater levels or other water features such as lochs or wetlands. In turn, reduced water level could have adverse hydro-ecological impacts. Further, surface water withdrawal may affect recharge to groundwater. Lowering of the water table through abstraction of groundwater could encourage the intrusion of saline water into non-saline groundwater.

6.13 However, as detailed in Chapter 7, the abstraction of water is tightly regulated in Scotland to prevent or minimise unacceptable impacts to the wider water environment, including other water users and water dependent ecosystems.

Hydroecological functioning

6.14 Linking infrastructure ( e.g. pipes to transport extractive products to a processing plant) may bisect important biodiversity corridors which improve biodiversity in fragmented landscapes. These corridors increase animal movement between patches, and facilitate pollination and seed dispersal (Tewksbury et al, 2002).

6.15 The burying of infrastructure may remove a surface barrier. However, if the infrastructure is protected by material of different hydraulic conductivity, this network may function as a preferential flow pathway or acts as a barrier to flow. That response could induce changes or surface flows or groundwater levels, which could have an adverse environmental impact.

Management of hydraulic fracturing fluids

6.16 To date, the only company in the UK to have carried out hydraulic fracturing as part of shale gas operations is Cuadrilla Ltd. Hydraulic fracturing was undertaken for coal bed methane using only water and sand at Airth in the mid-1990s ( DECC, 2010) and by Scottish Water to increase borehole yields for public water supplies, for example at Laggan Bridge and Alligin (Cobbing et al, 2007).

6.17 Substances added to fracturing fluids can be found in a number of different products and applications, see for example Table 3.3 in Pearson et al (2012), which provides an overview of the substances and their other common uses. Cuadrilla Ltd (2014) indicate that their fracturing fluids will comprise mostly water and sand (99.95%) with one or more of the following chemical additives:

• polyacrylamide friction reducers (0.04%);
• sodium chloride (0.00005%);
• hydrochloric acid;
• biocide, for when the water provided from the local supplier needs to be further purified and to kill bacteria that can produce hydrogen sulphide gas.

6.18 Only polyacrylamide has been used by the company to date (Cuadrilla Ltd, 2014). Substances added to the fracturing fluids are subject to the CAR licensing requirements ( Chapter 7 provides further detail on this licensing regime).

6.19 Surface spills of fracturing fluid may pose a greater contamination risk than hydraulic fracturing itself (Mair et al, 2012). Additive chemicals will generally be delivered and stored in concentrated form before being diluted to low concentrations with water to form fracturing fluid, which may then be stored in large tanks on site.

6.20 To mitigate spills, established best practices are generally incorporated in the regulatory consents. These include using non-hazardous chemicals wherever possible, storing them away from surface waters and important aquifers, ensuring sites are protected with impermeable liners and ensuring all stores of hazardous liquids are double-bunded as a precaution against leaks (Mair et al, 2012).

6.21 These practices will be beneficial for mitigating spillage of other chemicals that are stored on site, for example gas treatment chemicals which are used to 'sweeten' the gas as part of the clean-up before input to a national pipeline network. The regulations in place to mitigate these risks are described in Chapter 7.

Management of wastewater

6.22 Flowback waters and produced waters may contain fracturing/drilling fluids, natural inorganic and organic substances, and naturally occurring radioactive materials ( NORM). SEPA analysed water abstracted from exploratory drilling at DART Energy's coal bed methane exploration site at Airth. The water contained NORM, chloride, alkalinity (as calcium carbonate), iron, aluminium, nickel, zinc, lead and a number of organic compounds (benzene, xylene, naphthalene) and had electrical conductivity (a measure of dissolved charged substances), consistent with water from coal beds that are higher in dissolved material ( SEPA, 2013).

6.23 The Environment Agency analysed flowback water from exploratory drilling and fracturing by Cuadrilla at Preese Hall, Lancashire, and found substances typical of water coming from shale rock including sodium, chloride, bromide, iron, zinc, arsenic, lead, magnesium and chromium as well as NORM (Environment Agency, 2011).

6.24 The change in composition of flowback and produced water (in a hydraulically fractured site) from their pre-extraction composition means that, under existing regulations, both would now be regarded as waste and may require treatment prior to discharge back into the environment. Thus, unless there is illegal disposal of fluid or an undetected or mitigated leak, the environmental impacts of disposing of produced or flowback waters should be minimal given existing regulation in Scotland.

Naturally Occurring Radioactive Materials ( NORM)

6.25 Naturally Occurring Radioactive Materials ( NORM) are ubiquitous in the environment and are present in many geological formations, including oil- and gas-bearing rock strata. Produced water abstracted from coal seams may contain NORM, as may flowback fluids that are generated during hydraulic fracturing. NORM are also likely to be present as insoluble sediments and scales that adhere to the surface of gas or water process vessels and pipework.

