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This briefing reviews progress that was made at the 26th United Nations Climate Change Conference of the Parties (COP26) held in Glasgow, Scotland, UK over 1–12 November 2021. The context of the global climate change challenge is outlined, along with the aspirations of the major participating international groups. An overall balance sheet is provided that gives an assessment of the achievements and disappointments in the outcomes of COP26. This assessment sets a backdrop to what needs to be achieved when the Parties next meet at COP27 in Sharm El-Sheikh, Egypt in 2022 to address both immediate and longer-term climate change mitigation, adaptation and climate finance.

Steel products are widely used in the construction industry and for the development of infrastructure projects, because they are versatile, durable, and affordable. Energy demand and ‘greenhouse gas’ (GHG) emissions associated with the United Kingdom (UK) Iron & Steel sector principally result from the large consumption of coal/coke used in conjunction with the blast furnace. Like other sectors of industry, efforts are being made to ensure that processing becomes ever more environmentally benign, or ‘green’. Thus, the notion of ‘green steel’ has entered into the industrial vocabulary over the last decade or so. It is a steel-making process designed principally to lower GHG emissions, as well as potentially cutting costs and improving the quality of steel, in comparison to conventional methods. The aim of this study was therefore to (i) elicit the various ways in which the term ‘green steel’ has recently been used in the literature; and (ii) compare and contrast different options for making UK steel production more environmentally benign, particularly in regard to its decarbonisation. Some key ‘deep decarbonisation’, or ‘disruptive’, options for producing green steel in the UK are evaluated drawing on the experience from other nation-states and regions. These include the prospects for carbon capture and storage (CCS), the use of bioenergy resources, hydrogen-based production, electrification, and the least desirable option of deindustrialisation (i.e., reducing or out-sourcing of UK steel production ‘offshore’). ‘Circular economy’ interventions or resource efficiency improvements (‘reduce, reuse, recycle’) are also discussed. The potential reductions in GHG emissions from the UK Iron & Steel sector overall out to 2050 are then illustrated by comparison with previous technology roadmaps or transition pathways. The lessons learned are applicable across much of the industrialised world.

Environmental or ‘ecological’ footprints have been widely used as partial indicators of sustainability; specifically of resource consumption and waste absorption transformed in terms of the biologically productive land area required by a population. The environmental footprint of the Unitary Authority of Bath and North East Somerset (BANES) in the South West of England (UK) has been estimated in terms of global hectares (gha) required per capita. BANES has a population of about 184 870 and covers an area of 35 200 ha, of which two-thirds are on ‘green belt’ land. The UNESCO World Heritage City of Bath is the principal settlement, but there are also a number of smaller urban communities scattered among its surrounding area (‘hinterland’ or ‘bioregion’). The overall footprint for BANES was estimated to be 3.77 gha per capita (gha/cap), which is well above its biocapacity of 0.67 gha/cap and ‘Earthshare’ of 1.80 gha/cap. Direct energy use was found to exhibit the largest footprint component (a 31% share), followed by materials and waste (30%), food and drink (25%), transport (10%) and built land (4%), whereas the water footprint was negligibly small (∼0%) by comparison. Such data provide a baseline for assessing the Council's planning strategies for future development.

Building ‘zero carbon’ homes will be essential for achieving the carbon reductions within industrialised countries required to meet their commitments under the 2015 Paris Agreement on climate change. Such high performance buildings may need a combination or ‘cluster’ of micro-generators to be installed, such as a heat pump to provide heating and a solar photovoltaic (PV) array to produce electricity. When sized and installed appropriately, these technologies have lower emissions than the conventional systems they displace (centralised grid electricity and gas-fired boilers). However, if the ‘embodied’ energy and carbon is not recouped from that saved during the lifetime of the micro-generator, then there is no net saving overall. This study therefore assesses a range of clustered micro-generators using an ‘integrated approach’ that combines energy analysis, environmental life-cycle assessment, and an indicative financial appraisal. Eight clusters of micro-generators were designated to meet the heat and electricity requirements of five different dwelling types, each one specified to two different UK performance standards (2006 building regulations and a zero-carbon specification). For these 80 scenarios, various combinations of heat pumps with solar hot water and/or PV systems yield the most attractive performance metrics with all of the clusters having energy and carbon paybacks (4.5–5.5 and 5.0–7.0 years respectively) within their operational lifetimes, and would hence create net savings overall. But the clusters were generally found to have unattractive financial payback periods (50–80 years), although this result will be sensitive to the discount rate and prevailing energy prices and support mechanisms. The focus is on the use of clustered micro-generators in the context of UK transition pathways to a low-carbon economy out to 2050, but the lessons learned are applicable to many industrialised countries. Highlights •Eight clusters of micro-generators for heat and power in selected dwellings were analysed.•Each was aimed at satisfying low-carbon building regulations within the UK.•For 80 combinations, the energy, carbon, and financial payback periods were determined.•Heat pumps with solar hot water and/or photovoltaic arrays yield good energy and carbon metrics.

