Biomass Energy with Carbon Capture and Storage (BECCS) E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 703

Veröffentlichungsjahr: 2018

Beschreibung

An essential resource for understanding the potential role for biomass energy with carbon capture and storage in addressing climate change Biomass Energy with Carbon Capture and Storage (BECCS) offers a comprehensive review of the characteristics of BECCS technologies in relation to its various applications. The authors -- a team of expert professionals -- bring together in one volume the technical, scientific, social, economic and governance issues relating to the potential deployment of BECCS as a key approach to climate change mitigation. The text contains information on the current and future opportunities and constraints for biomass energy, explores the technologies involved in BECCS systems and the performance characteristics of a variety of technical systems. In addition, the text includes an examination of the role of BECCS in climate change mitigation, carbon accounting across the supply chain and policy frameworks. The authors also offer a review of the social and ethical aspects as well as the costs and economics of BECCS. This important text: * Reveals the role BECCS could play in the transition to a low-carbon economy * Discusses the wide variety of technical and non-technical constraints of BECCS * Presents the basics of biomass energy systems * Reviews the technical and engineering issues pertinent to BECCS * Explores the societal implications of BECCS systems Written for academics and research professionals, Biomass Energy with Carbon Capture and Storage (BECCS) brings together in one volume the issues surrounding BECCS in an accessible and authoritative manner.

Leseprobe

Biomass Energy with Carbon Capture and Storage (BECCS

Unlocking Negative Emissions

Edited by

Clair Gough

University of Manchester, UK

Patricia Thornley

University of Manchester, UK

Sarah Mander

University of Manchester, UK

Naomi Vaughan

University of East Anglia, Norwich, UK

Amanda Lea-Langton

University of Manchester, UK

Copyright

This edition first published 2018

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Library of Congress Cataloging-in-Publication Data

Names: Gough, Clair, editor. | Thornley, Patricia, editor. | Mander, Sarah, editor. | Vaughan, Naomi, editor. | Lea-Langton, Amanda, editor.

Title: Biomass energy with carbon capture and storage (BECCS) : unlocking negative emissions / edited by Clair Gough, Patricia Thornley, Sarah Mander, Naomi Vaughan, Amanda Lea-Langton.

Description: First edition. | Hoboken, NJ : John Wiley & Sons, 2018. | Includes bibliographical references and index. |

Identifiers: LCCN 2018001038 (print) | LCCN 2018007091 (ebook) | ISBN 9781119237631 (pdf) | ISBN 9781119237686 (epub) | ISBN 9781119237723 (cloth)

Subjects: LCSH: Carbon sequestration. | Biomass energy-Climatic factors. | Climate change mitigation.

Classification: LCC SD387.C37 (ebook) | LCC SD387.C37 B555 2018 (print) | DDC 577/.144-dc23

LC record available at https://lccn.loc.gov/2018001038

Cover design by Wiley

Cover images © Pobytov/Getty Images

List of Contributors

Gabrial Anandarajah

UCL Energy Institute University College London

UK

Kevin Anderson

Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering University of Manchester

UK

Gordon Andrews

School of Chemical and Process Engineering University of Leeds

UK

Amit Bhave

CMCL Innovations Castle Park, Cambridge

UK

Bill Buschle

Institute for Energy Systems School of Engineering University of Edinburgh

UK

Hannah Chalmers

Institute for Energy Systems School of Engineering University of Edinburgh

UK

Olivier Dessens

UCL Energy Institute University College London

UK

Temitope Falano

Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering The University of Manchester

UK

Paul Fennell

Bone Building Imperial College London

UK

Karen N. Finney

Energy 2050, Department of Mechanical Engineering University of Sheffield

UK

Dennis Gammer

Energy Technologies Institute Holywell Building

Loughborough

UK

Clair Gough

Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering The University of Manchester

UK

Geoffrey P. Hammond

Department of Mechanical Engineering Institute for Sustainable Energy and the Environment (ISEE) University of Bath

UK

Alice Larkin

Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering The University of Manchester

UK

Amanda Lea‐Langton

Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering The University of Manchester

UK

Mathieu Lucquiaud

Institute for Energy Systems, School of Engineering University of Edinburgh

UK

Leslie Mabon

Robert Gordon University Aberdeen

UK

Niall Mac Dowell

Centre for Environmental Policy Imperial College London

UK

Sarah Mander

Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering The University of Manchester

