The Strategies for Environmental Monitoring of Marine Carbon Capture and Storage (STEMM-CCS) monitoring and decision support tool provides guidance to identify and select the most appropriate techniques and technologies for the environmental monitoring of an offshore CO₂ storage complex (i.e. the storage site and the surrounding geological domain). Monitoring CCS storage complexes and, where appropriate, their surrounding environment to detect the migration and leakage of CO₂ and any adverse effects on the surrounding biosphere is a legal requirement under Article 13 of European Parliament Directive 2009/31/EC (also referred to as the CCS Directive). This tool summarises the relative performances and capabilities of the various monitoring techniques and technologies tested during the STEMM-CCS project, and provides data examples and recommendations with the aim of supporting CCS operators and regulators interested in establishing their own environmental monitoring programmes.

This tool has been designed to help users to establish the best combination of techniques and technologies that could be used to conduct environmental monitoring of a storage reservoir before, during, and after the injection of CO₂. It assumes that the potential storage reservoir has already been identified by the operator, and that all logistical, safety and structural storage requirements are met. The relative effectiveness of the methods and techniques tested during the STEMM-CCS project are presented for 5 monitoring tasks: (1) Characterisation of Injection Site; (2) Leakage Detection; (3) Source Attribution; (4); Leakage Quantification; (5) Environmental Impact Assessment.

Relevant methodologies are presented within each task, together with a short description about each technique that includes an image of the associated instruments, an example of data output acquired through the STEMM-CCS project or another relevant project, and a summary of the strengths and limitations of the approach. The different methods are ranked against 5 monitoring parameters, enabling to compare their relative effectiveness, and recommendations for their deployment and application are provided.

Further guidance on how to use the tool is provided within each of the monitoring tasks, which can be accessed through the links below.