6.26 NORM abundance depends on the geochemistry of the reservoir and the volume of water circulating through that reservoir. Shale beds already contain water (the formation water) but the volumes are less than formation water in offshore hydrocarbon reservoirs. Therefore, the concentration of NORM from shale bed formation water is expected to be much less than with the very large volumes of water associated with offshore oil production.

6.27 If NORM is above levels where regulation is required, contaminated vessels and pipework must be taken to specialist clean-up facilities, where the radioactive scale is removed, before disposal in a UK landfill regulated by one of the UK environment agencies. Flowback and produced waters containing NORM must also be treated. Thus, disposal of solid or liquid waste containing NORM could increase the risk of radiation exposure, but the regulatory framework, described in Chapter 7, ensures that this risk is minimised by keeping levels within acceptable limits.

Seismic activity

6.28 Felt seismicity ( i.e. that can be felt by people at the surface as opposed to microseismicity from an individual fracture) has been observed with both hydraulic fracturing to extract unconventional hydrocarbons and during disposal of waste fluids into sub-surface geological strata (Mair et al, 2012). However, it is worth noting that the latter practice is not allowed in Scotland under the EU Water Framework Directive.

6.29 As described in Chapter 5, hydraulic fracturing of the Bowland Shale caused two seismic events in the Blackpool area of 2.3 M _L and 1.5 M _L (Green et al, 2012). This led to the temporary moratorium on hydraulic fracturing introduced by the UK Government from November 2011 to June 2012.

6.30 Data compiled from American sources suggests the Blackpool hydraulic fracturing event was unusually large, and induced-seismicity associated with hydraulic fracturing is typically less than 0.75 M _L (Davies and Foulger, 2012). Natural events of this size occur hundreds of times each year and are felt by very few individuals (Mair et al, 2012).

6.31 However, with the recognition that activity associated with hydraulic fracturing could generate felt seismicity, the Department of Energy and Climate Change has proposed that operations be halted and remedial action implemented if events of magnitude 0.5 M _L or above are detected (Green et al, 2012). The DECC 'traffic light' monitoring system is discussed in Chapter 7.

6.32 Whether 0.5 M _L is an appropriate level or not is subject to debate, with higher limits ( e.g. 0.75M _L) advocated, based on large data sets documenting typical induced seismicity elsewhere ( e.g. Davies and Foulger, 2012; Westaway and Younger, 2014). These limits are viewed as pragmatic substitutes for true predictive understanding of local stress processes in the UK subsurface.

6.33 Better practice could be to use ground surface velocities rather than source magnitude (Westaway and Younger, 2014), to consider seismic limits in relation to natural seismicity based on historical instrumental records, and to understand if there is any cumulative effect of small tremors leading to larger events. The need for continued monitoring of the seismic effects is a reasonable expectation, both during borehole drilling and hydraulic fracturing and, if multiple hydraulic fracturing boreholes are operated, for up to 30 years after hydraulic fracturing was undertaken. The present evidence, from many decades of UK coal mining and deep drilling onshore, is that seismic effects are expected to be small in magnitude.

6.34 Establishing acceptable limits of seismicity prior to initiating hydraulic fracturing may also encourage developers to adopt practices to mitigate induced seismicity e.g. minimising pressure changes at depth (Zoback, 2012). The limits set are likely to be conservative if compared to natural seismicity. For example, the Blackpool area is of low natural seismicity and these atypical induced seismic events were within the range of natural seismicity recorded in this area, 2.5 - 4.4 M _L.

6.35 In Scotland, natural (background) earthquake activity almost all occurs north of the central belt, or south of the Southern Uplands ( Figure 6.1). There is a concentration of natural seismicity on the west side of Scotland due to uplift of the land surface since the last glaciation, and effects due to movements of tectonic plates. The coal mining induced seismicity is mainly associated with the Midlothian and Clackmannan coalfields. Most of these events occur at shallow depths and are small, not exceeding magnitudes of around 3 M _L. Natural earthquake activity tends to occur deeper in the crust where the rocks are much stronger.

6.36 Oil and gas extraction (fluid withdrawal) from a reservoir can potentially induce felt seismic events. These events are rare relative to the large number of oil and gas fields around the world ( NRC, 2012). It is unlikely that seismicity would be experienced with the extraction of CBM, which does not generally require hydraulic fracturing. In CBM extraction, other than the initial drill fluid, there is no introduction of additional liquid capable of lubricating planes under stress that can move and cause seismicity.

