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  • Journal article
    Cooper J, Balcombe P, Hawkes A, 2021,

    The quantification of methane emissions and assessment of emissions data for the largest natural gas supply chains

    , Journal of Cleaner Production, Vol: 320, Pages: 1-10, ISSN: 0959-6526

    Methane emitted from natural gas supply chains are a major source of greenhouse gas emissions, but there is uncertainty on the magnitude of emissions, how they vary, and which key factors influence emissions. This study estimates the variation in emissions across the major natural gas supply chains, alongside an estimate of uncertainty which helps identify the areas at the greatest emissions ‘risk’. Based on the data, we estimate that 26.4 Mt CH4 (14.5–48.2 Mt CH4) was emitted by these supply chains in 2017. The risk assessment identified a significant proportion of countries to be at high risk of high emissions. However, there is a large dependency on Tier 1 emission factors, inferring a high degree of uncertainty and a risk of inaccurate emission accounting. When emissions are recalculated omitting Tier 1 data, emissions reduce by 47% to 3.8-fold, downstream and upstream respectively, across regions. More efforts in collecting robust and transparent primary data should be made, particularly in Non-Annex 1 countries, to improve our understanding of methane emissions.

  • Journal article
    Balcombe P, Staffell I, Kerdan IG, Speirs JF, Brandon NP, Hawkes ADet al., 2021,

    How can LNG-fuelled ships meet decarbonisation targets? An environmental and economic analysis

    , Energy, Vol: 227, Pages: 1-12, ISSN: 0360-5442

    International shipping faces strong challenges with new legally binding air quality regulations and a 50% decarbonisation target by 2050. Liquefied natural gas (LNG) is a widely used alternative to liquid fossil fuels, but methane emissions reduce its overall climate benefit. This study utilises new emissions measurements and supply-chain data to conduct a comprehensive environmental life cycle and cost assessment of LNG as a shipping fuel, compared to heavy fuel oil (HFO), marine diesel oil (MDO), methanol and prospective renewable fuels (hydrogen, ammonia, biogas and biomethanol). LNG gives improved air quality impacts, reduced fuel costs and moderate climate benefits compared to liquid fossil fuels, but with large variation across different LNG engine types. Methane slip from some engines is unacceptably high, whereas the best performing LNG engine offers up to 28% reduction in global warming potential when combined with the best-case LNG supply chain. Total methane emissions must be reduced to 0.8–1.6% to ensure climate benefit is realised across all timescales compared to current liquid fuels. However, it is no longer acceptable to merely match incumbent fuels; progress must be made towards decarbonisation targets. With methane emissions reduced to 0.5% of throughput, energy efficiency must increase 35% to meet a 50% decarbonisation target.

  • Journal article
    Auger T, Truby J, Balcombe P, Staffell Iet al., 2021,

    The future of coal investment, trade, and stranded assets

    , Joule, Vol: 5, Pages: 1462-1484, ISSN: 2542-4351

    Coal is at a crossroads, with divestment and phase-out in the West countered by the surging growth throughout Asia. Global energy scenarios suggest that coal consumption could halve over the next decade, but the business and geopolitical implications of this profound shift remain underexplored. We investigate coal markets to 2040 using a perfect competition techno-economic model. In a well-below-2°C scenario, Europe, North America, and Australia suffer from over-capacity, with one-third of today’s mines becoming stranded assets. New mines are needed to offset retirements, but a new commodity cycle in the 2030s can be avoided. Coal prices decline as only the most competitive mines survive, and trade volumes fall to give more insular national markets. Regions stand to gain or lose tens of billions of dollars per year from reducing import bills or export revenues. Understanding and preparing for these changes could ease the transition away from coal following 150 years of dominance.

  • Journal article
    Lowes R, Woodman B, Speirs J, 2020,

    Heating in Great Britain: An incumbent discourse coalition resists an electrifying future

    , Environmental Innovation and Societal Transitions, Vol: 37, Pages: 1-17, ISSN: 2210-4224
  • Report
    Speirs J, Jalil-Vega F, Cooper J, Gerber Machado P, Giarola S, Brandon N, Hawkes Aet al., 2020,

    The flexibility of gas - what is it worth?

    , White Paper 5: The Flexibility of gas – what is it worth?, London, UK, Publisher: Sustainable Gas Institute, Imperial College London, 5

    What is the evidence on the flexibility value that gas vectors and gas networks can provide to support the future energy system?There is an increasing debate regarding the use of gas networks in providing support for the decarbonisation of energy systems.The perceived value of gas “vectors” – encompassing natural gas, hydrogen and biomethane – is that they may provide flexibility, helping to support daily and seasonal variation in energy demand, and increasingly intermittent electricity supply as renewable electricity generation increases as a proportion of the electricity mix.Arguments in support of gas suggest that electricity systems will find it difficult to maintain flexibility on their own, whilst also reducing greenhouse gas emissions and increasing production to meet new demand for heating and transport. Gas, on the other hand, is expected to provide flexibility at relatively low cost, and may be produced and used with relatively low greenhouse gas emissions.White Paper 5 investigates the evidence surrounding the flexibility provided by gas and gas networks and the cost of, and value provided by gas to the future energy system.

