Developing a framework for the optimal deployment of negative emissions technologies

In delivering on the world’s climate goals, removing carbon dioxide from the atmosphere is required in addition to deep mitigation efforts. As no carbon dioxide removal method stands out as an obvious winner, which, how, and how much of these technologies should be deployed to guarantee efficient, sustainable and permanent carbon dioxide removal remains a fundamental research challenge. One potential option, bioenergy with carbon capture and storage (BECCS) is likely to play an important role. BECCS’s ability to sustainably remove carbon dioxide from the atmosphere is, however, controversial. Given the range of potential outcomes, it is crucial to understand how, if at all, this technology can be deployed in a way which minimises its cost and impact on natural resources and ecosystems, while maximising both carbon removal and energy production. In this dissertation, we explore the regional drivers of BECCS sustainability and cost, and provide insights into the where, when, and extent of environmentally sustainable and economically viable BECCS deployment. We conclude that the total quantity of atmospheric carbon dioxide removal and energy production over the lifetime of a BECCS project, and the time required to start removing carbon dioxide from the atmosphere will likely vary from project to project. This has profound implications for the policy frameworks required to incentivise and regulate the widespread deployment of BECCS technology. When optimising regional biomass supply chains, we find that a myopic focus on energy generation and carbon dioxide removal can result in negative consequences for the broader environment, which warrants consideration for all impacts when assessing the performance of a BECCS project. Finally, when exploring least-cost BECCS deployment pathways to meet global carbon dioxide removal targets, an important finding is that inter-regional cooperation and collaboration are central to sustainably and affordably meeting these targets, with important value creation opportunities for key providers of carbon dioxide removal.Open Acces

Can BECCS efficiently and sustainably remove CO2 from the atmosphere?

Bioenergy combined with carbon capture and storage, BECCS, could provide firm base load power while removing CO2 from the atmosphere. This unique feature makes it the predominant solution in the IPCC AR5 scenarios (IPCC, 2014) where it accounts for a substantial fraction of primary energy supply in half of the emissions pathways (Fuss et al., 2014). Such a demand for biomass would require large, integrated supply chains, whose embedded emissions could not only challenge the carbon negativity of BECCS – the underpinning concept of this option – but would also compete with other resources – such as water and land - already affected by global warming (UN Water, 2005). In this contribution, we present a whole-systems analysis of the biomass supply chain associated with a range of bioenergy materials – both energy dedicated crops (miscanthus, switchgrass, short rotation coppice willow), and agricultural residues (wheat straw) – supplied from different regions and land types, and converted in dedicated fired power stations in conjunction with post-combustion CCS technology. The water, carbon and energy footprints of each combination were calculated and their impact on the overall system net water intensity, power generation efficiency, and carbon intensity was measured. The model was evaluated with a range of values for each input parameter to capture the high variability and uncertainty in literature data. In order to describe the dynamic greenhouse gases (GHG) emissions of such as system, a yearly accounting of the emissions was carried out over a BECCS power plant lifetime, and the system carbon breakeven time was determined (Withers et al., 2015). Finally, a sensitivity analysis was carried out on the dynamic GHG emissions profile, and alternate scenarios involving organic chemicals, biofuels with and without CCS and carbon neutral electricity were investigated. Direct and indirect land use changes (Fargione et al., 2008; Plevin et al., 2010; Searchinger et al., 2008) effects were measured on both static and dynamic balances, and were found to be driving the results and uncertainty range. Overall we concluded that depending on conditions of its deployment, BECCS could lead to both carbon positive and negative balances. The most sustainable case study, miscanthus-based BECCS from Brazil, could lead to break-even times between 1 year if grown on marginal land, and 50 years on a forest land. Regulating and rewarding policies will have to integrate this local specificity in order to assure BECCS sustainable development. References Fargione, J., Hill, J., Tilman, D., Polasky, S., & Hawthorne, P. (2008). Land Clearing and the Biofuel Carbon Debt. Science, 319(February), 1235–1237. Fuss, S., Canadell, J. G., Peters, G. P., Tavoni, M., Andrew, R. M., Ciais, P., … Yamagata, Y. (2014). Betting on negative emissions. Nature Climate Change, 4(10), 850–853. IPCC. (2014). Climate Change 2014, Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Plevin, R. J., O’HARE, M., Jones, A. D., Torn, M. S., & Gibbs, H. K. (2010). The greenhouse gas emissions from indirect land use change are uncertain, but potentially much greater than previously estimated. Environmental Science & Technology., 44(21), 8015–8021. Searchinger, T., Heimlich, R., Houghton, R. A., Dong, F., Elobeid, A., Fabiosa, J., … Yu, T. (2008). Emissions from Land-Use Change. Science, 423(February), 1238–1241. UN Water. (2005). Coping with water scarcity: Challenge of the twenty-first century. Waterlines, 24(1), 28–29. https://doi.org/10.3362/0262-8104.2005.038 Withers, M. R., Malina, R., & Barrett, S. R. H. (2015). Carbon, climate, and economic breakeven times for biofuel from woody biomass from managed forests. Ecological Economics, 112, 45–52

Can BECCS Deliver Sustainable and Resource-efficient Negative Emissions?