Noise from site activity and increased traffic

6.37 Environmental noise from unconventional gas sites has the potential to impact on local residents and wildlife ( AEA, 2012a). For a shale gas site consisting of 10 wells, it is estimated that 800 to 2,500 days of activity may be needed to undertake ground works, road construction and the hydraulic fracturing process ( AEA, 2012a). These activities may generate levels of noise in locations that had previously experienced relatively low background noise levels.

6.38 This may be more noticeable in rural areas than on a brownfield or industry fringe site. For example, the noise limit for Cuadrilla in Balcombe is 42 dB (decibels) at night and weekends, and 55 dB from 7.30am to 6.30pm weekdays for all operations. For comparison a normal conversation at 1 metre distance is between 60 and 65 dB.

6.39 During well-drilling activities, hydraulic fracturing and production pump and/or engine operations are likely to be the primary sources of noise ( AEA, 2012a). Drilling occurs 24 hours a day, typically for four weeks per well. However, drilling can be a relatively quiet activity (such that rig hands do not need ear guards) and diesel engines can be housed in acoustically insulated boxes. Further, these estimates of activity time come from hydraulic fracturing for shale gas extraction. Given the shallower drilling depths required for coal bed methane and the significantly reduced need for imported water, it is likely this will require less activity and therefore generate less noise and/or operate for a shorter period.

Figure 6.1. Recorded seismicity in Scotland. Instrumentally recorded earthquakes of magnitudes greater than 2 from 1970 to present are in red. The lower detection threshold of 2 reflects the fact that unless specialised networks are used, it is not possible to distinguish lower magnitude seismicity from background noise such as passing vehicles etc. Historical earthquakes of magnitudes greater than 3 from 1382 to 1970 are in yellow. Historical earthquake information is obtained from documents and reports that detail the effects of what people felt during past earthquakes. This allows locations and magnitudes to be estimated by comparing this information with similar reports for recent earthquakes. Earthquakes associated with coal mining activity with magnitudes of -1 and above are in green. The low detection thresholds for coal mining earthquakes were only possible because various temporary networks were deployed. In Scotland, these networks were mainly in Midlothian, so it is quite possible that there were small mining induced earthquakes in other coalfields, e.g. Fife, Lanark, of which the BGS have no record.

6.40 Flaring may also be a noise source ( AEA, 2012a). However, increased noise is generally associated with increased gas pressure and so flaring noise associated with unconventional hydrocarbons should be less than that associated with refinery activity or gas compression facility vent relief valves. These lift as a safety mechanism when the pressure builds up.

Light pollution

6.41 Light pollution may be caused by flaring or by lighting for safe working. This is required particularly during the drilling phase, which occurs around the clock until complete. Truck movements may also contribute to light pollution. Planned flaring and truck movements could be scheduled to primarily take place during daylight hours to reduce light pollution. Spotlights that shed light only on the working area can be used to minimise light pollution.

Landscaping and Visual Impact

6.42 Features such as soil bunds (created from the excavated site soil) represent landscaping undertaken as part of site preparation. These are common to many other construction projects and is generally considered to have a low risk of intrusive visual impact ( AEA, 2012a). However, the use of drilling rigs, where multiple pads are developed in a given area, is considered to have a moderate risk of significant visual effects, especially in residential areas ( AEA, 2012a).

6.43 To expand, for shale gas operations, the initial drilling requires a rig with a mast typically 30 m in height. Once initial drilling is complete, this rig is replaced with a work-over rig (typically with a mast 22 m high), which remains in place for several weeks during hydraulic fracturing (Cuadrilla Resources, 2014). These rigs are temporary structures and the drillhole is then capped with an extraction point and protective cage approximately 3 m high. The extraction configuration may influence visual impact: it is not yet apparent if drilling and workover for shale gas would be on multiple individual pads (as has been established with coal bed methane at Airth) or if tens of deviated bores for shale gas would be operated from one large pad, which could be operational for 20 or 30 years.

Air emissions and air quality

6.44 Changes to air quality as a result of unconventional hydrocarbon extraction may be direct, from site emissions, or indirect as a result of a changing fuel mix.

Direct Air Emissions:

6.45 Methane and higher hydrocarbons are potent greenhouse gases (Highwood et al, 1999) and their release into the atmosphere is not desirable. These hydrocarbon emissions and others, such as volatile organic compounds ( VOCs) and combustion products from site activities, can also impact on local air quality. In Scotland, such emissions currently occur from some landfill sites, peatlands and oil and gas processing and handling infrastructure.

6.46 Direct air emissions arising from unintentional leaks, venting and flaring are termed 'fugitive emissions'. With unconventional hydrocarbon extraction, fugitive emissions are predominantly released from flowback and produced water and leaking infrastructure. The composition of fugitive gas depends on the source geology. Coal bed methane typically contains a higher proportion of methane than in shale gas, and fugitive emissions can contain a wide range of VOCs (Public Health England, 2013; Bunch et al, 2014; Zielinska et al, 2010) _.

