Imperial College London

ProfessorNiallMac Dowell

Faculty of Natural SciencesCentre for Environmental Policy

Professor of Future Energy Systems
 
 
 
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Contact

 

+44 (0)20 7594 9298niall Website

 
 
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Location

 

16 Prince's GardensSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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138 results found

Landera A, Mac Dowell N, George A, 2021, Development of robust models for the prediction of Reid vapor pressure (RVP) in fuel blends and their application to oxygenated biofuels using the SAFT-γ approach, Fuel, Vol: 283, ISSN: 0016-2361

© 2020 The growing demand for inexpensive, environmentally benign fuels has sparked research into fuel properties that affect fuel production, handling and engine efficiency. Reid vapor pressure (RVP) has been shown to be one such important fuel property. Having models that can accurately predict the RVP of a fuel rapidly and robustly can aid in the design of de novo fuels and increase the value proposition to the refinery. Conventional fossil fuels typically consist of 100 s of highly non-ideal components, especially when oxygenates are involved, and current methods often fail to predict RVP correctly. The large number of components can render conventional modelling approaches burdensome and inaccurate. To overcome these barriers, a robust methodology for the rapid and accurate prediction of the RVP of complex base fuels blended with oxygenated biofuels via surrogate models was developed. The aim was to minimize the number of components necessary to accurately represent the complex mixture, whilst retaining the ability to accurately predict RVP of the base fuel. Three models were developed using the SAFT-γ approach, which varied in complexity and accuracy of prediction. The RVP for a suite of oxygenates, blended at 10, 20, and 30%, by weight into blendstocks for oxygentated blending (BOB) was studied in order to evaluate which oxygenate families have potential to reduce RVP. The majority of oxygenates evaluated decreased the RVP of the mixture, with the branched alcohols and the ketones showing the largest decrease. These results have promising implications for biofuels development and biorefinery economics.

Journal article

Firth AEJ, Mac Dowell N, Fennell PS, Hallett JPet al., 2020, Assessing the economic viability of wetland remediation of wastewater, and the potential for parallel biomass valorisation, Environmental Science: Water Research & Technology, Vol: 6, Pages: 2103-2121, ISSN: 2053-1400

Constructed wetlands have been shown to consistently remove a wide range of pollutants from contaminated water. However, no wide-ranging studies exist on the economic viability of this technology. This paper performs a high-level economic comparison between wetland remediation and conventional water remediation technologies, for a wide range of contaminant inputs, outputs, and flow rates. The cases considered are nutrient removal from wastewater, and remediation of low-pH and circumneutral acid mine drainage (AMD). The first-order P-k-C* model is used for nutrient removal, while a zeroth-order model is used for AMD remediation, with removal rate data taken from the literature. The number of wetland cells employed was found to significantly affect the overall cost of nutrient removal, allowing savings of up to 86% and 42% for biochemical oxygen demand and phosphorus removal, particularly for low concentrations and flow rates. For integrated secondary and tertiary treatment, wetland remediation was economically competitive down to stringent effluent standards. A sensitivity analysis was performed on sizing and costing parameters of nutrient removal wetlands, with required wetland size found to be most strongly correlated with the assumed removal rate, and land costs found to have relatively little effect on overall costs. Wetland remediation of AMD was only found to be economically favourable for less severe conditions and lower flow rates when treating low-pH drainage, and was heavily influenced by the acidity removal rate. However, the majority of site data from literature was found to fall within this range of conditions. For circumneutral AMD, wetland remediation was found to be cheaper for all simulated cases. The feasibility of offsetting wetland remediation costs through biomass valorisation was investigated for a range of products, with area requirements for minimum economic production identified as the principal barrier.

Journal article

Ganzer C, Mac Dowell N, 2020, A comparative assessment framework for sustainable production of fuels and chemicals explicitly accounting for intermittency, SUSTAINABLE ENERGY & FUELS, Vol: 4, Pages: 3888-3903, ISSN: 2398-4902

Journal article

Pozo C, Galán-Martín Á, Reiner DM, Mac Dowell N, Guillén-Gosálbez Get al., 2020, Equity in allocating carbon dioxide removal quotas, Nature Climate Change, Vol: 10, Pages: 640-646, ISSN: 1758-678X

The first nationally determined contributions to the Paris Agreement include no mention of the carbon dioxide removal (CDR) necessary to reach the Paris targets, leaving open the question of how and by whom CDR will be delivered. Drawing on existing equity frameworks, we allocate CDR quotas globally according to Responsibility, Capability and Equality principles. These quotas are then assessed in the European Union context by accounting for domestic national capacity of a portfolio of CDR options, including bioenergy with carbon capture and storage, reforestation and direct air capture. We find that quotas vary greatly across principles, from 33 to 325 GtCO2 allocated to the European Union, and, due to biophysical limits, only a handful of countries could meet their quotas acting individually. These results support strengthening cross-border cooperation while highlighting the need to urgently deploy CDR options to mitigate the risk of failing to meet the climate targets equitably.