The opportunities and challenges to reducing industrial energy demand and carbon dioxide (CO2) emissions in the iron & steel sector are evaluated with a focus is on the situation in the United Kingdom of Great Britain and Northern Ireland (UK), although the lessons learned are applicable across much of the industrialised world. It is the largest industrial sector in the UK in terms of energy demand and ‘ greenhouse gas’ (GHG) emissions, and accounts for some 26% of GHG emissions from British industry. Current Best Available Technologies (BAT) will lead to short-term energy and CO2 emissions savings in iron & steel processing, but the prospects for the commercial exploitation of innovative technologies by mid-21st century are far more speculative. The blast furnace is the most efficient energy conversion process in the sector, but also the largest energy user and consequently is a priority target for energy demand reduction. Many existing technologies, that have yet to be adopted, could reduce a significant proportion of process energy loss. These include, among others, heat recovery at the coke ovens, sinter plant, and electric arc furnace, and further heat and gas recovery from the basic oxygen furnace. The uptake of key BAT technologies for hot-rolling could reduce sector primary energy by 18% and GHG emissions by 12%. Further potential may be available for blast furnace operation by optimising chemical transfer to minimise blast furnace gas (BFG) production. Nevertheless, there are a number of non-technological barriers to the take-up of such technologies going forward. The transition to a low carbon future in UK industry by 2050 will therefore exhibit rather large uncertainties. The attainment of significant falls in carbon emissions over this period will depends critically on the adoption of a small number of key technologies [e.g., energy efficiency techniques, fuel switching towards bioenergy, and carbon capture and storage (CCS),], alongside the decarbonisation of national electricity supply. Other radical process technological innovations (such as the ‘electrowinning’ or so-called HISARNA process) are likely to be available in the longer term.

A large interdisciplinary consortium of engineers, social scientists and policy analysts has developed three low-emissions, more-electric transition pathways for the UK. The approach is based on earlier work on understanding transitions, applying a multi-level perspective with landscape, regime and niche levels to the development of socio-technical scenarios. The pathways to 2050 focus on the power sector, including the potential for increasing the use of low-emissions electricity for heating and transport. Part 1 describes studies of historical energy and infrastructure transitions that help to understand the dynamics and timing of past transitions. The role of large-scale and small-scale actors in the electricity sector and methods used to develop the pathways are then described. In part 2, associated technologies are evaluated to determine the choices that need to be made by UK energy policymakers and stakeholders. All three pathways are appraised in terms of their environmental performance using complementary life-cycle assessment and footprinting methods. Lessons can clearly be drawn for other industrialised nations attempting to reduce the emissions from their electricity generation systems, although local circumstances will determine country- and region-specific options.

A large interdisciplinary consortium of engineers, social scientists and policy analysts has developed three low-emissions, more-electric transition pathways for the UK. The approach is based on earlier work on understanding transitions, applying a multi-level perspective with landscape, regime and niche levels to the development of socio-technical scenarios. The pathways to 2050 focus on the power sector, including the potential for increasing the use of low-emissions electricity for heating and transport. Part 1 described studies of historical energy and infrastructure transitions that help to understand the dynamics and timing of past transitions. The role of large-scale and small-scale actors in the electricity sector and methods used to develop the pathways were also described. In part 2, associated technologies are evaluated to determine the choices that need to be made by UK energy policymakers and stakeholders. All three pathways are appraised in terms of their environmental performance using complementary life-cycle assessment and footprinting methods. Lessons can clearly be drawn for other industrialised nations attempting to reduce the emissions of their electricity generation systems, although local circumstances will determine country- and region-specific options.

Environmental or ‘ecological’ footprints have been widely used in recent years as indicators of resource consumption and waste absorption transformed on the basis of biologically productive land area [in global hectares (gha)] required per capita with prevailing technology. It has been employed here to estimate the footprints associated with three low carbon, more electric transition pathways for the United Kingdom (UK): described as ‘Market Rules’ (MR), ‘Central Co-ordination’ (CC) and ‘Thousand Flowers’ (TF) respectively. These pathways focus on the power sector, including the potential for increasing use of low-carbon electricity for heating and transport, within the context of critical European Union developments and policies. Their overall environmental footprint has been disaggregated into various components: bioproductive and built land, carbon emissions, embodied energy, materials and waste, transport, and water consumption. This component-based approach provides, for example, a means for evaluating the implications for the so-called ‘energy-land-water nexus’. Electricity demand was projected to decrease significantly under the TF pathway by 2050, but its total environmental footprint (EF) was greater than either that under the MR or CC pathways. This is mainly due to the increase in the use of bioproductive land associated with solid biofuel production and that of the carbon footprint, which are both seen to be larger than under either the MR or CC cases. Water and waste footprint components made almost negligibly small contributions under all three transition pathways. Lessons can clearly be drawn for other industrialised nations attempting to decarbonise their electricity generation systems, although local circumstances will determine the country-specific findings. Keywords: Environmental footprints, Resource burdens, Land use, Sustainability, Electricity supply industry, Transition pathways, United Kingdom

Several tidal power schemes have been proposed for the Severn estuary between south-west England and Wales, UK. In this paper the so-called Cardiff–Weston barrage is evaluated using various sustainability appraisal techniques to determine its net energy output, carbon dioxide footprint and financial investment criteria, alongside various critical technical and environmental issues. The barrage would be located seaward of the Severn Road crossings, involve an estimated cost of £21 billion to construct and could potentially generate some 16·8 TWh/year – about 4·4% of the UK electricity demand. An indicative energy technology assessment is undertaken to evaluate this tidal power scheme over its foreseen lifespan of 120 years in terms of its ‘cradle-to-site’, operation and maintenance requirements. The present analysis suggests that the proposed Cardiff–Weston barrage would yield relatively attractive ‘figures of merit’ in terms of its net energy and carbon dioxide emissions, although its financial performance is poorer than that of alternative power generators. Comparisons are also made with the much smaller Shoots barrage scheme proposed upstream of the Severn Road crossings, which is favoured by environmental groups due to its more benign ecological and environmental impacts.

