Components of CCS Infrastructure – Interim CO₂ Holding Options

Publication Overview

This work, undertaken on behalf of IEAGHG by TNO and SINTEF, provides an overview of temporary / interim CO₂ storage, or ‘holding’, options (also called buffers) and investigates the role of buffer storage and its potential to create flexible and robust carbon capture and storage (CCS) chains. The report looks at current and emerging buffer technologies, conducts simulations to demonstrate the temporary storage required for given flow-rate scenarios and discusses the impact of buffer capacity on transport costs. In the report, the storage requested in the chain for normal operation is presented as ” temporary storage” and storage to give buffer capacity is presented as ” buffer storage”. This report has focussed on buffering at the emitter site. The results of this study will benefit CO₂ storage site project developers, operators, financiers and regulators.

Publication Summary

• It is important for the transport of CO₂ to be flexible due to variations in the production of CO₂ and availability in the storage part of the chain; a buffer, or interim storage, may be needed to make up for the batch-like nature of a ship-based transport chain as well as to assist with varying transport and storage (T&S) availability and to absorb variations in CO₂ supply and / or demand.
• The choice of buffer solutions depends on the capacity needed and the cause for the variation to be dealt with and is best done with dense phase (liquid) CO₂ to minimise volume requirements.
• Current technology options for buffering include quayside facilities and on-site tanks, geological gas storage, and pipeline system line-packing.
• Emerging technology options may include offshore storage in salt and other caverns, and floating storage and injection units.
• Significant costs will be incurred when designing extra / interim / temporary CO₂ storage capacity into a CCS chain and as a rough estimate from research in this study, the cost for buffer storage will be in line with approximately 5-10% of the transport costs in examples considered in the Europe region.
• The most likely solution for buffer capacity is onshore facilities designed for shipping. It is unlikely that geological storage will be developed for these changes given the longer timescales for storage and injection cycles. Man-made underground storage tanks are likely to become more common as energy storage becomes more widely used.
• Line-packing is unlikely to provide interim storage for more than a few hours and will incur extra compression and costs.
• In the scenarios investigated in this study, the cost is between 1 to 2.7 € per tonne of CO₂ buffer storage provided.
• These buffer storages should be located close to the capture site to minimise costs.
• It will be more cost effective to design some level of flexibility into a T&S system through spare capacity in pipelines and wells, allowing some freedom to redirect CO₂ flows in cases of T&S downtime and an ability to handle flowrate variations.
• It will be more cost effective to group CO₂ sources together because when sources are connected in a T&S network, the inherent need for buffer capacity to prevent shutdowns is reduced.
• To assess whether a project should incorporate buffer storage, a full understanding is needed of the likelihood of having to close down specific wells due to the lack of CO₂ (including the time a shut-down may be needed for and the impact this will have on the well and reservoir) and also the impact of releasing CO₂ to the atmosphere (i.e. impact on project costs, climate and public perception).