Journal article

Olympios A, Hoisenpoori P, Mersch M, Pantaleo A, Simpson M, Sapin P, Mac Dowell N, Markides Cet al., 2020, Optimal design of low-temperature heat-pumping technologies and implications to the whole energy system, The 33rd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems.

This paper presents a methodology for identifying optimal designs for air-source heat pumps suitable for domestic heating applications from the whole-energy system perspective, accounting explicitly for a trade-off between cost and efficiency, as well as for the influence of the outside air temperature during off-design operation. The work combines dedicated brazed-plate and plate-fin heat-exchanger models with compressor efficiency maps, as well as equipment costing techniques, in order to develop a comprehensive technoeconomic model of a low-temperature air-source heat pump with a single-stage-compressor, based on the vapour-compression cycle. The cost and performance predictions are validated against manufacturer data and a non-linear thermodynamic optimisation model is developed to obtain optimal component sizes for a set of competing working fluids and design conditions. The cost and off-design performance of different configurations are integrated into a whole-energy system capacity-expansion and unit-dispatch model of the UK power and heat system. The aim is to assess the system value of proposed designs, as well as the implications of their deployment on the power generation mix and total transition cost of electrifying domestic heat in the UK as a pathway towards meeting a national net-zero emission target by 2050. Refrigerant R152a appears to have the best design and off-design performance, especially compared to the commonly used R410a. The size of the heat exchangers has a major effect on heat pump performance and cost. From a wholesystem perspective, high-performance heat pumps enable a ~20 GW (~10%) reduction in the required installed power generation capacity compared to smaller-heat-exchanger, low-performance heat pumps, which in turn requires lower and more realistic power-grid expansion rates. However, it is shown that the improved performance as a result of larger heat exchangers does not compensate overall for the increased technology cost, with

Conference paper

Al-Qahtani A, Gonzalez-Garay A, Bernardi A, Galan-Martin A, Pozo C, Mac Dowell N, Chachuat B, Guillen-Gosalbez Get al., 2020, Electricity grid decarbonisation or green methanol fuel? A life-cycle modelling and analysis of today's transportation-power nexus, APPLIED ENERGY, Vol: 265, ISSN: 0306-2619

Journal article

Rúa J, Bui M, Nord LO, Mac Dowell Net al., 2020, Does CCS reduce power generation flexibility? A dynamic study of combined cycles with post-combustion CO2 capture, International Journal of Greenhouse Gas Control, Vol: 95, Pages: 1-10, ISSN: 1750-5836

To date, the deployment, integration, and utilization of intermittent renewable energy sources, such as wind and solar power, in the global energy system has been the cornerstone of efforts to combat climate change. At the same time, it is recognized that renewable power represents only one element of the portfolio of technologies that will be required to deliver a technically feasible and financially viable energy system. In this context, carbon capture and storage (CCS) is understood to play a uniquely important role, providing significant value through flexible operation. It is therefore of vital importance that CCS technology can operate synergistically with intermittent renewable power sources, and consequently ensuring that CCS does not inhibit the flexible and dispatchable nature of thermal power plants. This work analyses the intrinsic dynamic performance of the power and CO2 capture plants independently and as an integrated system. Since the power plant represents the fast dynamics of the system and the steam extraction is the main point of integration between the CO2 capture and power plants, disturbances with fast dynamics are imposed on the steam extraction valve during steady state and dynamic operation of a natural gas combined cycle (NGCC) to study the effects of the integration on power generation capacity. The results demonstrate that the integration of liquid-absorbent based post-combustion CO2 capture has negligible impact on the power generation dynamics of the NGCC.

Journal article

Bui M, Flø NE, de Cazenove T, Mac Dowell Net al., 2020, Demonstrating flexible operation of the Technology Centre Mongstad (TCM) CO2 capture plant, International Journal of Greenhouse Gas Control, Vol: 93, Pages: 1-26, ISSN: 1750-5836