The thermodynamic implications of different bioethanol production routes from wheat straw (a cellulosic co-product or ‘waste’ stream) have been evaluated. Thermodynamic (energy and exergy) analysis gives rise to alternative insights into the relative performance of various process chains. The thermodynamic property known as ‘exergy’, for example, reflects the ability of undertake ‘useful work’, but does not represent well heating processes. Thus, energy analysis of four different production paths have been analysed via the consideration of mechanical work, temperature changes and separating techniques. The Net Energy Value (NEV) of each production path or route was then evaluated, including the effect of system boundary expansion. Exergetic efficiencies were be obtained through chemical and physical exergy calculations, along with some of the electrical inputs to the different processes. Improvement potentials of the process stages were then determined using the exergetic efficiencies and irreversibility values respectively. These estimates will enable industrialists and policy makers to take account of some of the consequences of alternative bioethanol production routes in a low carbon future.

The opportunities and challenges to reducing industrial energy demand and carbon dioxide (CO2) emissions in the Chemicals sector are evaluated with a focus is on the situation in the United Kingdom (UK), although the lessons learned are applicable across much of the industrialised world. This sector can be characterised as being quite heterogeneous, and as sitting on the boundary between energy-intensive (EI) and non-energy-intensive (NEI) industrial sectors. Currently-available technologies will lead to further, short-term energy and CO2 emissions savings in chemicals processing, but the prospects for the commercial exploitation of innovative technologies by mid-21st century are far more speculative. The chemicals sector has long been the largest owner of generating plant in UK industry. Most generation is from CHP plant with significant amounts of excess electricity exported to the grid or other industrial sectors. Special care was taken not to ‘double count’ auto-generation and grid decarbonisation; so that the relative contributions to decarbonisations of each was accounted for separately. There are a number of non-technological barriers to the take-up of such technologies going forward. Consequently, the transition to a low carbon future in UK industry by 2050 will exhibit rather large uncertainties. The attainment of significant falls in carbon emissions over this period will depends critically on the adoption of a small number of key technologies [e.g., carbon capture and storage (CCS), energy efficiency techniques, and bioenergy], alongside a decarbonisation of the electricity supply.

Energy system transition research has been experimenting with the integration of qualitative and quantitative analysis due to the increased articulation it provides. Current approaches tend to be heavily biased by qualitative or quantitative methodologies, and more often are aimed toward a single academic discipline. This paper proposes an interdisciplinary methodology for the elaboration of energy system sociotechnical scenarios, applied here to the low carbon transition of the UK. An iterative approach was used to produce quantitative descriptions of the UK's energy transition out to 2050, building on qualitative storylines or narratives that had been developed through the formal application of a transition pathways approach. The combination of the qualitative and quantitative analysis in this way subsequently formed the cornerstone of wider interdisciplinary research, helping to harmonise assumptions, and facilitating 'whole systems' thinking. The methodology pulls on niche expertise of contributors to map and investigate the governance and technological landscape of a system change. Initial inconsistencies were found between energy supply and demand and addressed, the treatment of gas generation, capacity factors, total installed generating capacity, installation rates of renewables employed and the amount of electricity used by battery electric vehicles. Knowledge gaps relating to the operation of combined heat and power, sources of waste heat and future fuel sources were also investigated. By adopting the methodological approached to integrate qualitative and quantitative analysis the resulting elaboration is far more comprehensive, providing a stronger basis for wider research, and for deducing more robust insights for decision-making. It is asserted that this formal process helps build robust future scenarios not only for socio political storylines but also for the quantification of any qualitative storyline.

The relationship between electricity systems (power plants and associated networks) and the land area that they occupy forms a significant element of their sustainability appraisal. Conventional and renewable power generators have therefore been evaluated in order to determine their energy densities and spatial footprints on a life-cycle, or ‘cradle-to-gate’, basis. It has previously been argued in the literature that some of the renewable power generators take up far more land than their fossil fuelled or nuclear-powered counterparts. This assertion has consequentially been tested over the ‘full fuel chain’ in order to provide a valuable evidence base for developers, policy makers, and other stakeholders. The energy densities over this domain were determined using ‘process energy analysis’, whereby the energy required to produce electricity is evaluated taking into account both the direct energy use and the indirect (or ‘embodied’) energy requirements for materials and capital outputs. The nuclear fuel cycle (both with diffusion and centrifuge enrichment) was found to have the highest energy density, with bioenergy plants having the lowest. Onshore wind power exhibited a relatively promising energy density; being greater than that for its offshore counterpart. The energy density of the latter fell below that of solar photovoltaic (PV) arrays. Thus, renewables produce ‘dilute electricity’ overall with a spatial footprint that is orders-of-magnitude higher than for conventional sources, although there are many other sustainability criteria that will determine their overall usefulness in the transition towards a low carbon future.