UK

Will McDowall

UCL Institute for Sustainable Resources University College London

UK

Alison Mohr

School of Sociology and Social Policy University of Nottingham

UK

Geraldine Newton‐Cross

Energy Technologies Institute Loughborough

UK

Juan Riaza

Institute for Energy Systems, School of Engineering University of Edinburgh

UK

Nilay Shah

Bone Building Imperial College London

UK

Raphael Slade

Centre for Environmental Policy Imperial College

London

UK

János Szuhánszki

Energy 2050, Department of Mechanical Engineering University of Sheffield

UK

Richard H.S. Taylor

Bone Building Imperial College London

UK

Patricia Thornley

Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering The University of Manchester

UK

Naomi Vaughan

School of Environmental Sciences University of East Anglia

Norwich

UK

Andrew Welfle

Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering The University of Manchester

UK

Foreword

This book is essential reading for anybody interested in understanding the role that biomass energy with carbon capture and storage (BECCS) can play in the transition to a low'carbon economy and the challenge of achieving the targets embedded in the Paris Agreement. It is the first comprehensive assessment of the technical, scientific, social, economic, ethical and governance issues associated with BECCS.

There is no doubt that human activities are changing Earth's climate with adverse consequences for socio‐economic sectors, ecological systems and human health. Recognising the danger associated with human‐induced climate change, literally every government in the world signed the Paris Agreement (the United States has since withdrawn from the agreement), which called for the increase in global average temperature should be held to well below 2 °C above pre‐industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre‐industrial levels. To realise these targets requires a rapid transition to a low'carbon economy involving unprecedented global cooperation and dramatic energy‐system transformations, and most models require global net negative emissions of greenhouse gases in the second half of this century through the widespread use of BECCS.

Key issues associated with BECCS such as the social and environmental sustainability of biomass production, sustainability of supply, state of pre‐ and post‐combustion technologies, energy penalty due to carbon capture, investment and operating costs, scale required to deliver global net negative emissions, life‐cycle analyses and accounting systems for greenhouse gas emissions and governance structures are all critically assessed in this book.

The analysis suggests that BECCS is a workable technology, but scaling up from the individual project level to the global scale requires a massive enhancement of the technical, biological, logistical, governance and social processes associated with BECCS. The analysis also suggests that the 1.5 °C target may be impossible to achieve without BECCS or other negative emissions processes and that without BECCS the carbon price in 2050 to achieve the 2 °C target could be doubled to about 300$/tCO2. Unfortunately, current uncertainties in technology development, enabling frameworks and policy development restrict quantification of the magnitude of global net negative emissions that can be delivered by BECCS, and hence its role in limiting human‐induced climate change.

Given the potential role that BECCS can play in limiting the magnitude of human‐induced climate change, it is imperative that governments and the private sector significantly enhance their research, development and demonstration agendas for this technology, and develop appropriate governance structures, transparent and reliable life‐cycle accounting systems for greenhouse gas emissions and incentives, policies and mechanisms to stimulate and account for negative emissions on a global scale.

Director of Strategic Development at the Tyndall Centre for Climate Change Research and

Chair of the Intergovernmental Science‐Policy Platform on Biodiversity and Ecosystem Services (IPBES)

Professor Sir Bob Watson CMG FRS.

Preface

There is a growing and significant dependence on biomass energy with carbon capture and storage (BECCS) in future greenhouse gas emission scenarios in global integrated assessment models, and it has become central to the discourse around achieving a target of 2 °C global average temperature rise. This reliance on BECCS hinges on its potential to deliver so‐called negative emissions in order to maintain a sustainable atmospheric concentration of CO2 cost‐effectively. As a young and untested group of technologies, there are many uncertainties associated with BECCS and there is strong imperative to understand better the conditions for and consequences of pursuing this group of technologies. BECCS technologies may offer a role in offsetting hard‐to‐abate sectors (e.g. agriculture and aviation) or may enable an ‘overshoot’ in reaching cumulative emissions budgets in the context of delayed action on mitigation. However, there is very little practical experience of implementing the technology in commercial applications and, indeed, relatively little research into its potential and the conditions for realising its deployment. This book aims to set out the technical and scientific parameters of delivering BECCS technologies within the wider social, economic and political context in which it sits, giving the reader a broad understanding of the key issues and potential consequences of pursuing BECCS.