6.47 If released in high concentrations (generally making up greater that 5% of the mix) in the presence of an ignition source, methane mixed with air can be flammable or explosive. Thus during hydrocarbon extraction, careful monitoring of wellhead areas with automated sensors fitted with alarms is common practice, being required by the Health and Safety Executive ( HSE), since accumulation of potentially explosive mixtures of methane and air are a mortal hazard to the workforce. If substantial methane releases are detected, alarms are sounded and the site is evacuated to a muster point at a safe distance from the wellhead. Any such incident is a major setback to operations, with fugitive emissions representing a loss of valuable product. This is in addition to a duty of care to protect the workforce from hazardous working environments.

6.48 Unconventional gas comprises a mixture of methane and higher hydrocarbons, such as ethane and propane ( e.g. in coal bed methane, Moore 2012) which are generally separated in order to isolate the methane. These fractions may be an important constituent of the Scottish unconventional shale gas reserve and, if they are of economic value, could be separated on-site or the product piped to a nearby processing plant or natural gas mains e.g. in Scotland at Grangemouth or Mossmorran. Either approach to separation presents opportunities for leakage of material to the environment and so these processes require to be monitored, especially given the uncertainty over emission levels.

6.49 Other gas emissions will arise through the use of vehicles and operation of equipment, such as compressor engines and on-site refining. These can emit oxides of nitrogen, which like methane and volatile organic compounds can generate ozone. Ozone is considered by the European Commission to be a 'risk of potentially high significance' due to its adverse effect on respiratory health when present at elevated concentrations ( AEA, 2012a) _. The European Commission consider that 'emissions from numerous well developments in a local area or wider region could have a potentially significant effect on air quality' due to the cumulative effects from intensity of development ( AEA, 2012a).

6.50 The environmental impact of planned and fugitive emissions can be reduced by appropriate technological adjustments, effective management, and by monitoring to identify when remedial action is required. Best available techniques ( BAT) for reducing greenhouse gas emissions from shale gas exploration have been documented, but these have not been formally accepted by the European Commission into a BAT Reference Document ( BREF) ( AEA, 2012a,b). These techniques include 'Reduced Emissions Completion,' also known as 'Green Completions', and represent approaches to minimise emissions that may already have been implemented to maintain safe working practice.

6.51 These approaches reduce emissions in two ways:

• through capture and harvest e.g. separation of gas from high pressure flowback water in a sealed system, which should be in place in sites with good husbandry;
• by conversion to a less potent greenhouse gas. Methane has a global warming potential 28 times greater than carbon dioxide when compared over 100 years and with no climate feedbacks (Myre et al. 2013). Thus flaring or a similar oxidation process to convert the methane to CO ₂ reduces the global warming impact.

6.52 However, the need to implement this technology may be site-specific. For example, in the USA, around 87% of the natural gas wells fractured in coal bed methane formations were not considered candidates for green completions as low pressure in these systems made technological installation unnecessary ( US EPA, 2012).

6.53 In the United States, the level of fugitive emissions from shale gas operations has been estimated to range from 0.42 - 7.9 % of total gas production ( US EPA, 2013; Allen et al, 2013; Tollefson, 2012; Howarth et al, 2011). Recent airborne measurements of a methane flux from a 2800 km ² area in Pennsylvania indicated that seven well pads in the drilling phase accounted for 4 - 30% of this flux. The size of the emission is 2 to 3 orders of magnitude greater than US Environmental Protection Agency estimates for this operational phase (Caulton et al, 2014).

6.54 However, the latter higher estimate of 7.9% of total production has been challenged on some of the assumptions underpinning the analysis, such as estimates that 100% of the gas is vented as opposed to flared, and green completions are not used ( e.g. Cathles, et al, 2012, Howarth, et al, 2012). Such venting would not be permitted except in emergencies in the UK and high emissions associated with venting are therefore unlikely. Additionally, as gas condensate is commercially valuable, most companies would prefer to separate and sell the gas condensates than flare them, thereby reducing the total greenhouse gas emitted from any flare.

6.55 The contrasts in geology and source material in Scotland are such that fugitive emission profiles from the US cannot be assumed to represent the Scottish situation. Additionally, the Scottish regulatory regime that controls monitoring and imposes remedial action differs from the US (discussed further in Chapter 7). A framework for quantifying fugitive emissions and attributing source is in early stages in England (National Physical Laboratories, 2013) but does not yet exist for Scotland.