This study demonstrates the feasibility of flexible operation of CO2capture plants with dynamic modelling and experimental testing at the Technology Centre Mongstad (TCM) CO2capture facility in Norway. This paper presents three flexible operation scenarios: (i) effect of steam flow rate, (ii) time-varying solvent regeneration, and (iii) variable ramp rate. The dynamic model of the TCM CO2capture plant developed in gCCS provides further insights into the process dynamics. As the steam flow rate decreases, lean CO2loading increases, thereby reducing CO2capture rate and decreasing absorber temperature. The time-varying solvent regeneration scenario is demonstrated successfully. During “off-peak” mode (periods of low electricity price), solvent is regenerated, reducing lean CO2loading to 0.16molqY:/molMEAand increasing CO2capture rate to 89–97%. The “peak” mode(period of high electricity price) stores CO2within the solvent by reducing the reboiler heat supply and in-creasing solvent flow rate. During peak mode, lean CO2loading increases to 0.48molqY:/molMEA, reducing CO2 capture rate to 14.5%, which in turn decreases the absorber temperature profile. The variable ramp rate scenario demonstrates that different ramp rates can be applied successively to a CO2capture plant. By maintaining constant liquid-to-gas (L/G) ratio during the changes, the CO2capture performance will remain the same, i.e., constant lean CO2loading (0.14–0.16molqY:/molMEA) and CO2capture rate (87–89%). We show that flexible operation in a demonstration scale absorption CO2capture process is technically feasible. The deviation between the gCCS model and dynamic experimental data demonstrates further research is needed to improve existing dynamic modelling software. Continual development in our understanding of process dynamics during flexible operation of CO2capture plants will be essential. This paper provides additional value by presenting a com-prehensive dy

Journal article

Cabral RP, Mac Dowell N, 2020, Chapter 6: Oxy-fuel combustion capture technology, RSC Energy and Environment Series, Pages: 168-188, ISBN: 9781788014700

© The Royal Society of Chemistry 2020. This chapter discusses oxy-fuel combustion for the capture and subsequent sequestration of carbon dioxide. Technologies for oxygen production based on air separation will be presented and the need to reduce energy consumption of these units will be discussed along with some potential strategies. A pulverized coal-fired power plant and a natural gas combined cycle will be analysed as case studies for oxy-combustion and the benefits of using pure oxygen will be discussed as well as how the changes in the thermodynamic properties affect boiler operation. Purification of carbon dioxide in the resulting flue gas to pipeline transport specifications will end the discussion of this chapter with two examples of gas processing units. The parasitic power consumption of this gas processing unit combined with the air separation unit reduces the net efficiency of the plant even though the thermal efficiency is increased, which emphasises the importance of developing new technologies, such as ion transport membranes for oxygen production. The possibility to reduce the energy consumption of both air separation unit and gas processing unit combined with the increased combustion efficiency by using pure oxygen make this a promising technology for carbon capture and storage.

Book chapter

Heuberger CF, Mac Dowell N, 2020, Chapter 12: CCS in electricity systems, RSC Energy and Environment Series, Pages: 392-425, ISBN: 9781788014700

© The Royal Society of Chemistry 2020. This chapter aims at evaluating CCS equipped power generation in a power system context. Initially, the main power system services and mechanisms are reviewed. Decarbonisation poses transformational challenges associated with system reliability and operability to the energy system. New approaches to evaluate power generation and storage technologies in a whole-systems context are discussed and demonstrated. CCS power plants are able to reduce the total system cost and lead to a least-cost decarbonisation of the power sector. Enhanced flexibility in CCS power generation can provide additional value to the system. Research, policies, and markets should aim at explicitly evaluating new technology services to the power system, such as flexibility, low CO2 emissions, or the provision of ancillary services.

Book chapter

Leeson D, Ramirez A, Mac Dowell N, 2020, Chapter 9: Carbon capture and storage from industrial sources, RSC Energy and Environment Series, Pages: 296-314, ISBN: 9781788014700

© The Royal Society of Chemistry 2020. The industrial sector is responsible for 21% of all global carbon dioxide emissions, and, as such, emissions mitigation is as important in this sector as in the power generation sector. Individual industries are sufficiently diverse that bespoke capture strategies must be created for them, with different technologies more appropriate for different industries. One major difference between industrial and power carbon capture and storage (CCS) is that industries often have numerous sources of varying sizes and CO2 concentration, requiring some degree of aggregation or multiple capture units in order to capture large proportions of flue gases, implying an important trade-off between capture rate and cost. Within the chemical manufacturing industries, there exist streams of high-purity CO2 which can be used for demonstration CCS schemes at a lower cost than other flue streams, and as a first mover towards wide scale deployment. However, attempting to calculate the cost of industrial CCS is difficult since there are a wide range of reported costs from literature, with little consensus even within technologies for the same industry. Policy challenges remain broadly similar to those encountered in the power industry, though due to the global markets for industrial products, some market mechanism would be required in the event of unilateral decarbonisation in order not to penalise first-mover entities.