To understand BECCS, what it can offer and how it might contribute to climate‐change mitigation, it is essential to consider the variety of technical and non‐technical constraints in a joined‐up manner. Bringing together modern biomass energy systems with CCS not only presents technical and scientific challenges but also, to be delivered at scales large enough to contribute to substantive negative emissions, depends on other factors, such as geopolitics and supply chain integration and may have significant implications at a societal level. This book brings the issues together in a clear and accessible way that will support a more informed debate around the potential for this technology to unlock negative emissions.

List of Abbreviations/Acronyms

AFT

Adiabatic flame temperature.

ASU

Air separation unit.

BECCS

Biomass energy with carbon capture and storage.

BIGCC

Biomass integrated gasification combined cycle.

CCS

Carbon capture and storage.

CFBC

Circulating fluidized bed combustion.

CO

2

Carbon dioxide.

CV

Calorific value.

EOR

Enhanced oil recovery.

EJ

Exajoules (1 × 10

18

, J), unit of energy.

FGR

Flue gas recirculation/recycling.

Gha

Giga hectares (1 × 10

9

, ha).

HP

High pressure (steam turbine).

IAM

Integrated assessment model.

IGCC

Integrated gasification combined cycle.

IP

Intermediate pressure (steam turbine).

LCOE

Levelised cost of electricity.

LP

Low pressure (steam turbine).

LHV

Lower heating value.

MEA

Monoethanolamine.

NET

Negative emission technology.

NOAK

nth of a kind.

PJ

Petajoules (1 × 10

15

, J), unit of energy.

PM

Particulate matter.

PSA

Pressure swing adsorption.

RCP

Representative concentration pathway.

RFG

Reformulated gasoline.

SNG

Synthetic natural gas.

TRL

Technology readiness level.

UNFCCC

United Nations Framework Convention on Climate Change.

Part IBECCS Technologies

Chapter 1Understanding Negative Emissions From BECCS

Clair Gough1, Sarah Mander1, Patricia Thornley1, Amanda Lea‐Langton1, and Naomi Vaughan2

1Tyndall Centre for Climate Change Research, School of Mechanical Aerospace and Civil Engineering, University of Manchester, UK

2School of Environmental Sciences, University of East Anglia, Norwich, UK

1.1 Introduction

Changes in our climate are driven by human activity such as agriculture, deforestation and burning coal, oil and gas. The single most significant driver of climate change is the increase in the greenhouse gas carbon dioxide (CO2) in our atmosphere from the combustion of fossil fuels. Efforts to limit the impacts of climate change focus on reducing the emissions of CO2 and other greenhouse gases and adapting to live with the changing climate. In recent years, a third approach has gained significant attention: action to remove CO2 from the atmosphere and store the CO2 for long timescales (over hundreds of years). Recent negotiations under the UN Framework Convention on Climate Change (UNFCCC) delivered the 2015 Paris Agreement, which set a target of limiting global average temperature rise to ‘well below 2 °C’ (the 2 °C target having been agreed within the UNFCCC in 2010) while ‘pursuing efforts to limit the temperature increase to 1.5°C’ (UNFCCC, 2015). These are ambitious goals that will require immediate and radical emissions reductions if they are to be met. The idea of introducing ‘negative emissions’ is born out of the gap between the current trajectory in global emissions and the pathway necessary to avoid dangerous climate change. The most prominent proposal for achieving such negative emissions is to use biomass as a feedstock to generate electricity (or produce biofuels or hydrogen), capture the CO2 during production and store it underground in geological reservoirs – biomass energy with carbon capture and storage, or BECCS for short. However, the negative emissions concept remains just that, a concept; in principle, technologies such as BECCS can deliver net CO2 removal at a project scale, or potentially at a global scale sufficient to impact atmospheric concentrations of CO2 and associated global average temperatures – but in practice, this potential has yet to be accessed at anything like a global scale. This book explores the challenges of unlocking negative emissions using BECCS.

Future climate change is most commonly explored using a suite of models that represent the Earth’s climate system, the physical and socio‐economic impacts of a changing climate and the greenhouse gases and other drivers generated by the global economy and energy systems. Integrated assessment models (IAMs) are used to create scenarios of future emissions that are used by climate and impact models. The growing and significant dependence on BECCS in future emissions scenarios in global IAMs has placed BECCS at the centre of the discourse around achieving targets of 2 °C global average temperature rise and, following the 2015 Paris Agreement, 1.5 °C. This reliance on BECCS hinges on its potential to remove CO2 from the atmosphere in order to maintain a sustainable atmospheric concentration of CO2 in a cost‐effective manner.