Indirect changes to air quality

6.56 It is difficult to say with any certainty whether extraction and exploitation of unconventional gases could result in changes to air quality on a national scale. If gas is available at sufficiently low prices, this could encourage greater uptake of gas for energy generation and domestic heating and conversion of vehicles from liquid hydrocarbons to liquid petroleum gas and electric power sources. Increased use of gas as a fuel could result in lower emissions of sulphur dioxide, oxides of nitrogen and particulate matter both from point sources ( e.g. power stations) and locally ( e.g. transport). Further, a reduction in atmospheric loading of air pollutants through use of unconventional hydrocarbons could represent an environmental benefit.

6.57 Fuel-switching could have local and transboundary impacts on air quality; however this would ultimately be dependent on costs of fuel and uptake of alternative technologies (which are not guaranteed). Also, due to the transboundary nature of air pollution, secondary PM2.5 produced elsewhere accounts for 30-40% of the total modelled background PM2.5 concentrations in Scotland (Air Quality Consultants, 2012) so it may require a European-wide conversion to reduce air pollutant concentrations.

6.58 The future scenarios for fuel-switching are uncertain and unpredictable at this time so it is not possible to quantify potential impacts on air quality (either positive or negative).

Compatibility with Scottish Government GHG reduction targets

6.59 The Climate Change (Scotland) Act 2009 has set ambitious targets for reducing greenhouse gas ( GHG) emissions, with an interim 42% reduction target for 2020 and an 80% reduction target for 2050. The impact of unconventional gas extraction on meeting these targets needs to be assessed as follows:

• their overall contribution to Scottish emissions;
• the comparison of unconventional gases against other fuel types;
• the implications of developing and using unconventional gases over time.

6.60 Scottish emissions are accounted for on a national accounting basis within Europe. A robust EU Emissions Trading System, an EU emission target and an effective international agreement on capping emissions are also highly relevant to discussion of unconventional gas in this context.

6.61 The emissions from unconventional gas fall into both the traded sector and the non-traded sector. The traded sector is from large point sources and power plants of 50 MW or greater. If used in plants to generate electricity or heat, then unconventional gas will simply displace existing North Sea or imported gas, with minimal net effect.

6.62 The rate of decrease in traded sector emissions is controlled by the European emissions cap, and cannot be altered by an individual European Member States. Over-achieving by Scotland, will simply allow more emissions to be purchased in the market by a second Member State, to continue their current operations.

6.63 Emissions counted within the untraded sector include those associated with development of the site(s), operations of equipment on site, and fugitive emissions. These will all be counted into a Scottish inventory and will increase and maintain Scottish direct emissions now, and into the future, if more gas is consumed.

6.64 Unconventional hydrocarbon extraction will maintain and continue Scottish emissions above an alternative scenario of importing more gas - because ownership of all this group of emissions during extraction lies locally with the state where the extraction occurs. Importing methane gas brings less liability than home-produced gas. This is consistent with the current position on production and export of other hydrocarbons.

6.65 The effects of using unconventional gas on global emissions and atmospheric CO ₂ concentration will depend on whether this gas is displacing another fuel, or whether this is an additional source. While unconventional gases used in Scotland will impact on the domestic GHG inventory, if that gas is alternatively exported, then Scotland's emissions and GHG targets will not be affected. Again this is consistent with the current position on production and export of other hydrocarbons.

6.66 Although subject to debate (Cathles et al, 2011; Howarth et al, 2012), current thinking is that the carbon footprint of shale gas emissions will be comparable to conventional gas sources and lower than coal if used for electricity generation (Mackay and Stone, 2013). Unabated gas emits 350 g CO ₂ per kWh of electricity generated, whereas unabated "old" coal emits about 900 g CO ₂ per kWh electricity generated, which is considerably more.

6.67 However, the position is complex. For example, as a result of the greater use of indigenous shale gas in the United States for electricity production, there has been increased use of North American coal in Europe. This has made it more economically favourable to use exported North American coal in power stations. This global energy substitution further increases the carbon footprint of coal. While the use of gas may bring a benefit through replacing coal use, there is a longer term risk that investment in gas, particularly gas power generation, will replace investment in lower-carbon renewable technologies.

6.68 DECC (Mackay and Stone, 2013) considers that "without global climate policies (of the sort already advocated by the UK) new fossil fuel exploitation is likely to lead to an increase in cumulative GHG emissions and the risk of climate change". The report recommends that Government should discuss with regulators appropriate mandatory requirements to require emission reduction techniques at each stage.

6.69 All of these present significant challenges to the Scottish Government in ensuring management of unconventional gas production and use, remains consistent with its ambitions on climate change and specifically carbon reductions. Life cycle assessments of the carbon footprint of unconventional hydrocarbon extraction are becoming more common ( e.g. Skone et al. 2011, Forester and Jonathon, 2012). However, these are largely from outside the UK and, given the differences in resource storage, accessibility, extraction, processing and geographical reach of infrastructure, it suggests the findings from geographically distinct areas are unlikely to be directly transferable.

