The UK is undergoing a period of intense scrutiny of shale gas’s local environmental impacts and regulation. But attention is now shifting on to how it might affect global climate change.
Policymakers in the US and now in the UK see natural gas providing a comparatively low-carbon transition or ‘bridging’ fuel on the route to a low-carbon economy. Shale gas could potentially account for a substantial portion of gas consumed in the UK by the 2020s.
But the carbon footprint of shale gas is uncertain, with concerns focused on local emissions during exploration and production. And because there is little experience in the UK, further drilling will be needed to address these uncertainties.
The wider impacts on global emissions through fossil fuel markets and on low-carbon technologies are even harder to quantify.
At the development stage, emissions include exploration, site preparation, drilling and casing, hydraulic fracturing (fracking), well completion and waste treatment. Emissions are dominated by methane, with a global warming potential over 100 years 25-times greater than CO2.
Fracking has the potential to be more carbon intensive than conventional natural gas well development because drilling and the drill-out after fracking takes longer. In the US venting methane is allowed, with significant quantities found in ‘flowback’ of hydraulic fluids.
During production, emissions are mainly released through onsite diesel use, unplanned fugitive emissions, gas flaring and deliberate venting. Energy-intensive processing such as clean-up and compression before grid injection may be needed and further potential losses during transmission and distribution addressed.
Given that many of the emissions occur shortly after fracking and drill-out during well completion, the carbon intensity of production will be lower the longer the productive life of the well.
Current emission assessments during exploration and production draw on the US experience of the Marcellus Shale. They are generally in areas of low population density with a regulatory regime that has allowed uncontrolled gas venting. These studies (see figure), mostly published from 2011, are not all directly comparable in scope or method. All are based on a narrow sample of wells and cite the need for better monitoring data.
A range of studies estimate life cycle carbon intensity at 6% lower than conventional natural gas and up to 50% lower than coal at one extreme to 22-43% higher than conventional gas and at least 20% greater than coal at the other.
The upper estimates, by the US-based University of Cornell team, were criticised for using a 20-year time horizon, but even over the standard 100 years cite emissions 14-19% higher than conventional gas and comparable with coal. It assumed emissions over a well’s lifetime were up to double those from conventional gas.
So-called green completions capture emissions during well finishing, minimising or avoiding venting and flaring. These can cut emissions by about 90%. For its part, Cuadrilla has told DECC it will aim for 100% capture of methane in well completions.
But there is a cost because they reduce the effectiveness of well clean-out after fracking. They also increase pipeline backpressure leading to reduced gas production and may not be feasible or economic in low-pressure fields. Green completions also need costly equipment and greater investment in pipelines.
Even so, the Environmental Protection Agency will require green completions on all new wells from 2015 to curb emissions.
More recently, reviews have appeared in the EU and particularly the UK, attempting to draw lessons from the US experience.
A joint report by the Royal Academy of Engineering and Royal Society in 2012 found that UK shale gas would most probably be clean enough to inject directly into the gas grid without processing. Even so, it recommended that: “Operators should monitor potential leakages of methane or other emissions to the atmosphere before, during and after shale gas operations.” The report added that there is as yet no requirement for green completion technology at the exploration stage in the UK and that this should be considered.
An EU report for DG Climate Action prepared by AEA consultants in 2012 reviewed a wide range of US papers and found a wide range of greenhouse gas emissions estimates.
Its estimates for electricity-generation emissions are therefore tentative. These would be about 4-8% higher than generation from conventional pipeline gas within Europe, mainly through flowback in well completion, it suggests. But it found that the difference could shrink to just 1-5% with flaring and capture.
Compared with generation from conventional pipeline gas from Russia and Algeria, GHG CO2e emissions would be at least 2-10% lower and 7-10% lower than electricity generated from imported LNG, it says.
But it warns that with uncontrolled venting, generation emissions would match or even top the highest from imported LNG or Russian pipeline gas. That would wipe out any low-carbon benefits from shale gas.
But compared with coal, shale-gas based generation GHG CO2e emissions would be substantially lower by 41-49% over a 100-year timescale, it estimates.
The report anticipates best practice in minimising emissions from pre-production and production in the EU, but cautions that green completions may not be feasible in some lower-pressure fields.
Downstream emission reduction measures such as more efficient compressors and better leak detection can slash shale and conventional natural gas footprints further, it says.
It calls for best available technology, additional guidance on technologies, use of directives and regulation. Voluntary agreements would need to be monitored for rigorous application, it says.
In April this year, the government’s advisory Committee on Climate Change (CCC) launched a report into cutting the UK’s carbon footprint while ensuring competitiveness. It noted that shale gas, like other forms of natural gas, “cannot be regarded as a low-carbon fuel source”. But it concluded that shale gas can have comparable emissions to conventional pipeline gas and lower than imported LNG “if regulatory arrangements are in place to manage methane released during its production”.
Subject to effective environmental regulation, it cautiously concluded that “shale gas may have a useful role to play in meeting heat demand and to a limited extent, electricity demand”.