There are many different technical options that could deliver negative emissions via BECCS and these vary in their technology readiness level (TRL). Some of the closer‐to‐market BECCS technologies are composed of component parts that have been proven and tested, but integration and deployment have not yet been demonstrated at commercial scale. Consequently, there remain significant uncertainties associated with BECCS performance and costs. Understanding the potential for, and implications of, pursuing BECCS requires an interdisciplinary approach. It has been suggested that BECCS could play a role in offsetting hard‐to‐abate sectors (e.g. agriculture and aviation) or enable delayed action on mitigation. While the atmospheric concentration of CO2 continues to rise and policy objectives focus on limiting warming to 1.5 °C, it becomes increasingly likely that a means of delivering negative emissions will be required. Whether or not limiting warming to 1.5 °C is feasible without negative emissions remains unclear. In 2018, the IPCC will deliver a special report devoted to understanding the emissions pathways and impacts associated with 1.5 °C.

Despite its significance within the formal policy goals, there is very little practical experience of implementing the technology in commercial applications and limited research into the practicalities of implementation and conditions for accelerating deployment. Combining modern biomass energy systems with CCS not only presents technical and scientific challenges but, to be implemented at scales large enough to deliver global net negative emissions, also depends on other factors, such as geopolitics and supply‐chain integration and may have significant societal implications. To understand BECCS, what it can offer and how it might contribute to climate‐change mitigation, it is essential to consider the technical and non‐technical constraints in a holistic manner.

This book aims to provide a comprehensive assessment of BECCS, describing the technology options available and the implications of its future deployment. While there is a rich literature relating to bioenergy and carbon capture and storage (CCS) separately, there is currently very little published research on the integration of these components. Our aim is to address this gap, bringing together technical, scientific, social, economic and governance issues relating to the potential deployment of BECCS as a key climate‐change mitigation approach. The uniqueness of the book lies in bringing these subjects together and imposing order on the disparate sources of information. Doing this in a clear and accessible way will support a more informed debate around the potential for this technology to deliver deep cuts in emissions.

1.2 Climate‐Change Mitigation

In its Fifth Assessment Report (AR5), the Intergovernmental Panel on Climate Change (IPCC, 2014) identified four so‐called representative concentration pathways (RCPs), describing time‐dependent ranges of atmospheric greenhouse gas concentration trajectories, emissions and land‐use data between 2005 and 2100 (van Vuuren et al., 2011). Created by IAMs, each RCP is associated with emissions pathways that result in atmospheric concentrations correlated with different levels of radiative forcing; these are RCP2.6 (i.e. a radiative forcing of 2.6 W m−2), RCP4.5, RCP6, RCP8.5 (IPCC, 2014). Greenhouse gas concentrations within each RCP are associated with a probability of limiting temperature rise to below certain levels; only the lower concentrations within RCP2.6 are considered ‘likely’ (i.e. associated with a greater than 66% chance) to limit global atmospheric temperature rise to below 2 °C, or ‘more unlikely than likely’ (i.e. a less than 50% chance) for 1.5 °C (IPCC, 2014). The RCPs provide a consistent framework for analysis in different areas of climate‐change research – for example, by climate modellers to analyse potential climate impacts associated with the pathways (including projected global average temperature rise) and in IAMs to explore alternative ways in which the emissions pathways for each RCP could be achieved (i.e. mitigation scenarios) under different economic, technological, demographic and policy conditions (IPCC, 2014; van Vuuren et al., 2011). The shared socio‐economic pathways (SSPs) offer a further framework for IAMs to explore alternative emission pathways, by detailing different socioeconomic narratives that are consistent with the RCPs (O’Neill et al., 2017).

Climate‐change mitigation policies are focused around limiting the increase in the global average temperature as described earlier. Achieving these targets is dependent on tight limits to cumulative emissions of CO2 (and other greenhouse gases) in order to stabilise their atmospheric concentration. The cumulative emissions associated with a particular temperature goal is known as a carbon budget – the remaining budget for a 66% chance of keeping temperatures below a 2 °C increase is 800 Gt CO2 (from 2017) (Le Quéré et al., 2016). With global emissions currently at about 36 Gt CO2/year, this equates to about 20 years at current emissions rates before the budget is exceeded; until emissions are reduced to near zero, atmospheric CO2 concentration will continue to rise (ibid).