Energy security and climate change mitigation are two of the most significant challenges facing governments in countries across the world. The United Kingdom (UK) government therefore passed the 2008 Climate Change Act that legally commits Britain to reducing ‘greenhouse gas’ (GHG) emissions by 80% over 1990 levels by the year 2050. Bioenergy (as a potentially low carbon and renewable energy source) is recognised as having the potential to contribute to mitigating GHG emissions and, through utilising domestic biomass resources, can help Britain reduce its reliance on fuel imports and thereby enhance energy security. In order to help guide the UK towards achieving its ambitious targets, a number of forecasting studies have been carried out, each proposing different pathways to securing its 2050 GHG emissions reduction target. The extent to which bioenergy can contribute to future energy supply is appraised, given the biomass resources available to Britain. Analysis of three notable low or zero carbon energy scenario sets developed by, respectively, the British Government’s Department of Business, Energy and Industrial Strategy (BEIS), the UK Energy Research Centre (UKERC), and the Centre for Alternative Technology (CAT) enabled a comparative evaluation to be made of each projection and their realism. They reflect alternative modelling approaches that seek to meet the statutory 2050 carbon reduction target (BEIS and UKERC), to that (by CAT) of fully decarbonising Britain by 2030. The spotlight is on the use of dedicated energy crops and their implications, with a particular emphasis on the critical factors and issues of land availability, conversion technologies [including bioenergy carbon capture and storage (BECCS)], and foreign imports. Likewise, the deployment of bioenergy resources may have significant deleterious impacts in terms of direct and indirect land use change, loss of biodiversity and the impairment of eco-system services, and competition with food production. A ‘gap analysis’ leads to recommendations for the improvement of the next generation scenarios and forecasts in order to provide more realistic projections for bioenergy uptake in the UK, although the lessons learned are applicable across much of the industrialised world. It was found that while all three low or zero carbon scenario studies had internal shortcomings from a bioenergy perspective, the analysis by BEIS stood out as having the greatest level of realism due to the account given to many of the critical factors and underlying issues relating to bioenergy uptake.

This editorial accompanies the full launch of the latest new BMC Series journal, BMC Energy. Written jointly by the journal Section Editors, the Chair of the Editorial Advisory Board and the Editor at Springer Nature, this editorial outlines how this new journal plans to serve the energy research community and describes in detail the scope of the work that it hopes to attract. BMC Energy joins a number of new physical science journals that have been launched recently in the BMC Series, each following BMC Series’ ethos of openness and inclusivity, aiming to publish quality research that is accessible for all.

There is at present much interest in unconventional sources of natural gas, especially in shale gas which is obtained by hydraulic fracturing, or ‘fracking’. Boreholes are drilled and then lined with steel tubes so that a mixture of water and sand with small quantities of chemicals – the fracking fluid – can be pumped into them at very high pressure. The sand grains that wedge into the cracks induced in the shale rock by a ‘perforating gun’ then releases gas which returns up the tubes. In the United Kingdom (UK) exploratory drilling is at an early stage, with licences being issued to drill a limited number of test boreholes around the country. However, such activities are already meeting community resistance and controversy. Like all energy technologies it exhibits unwanted ‘side-effects’; these simply differ in their level of severity between the various options. Shale gas may make, for example, a contribution to attaining the UK’s statutory ‘greenhouse gas’ emissions targets, but only if appropriate and robust regulations are enforced. The benefits and disadvantages of shale gas fracking are therefore discussed in order to illustrate a ‘balance sheet’ approach. It is also argued that it is desirable to bring together experts from a range of disciplines in order to carry out energy technology assessments. That should draw on and interact with national and local stakeholders: ‘actors’ both large and small. Community engagement in a genuinely participative process – where the government is prepared to change course in response to the evidence and public opinion – will consequently be critically important for the adoption of any new energy option that might meet the needs of a low carbon future.

Progress in reducing industrial energy demand and carbon dioxide (CO2 ) emissions is evaluated with a focus is on the situation in the United Kingdom (UK), although the lessons learned are applicable across much of the industrialized world. The UK industrial sector is complex, because it may be viewed as consisting of some 350 separate combinations of subsectors, devices and technologies. Various energy analysis and carbon accounting techniques applicable to industry are described and assessed. The contributions of the energy-intensive (EI) and nonenergy-intensive (NEI) industrial subsectors over recent decades are evaluated with the aid of decomposition analysis. An observed drop in aggregate energy intensity over this timescale was driven by different effects: energy efficiency improvements; structural change; and fuel switching. Finally, detailed case studies drawn from the Cement subsector and that associated with Food and Drink are examined; representing the EI and NEI subsectors, respectively. Currently available technologies will lead to further, short-term energy and CO2 emissions savings in manufacturing, but the prospects for the commercial exploitation of innovative technologies by mid-21st century are far more speculative. There are a number of nontechnological barriers to the take-up of such technologies going forward. Consequently, the transition pathways to a low carbon future in UK industry by 2050 will exhibit large uncertainties. The attainment of significant falls in carbon emissions over this period depends critically on the adoption of a limited number of key technologies [e.g., carbon capture and storage (CCS), energy efficiency techniques, and bioenergy], alongside a decarbonization of the electricity supply. WIREs Energy Environ 2016, 5:684–714. doi: 10.1002/wene.212 For further resources related to this article, please visit the WIREs website.

District heating schemes can act as enablers for the use of low carbon heat sources. Heat rejected by industrial sites could potentially be used in supplying such schemes but various constraints limit the extent to which this is likely to occur. This study estimates the quantity of heat that could be supplied to district heating networks from industrial sites in Great Britain (GB), in the context of a range of limiting criteria. An existing spatially disaggregated database of GB's heat demands was combined with previous analysis of the magnitude, temperature and location of the heat that is rejected by industrial sites. The heat that could be supplied from the industrial sites to the heat demands was then calculated with a range of different criteria applied. The criteria which were considered included the maximum allowable distance between the heat sources and demands, the minimum heat density of the demands which was considered feasible, the heat losses that may occur, and the seasonal profile of the heat demands. The potential gains from using absorption heat pumps, driven by high temperature heat to supply lower grade heat were found to be limited. High and low estimates of the heat rejected by the industrial sites were compared. Domestic and non-domestic heat demands were examined. Although the domestic demands have a greater total, they tend to occur at lower densities and so it is likely that both demands will take a significant share of the heat supplied. The seasonality of the heat demands has a greater impact on the need for supplementary heat sources than on the total heat delivered. For the distance and heat demand density criteria considered most appropriate, only half of the heat which is rejected by industry could be utilised by district heating networks.