6.70 This contrasts with surface developments, such as windfarm infrastructure, where the Scottish Government commissioned the development of a carbon calculator for payback time (Smith et al 2011), which is considered valuable internationally ( e.g. SEIA 2011).

6.71 To address the lack of knowledge of the carbon footprint of the unconventional hydrocarbon industry, the Scottish Government has commissioned a desk-based study of estimated GHG emissions from exploration to the point of fuel production, which could be used to identify practises to minimise GHG emissions, such as the non-disturbance of Scotland's precious peat resources (an important European terrestrial carbon store and on-going sink for atmospheric CO ₂) ( e.g. Scottish Parliament Information Centre ( SPICe), 2012).

6.72 However, unless there is comparison of the emissions that will be saved by the change in energy generation from other fossil fuel or renewable sources, which in turn requires their complete carbon footprint to be calculated, the net loss or gain in greenhouse gas emissions that unconventional hydrocarbons will offer cannot be ascertained.

6.73 In summary on GHG:

• the decarbonisation benefits of unconventional hydrocarbons from Scotland are not clear or guaranteed;
• Scottish emissions during appraisal and production of unconventional gas may increase;
• benefits from the use of unconventional hydrocarbons in power plant for electricity generation depends on displacing coal in Scotland, which could amount to millions of tonnes CO ₂ per year, but depends on many other market factors;
• benefits in use of unconventional gas in gas powered electricity are negligible;
• use in fuel switching of domestic customers from coal or oil could reduce Scottish GHG emissions by a small amount;
• continuing gas usage in domestic heat and cooking is better than unabated coal- or gas-fuelled electricity, but domestic combustion needs to be phased out on the Scottish decarbonisation pathway;
• using Scottish unconventional hydrocarbons as feedstock for petrochemicals may be the minimal GHG impact;
• additional greenhouse gases from fossil carbon will be emitted to atmosphere globally, by extraction of Scottish unconventional hydrocarbons;
• developing and operating CCS is one way to extend the lifetime of use for fossil hydrocarbons.

Baseline characterisation, post-production remediation issues and reinstatement of assets

6.74 There have been relatively few reports of groundwater contamination when compared to the vast majority of operations in North America, with many reports demonstrating that high groundwater methane levels appear to be unrelated to recent hydraulic fracturing ( e.g. Molofsky et al. 2011). However, recent chemical and isotopic studies appear to show that, in some instances, groundwater contamination may have resulted from recent gas exploitation (Jackson et al. 2013).

6.75 Additional monitoring prior to and during activity could help to provide assurance over the contamination of groundwater. The frequency and density of monitoring could be guided by a number of factors including:

• the number and locations of gas extraction boreholes;
• whether fracturing is required;
• the number and proximity of sensitive receptors (water users, water features) and potential pathways (groundwater, faulting, mineworkings).

6.76 The UK Onshore Operators Group ( UKOOG, the trade body for onshore oil & gas operators) has developed industry best practice guidelines for decommissioning boreholes ( OGUK, 2012).

6.77 The longevity of casing and cement in abandoned boreholes must be considered, as even correctly sealed boreholes may eventually allow leakage (Miyazaki, 2009). However, this will occur only if there is a powerful hydraulic head in the aquifer, and this is unlikely in spent, unconventional hydrocarbon reservoirs with under-pressured conditions. Inspection and monitoring can also ensure that decommissioned unconventional gas boreholes and seals/plugs retain their integrity.

6.78 Other pathways for leakage may also exist, such as through faulting, mine workings or other boreholes which may be some distance from the wellhead. However, this requires artesian groundwater pressures. The likelihood of this threat could be assessed by hydrogeologists and the post-production monitoring plans could be developed, based on assessment of risk that is sensitive to hydrogeological controls.

6.79 Examples of good practice can be drawn from other industrial sectors, such as landfills and coal mining. Abandonment monitoring at surface coal mining sites generally continues for five years, extendable to ten years for higher risk sites (Younger and Sapsford 2004). The Landfill (Scotland) Regulations 2003 do not state explicitly a minimum duration for aftercare monitoring of groundwater and gas, but they do require a minimum frequency of 6 monthly monitoring. Currently there is no specific legislation for monitoring once a PEDL, CAR or PPC licence is surrendered. This regulatory gap in minimising and eliminating future environmental impact is discussed further in Chapter 7.

Risk of pollution

6.80 There may be different environmental impacts depending on whether waste mitigation is undertaken at the point of production (local containment) or at a central location (pollution may be possible en route, but some chemical storage would be restricted to one site). However, alongside monitoring and mitigation approaches, pollution risk can be minimised by planning to reduce the likelihood.