In this context, by offering a route to delivering negative emissions, BECCS appears to be an attractive approach to potentially enabling mitigation costs to be reduced, more ambitious targets to become feasible than would otherwise be possible or allowing a delay to the year in which emissions will peak by enabling removal of CO2 from the atmosphere in the future (Friedlingstein et al., 2011; van Vuuren et al., 2013). Typically, scenarios that are ‘likely’ to stay within 2 °C include such an overshoot in the concentration achieved through large‐scale deployment of carbon dioxide removal (CDR) techniques (i.e. BECCS or afforestation) (IPCC, 2014).

A large majority of the pathways that deliver atmospheric CO2 concentrations consistent with the 2 °C target (and indeed many of those associated with temperature increases up to 3 °C) require global net negative emissions by about 2070 (Fuss et al., 2014). The range of CO2 removal through BECCS assumed in the IPCC scenarios is typically between 2 and 10 Gt CO2/year by 2050 (Fuss et al., 2014; van Vuuren et al., 2013) with a median value of around 608 Gt CO2 cumulatively removed by 2100 using BECCS (Wiltshire et al., 2015). Global net negative emissions are achieved when the amount of CO2 removed from the atmosphere is greater than emissions from all other anthropogenic (i.e. resulting from or produced by human activities Allwood et al., 2014) sources (Fuss et al., 2014). When discussing the contribution of negative emissions from BECCS, it is useful to distinguish between three metrics that are typically used (Gough et al., 2018), as described in Figure 1.1:

CO

2

stored from BECCS systems

: this is the total CO

2

stored in a geological formation following capture in a CCS system and gives an indication of the geological storage capacity needed;

Negative emissions from BECCS

: this is the net emissions from the BECCS supply chain, at a project scale, or cumulatively across all BECCS projects, accounting for system losses, emissions associated with land‐use change and fossil fuel emissions;

Global net negative emissions

: occur when the amount of global negative emissions (from all negative emissions approaches combined) exceeds the CO

2

emissions from all other human sources, e.g. energy, transport and agriculture.

Figure 1.1 Schematic illustrating terminology for negative emissions from BECCS. (a) CO2stored, which can be calculated at a project, national or global level. (b) Negative emissions, which can be calculated at a project or national level, are achieved when the CO2 removed from the atmosphere during biomass growth is greater than the CO2 emissions from all the other processes in the supply chain. (c) Global negative emissions, the global sum of all negative emissions activity, this removes carbon dioxide from the atmosphere and can be used to ‘offset’ other anthropogenic CO2 emissions. (d) Global net negative emissions occur when the global amount of negative emissions exceeds the CO2 emissions from all other human sources, e.g. energy, transport and agriculture.

Thus, global net negative emissions are used within the IAMs to offset outstanding anthropogenic emissions to deliver a ‘net’ emission trajectory in line with the RCP associated with a given temperature goal, such as 2 °C (Fuss et al., 2014). This is illustrated in Figure 1.2 to reveal how global net negative emissions are envisaged to contribute to keeping emissions within the carbon budget and the scale of the challenge (Anderson and Peters, 2016). Parties to the UNFCCC are required to submit Intended Nationally Determined Contributions (INDCs); revised every 5 years, the INDCs are pledges for proposed emissions reductions at a national level. Figure 1.2 also shows that the current INDCs are not currently in line with the rapid decline in emissions necessary to stay within the budget – i.e. we are currently on track for an ‘overshoot’. The further emissions rise above the 2 °C pathway, the greater the negative emissions required to stay within the total carbon budget. Results of the IAMs that describe alternative mitigation scenarios associated with achieving 2 °C include negative emissions from BECCS from around 2020 (Figure 1.1b,c), with global net negative emissions (Figure 1.1d) setting in around 2070 (Figure 1a in Fuss et al., 2014).

Figure 1.2 The role of negative emissions in relation to global CO2 scenarios. Note that ‘realised negative emissions’ correspond to ‘negative emissions described in Figure 1.1b and that ‘net negative emissions in this figure correspond to ‘global net negative emissions’ described in Figure 1.1d.

Source: Anderson and Peters (2016). (See colour plate section for the colour representation of this figure.)