Book chapter

Bui M, Mac Dowell N, 2020, Chapter 1: Introduction-Carbon capture and storage, RSC Energy and Environment Series, Pages: 1-7, ISBN: 9781788014700

© The Royal Society of Chemistry 2020. CO2 capture and storage (CCS) and greenhouse gas removal (GGR) are considered vital to meeting global climate change targets. However, despite their technical maturity, their deployment consistently lags behind what is known to be required. This introductory chapter explores why, and suggests some possible paths forward.

Book chapter

Algunaibet IM, Pozo C, Galan-Martin A, Huijbregts MAJ, Mac Dowell N, Guillen-Gosalbez Get al., 2020, Reply to the 'Comment on "Powering sustainable development within planetary boundaries"' by Y. Yang, Energy Environ. Sci., 2020, 13, DOI: 10.1039/C9EE01176E, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 13, Pages: 313-316, ISSN: 1754-5692

Journal article

Daggash HA, Fajardy M, Mac Dowell N, 2020, Chapter 14: Negative emissions technologies, RSC Energy and Environment Series, Pages: 447-511, ISBN: 9781788014700

© The Royal Society of Chemistry 2020. The Paris Agreement signalled global consensus to keep average temperature rise "well below" 2 °C by the end of the century. Results from integrated assessment models have made it increasingly evident that negative emissions (removing CO2 from the atmosphere) are crucial to achieving this. Consequently, negative emissions technologies (NETs) have come to the forefront of mitigation discussions. NETs must however overcome challenges if they are to be realised at scale. Uncertainties around the large-scale biomass supply have fuelled a debate on whether negative emissions from bio-energy with carbon capture and storage (BECCS) are sustainably achievable, if at all. Reliable carbon accounting frameworks and policy incentives are needed to improve investment prospects. The direct extraction of CO2 from air, or direct air capture (DAC), has since been demonstrated as a source of negative emissions. The large energy and economic costs associated with extracting CO2 from air are proving prohibitive to achieving commercial viability of DAC technology. Without dedicated policy support for technological innovation, and further interdisciplinary research to constrain a variety of uncertainties, the world risks foregoing a portfolio of technologies that add much-needed flexibility in the mitigation toolbox. This chapter details the evidence for negative emissions, proposed means of achieving them and their barriers to commercial effectiveness.

Book chapter

Heuberger CF, Bains PK, Mac Dowell N, 2020, The EV-olution of the power system: a spatio-temporal optimisation model to investigate the impact of electric vehicle deployment, Applied Energy, Vol: 257, Pages: 1-18, ISSN: 0306-2619

Power system models have become an essential part of strategic planning and decision-making in the energy transition. While techniques are becoming increasingly sophisticated and manifold, the ability to incorporate high resolution in space and time with long-term planning is limited. We introduce ESONE, the Spatially granular Electricity Systems Optimisation model. ESONE is a mixed-integer linear program, determining investment in power system generation and transmission infrastructure while simultaneously optimising operational schedule and optimal power flow on an hourly basis. Unique data clustering combined with model decomposition and an iterative solution procedure enable computational tractability. We showcase the capabilities of the ESONE model by applying it to the power system of Great Britain under CO2 emissions reduction targets. We investigate the effects of a spatially distributed large-scale roll-out of electric vehicles (EVs). We find EV demand profiles correlate well with offshore and onshore wind power production, reducing curtailment and boosting generation. Time-of-use-tariffs for EV charging can further reduce power supply and transmission infrastructure requirements. In general, Great Britain’s electricity system absorbs additional demand from ambitious deployment of EVs without substantial changes to system design.

Journal article

Danaci D, Bui M, Mac Dowell N, Petit Cet al., 2020, Exploring the limits of adsorption-based CO2 capture using MOFs with PVSA – from molecular design to process economics, Molecular Systems Design and Engineering, Vol: 5, Pages: 212-231, ISSN: 2058-9689

Metal-organic frameworks (MOFs) have taken the materials science world by storm, with potentials of near infinite possibilities and the panacea for adsorption-based carbon capture. Yet, no pilot-scale (or larger-scale) study exists on MOFs for carbon capture. Beyond material scalability issues, this clear gap between the scientific and engineering literature relates to the absence of suitable and accessible assessment of MOFs in an adsorption process. Here, we have developed a simple adsorbent screening tool with process economics to evaluate adsorbents for post-combustion capture, while also considering factors relevant to industry. Specifically, we have assessed the 25 adsorbents (22 MOFs, 2 zeolites, 1 activated carbon) against performance constraints – i.e. CO2 purity and recovery – and cost. We have considered four different CO2 capture scenarios to represent a range of CO2 inlet concentrations. The cost is compared to that of amine-based solvents for which a corresponding model was developed. Using the model developed, we have conceptually assessed the materials properties and process parameters influencing the purity, recovery and cost in order to design the ‘best’ adsorbent. We have also set-up a tool for readers to screen their own adsorbent. In this contribution, we show that minimal N2 adsorption and moderate enthalpies of adsorption are key in obtaining good process performance and reducing cost. This stands in contrast to the popular approaches of maximizing CO2 capacity or surface area. Of the 22 MOFs evaluated, UTSA-16 shows the best performance and lowest cost for post-combustion capture, having performance in-line with the benchmark, zeolite 13X. Mg-MOF-74 performs poorly. The cost of using the adsorbents remains overall higher than that of an amine-based absorption process. Ultimately, this study provides specific directions for material scientists to design adsorbents and assess their performance at the process scale. This