Negative emissions technologies (NETs) in general and Bioenergy with CO2 Capture and Storage (BECCS) in particular are commonly regarded as vital yet controversial to meeting our climate goals. In this contribution we present a whole-systems analysis of the BECCS value chain associated with the cultivation, harvesting, transport and conversion in dedicated biomass power stations in conjunction with CCS, of a range of biomass resources – both dedicated energy crops (miscanthus, switchgrass, short rotation coppice willow), and agricultural residues (wheat straw). We explicitly consider the implications of sourcing the biomass from different regions, climates and land types. The water, carbon and energy footprints of each value chain were calculated, and their impact on the overall system water, carbon and power efficiencies were evaluated. An extensive literature review was performed and a statistical analysis of the available data is presented. In order to describe the dynamic greenhouse gas balance of such as system, a yearly accounting of the emissions was performed over the lifetime of a BECCS facility, and the carbon breakeven time (Withers et al., 2015) and lifetime net CO2 removal from the atmosphere were determined. The effects of direct and indirect land use change were included (Searchinger et al., 2008; Fargione et al., 2008; Plevin et al., 2010), and were found to be a key determinant of the viability of a BECCS project. Overall we conclude that, depending on the conditions of its deployment, BECCS could lead to both carbon positive and negative results. The total quantity of CO2 removed from the atmosphere over the project lifetime and the carbon breakeven time were observed to be highly case specific. This has profound implications for the policy frameworks required to incentivise and regulate the widespread deployment of BECCS technology. The results of a sensitivity analysis on the model combined with the investigation of alternate supply chain scenarios elucidated key levers to improve the sustainability of BECCS: 1) measuring and limiting the impacts of direct and indirect land use change, 2) using carbon neutral power and organic fertilizer, 3) minimising biomass transport, and prioritising sea over road transport, 4) maximising the use of carbon negative fuels, and, 5) exploiting alternative biomass processing options, e.g., natural drying or torrefaction. A key conclusion is that, regardless of the biomass and region studied, the sustainability of BECCS relies heavily on intelligent management of the supply chain. References Fargione, J., Hill, J., Tilman, D., Polasky, S., & Hawthorne, P. (2008). Land Clearing and the Biofuel Carbon Debt. Science, 319(February), 1235–1237. Plevin, R. J., O’HARE, M., Jones, A. D., Torn, M. S., & Gibbs, H. K. (2010). The greenhouse gas emissions from indirect land use change are uncertain, but potentially much greater than previously estimated. Environmental Science & Technology., 44(21), 8015–8021. Searchinger, T., Heimlich, R., Houghton, R. A., Dong, F., Elobeid, A., Fabiosa, J., … Yu, T. (2008). Emissions from Land-Use Change. Science, 423(February), 1238–1241. Withers, M. R., Malina, R., & Barrett, S. R. H. (2015). Carbon, climate, and economic breakeven times for biofuel from woody biomass from managed forests. Ecological Economics, 112, 45–52

The water-energy-carbon-land nexus: Optimising the BECCS supply chain

Negative Emissions Technologies (NETs) are necessary to meet the climate change targets identified at the 2015 Paris COP. In particular, Bioenergy with CO2 Capture and Storage (BECCS) is being put forth as a key mitigation option to decarbonise the atmosphere in most IPCC AR5 scenarios (IPCC, 2014). Incurring high emissions through biomass supply chain and competing with land and water, BECCS sustainability and carbon negativity has been shown to be greatly dependent on the conditions – feedstock production, processing, transport and conversion – of its deployment (Fajardy and Mac Dowell, 2017). In this contribution, we present a biomass supply chain optimization framework, implemented in the AIMMS software, based on a BECCS whole-systems model. This model calculates the carbon, energy, water and land intensity associated with biomass production, processing, transport and conversion in a 500 MW UK based BECCS power plant, for a range of biomass feedstock, either energy dedicated crops – miscanthus, switchgrass, willow or agricultural residues – wheat straw, importing regions and land types. This last parameter is particularly significant as it accounts for the impact of direct and indirect land use change and hence plays a decisive role in the determination of BECCS carbon break-even time. Given an UK annual CO2 removal target and constrained amount of arable land per importing region, the optimal combination of feedstocks, importing regions and land types is determined to minimize either water or land use. Regardless of the criteria which is being minimised, marginal land is found to be the optimal choice, as it is associated with very limited land use changes. Finally, the choice of the resource to be conserved drives the biomass and region selection. For example, when minimizing BECCS water use, wheat straw is prioritised over other feedstocks. However, when minimizing the land use, miscanthus is preferred because of its relatively high yield. Overall, we conclude that given an annual carbon removal target and constrained amount of arable lands, the resources aimed to be preserved – arable land or fresh water – will have profound implications on the potential feedstocks and supply chains for BECCS. References Fajardy, M., & Mac Dowell, N. (2017). Can BECCS deliver sustainable and resource efficient negative emissions? Energy Environ. Sci. https://doi.org/10.1039/C7EE00465F IPCC. (2014). Climate Change 2014, Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change