Societal challenges and impacts:

6.81 The social impact of development is dependent on the proximity, population density, socio-demographics and economics of the development area. As part of the consultation process, dialogue will take place between industry and local communities to discuss these social impacts. This dialogue should enable communities, operators and regulators to develop strategies to mitigate negative impacts and enhance positive impacts (Joao et al. 2011). The social impact can be managed to some extent by the design of the development and its operation ( e.g. local procurement of labour). Issues around effective communication of risk and dialogue with affected publics are discussed further in Chapter 8.

Population growth and demographic profile

6.82 An influx of industry-related workers can have positive effects (for example, increased demand in local shops or restaurants), or negative effects (for example, increasing demand for local medical provision, or socio-demographic differences between the workforce and the local community) (Cook et al 2013). The consequences of rapid population growth and demographic change, both long-term and short-term, are known from examples from the extractive industry developments worldwide. For instance, a detailed study of a single county in Colorado that had experienced a 39% increase in oil and gas drilling from 2000-2007 found significant increase in demand for private and rented housing, but also increased traffic congestion, crime and drug violations (Witter et al, 2008).

Impact on house prices and insurance

6.83 In the US areas where shale gas has been developed, house prices have gone up as well as down (Muehlenbachs, et al 2014). It is too early to tell if UK/Scottish unconventional gas industry would influence house prices. UK mortgage and estate agent industry blogs report a 20 -30% drop in house prices in areas near Cuadrilla's shale gas site in the UK (Property and Land Information blog), though others state that "it is too early to tell". Other industry blogs have suggested that unconventional gas developments could open up a new buy-to-let market (Faith, 2013).

6.84 The UK Association of British Insurers has stated that damage caused by either explosion or earthquake would be covered by house insurance and that insurers do not at present perceive there to be a risk of seismic activity due to fracking that could damage properties (Insley, 2012). This is in accordance with the scientific statements on the very low likelihood of felt seismicity from fracking (Mair et al, 2012; Cook et al 2013).

Health impacts of unconventional oil & gas development

6.85 Health impacts from any new industry include occupational health issues for workers, public health impacts for local or regional populations, and the health impacts of any wider effects such as the effect of increased greenhouse gas or particulate emissions (Adgate et al 2014). These impacts can include:

• Known or predictable hazards for workers, the immediate local resident and transient population and the wider general population arising from technology and processes used in the exploration and exploitation phases;
• Hazards associated with the ongoing support infrastructures, waste disposal, drainage, increased transport, accidents, heavy goods traffic emissions;
• The impacts arising from climate change induced by increased atmospheric CO ₂ concentrations, due to extending fossil fuel use for longer than might otherwise have occurred if zero/low carbon emission renewable sources substituted fossil fuels.

6.86 Media coverage of the possible health impacts of unconventional oil and gas developments has been increasing. Health impacts on humans (and animals) have been alleged by communities living near to shale gas and CBM sites in the USA and Australia (Adgate et al. 2014; Cook et al 2013). At the present time, many of these reports are 'anecdotal' in the sense that the observations have not been corroborated by objective study using factual evidence or properly quantified.

6.87 A second problem with many of the reported impacts is that the data gathered have not been compared against baseline statistics describing the population's health before the shale gas or CBM developments. This is partly because, in most cases, such baseline public health studies do not exist. Lack of adequate baseline data on local populations is a fundamental problem in trying to assess the evidence of adverse health impacts associated with the use of these technologies. In Scotland and the rest of the UK, this could represent an opportunity to ensure that this fundamental problem is addressed before the chance to conduct adequately robust epidemiological studies is lost (c.f. Kovats et al, 2014; Law et al, 2014).

6.88 Risk (in the context of the science of Risk Assessment) is described as the combination of the hazard posed by a given event and the likelihood (statistical probability) that the event will occur. For example, the risk of fracking-induced felt seismicity causing damage to properties or people at the surface is considered to be very low: very few earthquakes have been triggered by fracking for shale gas (3-5 documented cases of felt seismicity over millions of frack jobs, Davies et al 2013), and the hazard they pose is very small since the few incidences of felt seismicity were at such small magnitudes that they caused little or no environmental effect or damage to the built environment.

6.89 In practice, this objective approach has to be adjusted to allow for the role that public perception plays in determining the acceptability of any identified or potential "risk". For instance public opinion surveys consistently show that shale gas extraction is "associated with" earthquakes (see Chapter 8). Equal risks in terms of probability are not perceived equally due to a host of factors (fear factors) with which the public interpret the significance personally or to their family (Health Protection Network 2008).