Journal article

Danaci D, 2019, CO2 Capture by Adsorption Processes, Carbon Capture and Storage, Editors: Bui, Mac Dowell, Publisher: Royal Society of Chemistry, Pages: 106-167, ISBN: 978-1-78801-145-7

Adsorption is a reliable process technology that has been in use since the 1960s for gas separation applications. Since the mid 90s, interest has grown around CO2 emissions abatement with adsorption being one of the first technologies considered. There has since been significant research and development on both the materials science, and engineering aspects of adsorption for CO2 capture. Adsorbents with extensive histories such as zeolites, activated carbons, and layered double hydroxides have experienced resurgences, and novel adsorbents such as metal–organic frameworks and microporous organic polymers were conceived. Adsorption-based separations are cyclic processes, and methods to improve the attainable purity and recovery of the CO2 have also been investigated; this work has shown that 90%mol recovery and 95%mol purity are possible for post-combustion capture. Work is also underway to improve the throughput of gas–solid contacting devices as a form of process intensification, which is required for high volumetric flow rate applications. Although there are still some concerns around the stability of some adsorbents to impurities, there have been meaningful and significant advancements over the last 20–25 years. These have made adsorption a viable technology for carbon capture applications.

Book chapter

Bahzad H, Katayama K, Boot-Handford ME, Mac Dowell N, Shah N, Fennell PSet al., 2019, Iron-based chemical-looping technology for decarbonising iron and steel production, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 91, ISSN: 1750-5836

Journal article

Algunaibet IM, Pozo C, Galan-Martin A, Huijbregts MAJ, Mac Dowell N, Guillen-Gosalbez Get al., 2019, Powering sustainable development within planetary boundaries (vol 12, pg 1890, 2019), ENERGY & ENVIRONMENTAL SCIENCE, Vol: 12, Pages: 3612-3616, ISSN: 1754-5692

Journal article

Hepburn C, Adlen E, Beddington J, Carter EA, Fuss S, Mac Dowell N, Minx JC, Smith P, Williams CKet al., 2019, The technological and economic prospects for CO2 utilization and removal, Nature, Vol: 575, Pages: 87-97, ISSN: 0028-0836

The capture and use of carbon dioxide to create valuable products might lower the net costs of reducing emissions or removing carbon dioxide from the atmosphere. Here we review ten pathways for the utilization of carbon dioxide. Pathways that involve chemicals, fuels and microalgae might reduce emissions of carbon dioxide but have limited potential for its removal, whereas pathways that involve construction materials can both utilize and remove carbon dioxide. Land-based pathways can increase agricultural output and remove carbon dioxide. Our assessment suggests that each pathway could scale to over 0.5 gigatonnes of carbon dioxide utilization annually. However, barriers to implementation remain substantial and resource constraints prevent the simultaneous deployment of all pathways.

Journal article

Yao JG, Bui M, Dowell NM, 2019, Grid-scale energy storage with net-zero emissions: comparing the options, Sustainable Energy and Fuels, Vol: 3, Pages: 3147-3162, ISSN: 2398-4902

The transition to a low-carbon economy is an enormous challenge. With increasing deployment of intermittent renewable energy, there is a recognised need for scalable options for grid-scale, long-term, high energy density, energy storage. Grid-scale energy storage combined with carbon capture and utilisation (CCU) potentially provides a high level of flexibility and reliability. However, previous power-to-gas (P2G) studies have only examined the use of synthetic natural gas (SNG) derived from electrolytic hydrogen and either biomass- or industrially-derived CO2 for this application; making the whole power-to-power (P2P) value chain low carbon at best. Instead, our work assesses the techno-economic feasibility of using direct air capture to develop truly carbon-neutral P2P pathways. After assessing nine net-zero emission configurations using existing technologies, we found that using SNG as an energy storage carrier may be the least expensive route despite being more complex than power-to-hydrogen (P2H). P2H is currently held back by the high cost of H2 storage and the low volumetric density of H2 relative to SNG. Thus, bringing down the cost of H2 storage and building more salt caverns will be imperative for P2H, whereas reducing the cost of carbon capture should be a key priority for accelerating the deployment of power-to-methane (P2M) technologies.

