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International Journal of Greenhouse Gas Control 109 (2021) 103388
Available online 9 July 2021
1750-5836/© 2021 Elsevier Ltd. All rights reserved.Efficient marine environmental characterisation to support monitoring of
geological CO2 storage
Jerry Blackford a,*, Katherine Romanak b, Veerle A.I. Huvenne c, Anna Lichtschlag c,
James Asa Strong c, Guttorm Alendal d, Sigrid Eskeland Schütz e, Anna Oleynik d,
Dorothy J. Dankel f
a Plymouth Marine Laboratory, Prospect Place Plymouth, PL1 3DH UK
b Bureau of Economic Geology, The University of Texas at Austin, University Station, Box X, Austin, TX 78713-8924, United States
c National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK
d Department of Mathematics, University of Bergen, N-5020 Bergen, Norway
e Faculty of law, University of Bergen, Norway
f Department of Biological Sciences, University of Bergen, Norway
Carbon capture and storage
Impact assessment
Oceanographic data
Carbon capture and storage is key for mitigating greenhouse gas emissions, and offshore geological formations
provide vast CO2 storage potential. Monitoring of sub-seabed CO2 storage sites requires that anomalies signifying
a loss of containment be detected, and if attributed to storage, quantified and their impact assessed. However,
monitoring at or above the seabed is only useful if one can reliably differentiate abnormal signals from natural
variability. Baseline acquisition is the default option for describing the natural state, however we argue that a
comprehensive baseline assessment is likely expensive and time-bound, given the multi-decadal nature of CCS
operations and the dynamic heterogeneity of the marine environment. We present an outline of the elements
comprising an efficient marine environmental baseline to support offshore monitoring. We demonstrate that
many of these elements can be derived from pre-existing and ongoing sources, not necessarily related to CCS
project development. We argue that a sufficient baseline can be achieved by identifying key emergent properties
of the system rather than assembling an extensive description of the physical, chemical and biological states.
Further, that contemporary comparisons between impacted and non-impacted sites are likely to be as valuable as
before and after comparisons. However, as these emergent properties may be nuanced between sites and seasons
and comparative studies need to be validated by the careful choice of reference site, a site-specific understanding
of the scales of heterogeneity will be an invaluable component of a baseline.
1. Introduction
Carbon capture and storage (CCS) is a technology to mitigate emis-
sions from large point-source industries such as cement, iron, steel,
chemical production and from power generation. Technology is also
currently being developed for capturing CO2 directly from the atmo-
sphere. In all these cases, captured CO2 is compressed, transported and
stored permanently in suitable deep geological formations. CCS is an
essential component of the global climate change mitigation portfolio (e.
g. IPCC 2005; IPCC 2014; IEA, 2015), and will be required for at least
13% of total emissions reductions (e.g. approx. 94 GtCO2) required to
meet the 2 C goal (IEA, 2016). Although several methods exist for
estimating global geologic storage capacity (Ganjdanesh and Hosseini,
2018; Hosseini et al., 2018; Kearns et al., 2017; Ringrose and Meckel,
2019; van der Meer, 1995), one conclusion is common to all; that there is
more than enough storage capacity to receive the needed volumes of
CO2. Whereas storage formations underlie both onshore and offshore
areas, Ringrose and Meckel (2019) surmise that the global offshore
contains the most significant gigatonne-scale storage resource for
geological CO2 storage. Whilst IPCC scenarios include large-scale CCS
infrastructures as an essential technology to meet the Paris Agreement
goal of well below 2 C, public support for future CCS projects is an
important feature of the social licence to operate CCS technologies.
Local environmental impact assessment, via monitoring, is one of the
criteria on which the public will judge CCS. Different strategies for
environmental monitoring must provide enough coverage to detect and
* Corresponding author.
Contents lists available at ScienceDirect
International Journal of Greenhouse Gas Control
journal homepage:
Received 17 December 2020; Received in revised form 2 June 2021; Accepted 15 June 2021
International Journal of Greenhouse Gas Control 109 (2021) 103388
2attribute CO2 leaks and, at the same time, foster and build public trust in
the safety and integrity of a CCS project; requiring the weighing together
of many factors in developing a responsible and transparent environ-
mental monitoring program in a dialogue with relevant stakeholder
In this paper we consider the process of monitoring in the marine
environment and discuss an approach to acquiring a sufficient baseline
understanding to efficiently underpin such monitoring. Here we use
marine environment to refer to the upper few meters or so of seabed
sediments and the overlying water column, i.e. the zone housing com-
plex ecosystems.
1.1. Monitoring and regulatory requirements
Unlike many industries with long national traditions and diversified
national regulation, CCS law and regulations stem from international
cooperation, generating national regulation with clear similarities
across jurisdictions. In general, law requires demonstration of storage
integrity, absence of environmental impact, and accounting of emissions
in the unlikely event of leakage. For emissions accounting, and because
of the geological variability amongst sites, an emissions factor approach
is not suitable for geological CO2 storage, rather a measurement-based
approach is required (Dixon et al., 2015). Specific permitting and
related monitoring requirements are closely related to CCS site charac-
terisation and selection, risk and project impact assessments, stake-
holder, and public participation, including access to information. The
IPCC Guidelines chapter on carbon dioxide capture and geological
storage (IPCC, 2005) set the foundation for all global monitoring regu-
lations and can be reduced to the following components as outlined by
Dixon and Romanak (2015): 1) site characterisation and identification
of potential leakage pathways, 2) assessment of risk of leakage through
site characterisation and modelling of CO2 behaviour, 3) monitoring of
CO2 behaviour during injection and subsequent updating of models, and
4) reporting of CO2 injected and emissions from storage. Offshore,
leakage is defined as CO2 flux from beneath the seabed into the ocean
(with connection between ocean and atmosphere implied). With respect
to the environmental portion of these regulations, the methodology re-
quires that a monitoring plan include measurement of background CO2
fluxes through the seabed as well as any leakage flux that may occur.