1.3 Negative Emissions Technologies

To date, climate‐change mitigation has focused on ways to reduce the amount of greenhouse gases emitted to the atmosphere by reducing energy consumption or through the use of alternative technologies (such as renewable energy technologies) that emit less greenhouse gases. However, in the context of the rapidly diminishing carbon budgets described in Section 1.2, possibilities for geoengineering the climate have been raised; geoengineering is defined as ‘deliberate large‐scale manipulation of the planetary environment to counteract anthropogenic climate change’ (Royal Society, 2009). Approaches for geoengineering include solar radiation management (reflecting the sun’s energy back into space, for example, by cloud brightening or stratospheric aerosol injection) or removing CO2 from the atmosphere (so‐called CDR or negative emission technologies) (Royal Society, 2009; Vaughan and Lenton, 2011; McLaren, 2012). By removing CO2from the atmosphere and storing it underground, thus delivering ‘negative emissions’, BECCS can be considered part of this latter type of climate intervention. BECCS can be used to reduce emissions, i.e. mitigation, by, for example, co‐firing biomass with coal in a power plant with CCS. Some consider it to be a form of climate‐change mitigation rather than a geoengineering approach (Boucher et al., 2013). Others suggest BECCS is mitigation because it can be used to ‘offset’ hard‐to‐abate sectors. But there are those who consider BECCS at a scale sufficient to deliver global net negative emissions (see Figure 1.1d) to be geoengineering the climate, due to its large‐scale intervention in the Earth system (Royal Society, 2009).

Later we set BECCS in the context of other CDR approaches. Solar radiation management approaches are not addressed in this book. CDR approaches seek to enhance existing carbon sinks (such as ocean or forest systems) or, like BECCS, create novel carbon sinks (i.e. using geological formations for CO2 storage) (Vaughan and Lenton, 2011). CDR approaches can be classified according to the means of CO2 capture or removal and their means of storage or sequestration. Tavoni and Socolow (2013) distinguish between biological and non‐biological capture (i.e. ‘drawdown’ from the atmosphere) and storage processes. Others distinguish between whether capture is direct (i.e. chemical) or indirect (i.e. biological) and four types of storage (mineralised, pressurised, oceanic, biotic) (McLaren, 2012). Table 1.1 summarises the main families of negative emissions approaches currently considered in the wider literature. The purpose of this type of classification is to support understanding of the different types of approaches associated with delivering negative emissions. Although the approaches are highly heterogeneous, grouping them in this way may also help signpost where certain issues or challenges might be applicable to several quite different approaches, or identify potential conflicts between approaches (for example, BECCS and Direct Air Capture may both require large volumes of underground storage).

Table 1.1 Negative emissions approaches, classified according to the type of capture and storage processes involved.

Approach

Capture

Storage

Description

Biomass energy and carbon capture and storage (BECCS)

Biological

Geological

Power generation using biomass feedstocks followed by CO

2

capture from flue gases for subsequent geological storage

Indirect

Pressurised

Direct air capture (DAC)

Non‐biological

Geological

Uses chemical sorbents to absorb and then release CO

2

for subsequent geological storage

Direct

Pressurised

Ocean fertilisation

Biological

Biological

Addition of nutrients to enhance growth of photosynthesising organisms, which eventually fall to the ocean floor

Indirect

Oceanic

Ocean liming

Non‐biological

Non‐biological

Calcium or magnesium oxides (lime) dissolved in sea water to increase the ocean absorption of atmospheric CO

2

Indirect

Oceanic

Enhanced weathering

Non‐biological

Non‐biological

Finely ground silicate rocks are dissolved in oceans or soils, these absorb CO

2

and are eventually sequestered in shells of organisms

Indirect

Mineralised

Biochar

Biological

Biological

Heat treatment of biomass, locking up the carbon and can be used as a soil improver

Indirect

Biotic

Afforestation

Biological

Biological

Establishing and maintaining forests that have not previously been forested for a given period (e.g. 50 years) (UNFCCC,

2015

)

Indirect

Biotic

Source: McLaren (2012) and Tavoni and Socolow (2013). Reproduced with permission of Elsevier.

1.4 Why BECCS?

It is clear from Section 1.2 that the categorisation of negative emissions technologies covers a wide variety of extremely different approaches, the unifying feature being their potential to remove CO2 from the atmosphere. This book focuses on the group of technologies that combines bioenergy feedstocks for energy conversion processes linked to industrial capture of CO2 for subsequent geological storage – otherwise known as BECCS.

