Life Cycle Assessment

Methods

As stipulated in the international standards ISO 14040:2006, there are four phases in an LCA study: goal and scope definition; inventory analysis; impact assessment; and interpretation. The final report follows this structure, with the first three phases presented as part of the methodological foundation of the work.

Goal and Scope

This is a benchmarking exercise that aims to quantify the carbon footprint of an SNRG module under certain operational use and EoL scenarios, it is not intended for comparative assertions to be disclosed to the public. The SNRG module was developed and built to be demonstrated at COP26, and primary data for material quantities and types, as well as energy demand, were collected on- and off-site wherever possible. Where primary data was unavailable, representative proxy data was obtained from Environmental Product Declarations (EPDs), peer reviewed literature, the ecoinvent database, and personal communications with the design team.

To achieve this goal, the scope of this LCA includes a cradle-to-grave analysis with an additional assessment of Stage D benefits. All raw materials and energy inputs related to core, roof, internal partitions and façade of the functional unit (FU) are included, as far as they are known.

Life Cycle Inventory

The life cycle inventory (LCI) is an inventory of input/output data regarding the system being studied and it involves the collection of the data necessary to meet the goals of the defined study. Here, the LCI comprises the material quantities (in kg, m3 or m2 ) and transport distances (in km) required to build one SNRG module. The full LCI and quantity breakdown can be found in the accompanying Excel calculator. This is built on primary data collected on-site as well as off-site data extracted from technical drawings and information provided by the design and project team.

Life cycle impact assessment

The purpose of life cycle impact assessment (LCIA) is to provide additional information to help assess a product system’s LCI results to better understand their environmental significance. In line with the goal and scope of this report, only the global warming potential (GWP) impacts are assessed, i.e. the carbon footprint of the SNRG module and functional unit. The main goal of LCA is to promote increased awareness of the importance of environmental protection, and the possible impacts associated with products and services, both manufactured and consumed. Thus, it is important to consider environmental indicators other than GWP, such as ecotoxicity and resource depletion. However, this is out with the scope of the current study but is highlighted as a caveat that the results presented here are not a holistic representation of environmental sustainability.

Results, Interpretations and Scenarios

The final section presents the results of the LCA. They are divided according to two main criteria. First, impacts are separated between cradle-to-practical completion (A1-A5) and cradle-to-grave (A1-C4) to highlight the significant difference in the confidence that can be posed over the two numbers. A1-A5 impacts are much more likely to be correct (bar the omissions and limitations declared) as they are either based on primary collected data of a project executed only few months ago or are derived from recent, historical data (such as that in EPDs). A1-C4 impacts are instead comprised of the same good quality data for the pre-occupancy phase but also muddled by the uncertainty introduced by (i) the significant uncertainty around the decarbonisation rate of the electricity grid and (ii) the vastly unknown impacts that will occur in the future at EoL (currently modelled as happening after 60 years of useful life, which is a further uncertain element per se).