The laws of thermodynamics set a theoretical limit on the energy savings that can be realised in a given application. This thermodynamic potential cannot be reached in practice, and a technical potential for energy savings is defined by the performance of available technology. Only applications of the technology that are considered economic will usually be considered for installation. This economic potential will itself not be fully realised, with the actual savings that are achieved limited by further barriers. A database on surplus heat availability within UK industry was used to estimate the thermodynamic, technical, and economic potentials when converting this surplus heat to electricity using organic Rankine cycles (ORCs). Technical and economic information was based on that reported from existing installations and manufacturers. Installations economic over the target payback period totalled approximately 3.5 PJ/yr of electricity generation, primarily in the steel, chemicals and cement subsectors. However, this result is sensitive to the input parameters, particularly the future price of electricity and required payback period, which are uncertain. Therefore a range of possible scenarios were investigated. The results form a basis for discussion on how to close this “gap” between the identified potentials and the savings realised in practice.

An indicative appraisal has been undertaken of a combined Anaerobic Digestion and Steam Methane Reforming process to produce sustainable hydrogen from organic waste. The anaerobic digestion plant was based on the plant in Tilburg (The Netherlands), and was modelled from the kerbside organic waste collections through to methane production. Data on biogenic waste was obtained from a collection trial in a municipal area in the UK. This was scaled-up to match that of a Tilburg-like anaerobic digestion plant. The waste collection trials enabled the catchment area for an anaerobic digestion plant on a commercial scale to be estimated. A thermodynamic evaluation of the combined process included energy and exergy analysis in order to determine the efficiency of each process, as well as to identify the areas that lead to inefficiencies. The overall energy efficiency was 75% and the overall exergy efficiency was 60%. The main energy losses were associated with compressor inefficiencies. In contrast, the main exergy consumption was found to be due to the fermentation in the digestion tanks. Other hydrogen process efficiencies vary from 21% to 86%, with the higher efficiencies belonging to non-renewable processes. However, the sustainable hydrogen produced comes from entirely renewable sources (biogenic waste) and has the benefit of near-zero carbon emissions in contrast to fossil fuels. Finally, the case study included an indicative financial assessment of the collection to processing chain. A discounted payback period of less than 20 years was estimated with a modest annual charge for householders.

This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Addressing GHG emissions from industry is vital to achieving decarbonisation targets. However, finding alternatives to many industrial energy requirements remains a challenge. Many processes in the food sector require heat at relatively low temperatures (i.e. 80°C to 200°C). High temperature heat pumps under development present a heat source that is efficient (especially if coupled with waste heat sources) and low carbon (especially if powered by decarbonised electricity). This study analysed their potential in the UK Dairy sub-sector and extrapolates this to the wider Food and Drink sector. There is potential to save approximately 164 kt-CO2/yr in the modelled processes. Applied to similar processes across the Food and Drink sector, there is scope to save 2.6 Mt-CO2/yr with projected 2030 grid electricity emissions factors. High temperature heat pumps have the potential to save energy and reduce GHG emissions. These GHG savings will increase further as the electrical grid continues to be decarbonised. While fuel cost savings are possible, these depend upon the processes and become more significant with projected fuel prices. UK Engineering and Physical Sciences Research Council

By relating to both the quality and quantity of energy flows, exergy analysis can be used to assess the improvement potential of thermodynamic systems. Exergy analysis has previously been applied at the economy level in order to provide a measure of the scope for efficiency improvement. While this approach can help to guide progress, meaningful analysis that takes full advantage of the insights of exergy, at this scale, retains some challenges. This study explores three relevant considerations to the interpretation and use of exergetic improvement potential applied at the macro (economy) scale. Specifically: (i) the nature of the relationship between improvement potential and the changes in efficiency that occur, (ii) the relative significance of exergy embodied in flows and (iii) the sensitivity of efficiency calculations to the definition of systems outputs. The nature of these considerations is evaluated empirically, using historic data. It is shown that exergy can provide useful information but that there is a complementary role for energy analysis. The scope for savings outside of direct “improvement potential” is also noted. It is hoped that appreciation of these considerations will lead to more effective exergy analysis at the economy scale, with its advantages and also limitations properly understood.

Several tidal power schemes have been proposed for the River Severn Estuary between the South West of England and Wales. An indicative technology assessment has been undertaken in order to evaluate the so-called ‘Shoots Barrage’ over its foreseen lifespan of 120 years in terms of its cradle-to-site, operation and maintenance requirements. It would be located just upriver of the Severn road crossings in the United Kingdom (UK), involve an estimated cost of £3.2 bn to construct, and could potentially generate around 2.7 TWh per year (or a little under 1% of UK electricity demand). This scheme is favoured by environmental groups, because to its more benign environmental impacts compared with the much larger, Cardiff-Weston scheme. The present analysis suggests that the proposed Shoots Barrage would yield relatively attractive ‘figures of merit’ in terms of its net energy and carbon emissions, although its financial performance is poorer than alternative power generators.