The impact of 100% electrification of domestic heat in Great Britain

Britain has been a global leader in reducing emissions, but little progress has been made on heat, which accounts for almost one-third of UK emissions and the largest single share is domestic heat, which is responsible for 17% of the national total. Given the UK’s 2050 “Net-Zero” commitment, decarbonizing heat is becoming urgent and currently one of the main pathways involves its electrification. Here, we present a spatially explicit optimization model that investigates the implications of electrifying domestic heat on the operation of the power sector. Using hourly historical gas demand data, we conclude that the domestic peak heat demand is almost 50% lower than widely cited values. A 100% electrification pathway can be achieved with only a 1.3-fold increase in generation capacity compared to a power-only decarbonization scenario, but only by leveraging the role of thermal energy storage technologies without which a further 40% increase would be needed

Recognizing the value of collaboration in delivering carbon dioxide removal

In delivering the Paris climate target, bioenergy with carbon capture and storage (BECCS) is likely to play an important role, both as a climate mitigation and a carbon dioxide removal technology. However, regional drivers of BECCS sustainability and cost remain broadly unknown and the regional attribution of a global CO2 removal burden remains largely undetermined. This study explores the mechanisms behind cost-optimal BECCS deployment with evolving regional CO2 removal targets and energy sectors to provide insights into the ways in which different regional players will interact as a function of their bio-geophysical endowments and their ability to trade these assets. An important finding is that inter-regional cooperation—in choosing the right burden-sharing principle to establish regional targets—and collaboration—in trading negative emissions credits and biomass—are central to sustainably and affordably meeting these targets. This multilateralism in biomass and carbon credits trading constitutes important value creation opportunities for key providers of CO2 removal.The authors thank Imperial College London for the funding of a President's PhD Scholarship, as well as the Greenhouse Gas Removal (GGR) grant, funded by the Natural Environment Research Council (NERC), under grant NE/P019900/1. The authors also thank Solène Chiquier from Imperial College London for curating the CO2 storage capacity dataset

Thermodynamic Evaluation of Carbon Negative Power Generation: Bio-energy CCS (BECCS)

Bio-energy with carbon capture and storage (BECCS) is an important greenhouse gas removal (GGR) technology with the potential to provide significant reductions in atmospheric CO2 concentration. The power generation efficiency of BECCS can be improved by using heat recovered from flue gas to supply energy requirements of the solvent regeneration process. This paper assesses the influence of solvent selection and biomass co-firing proportion on recoverable heat, energy efficiency and carbon intensity of a 500 MW pulverized fuel BECCS system. The effects of (i) coal type (high and medium sulphur content), (ii) biomass type (wheat straw and clean wood chips, (iii) variable moisture content, and (iv) biomass co-firing % on AFT and emissions of SOX and NOX was evaluated. Compared to firing of coal alone, co-firing low moisture biomass generated higher adiabatic flame temperature. As biomass co-firing proportion increased, SOX emissions decreased, whereas NOX emissions increased with greater AFT. Factors that enhanced BECCS efficiency included the use of high performance solvents and higher heat recovery (higher AFT and flue gas flow rate). These results lead to the development of a performance matrix which summarizes the effect of key process parameters

The Economic Value of Flexible Ccs in Net-Zero Electricity Systems the Case of the UK

We build a unit-commitment optimisation model of a flexible combined-cycle gas turbine (CCGT) with solvent-based post-combustion carbon capture and storage (CCS). We derive the economic benefits of CCS with solvent storage for a 20-year investment (2030-2050) based on the expected long-term increase in carbon prices and the volatility of electricity prices. Drawing on National Grid’s Future Energy Scenarios for the UK, our model shows that the CCGT-CCS plant profit is, on average, higher with solvent storage because of intertemporal arbitrage opportunities created by having this storage solution available. We find that the economic value of this intertemporal flexibility increases with greater electricity price volatility. Under high price volatility, the total return on investment (ROI) could reach 81- 246%. In relative terms, this is much higher than the total ROI of the CCGT-CCS plant itself (7-64%). While there is an economic case for investing in flexible CCS with solvent storage, there are wider system benefits too. A flexible solvent storage solution should be seen in the context of the overall system ‘flexibility’ requirements of a low-carbon power system. On a cost basis, solvent storage represents just a fraction of the capital costs of more “mainstream” energy storage technologies, such as lithium-ion batteries or hydro pumped storage, while CCGT-CCS offers firm power. Overall, while seen as a rather technical solution, if abated fossil fuel generation is to be part of a future low-carbon power system having this flexibility adds economic benefits not just to operators but also improves overall system security and complements high shares of variable renewables on the grid