Assessments of key negative emissions approaches have considered technical status, potential capacity and limitations; these place BECCS at a TRL between 4 and 7, depending on the particular approach under consideration (Lomax et al., 2015; McLaren, 2012). TRLs, originally used by NASA but now widely applied, provide a means of comparing the maturity of different technologies, from the lowest level, TRL1, up to TRL9 when a system is mass deployed. Other negative emissions approaches may be considered to be at higher TRLs than BECCS but are more limited in their potential at sufficiently large scale (i.e. above 1 Gt CO2/year); for example, those sequestering CO2 in materials such as magnesium silicate cement (limited by demand for cement) or timber in construction (limited by demand for timber and availability of a sustainable supply of timber) and land‐based approaches such as forest restoration and peatland and wetland habitat restoration, which is limited by land availability and climate impacts (McLaren, 2012). Chapter 5 considers TRL for BECCS approaches in more detail.

BECCS has further advantages, compared to other CDR or negative emissions approaches, that electricity (or liquid biofuels or hydrogen) is generated during the process and it is broadly compatible with current energy and social infrastructures (McGlashan et al., 2012). Although it is often described as being the most mature or least costly of the alternative negative emissions approaches (Kriegler et al., 2013; McGlashan et al., 2012) and, given its prominence in the mitigation pathways described earlier, there is relatively little research into the challenges and viability of bringing BECCS into mainstream commercial deployment. There are around 15 pilot‐scale BECCS plants across the world, and the first large‐scale BECCS project is a corn‐to‐ethanol plant in Decatur, Illinois, storing 1 Mt CO2/year in an onshore saline aquifer; an overview of the status of these projects may be found in GCCSI (2016). BECCS is therefore dominant among the options with the potential to deliver large‐scale negative emissions over the next 10–20 years.

BECCS is featured as the dominant emissions technology in the IAM model runs, alongside, to a much lesser extent, afforestation (i.e. establishing and maintaining forests that have not previously been forested for a given period, e.g. 50 years) (UNFCCC, 2013). IAMs calculate cost‐optimal pathways to satisfy carbon budget constraints; thus, a key feature of BECCS is its role in energy supply; allowing the production of a commodity (e.g. electricity) while delivering negative emissions makes it an attractive option in cost‐optimised scenarios. However, although there is limited commercial experience of integrated BECCS systems, the component technologies and techniques are well developed. Although, at the time of writing, IAMs started to include other negative emissions technologies such as direct air capture (Detlef van Vuuren, personal communication) and enhanced weathering (Taylor et al., 2016), BECCS dominates the negative emissions scenarios; understanding both the technical and non‐technical constraints on its potential is critical to the feasibility of these scenarios. This book aims to unpack the issues associated with developing integrated BECCS systems at scales sufficient to deliver global net negative emissions.

1.5 Structure of the Book

In the following chapters, we set out and consider the key issues associated with the challenge of using BECCS to deliver negative emissions. The book is divided into three sections, described later, covering: BECCS technologies (describing the various technologies involved in BECCS systems); BECCS system assessments (considering key system characteristics across the life cycle and the relative performance of technical systems) and BECCS in the energy system (including the role of BECCS as a mitigation approach, its role within integrated assessment modelling, governance and supply‐chain accounting frameworks and its social and ethical implications). Thus, the book sections reflect increasing scales of analysis, moving from consideration of the component technologies (Part I) that may contribute to the overall operation of a BECCS system (Part II) to the role of BECCS within the wider energy, climate and societal systems (Part III).

As an edited book, the chapters reflect the specific viewpoints of the different authors; BECCS remains a controversial technology in relation to the current significance placed on it within global climate‐change assessments and the implicit reliance on it within the Paris Agreement. Different perspectives anticipate different extents for its potential. Our aim here is to present some of the key arguments associated with the deployment of BECCS to deliver negative emissions from a variety of perspectives; in the final chapter, we aim to bring these arguments together to consider if and under what circumstances BECCS may provide a route to unlocking negative emissions on a global scale.

1.5.1 Part I: BECCS Technologies

This section describes the biomass energy and carbon capture components of BECCS technologies. The four chapters in this section present the issues related to the supply of biomass for use in energy systems (Chapter 2), the specific issues that the use of biomass feedstocks brings to CO2 capture (Chapters 3 and 4) and the techno‐economic performance of these systems (Chapter 5). In contrast, the processes that occur after CO2 capture (i.e. those involved in compression, transport and geological storage) are the same as those used for fossil CCS and hence are beyond the remit of this book.