Journal article

Cumicheo C, Mac Dowell N, Shah N, 2019, Natural gas and BECCS: A comparative analysis of alternative configurations for negative emissions power generation, International Journal of Greenhouse Gas Control, Vol: 90, Pages: 1-11, ISSN: 1750-5836

There is a reliance on negative emissions technologies (NETs), primarily in the form of Bioenergy with Carbon Capture and Storage (BECCS) in most Integrated Assessment Model (IAM) scenarios which are capable of limiting the maximum global temperature rise to 1.5–2 °C. Two currently independent features of transition pathways are fuel switching from a coal to gas, and the deployment of BECCS. The former makes natural gas an important transition fuel which at the same time could be combined with biomass to further abate emissions. To date the majority of studies have considered BECCS in the context of a conversion from coal-fired base configuration. There is therefore a pressing need to identify routes for the effective utilization of biomass-derived fuels in the context of gas-fired power generation infrastructure. In this contribution, we study three distinct CCS-based processes which combine natural gas and biomass capable of producing low-, or carbon-negative power. Both fuel supply chains are considered in order to quantify the net overall CO2 emissions. An important insight is the configuration-specific impact of biomass co-combustion on the overall carbon intensity of power generated. We found that an external biomass combustion configuration was the most carbon negative, removing between 0.5–1 ton of CO2 per MWh of power generated. Results revealed a trade-off between carbon negativity and efficiency of the processes. The generation of net carbon negative power is observed to be highly sensitive to the carbon footprint of the biomass supply chain.

Journal article

Albanito F, Hastings A, Fitton N, Richards M, Martin M, Mac Dowell N, Bell D, Taylor SC, Butnar I, Li P-H, Slade R, Smith Pet al., 2019, Mitigation potential and environmental impact of centralized versus distributed BECCS with domestic biomass production in Great Britain, Global Change Biology Bioenergy, Vol: 11, Pages: 1234-1252, ISSN: 1757-1693

New contingency policy plans are expected to be published by the United Kingdom government to set out urgent actions, such as carbon capture and storage, greenhouse gas removal and the use of sustainable bioenergy to meet the greenhouse gas reduction targets of the 4th and 5th Carbon Budgets. In this study, we identify two plausible bioenergy production pathways for bioenergy with carbon capture and storage (BECCS) based on centralized and distributed energy systems to show what BECCS could look like if deployed by 2050 in Great Britain. The extent of agricultural land available to sustainably produce biomass feedstock in the centralized and distributed energy systems is about 0.39 and 0.5 Mha, providing approximately 5.7 and 7.3 MtDM/year of biomass respectively. If this land‐use change occurred, bioenergy crops would contribute to reduced agricultural soil GHG emission by 9 and 11 urn:x-wiley:17571693:media:gcbb12630:gcbb12630-math-0001/year in the centralized and distributed energy systems respectively. In addition, bioenergy crops can contribute to reduce agricultural soil ammonia emissions and water pollution from soil nitrate leaching, and to increase soil organic carbon stocks. The technical mitigation potentials from BECCS lead to projected CO2 reductions of approximately 18 and 23 urn:x-wiley:17571693:media:gcbb12630:gcbb12630-math-0002/year from the centralized and distributed energy systems respectively. This suggests that the domestic supply of sustainable biomass would not allow the emission reduction target of 50 urn:x-wiley:17571693:media:gcbb12630:gcbb12630-math-0003/year from BECCS to be met. To meet that target, it would be necessary to produce solid biomass from forest systems on 0.59 or 0.49 Mha, or alternatively to import 8 or 6.6 MtDM/year of biomass for the centralized and distributed energy system respectively. The spatially explicit results of this study can serve to identify the regional differences in the potential capture of CO2 from BECC

Journal article

Zhang D, Bui M, Fajardy M, Patrizio P, Kraxner F, Mac Dowell Net al., 2019, Unlocking the potential of BECCS with indigenous sources of biomass at a national scale, Sustainable Energy and Fuels, Vol: 4, Pages: 226-253, ISSN: 2398-4902