6.90 The pollution source-pathway-receptor model is the international regulatory standard paradigm to assess pollution risks ( e.g. Health Protection Agency 2009). For a risk to human health to exist, it is not sufficient to have a "hazard" source alone, there must be a "source-pathway-receptor" linkage i.e. there must be a plausible means whereby humans may be exposed to the hazard in sufficient amounts to cause harm.

6.91 For instance a harmful substance (source/ hazard) may not represent a significant possibility (risk) of causing harm to humans (or other receptors) if:

(i) there is no pathway (exposure route) by which receptors (humans) may encounter the substance physically; or
(ii) the concentration of pollutant in the environment is so low that the substance cannot be inhaled/ingested, or otherwise absorbed, in a dose large enough to cause an adverse physiological or clinical impact to humans.

Other potential receptors include ground and surface water, protected ecological systems, and property including livestock, crops and buildings.

6.92 Concerns have been raised about the health effect of chemicals added to hydraulic fracturing fluids. Of 353 different chemical additives identified that have been used in fracking fluids (Colborn et al, 2011), the accompanying material safety data sheets ( MSDS) indicate that 75% of these chemicals could have negative health effects.

6.93 However, in high concentrations many chemicals have adverse health effects, including everyday compounds. For example, the MSDS for sodium chloride (common salt, CAS #7647-14-5) includes serious potential health effects. These would only occur for concentrations of salt far higher than would be used in normal household or industrial food preparation: hence salt is a permitted substance. Thus, while some chemicals used in fracking may be potentially harmful to health if the dose to which people can be exposed is not adequately controlled, approval for use would only occur if consideration of the likely concentrations and pathways from a source to a given receptor identified an acceptable level of risk.

6.94 Determining whether a given hazard (source) is entirely or even partly responsible for a recorded health impact is a complex matter. Unlike communicable disease, where a specific organism causes a specific health impact ( e.g. Salmonella and the predominantly gastro-intestinal illness salmonellosis), Environmentally Associated Disease ( EAD) is rarely a case of "single hazard - single impact". In general, environmental factors are one of several factors that interact to determine the probability of developing a clinical illness.

6.95 Societal factors may act as confounding factors that skew the data on health impacts and make it difficult to determine the attributable fraction of EAD actually associated with any specific environmental hazard. For instance changes in cancer rates and mortality, low birth weight and chronic obstructive pulmonary disease were health problems found in regions of shale gas extraction (Witter et al, 2008). However it was recognised that the lack of good public health baseline data for the local population, and subsequent on-going monitoring, made it difficult to be certain of the cause.

6.96 Further, social effects, such as the influx of predominantly male drilling workers (a gender more prone to heart disease), could have confounding effects on public health observations of increased heart disease in a shale gas region. Thus, assessing the degree of change associated with the industry is subject to major uncertainties (Adgate et al, 2014).

6.97 It appears that for communities near unconventional oil and gas development sites, the main health impact "stressors" ( i.e. areas of perceived concern, even if unproven) are "air pollutants, ground and surface water contamination, truck traffic and noise pollution, accidents and malfunctions and psychosocial stress associated with community change" (Adgate et al, 2014). Despite these broad public concerns, no comprehensive population based studies of the public health effects of unconventional hydrocarbon operations currently exist (Adgate et al, 2014).

6.98 Whilst a draft report by Public Health England (2013) considers that "currently available evidence indicates that potential risks to public health from … shale gas operations are low if the operations are properly run and regulated", the case studies discussed earlier indicate that careful thought needs to be given to epidemiological assessments to allow direct risk to be assessed and so mitigated.

Conclusions

6.99 Although there are potential threats to the environment and the individual from unconventional hydrocarbon extraction, there are considerable legislative safeguards to ensure these threats are not realised. There has, however, to be recognition that the unexpected can happen. Some examples of best practice in addressing these challenges have environmental and health and safety legislation as a primary driver; others are being refined as the industry matures. Thus mitigating a potential or realised impact depends on strong and visionary environmental, and health and safety, regulators to enforce legislation and identify and respond rapidly to gaps that may emerge.

6.100 The impact on the Scottish Government policy for reducing GHG emissions needs strategic consideration as unconventional hydrocarbon extraction will maintain and continue Scottish fossil fuel-derived GHG emissions above an alternative scenario of reliance on renewable energy (noting our remit here is not to consider the feasibility of renewable sources in meeting complex energy demands).

6.101 The development of any new industry will potentially impact society. It is clear that detecting and alleviating negative impacts, and enhancing positive impacts, is complicated unless careful planning of how to identify impact is undertaken. Without such understanding, whether the negative impacts are acceptable outcomes of industrial development that offers intrinsic positive impacts, cannot be considered.