  • Journal article
    Speirs J, Balcombe P, Blomerus P, Stettler M, Achurra-Gonzalez P, Woo M, Ainalis D, Cooper J, Sharafian A, Merida W, Crow D, Giarola S, Shah N, Brandon N, Hawkes Aet al., 2020,

    Natural gas fuel and greenhouse gas emissions in trucks and ships

    , Progress in Energy, Vol: 2, Pages: 012002-012002
  • Journal article
    Cooper J, Balcombe P, Hawkes A, 2019,

    Life cycle environmental impacts of natural gas drivetrains used in UK road freighting and impacts to UK emission targets

    , Science of the Total Environment, Vol: 674, Pages: 482-493, ISSN: 0048-9697

    Using natural gas as a fuel in the road freight sector instead of diesel could cut greenhouse gas and air quality emissions but the switch alone is not enough to meet UK climate targets. A life cycle assessment (LCA) has been conducted comparing natural gas trucks to diesel, biodiesel, dimethyl ether and electric trucks on impacts to climate change, land use change, air quality, human health and resource depletion. This is the first LCA to consider a full suite of environmental impacts and is the first study to estimate what impact natural gas could have on reducing emissions form the UK freight sector. If LNG is used, climate change impacts could be up to 33% lower per km and up to 12% lower per kWh engine output. However, methane emissions will eliminate any benefits if they exceed 1.5–3.5% of throughput for typical fuel consumption. For non-climate impacts, natural gas exhibits lower emissions (11–66%) than diesel for all indicators. Thus, for natural gas climate benefits are modest. However, emissions of CO, methane and particulate matter are over air quality limits set for UK trucks. Of the other options, electric and biodiesel trucks perform best in climate change, but are the worst with respect to land use change (which could have significant impacts on overall climate change benefits), air quality, human toxicity and metals depletion indicators. Natural gas could help reduce the sector's emissions but deeper decarbonization options are required to meet 2030 climate targets, thus the window for beneficial utilisation is short.

  • Journal article
    Crow DJG, Balcombe P, Brandon N, Hawkes ADet al., 2019,

    Assessing the impact of future greenhouse gas emissions from natural gas production

    , Science of the Total Environment, Vol: 668, Pages: 1242-1258, ISSN: 0048-9697

    Greenhouse gases (GHGs) produced by the extraction of natural gas are an important contributor to lifecycle emissions and account for a significant fraction of anthropogenic methane emissions in the USA. The timing as well as the magnitude of these emissions matters, as the short term climate warming impact of methane is up to 120 times that of CO 2 . This study uses estimates of CO 2 and methane emissions associated with different upstream operations to build a deterministic model of GHG emissions from conventional and unconventional gas fields as a function of time. By combining these emissions with a dynamic, techno-economic model of gas supply we assess their potential impact on the value of different types of project and identify stranded resources in various carbon price scenarios. We focus in particular on the effects of different emission metrics for methane, using the global warming potential (GWP) and the global temperature potential (GTP), with both fixed 20-year and 100-year CO 2 -equivalent values and in a time-dependent way based on a target year for climate stabilisation. We report a strong time dependence of emissions over the lifecycle of a typical field, and find that bringing forward the stabilisation year dramatically increases the importance of the methane contribution to these emissions. Using a commercial database of the remaining reserves of individual projects, we use our model to quantify future emissions resulting from the extraction of current US non-associated reserves. A carbon price of at least 400 USD/tonne CO 2 is effective in reducing cumulative GHGs by 30–60%, indicating that decarbonising the upstream component of the natural gas supply chain is achievable using carbon prices similar to those needed to decarbonise the energy system as a whole. Surprisingly, for large carbon prices, the choice of emission metric does not have a significant impact on cumulative emissions.

  • Journal article
    Cooper J, Balcombe P, 2019,

    Life cycle environmental impacts of natural gas drivetrains used in road freighting

    , Procedia CIRP, Vol: 80, Pages: 334-339, ISSN: 2212-8271
  • Journal article
    Balcombe P, Brierley J, Lewis C, Skatvedt L, Speirs J, Hawkes A, Staffell Iet al., 2019,

    How to decarbonise international shipping: Options for fuels, technologies and policies

    , Energy Conversion and Management, Vol: 182, Pages: 72-88, ISSN: 0196-8904

    International shipping provides 80–90% of global trade, but strict environmental regulations around NOX, SOX and greenhouse gas (GHG) emissions are set to cause major technological shifts. The pathway to achieving the international target of 50% GHG reduction by 2050 is unclear, but numerous promising options exist. This study provides a holistic assessment of these options and their combined potential to decarbonise international shipping, from a technology, environmental and policy perspective. Liquefied natural gas (LNG) is reaching mainstream and provides 20–30% CO2 reductions whilst minimising SOX and other emissions. Costs are favourable, but GHG benefits are reduced by methane slip, which varies across engine types. Biofuels, hydrogen, nuclear and carbon capture and storage (CCS) could all decarbonise much further, but each faces significant barriers around their economics, resource potentials and public acceptability. Regarding efficiency measures, considerable fuel and GHG savings could be attained by slow-steaming, ship design changes and utilising renewable resources. There is clearly no single route and a multifaceted response is required for deep decarbonisation. The scale of this challenge is explored by estimating the combined decarbonisation potential of multiple options. Achieving 50% decarbonisation with LNG or electric propulsion would likely require 4 or more complementary efficiency measures to be applied simultaneously. Broadly, larger GHG reductions require stronger policy and may differentiate between short- and long-term approaches. With LNG being economically feasible and offering moderate environmental benefits, this may have short-term promise with minor policy intervention. Longer term, deeper decarbonisation will require strong financial incentives. Lowest-cost policy options should be fuel- or technology-agnostic, internationally applied and will require action now to ensure targets are met by 2050.

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