Bioenergy with carbon capture and storage (BECCS) could play a large role in meeting the 1.5C argets, but faces well-documented controversy in terms of land-use concerns, competition with food production, and cost. This study presents a bottom-up assessment of the scale at which BECCS plants – biomass pulverised combustion plants (“BECCS” in this study) and bioenergy combustion in combined heat and power plants (BE-CHP-CCS) – can be sustainably deployed to meet national carbon dioxide removal (CDR) targets, considering the use of both primary and secondary (waste-derived) biomass. This paper also presents a comprehensive, harmonised data set, which enables others to build upon this work. Land availability for biomass cultivation, processing, and conversion is quantified based on a land-use analysis, avoiding all competition with land used for food production, human habitation, and other protected areas. We find that secondary biomass sources provide a valuable supplement to primary biomass, augmenting indigenous biomass supplies. In initial phases of deployment, we observe that infrastructure is initially clustered near cities, and other sources of low cost, secondary biomass, but as CDR targets are increased and indigenous secondary biomass supplies are exhausted, infrastructure begins to move closer to potential biomass planting areas with higher yield. In minimising the cost of CDR on a cost per tonne CO2 removed basis, we find that the availability of secondary biomass, land availability, and yield are key factors that drive the cost of CDR. Importantly biomass conversion efficiency of a BECCS plant has an inverse effect on CDR costs, with less efficient plants resulting in lower costs compared to their more efficient counterparts. By consuming secondary biomass in BECCS and BE-CHP-CCS plants, the UK is able to be self-sufficient in biomass supply by utilising available indigenous biomass to remove up to 50 MtCO2 /yr, though for cost reas

Journal article

Daggash HA, Mac Dowell N, 2019, Higher carbon prices on emissions alone will not deliver the Paris agreement, Joule, Vol: 3, Pages: 2120-2133, ISSN: 2542-4351

Limiting global warming to 2°C by 2100 requires anthropogenic CO2 emissions to reach zero by 2070 and become negative afterwards; therefore, large-scale carbon dioxide removal (CDR) from the atmosphere is critical. We investigate the effectiveness of carbon prices in achieving the deep decarbonization needed in the power system. We find that if only CO2 emitters are penalized, increasing prices to the social cost of carbon is sufficient to achieve a decarbonized system in the medium-term but not maintain it in the long-term. Unless carbon pricing mechanisms are adapted to remunerate CDR services, CDR technologies are not deployed. Incentivizing CDR could mean that lower levels of carbon taxation are needed to meet the Paris Agreement, which in turn lowers electricity costs.However, the deployment of CDR technologies could prolong the use of unabated fossil fuels in a carbon-constrained system, therefore, disincentives must be implemented to prevent this moral hazard from manifesting.

Journal article

Bahzad H, Shah N, Dowell NM, Boot-Handford M, Soltani SM, Ho M, Fennell PSet al., 2019, Development and techno-economic analyses of a novel hydrogen production process via chemical looping, International Journal of Hydrogen Energy, Vol: 44, Pages: 21251-21263, ISSN: 0360-3199

In this work, a novel hydrogen production process (Integrated Chemical Looping Water Splitting “ICLWS”) has been developed. The modelled process has been optimised via heat integration between the main process units. The effects of the key process variables (i.e. the oxygen carrier-to-fuel ratio, steam flow rate and discharged gas temperature) on the behaviour of the reducer and oxidiser reactors were investigated. The thermal and exergy efficiencies of the process were studied and compared against a conventional steam-methane reforming (SMR) process. Finally, the economic feasibility of the process was evaluated based on the corresponding CAPEX, OPEX and first-year plant cost per kg of the hydrogen produced. The thermal efficiency of the ICLWS process was improved by 31.1% compared to the baseline (Chemical Looping Water Splitting without heat integration) process. The hydrogen efficiency and the effective efficiencies were also higher by 11.7% and 11.9%, respectively compared to the SMR process. The sensitivity analysis showed that the oxygen carrier–to-methane and -steam ratios enhanced the discharged gas and solid conversions from both the reducer and oxidiser. Unlike for the oxidiser, the temperature of the discharged gas and solids from the reducer had an impact on the gas and solid conversion. The economic evaluation of the process indicated hydrogen production costs of $1.41 and $1.62 per kilogram of hydrogen produced for Fe-based oxygen carriers supported by ZrO2 and MgAl2O4, respectively - 14% and 1.2% lower for the SMR process H2 production costs respectively.

Journal article

Cabral RP, Bui M, Dowell NM, 2019, A synergistic approach for the simultaneous decarbonisation of power and industry via bioenergy with carbon capture and storage (BECCS), International Journal of Greenhouse Gas Control, Vol: 87, Pages: 221-237, ISSN: 1750-5836