The UK cement sector was responsible for around 7 Mt of carbon dioxide emissions in 2010. These emissions were due to direct fuel use, the chemical reactions that occur as part of the production process, and electricity use (leading to indirect emissions). Historical trends show that the sector has made considerable reductions in its emissions. This was due to a combination of reduced output, the substitution of emissions-intensive clinker, improved efficiency and fuel switching. The prospects for reductions in the specific energy use and emissions were explored under a range of scenarios out to 2050. Further efficiency improvements were found to be limited. There is potential for additional clinker substitution and fuel switching – although such options are not without their difficulties. The use of carbon capture and storage technology, and alternative (low carbon) cements could lead to larger reductions in specific emissions, but the widescale use of these options is unproven. The approach taken in analysing the cement sector is an example of the bottom-up analysis of the UK industrial sector that has been undertaken in order to produce a database of industrial energy use and improvement potential aimed at meeting the modelling needs of policy makers.

A database of the heat demand, and surplus heat available, at United Kingdom industrial sites involved in the European Union Emissions Trading System, was used to estimate the technical potential of various heat recovery technologies. The options considered were recovery for use on-site, using heat exchangers; upgrading the heat to a higher temperature, using heat pumps; conversion of the heat energy to fulfill a chilling demand, using absorption chillers; conversion of the heat energy to electrical energy, using Rankine cycles; and transport of the heat to fulfill an off-site heat demand. A broad analysis of this type, which investigates a large number of sites, cannot accurately identify site level opportunities. However the analysis can provide an indicative assessment of the overall potential for different technologies. The greatest potential for reusing this surplus heat was found to be recovery at low temperatures, utilising heat exchangers; and in conversion to electricity, mostly using organic Rankine cycle technology. Both these technologies exist in commercial applications, but are not well established, support for their development and installation could increase their use. The overall surplus heat that was technically recoverable using a combination of these technologies was estimated at 52PJ/yr, saving 2.2MtCO2e/yr in comparison to supplying the energy outputs in a conventional manner. It is thought that a network and market for trading in heat and the wider use of district heating systems could open considerable potential for exporting heat from industrial sites to other users.

Conventional and renewable power generators have been evaluated in order to determine their energy densities and spatial footprints on a life-cycle (or ‘cradle-to-gate’) basis. The nuclear fuel cycle (both with diffusion and centrifuge enrichment) was found to have the highest energy density, with bioenergy plants having the lowest. Onshore wind power exhibited a relatively promising energy density; being greater than that for its offshore counterpart. The energy density of the latter fell below that of solar photovoltaic (PV) arrays. Thus, renewables produce ‘dilute electricity’ overall with a spatial footprint that is orders-of-magnitude higher than for conventional sources, although there are many other sustainability criteria that will determine their usefulness in the transition towards a low carbon future.

Electricity generation contributes a large proportion of the total greenhouse gas emissions in the United Kingdom (UK), due to the predominant use of fossil fuel (coal and natural gas) inputs. Indeed, the various power sector technologies [fossil fuel plants with and without carbon capture and storage (CCS), nuclear power stations, and renewable energy technologies (available on a large and small {or domestic} scale)] all involve differing environmental impacts and other risks. Three transition pathways for a more electric future out to 2050 have therefore been evaluated in terms of their life-cycle energy and environmental performance within a broader sustainability framework. An integrated approach is used here to assess the impact of such pathways, employing both energy analysis and environmental life-cycle assessment (LCA), applied on a ‘whole systems’ basis: from ‘cradle-to-gate’. The present study highlights the significance of ‘upstream emissions’, in contrast to power plant operational or ‘stack’ emissions, and their (technological and policy) implications. Upstream environmental burdens arise from the need to expend energy resources in order to deliver, for example, fuel to a power station. They include the energy requirements for extraction, processing/refining, transport, and fabrication, as well as methane leakage that occurs in coal mining activities – a major cotribution – and from natural gas pipelines. The impact of upstream emissions on the carbon performance of various low carbon electricity generators [such as large-scale combined heat and power (CHP) plant and CCS] and the pathways distinguish the present findings from those of other UK analysts. It suggests that CCS is likely to deliver only a 70% reduction in carbon emissions on a whole system basis, in contrast to the normal presumption of a 90% reduction. Similar results applied to other power generators.

NOTICE: this is the author’s version of a work that was accepted for publication in Energy Policy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Energy Policy, vol 52, 2013, DOI 10.1016/j.enpol.2012.10.052

Environmental or ‘ecological’ footprints have been widely used in recent years as indicators of resource consumption and waste absorption presented in terms of biologically productive land area [in global hectares (gha)] required per capita with prevailing technology. In contrast, ‘carbon footprints’ are the amount of carbon (or carbon dioxide equivalent) emissions for such activities in units of mass or weight (like kilograms per functional unit), but can be translated into a component of the environmental footprint (on a gha basis). The carbon and environmental footprints associated with the world production of liquid biofuels have been computed for the period 2010–2050. Estimates of future global biofuel production were adopted from the 2011 International Energy Agency (IEA) ‘technology roadmap’ for transport biofuels. This suggests that, although first generation biofuels will dominate the market up to 2020, advanced or second generation biofuels might constitute some 75% of biofuel production by 2050. The overall environmental footprint was estimated to be 0.29 billion (bn) gha in 2010 and is likely to grow to around 2.57 bn gha by 2050. It was then disaggregated into various components: bioproductive land, built land, carbon emissions, embodied energy, materials and waste, transport, and water consumption. This component‐based approach has enabled the examination of the Manufactured and Natural Capital elements of the ‘four capitals’ model of sustainability quite broadly, along with specific issues (such as the linkages associated with the so‐called energy–land–water nexus). Bioproductive land use was found to exhibit the largest footprint component (a 48% share in 2050), followed by the carbon footprint (23%), embodied energy (16%), and then the water footprint (9%). Footprint components related to built land, transport and waste arisings were all found to account for an insignificant proportion to the overall environmental footprint, together amounting to only about 2%