Chapter 2 provides an assessment of the overall extent of different forms of biomass at both the UK and international scales and the potential availability of these resources for the bioenergy sector, drawing upon current reports and published research. The use of these biomass resources should not impact the sustainability of other sectors, such as industries that directly compete for biomass resource, or the availability of land to meet demands for food. The interfaces between the supply of biomass for energy and the competing land and resource demands of industry are highlighted, providing an indication of the levels of biomass resource that may be used for energy end uses without causing adverse impacts to other sectors. Finally, the chapter draws on published research to provide an evaluation of the best uses of available biomass resource and to conclude whether there will be sufficient sustainable biomass for a future bio‐CCS sector.

Chapter 3 first explores the different technologies and configurations used to attain CO2 capture from biomass fuel sources, comparing post‐combustion capture (based on air‐firing) and oxy‐fuel combustion capture techniques. For post‐combustion capture, a range of separation technologies can be utilised to remove the CO2 from the rest of the flue gas stream, including solvent‐based (wet scrubbing) capture, which is assessed in detail, and membrane separation, which is overviewed briefly. The potential locations of steam extraction from the power plant to regenerate the capture solvents used for absorption are also considered. The relative merits of enriched‐air firing and oxy‐fuel options are evaluated, consisting of an assessment of flue gas recirculation configurations. As the nature of biomass is so dissimilar to fossil fuels in terms of composition and properties, the specific challenges associated with biomass utilisation under BECCS operating conditions are then outlined, focusing primarily on trace elements and impurities and their impacts on capture performance. The deployment potential of these various BECCS options is subsequently overviewed in light of these challenges, based on existing technical knowledge.

Chapter 4 gives an overview of the pre‐combustion technologies used for the capture and storage of CO2 for both power generation and chemical production processes. These techniques involve removal of CO2 from a feedstock before combustion is completed, involving its conversion to a synthesis gas (syngas) containing predominantly hydrogen and CO2; the CO2 can then be separated from this gas mixture. The main technical features involved are detailed and the relevant chemistry is provided. The applications of this technology include uses for power via the integrated gasification combined cycle (IGCC) and uses in fuel refineries for syngas upgrading and liquid fuels. Applications based on conventional fuels are described and the opportunities and issues regarding their uptake into biomass systems are discussed, providing case studies and examples of ongoing research activity.

Chapter 5 describes a unique collaboration between industry, consultancies and academia in a study commissioned and funded by the Energy Technologies Institute (ETI) UK to explore the potential for BECCS technologies to be utilised to enable large‐scale CO2 removal from the air, at the same time producing electricity. The study compares an initial long list of 28 gasification or combustion technologies integrated with CCS (pre‐, post‐ or oxy‐combustion) and considers current progress towards market, likely future progress to market, cost, efficiency and feasibility, all with as many assumptions as possible harmonised across the investigated technologies. Detailed process modelling is conducted on a shortlist of eight of the technologies, which are considered to be most promising for wide‐scale deployment by 2050. These technologies are co‐fired power generation with amine scrubbing, oxy‐fuel combustion, carbonate looping or utilising integrated gasification combined cycle (IGCC); and dedicated fully biomass fired power stations utilising amine scrubbing, oxy‐fuel, chemical looping or IGCC. An important part of the results is an attempt to quantify the uncertainties associated with the parameters discussed, considering how far away from market they are.

1.5.2 Part II: BECCS System Assessments

This section explores the technical performance of various BECCS approaches and their component technologies at a project level. Quantifying the negative emissions from BECCS requires analysis across its entire supply chain from growing, harvesting, treating and transporting biomass energy to its combustion and through the CO2 capture process and the subsequent compression, transport and storage of the CO2. Currently, there is very limited experience of conducting such a life‐cycle analysis for BECCS, and Chapter 6 sets out the requirements and challenges associated with conducting such an assessment. Looking in more detail at the performance of some of the component technologies, Chapter 7 focuses on the CCS elements and Chapter 8 explores the potential and performance of full‐chain BECCS systems in the UK.

Chapter 6 examines the rationale for applying a supply‐chain life‐cycle assessment approach in order to assess potential emissions savings and critiques the importance of key decisions around choice of system boundary and assessment methods that directly affect results. There are many uncertainties with this emerging technology, including the possible greenhouse gas savings that have not been extensively verified. Key uncertainties are probed and recommendations made on methodological approaches that will deliver appropriately informed assessments of the actual emissions reduction potential associated with deployment of BECCS.

Chapter 7 presents parameters relating to the performance of power plants with carbon capture and storage (CCS), which can be characterised and evaluated according to a number of sustainability criteria; these can be based on well‐established, often quantifiable, economic, energy‐related and environmental (including climate change) criteria. However, CCS is at an early stage of research, development and demonstration (RD&D