On 9 September, DECC published the most definitive UK report to date on shale’s emissions written by chief scientific adviser Professor David MacKay and Dr Timothy Stone, senior adviser to energy and climate secretary Ed Davey.
As with the earlier Royal Society report, its recommendations have been accepted by Davey, though due to a continuing lack of data, many of its conclusions are provisional.
The report found that: “The total carbon footprint of shale gas exploration, extraction and transmission and use is likely to be similar to that of gas derived from conventional wells in the UK, LNG (liquefied natural gas) and non-EU piped gas.” It also points out that all gas scenarios are less carbon-intensive than coal generation – assuming no onsite venting being permitted in the UK.
Taking into account both pre-production and production emissions, the report assumes a carbon intensity of nine grams CO2 equivalent/kilowatt hour, in line with conventional gas production. Wells would undergo one fracking ‘workover’ to offset declining production in this scenario. It disregarded the Cornell study as an anomaly.
The report warns venting in pre-production, exploration or production could double carbon intensity overall, so it recommends operators adopt levels as low as reasonably practicable (ALARP). It says DECC should consider mandatory requirements with regulators to ensure best available technology and ensure careful monitoring and inspection at all stages. It stresses that further research is needed into methane leakage at all stages, including water sampling, as well as into more efficient extraction methods and their effectiveness.
But it noted the largest emissions from both shale and conventional gas normally come from combustion during use, with a carbon intensity of about 190gCO2e/kWh. In the UK, of all the gas we use almost 70% of natural gas is used for domestic and industrial heating, with the rest used in power generation. However, this amount does vary from year to year. For example, in 2012 about 25% was used for power generation.
In terms of shale’s overall carbon footprint assuming rigorous control measures, the report is reassuring. It projects emissions intensity of shale gas extraction and use as between 200-253gCO2e/kWh. This is lower than LNG at 233-270gCO2e/kWh and similar to conventional gas at 199-207gCO2e/kWh.
For electricity generation, the DECC report finds well-regulated shale gas carbon intensity is in most cases set to be lower than LNG and non-EU piped gas, but that most sources are significantly higher than conventional gas. Compared with coal, shale’s footprint is much lower, at 423–535gCO2e/kWh electricity, compared with 837–1130gCO2e/kWhe.
But Ed Davey has stressed the importance not only of regulation but of ensuring it is respected and that it leads to good practice: “We must make sure that the rigorous regulation we are putting in place is followed to the letter, to protect the local environment.”
At EU level, there is also heated debate over regulation to cut well emissions and over how closely practices should be audited as opposed to self-monitored.
Given the stakes, it will be crucial for emissions mitigation and public support that any regulations and good practices are indeed effective and transparent.
As regulator, the Environment Agency is in discussions with operators over how best to mitigate fugitive emissions. It recommended monitoring programmes before and during shale gas production, greater detail in onsite reporting and research into the cost-effectiveness of mitigation technologies in the UK.
DECC guidance calls to avoid venting as far as is technically possible. It also calls for minimal flaring, but this will depend on availability of gas pipelines for injection.
In July, Cuadrilla said in its EIA scoping report that injection into the gas grid was not feasible during exploration, so it would instead collect, measure and flare gas during well completion at Preese Hall.
But the impact of a shale gas boom in the UK could also have a wide range of indirect effects on domestic and global emissions. Many of these are controversial, hard to predict and often beyond the UK’s control.
The overall impact will also depend on total reserves that can be recovered and on the productive life of wells. Both remain highly uncertain for the UK.
In the USA, a glut of shale gas production has led to a fall in gas prices domestically, leading to fuel switching in generation from coal to gas.
But while this has reduced emissions domestically, burning cheap coal has raised emissions elsewhere, including in the EU. This could be said of any new fossil fuel source in a world without global emission caps, though the result has worried climate policymakers.
But the development of such a new fossil fuel source is also problematic given the UK’s binding carbon budgets. The UK is committed to cutting emissions by 50% in its fourth carbon budget from 2023-27 relative to 1990 and to largely decarbonising the electricity grid by 2030. It is set to miss this by a growing margin (endsreport.com/40744).
Without CCS, which remains unproven at scale, gas generation could only have a role in back-up by this time, with grid average carbon intensity falling to just 50gCO2/kWh. Even so, heating uses in industry and homes would continue for longer.
In its May 2011 report into shale gas, the House of Commons Energy and Climate Change Committee concluded that UK shale could provide energy security benefits as North Sea reserves decline. But it warned a shale gas boom could also damage renewable generation, It stressed that “the emergence of shale gas increases the urgency of making carbon capture and storage (CCS) technology work for gas as well as coal”.
Even assuming best practice in development, opinions are deeply divided over whether shale gas as a ‘transition fuel’ will displace fuels with higher carbon intensity such as coal, or merely supplement them and boost global emissions.
A report by the Tyndall Centre in Manchester, also in 2011, took the latter view, pointing out unabated coal generation in the UK would be phased out anyway. It warned of carbon lock-in from new infrastructure and that investment in renewables and CCS development could potentially be diverted into lower-cost shale gas.