This study quantifies the increase in the peak power demand, net of non-dispatchable generation, that may be required by widespread adoption of heat pumps. Electrification of heating could reduce emissions but also cause a challenging increase in peak power demand. This paper expands on previous studies by quantifying the increase in greater detail; considering a wider range of scenarios, the characteristics of heat pumps and the interaction between wind generation and demand side management. A model was developed with dynamic simulations of individual heat pumps and dwellings. The increase in peak net-demand is highly sensitive to assumptions regarding the heat pumps, their installation, building fabric and the characteristics of the grid. If 80% of dwellings in the UK use heat pumps, peak net-demand could increase by around 100% (54GW) but this increase could be mitigated to 30% (16GW) by favourable conditions. Demand side management could reduce this increase to 20%, or 15% if used with extensive thermal storage. If 60% of dwellings use heat pumps, the increase in peak net-demand could be as low as 5.5GW.High-performance heat pumps, appropriate installation and better insulated dwellings could make the increase in peak net-demand due to the electrification of heating more manageable.

Electricity generation contributes a large proportion of the total greenhouse gas emissions in the United Kingdom (UK), due to the predominant use of fossil fuel (coal and natural gas) combustion for this purpose. A range of future UK energy scenarios has been employed to determine their resulting environmental and carbon footprints. Methodologies have been established to calculate these footprints for the UK electricity supply industry on both a historic timescale and in accordance with the three selected scenarios. The latter scenarios, developed by the UK SUPERGEN Consortium on 'Highly Distributed Power Systems' (HDPS), were characterised as 'Business As Usual' (BAU), 'Low Carbon' (LC) and 'Deep Green' (DG) futures, and yielded possible electricity demands out to 2050. It was found that the environmental footprint of the current power network is 41 million (M) global hectares (gha). If future trends follow a 'Business As Usual' scenario, then this footprint is observed to fall to about 25 Mgha in 2050. The LC scenario implies an extensive penetration of micro-generators in the home to satisfy heat and power demands. However, these energy requirements are minimised by way of improved insulation of the building fabric and other demand reduction measures. In contrast, the DG scenario presupposes a network where centralised renewable energy technologies - mainly large-scale onshore and offshore wind turbines - have an important role in the power generation. However, both the LC and DG scenarios were found to lead to footprints of less than 4 Mgha by 2050. These latter two scenarios were found to give rise to quite similar trajectories over the period 2010-2050. They are therefore more likely to reflect an effective transition pathway in terms of meeting the 2050 UK CO 2 reduction targets associated with decarbonisation of its power network. However, this appears unlikely to be achieved by 2030-2040 as advocated by the UK Government's advisory Committee on Climate Change in order to meet overall national carbon reduction targets.

Bioenergy from lignocellulosic biomass offers the potential to provide a significant source of clean, low carbon and secure energy. In recent years, a number of studies have been carried out to assess the environmental performance of lignocellulosic ethanol fuel. However, the complexity of biofuel systems generates significantly different results due to the differences in input data, methodologies applied, and local geographical conditions. Moreover, much attention has been placed on assessing climate change potential and energy consumption. This study draws on 53 published life cycle assessment of the lignocellulosic ethanol. More than half of the articles reviewed focus on assessing greenhouse gas (GHG) emission or fossil energy consumption or combination of both. All studies but two reviewed conclude that there is a reduction of GHG emission when using lignocellulosic ethanol in comparison to fossil fuel reference system. However, different studies have reported different sources contributing to GHG emission: some reports majority of GHG emissions come from biomass cultivation stage; others argue significant GHG emissions from ethanol conversion process. All articles suggest a reduction of fossil consumption in all cases of ethanol fuel. Contrary results for the impact of acidification and eutrophication potential from lignocellulosic ethanol are also observed—some reports less impact in comparison to conventional gasoline whiles others report significant increase of acidification and eutrophication potential by ethanol production. Studies also show water consumption varies significantly depending on biomass types, irrigation requirement, and regional irrigation practices; with different findings on whether agricultural practices or ethanol conversion being the main sources for water consumption. Contrary findings on emissions contributing to ecotocixity and human health have also been reported with some being favourable while others not. Results from the literature also suggest strong dependency of LCA results on system boundary, functional unit, data quality and allocation methods chosen.

Governments face pressures to improve national energy efficiency that are comparable to those caused by the energy crises of the 1970s. In UK industry a public programme of research, development and demonstration (RD&D) emanated from the crises and persisted until the end of the 1980s. The main element of this strategy was a full-scale commercial demonstration scheme: the Energy Efficiency Demonstration Scheme (EEDS). This work presents a bottom-up/top-down data analysis to examine the influence of the scheme on the overall energy demand trend of the UK industrial sector as separated from structural and output effects. It was concluded that earlier deployment of efficiency technologies as a result of their demonstration under the scheme may have provided a quarter of the observed energy demand reduction over the period 1979–1989. However, it should be noted that it is inherently difficult to accurately determine the extent to which earlier technology investments occur as a result of supported demonstration. The scheme’s mechanism and replacement was also discussed in order to derive lessons. Policy and economic implications for the UK were examined.

