Carbon Dioxide Transport for Geological Sequestration - The Issues and Decision Parameters for T&T

Abstract

Based on an increasing emphasis on Carbon Dioxide (CO2) sequestration as a carbon management strategy coupled with the growing acceptance that geological sequestration in particular is perhaps one of the most promising carbon management techniques, the inherent aspect of this technique i.e. transportation of CO2 from sources to sinks in a cost effective and safe manner is gaining widespread attention. Emphasis of this mitigation strategy is justified as CO2 transport is often one of the more underestimated components of any geological sequestration capture, transportation and storage chain. Studies were done in evaluating Carbon Capture, Utilisation and Storage (CCUS) economics for Trinidad and Tobago (T&T), however these did not place any great emphasis on critical aspects of CO2 transportation cost estimation through widespread informed estimates and proper transportation modes and infrastructure options. This paper attempts to address this gap for (T&T).

The transported CO2 is normally processed in liquid or supercritical phases. The supercritical phase is used with pipelines in continuous flux and the liquid type mainly for batch transportation (e.g. train, truck, ship). CO2 can also be transported in a solid state however this process requires much more energy compared to the other options and is therefore inferior from a cost and energy requirement viewpoint. Transport of CO2 is already a reality, occurring daily in many parts of the world. However, the scale of the transportation infrastructure and investment required to enable large-scale deployment of CCS cannot be underestimated. Since data in these areas is limited for T&T, one of the objectives of this paper is to compare different ways of CO2 transportation from the selected source to the targeted fields in T&T. This analysis will allow for a level of source-sink matching to be incorporated. Among all the options for CO2 transportation, the most economic method of transport depends on factors such as the locations of capture and storage, distance from source to sink, and the quantities of CO2 to be transported. In the case of large amounts of CO2 are to be transported, as may be in the case of T&T, the utilization of pipelines and ships may be the only viable transportation alternatives for CCS purposes. For T&T, the threshold volumes beyond which batch transportation will no longer feasible when compared with the use of pipelines is unknown and the determination of this key threshold value is expected to be another major output of this study.

The initial methodology employed in this study involved conducting a comprehensive literature review in the area of CO2 transportation. The sources of data for this review were not limited to T&T alone however, where applicable, local data was incorporated to integrate certain key indigenous parameters (such as relatively cheaper electricity rates) that would significantly influence the transportation cost. Once the data was acquired and contextualized for T&T, a financial operational model was built using Excel software to compute the costs for the various transportation modes. In order to account for fluctuations of parameters associated with the various modes of transport, the models were built incorporating sensitivity analyses to simulate these variations. Since no transport simulations were done in this study, the robustness of data was imperative for the results to be meaningful. The results of this study presents enormous benefits for T&T as this study not only measured but illustrated a functional methodology of the costs associated for transporting up to 6 Mt/yr of CO2 for the different modes while taking into account the effect of internal variations. It is expected that this information will be critical in evaluating overall CCS economics for T&T.

It was found that:
Transporting 6 MtCO2/y over 71.5km for 10 years would have an estimated capital cost of USD 61.7 million and an O&M cost of USD 3.7 million;

Considering inflation, the unit cost ranged between 0.62-1.09 US$/tCO2 using the variable pipeline lengths of 40-71.5 km; and

The length of the pipeline was shown to have the greatest effect on the transport cost.