For its part, the CCC footprint report advised that despite a role for well-regulated shale gas, over the next two decades it will be necessary to invest in “a range of low-carbon power generation technologies rather than to have a ‘dash for gas’”.
CCC chief executive David Kennedy told ENDS decarbonisation will depend on the success of electricity market reforms (EMR). But he stressed uncertainty is undermining investment, “exacerbated by the possibility of a focus on gas-fired generation in the 2020s”.
He added this is “driven by a misconception that shale gas will significantly reduce the price of gas” and “a further misconception that this would undermine the economics of investment in low-carbon technologies”.
The MacKay report for DECC judges that in the open European gas market any reduction in price is likely to be small, with shale reducing LNG and perhaps non-European piped gas.
It considers that the impact on UK emissions would be small, but also stresses that there is a risk displaced fossil fuels will increase emissions elsewhere. To deal with this climate threat, it proposes expansion of shale gas should be accompanied by “equivalent and additional emissions-reduction measures” internationally, such as reforestation, CCS, carbon taxes and ultimately a global climate deal.
The big picture
So can shale have a role in a carbon-constrained world? Given best practice and strict regulation in the UK at least it probably can.
For his part, energy and climate secretary Ed Davey has committed to a well-regulated shale gas sector. He also stresses that the government “must not and will not allow shale gas production to compromise our focus on boosting renewables, nuclear and other low carbon technologies”.
He argues that properly regulated shale gas would support the low-carbon transition, and suggested its tax revenues could aid this.
But shale’s appearance on the energy stage comes at a sensitive time for energy and climate policy with the fourth carbon budget up for review in 2014 and -negotiations over a global climate agreement in 2015.
There have also been widely publicised spats in the Coalition between those favouring renewables and those opting for cheaper gas generation, resulting in mixed signals.
DECC sees a continuing role for gas beyond the 2020s, but has failed to include a carbon intensity target for the grid by 2030 in the Energy Bill. In 2012, it also effectively exempted consented gas generation plants from CCS until 2045 (endsreport.com/35371). Both have drawn criticism from the CCC as risking a ‘dash for gas’ that could undermine carbon budgets.
While the renewable sector accepts shale could have a role as gas-fired back-up generation, investors are concerned at lack of clarity over longer-term funding and targets up to 2030.
One area where shale gas development could potentially be in direct conflict with renewables is that of biomethane. Biomass expert and renewable energy consultant Stewart Boyle argues that animal and food wastes can be used as feedstock for “carbon-neutral” methane for heating and in transport, slashing emissions from the waste sector with digestate fertiliser as a by-product.
Boyle argues: “With so much going for it and a potential resource of 6%-10% of current domestic gas supplies within 10-15 years, it should have a very high priority within government energy strategy.” But he stresses “the contrast with the attention and priority given to shale gas is stark”, with attention focused on tax breaks for shale while biomethane has been left largely to advocates in the sector.
Dr Nina Skorupska, chief executive of the Renewable Energy Association, told ENDS that shale gas could indeed act as a relatively low-carbon bridging fuel providing energy security. But she cautioned it was not a “silver bullet” and that it could not resolve the looming energy generation capacity crunch because it would not come onstream until the 2020s.
She stressed that under the circumstances “government should be welcoming new biomass power plants, not restricting the support”, though these projects have raised concerns over sustainability of imported feedstocks. Skorupska also wants assurances on market access for independent renewable generators, such as wind, solar, marine, geothermal and waste to energy under market reforms.
Skorupska meanwhile warned of the dangers of focusing too heavily on shale gas: “We trust DECC’s new shale gas work stream will not delay or derail the resolution of these vital EMR issues, as timely passage of the Energy Bill is crucial so that industry can start building these vital projects.”
CCS commercialisation will be crucial if gas is used in power generation beyond the 2020s, but setbacks at UK (ENDS Report 445, p36) and EU level have cast doubt on this timescale. In the latest £1bn competition aimed at commercialising CCS, DECC has selected two projects, a gas power plant retrofit at Peterhead and a proposed purpose-built CCS coal plant in Yorkshire.
But signing of contracts for early engineering studies is already behind schedule and a final decision on plant funding will not be taken until after the election in 2015, so the earliest date for any plant to be up and running will be 2019.
Judith Shapiro, communications and policy manager for the Carbon Capture and Storage Association believes the timetable for the 2020s is still doable, but warns it is increasingly tight. She also points out there is still no certainty over funding of further projects, with minimum unit price support levels under ‘contracts for difference’ in the reformed electricity market still to be settled. A further issue is lack of certainty for the wider CCS supply chain.
In the meantime, the UK objected in July to moves by the European Commission to boost the technology through a levy on fossil fuels to pay for projects and through a CCS obligation. DECC is calling for a technology-neutral EU decarbonisation for 2030 and says these measures would go against this principle.
So the bigger question is whether the government will stick to its timetable for decarbonisation under current carbon budgets, particularly in the event of a shale gas boom. If shale gas is to be a bridge, then there will need to be a portfolio of renewables and other low-carbon generation with CCS at the end of it.
UK shale gas and the environment
A special report, sponsored by RPS(energy and environmental consultants)