Under the Kyoto Protocol many countries have targets to reduce carbon emissions and increase renewable energy production. In order to do this effectively the impact and efficacy of differing schemes must be determined. One option for producing electricity is through the use of a tidal barrage. The largest potential barrage scheme considered in the UK is the Cardiff–Weston barrage scheme in the Severn estuary. The scheme would be a single, renewable installation and is predicted to constitute 4% of the UK electricity supply. Therefore a carbon and energy assessment was completed on the Cardiff–Weston Severn barrage scheme. The assessment shows that the energy and carbon intensity of the Severn barrage is small in comparison to the National Grid mix and that, given reasonable assumptions, the Severn barrage can contribute to meeting the UK carbon reduction target. Importantly, the operation stage was identified as both the most energy and carbon intense by a large margin. This is a notable finding as preceding studies have tended to dismiss the consequences of the barrage operation as minimal or nil. Whilst these findings are for the Cardiff–Weston barrage, the implications will be similar for tidal barrages in other sites in the UK and globally.

A range of major risks associated with the production and use of biofuels in the rapidly changing United Kingdom (UK) energy and transport sectors have been identified and quantified. This was achi...

‘Carbon footprints’ represent the amount of carbon (or carbon dioxide equivalent) emissions associated with a given activity or community, and are closely related to ecological or environmental footprints. But, unlike the latter, they are generally presented in terms of units of mass or weight (kilograms per functional unit), rather than in spatial units (such as global hectares). These carbon footprints have become the ‘currency’ of debate in a climate-constrained world. They are increasingly popular ecological indicators, adopted by individuals, businesses, governments, and the media alike. The influence of economic wealth, population density, and pollutant emission intensity upon national carbon footprints has been correlated using a ‘power–law’ equation. This analysis provides a greater understanding of the carbon footprint concept and its national determinants in a bipolar world: one embracing the countries of the prosperous or industrialised North of the planet and the other covering the developing, ‘Majority’ South, where some 80% of the global population resides. Such a bipolar world is depicted by highlighting the countries that make up some of the largest economies in the form of the G-20 nations. This international grouping encompasses nation states from both the North and South. Emerging countries from the South with large populations (such as China and India) now have economies whose overall size rivals those of the North. Here the factors that are principally responsible for driving national carbon footprints are illustrated in the context of their potential consequences for global warming. An insight into these parameters is important in a period when the international community is seeking to agree a successor regime to the Kyoto Protocol on climate change mitigation.

Energy analysis, environmental life-cycle assessment (LCA) and economic appraisals have been utilised to study the performance of a domestic building integrated photovoltaic (BIPV) system on a ‘whole systems’ basis. Energy analysis determined that the system paid back its embodied energy in just 4.5 years. LCA revealed that the embodied impacts were offset by the electricity generated to provide a net environmental benefit in most categories. Only carcinogens, ecotoxicity and minerals had a small net lifetime burden. A financial analysis was undertaken from the householder's perspective, alongside cost-benefit analysis from a societal perspective. The results of both indicated that the systems are unlikely to pay back their investment over the 25 year lifetime. However, the UK is in an important period (2010/11) of policy transition with a move away from the ‘technology subsidies’ of the Low Carbon Buildings Programme (LCBP) and towards a ‘market development policy’ of feed-in tariffs. Representing the next stage on an innovation S-curve this is expected to facilitate rapid PV uptake, as experienced in countries such as Germany, Denmark, and Spain. The results of the present study clearly demonstrate the importance of the new government support scheme to the future uptake of BIPV.

Biofuels have been identified as a potential short-term solution for reducing greenhouse gas (GHG) emissions from road transport. Currently, '1st generation' biofuels are produced from food crops, but there are concerns with the indirect effects of utilising edible crops for fuel. There is increased interest in producing '2nd generation' biofuels from woody crops and straw, as these can be grown on lower grade land or do not compete directly with food. In order to ensure that biofuels actually deliver emission savings, the overall GHG balance of producing them must be calculated accurately, and compared with conventional fossil fuels. The GHG balance can vary significantly however, depending on biomass type, the production processes, the indirect effects, and also by the method by which the GHG emission balance is calculated. Currently, in the UK, there are three main GHG methodologies that potentially affect biofuel producers. Each has a different approach to measure GHG emissions from biofuel production, and each provides a different result, causing difficulties for policy makers. This study performs a partial life cycle assessment for bioethanol production from wheat grain and wheat straw to demonstrate the variability of the results between methodologies.

Barriers to UK bioenergy development arise from a number of technical, financial, social and other constraints. Likewise, the drivers for using bioenergy are numerous and diverse. A range of these barriers and drivers have been identified through a comprehensive literature and case study review, and then assessed through an online questionnaire, completed by stakeholders from across the UK bioenergy industry: farmers/suppliers, developers/owners of bioenergy projects, primary end-users, and government/policy stakeholders. The results are presented in the form of 'spider web' diagrams. The most critical barriers and drivers relate to economic factors of bioenergy projects. Farmers/suppliers and developers are influenced by production costs and benefits, whilst primary end-users of bioenergy are concerned mainly with the cost of purchasing energy resources. Common drivers for all stakeholders were found to be reducing carbon emissions and the dependency on fossil fuels. In order to satisfy the needs of stakeholders schemes must be both economically attractive and environmentally sustainable for projects to be successful.