This activity therefore requires methods that can distinguish between
the two types of fluxes, known as attribution. The resultant protocol
for environmental monitoring could be summarized as 1) measurement
of background CO2 concentration, 2) detection of an anomaly, 3) source
attribution of that anomaly, and 4) quantification of leakage emissions if
attributed to leakage.
CCS is operating in a rapidly changing socio-economic, technolog-
ical, and physical environment. Adaptive management facilitated by the
latest scientific knowledge on the condition and functioning of the
marine environment and the management of human activities at sea will
be desirable, (Platjouw and Soininen, 2019). In line with adaptive
management, regulations on CCS monitoring advocate management
that can adapt and incorporate new information as it becomes available.
Typically, CCS monitoring plans are not fixed for the whole lifespan of
the storage site, but revised to account for changes to the assessed risk of
leakage, risks to the environment and human health, new scientific
knowledge, and improvements in best available technology (see i.e. the
European Union CCS Directive 2009/31/EC art 13 (2)). The specific
monitoring requirements within a CCS project are designed in a
dialogue-based process between the operator, proposing the monitoring
plan, third-party stakeholders, i.e. the general public, fisheries sector
etc. partaking in the impact assessment process, and the regulators.
Globally, soft law instruments, or guidelines, recognize CCS as an
emissions reduction technology. The IPCC Guidelines for National
Greenhouse Gas Inventories, Volume 2, Energy, Chapter 5 (IPCC, 2006,
refined IPCC 2019), has inventory methods consistent with the IPCC
Special Report on Carbon Dioxide Capture and Storage (IPCC, 2005).
The guidelines are foremost aiming for GHG accounting and provide
methodologies for estimating and reporting national anthropogenic
greenhouse gas sources and sinks. The guidelines (sec. 5.7) state that
the choice of monitoring technologies will need to be made on a
site-by-site basis, and as monitoring technologies are advancing rapidly
it would be good practice to keep up to date on new technologies.
Dixon and Romanak (2015) state that the methodology of the IPPC
Guidelines has become the basis for all subsequent international
regulation and legal guidance for CO2 geological storage.
The United Nations Framework Convention on Climate Change
(1997), the 1997 Kyoto Protocol, Article 12, has been in force since
2005. The Kyoto Protocol is legally binding upon developed countries,
but still only includes non-prescriptive commitments, for example ref.
Art 3 nr 1 do not exceed their assigned amounts. The aim of the Pro-
tocol relates to GHG accounting and protection of the environment,
particular for developing countries. The Kyoto Protocol offers Interna-
tional Emissions Trading, Joint implementation, and the Clean Devel-
opment Mechanism, rewarding low-carbon projects in developing
countries by the creation of carbon credits. In 2011, ‘Modalities and
Procedures for CCS were agreed (Decision 10/CMP.7), stating that the
monitoring plan shall reflect the principles and criteria of international
good practice for the monitoring of geological storage sites and consider the
range of technologies described in the IPPC Guidelines and other good
practice guidance. Thus, the IPCC guidelines which do not prescribe
specific technologies but focus on site-specific monitoring technologies
and best available technology, guide the Kyoto Protocol.
Leaving the global arena, regional cooperation has led to legally
binding commitments for signatory states, as under the 1992 OSPAR
Convention and the 1972 London Protocol. The 1996 monitoring pro-
tocol of the London Protocol, amended in 2006 to allow CCS, and the
monitoring protocol of OSPAR, (OSPAR Guidelines for Risk Assessment
and Management of Storage of CO2 Streams in Geological Formations,
Reference Number: 200712, OSPAR 2007) set out, from a legal
perspective, mere recommendations, both using the phrase that the
monitoring may include. Read in context they encompass monitoring
of sub-seabed geological formations, surrounding geological layers and
geological layers above the formation, monitoring to detect migration,
monitoring the seafloor and overlaying water to detect leakage, and
monitoring seafloor and marine communities (benthic and water col-
umn) to detect and measure the effects of leakages on marine organisms.
Description of the normal or baseline is part of regional and na-
tional legally binding impact assessment and monitoring requirements.
In the EU this follows from the EIA Directive 2011/92/EU as amended
by 2014/52/EU (European Union, 2014). According to § 4 nr 1 and
Annex I nr. 22, CCS storage sites pursuant to the CCS Directive shall be
made subject to an impact assessment. Art 5, 1) requires the developer to
provide, prior to any development consent, information on the (a) site
and (b) the likely significant effects of the project on the environment, ...
and (f) any additional information specified in Annex IV relevant to the
particular project. This is specified in Annex IV as a description of the
relevant aspects of the current state of the environment (baseline) and
an outline of the likely evolution thereof without implementation of the
project as far as natural changes from the baseline scenario can be
assessed with reasonable effort on the basis of the availability of envi-
ronmental information and scientific knowledge. Further, the CCS
Directive Article 7(6) and Article 9(5) requires a monitoring plan sub-
mitted to and approved by the competent authority, updated every five
years. According to Annex II, (1.1), the monitoring plan shall provide
details of the monitoring to be deployed at the main stages of the project,
including baseline, operational and post-closure monitoring. National
legislation in EU and EEA member states shall, according to EU law,
fulfil these minimum requirements stemming from the EIA and CCS
Directives. In accordance with international soft law instruments, the EU
Directives also build on site-specific monitoring programs and the
principle of best available technology.
Prior to site licensing, the assessment of potential environmental
J. Blackford et al.