There is a need for a rapid and large scale decarbonisation to reduce CO2 emissions by 45% within 12 years. Thus, we propose a method that accelerates decarbonisation across multiple sectors via a synergistic approach with bioenergy with CCS (BECCS), which is able to remove 740 kgCO2 from air per MWh electricity generated. Industry is a hard-to-decarbonise sector which presents a unique set of challenges where, unlike the power sector, there are no obvious alternatives to CCS. One of these challenges is the significant variation of CO2 concentration, which directly influences CO2 capture costs, ranging from $10/tCO2 to over $170/tCO2 for high (95–99% CO2) and low CO2 concentration (4% CO2) applications, respectively. Re-purposing the existing coal-fired power plant fleet into BECCS displaces CO2 emissions from coal-use and enables a just transition, i.e., avoiding job loss, providing a supportive economic framework that does not rely on government subsidies. Negative emissions generated from capturing and storing atmospheric CO2 can be converted into negative emission credits (NECs) and auctioned to hard-to-decarbonise sectors, thus providing another revenue stream to the power plant. A levelised cost of electricity (LCOE) between $70 and $100 per MWh can be achieved through auctioning NECs at $90–$135 per tCO2. Offsetting the global industrial CO2 emissions of 9 GtCO2 would require 3000 BECCS plants under this framework. This approach could jumpstart industrial decarbonisation whilst giving this sector more time to develop new CCS technologies.

Journal article

Hankin A, Guillen Gosalbez G, Kelsall G, Mac Dowell N, Shah N, Weider S, Brophy Ket al., 2019, Assessing the economic and environmental value of carbon capture and utilisation in the UK, Briefing Note – summary of Briefing Paper No 3

• As a signatory to the 2015 Paris Climate Change Agreement, the UK has committed to an ambitious transformation of its economy.• Decarbonisation of the UK’s economy must be a priority, but carbon-based fuels and platform chemicals will remain important to the global economy; their production from captured carbon dioxide and renewable energy can support this industrial need.• In this Briefing Paper, we report on results of a systematic procedure developed to assess the viability of different carbon capture and utilisation (CCU) pathways.• Our findings on three CCU pathways show that proposed CCU projects should always be assessed on a case-by-case basis, using detailed, UK centric, cradle-to-grave life cycle analyses.• CCU cannot provide the emission mitigation rate of carbon capture and storage (CCS), but as the UK’s entire geological storage capacity is offshore, CCU could mitigate emissions from inland point sources.• Of the considered CCU pathways, presently the production of polyurethane is the most promising for the UK and could provide an immediate short-term mitigation solution for greenhouse gas (GHG) emissions. Currently, methanol production does not appear to be a viable solution.

Report

Hankin A, Guillen Gosalbez G, Kelsall G, Mac Dowell N, Shah N, Weider S, Brophy Ket al., 2019, Assessing the economic and environmental value of carbon capture and utilisation in the UK, Briefing paper, 3

• As a signatory to the 2015 Paris Climate Change Agreement, the UK has committed to an ambitious transformation of its economy.• Decarbonisation of the UK’s economy must be a priority, but carbon-based fuels and platform chemicals will remain important to the global economy; their production from captured carbon dioxide and renewable energy can support this industrial need.• In this Briefing Paper, we report on results of a systematic procedure developed to assess the viability of different carbon capture and utilisation (CCU) pathways.• Our findings on three CCU pathways show that proposed CCU projects should always be assessed on a case-by-case basis, using detailed, UK centric, cradle-to-grave life cycle analyses.• CCU cannot provide the emission mitigation rate of carbon capture and storage (CCS), but as the UK’s entire geological storage capacity is offshore, CCU could mitigate emissions from inland point sources.• Of the considered CCU pathways, presently the production of polyurethane is the most promising for the UK and could provide an immediate short-term mitigation solution for greenhouse gas (GHG) emissions. Currently, methanol production does not appear to be a viable solution.

Report

Algunaibet I, Pozo Fernandez C, Galan Martin A, Huijbregts M, Mac Dowell N, Guillen Gosalbez Get al., 2019, Powering sustainable development within planetary boundaries, Energy and Environmental Science, Vol: 12, Pages: 1890-1900, ISSN: 1754-5692

The concept of planetary boundaries identifies a safe space for humanity. Current energy systems are primarily designed with a focus on total cost minimization and bounds on greenhouse gas emissions. Omitting planetary boundaries in energy systems design can lead to energy mixes unable to power our sustainable development. To overcome this conceptual limitation, we here incorporate planetary boundaries into energy systems models, explicitly linking energy generation with the Earth’s ecological limits. Taking the United States as a testbed, we found that the least cost energy mix that would meet the Paris Agreement 2 degrees Celsius target, still transgresses five out of eight planetary boundaries. It is possible to meet seven out of eight planetary boundaries concurrently by incurring a doubling of the cost compared to the least cost energy mix solution (1.3% of the United States gross domestic product in 2017). Due to the stringent downscaled planetary boundary on biogeochemical nitrogen flow, there is no energy mix in the United States capable of satisfying all planetary boundaries concurrently. Our work highlights the importance of considering planetary boundaries in energy systems design and paves the way for further research on how to effectively accomplish such integration in energy related studies.

Journal article

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