Twenty thousand leagues under the sea: A life cycle assessment of fibre optic submarine cable systems Craig Donovan Stockholm 2009 KTH, Department of Urban Planning and Environment Division of Environmental Strategies Research – fms Kungliga Tekniska högskolan Degree Project SoM EX 2009 -40 www.infra.kth.se/fms Twenty thousand leagues under the sea: A life cycle assessment o f fibre optic submarine cable systems Abstract Submarine cables carry the vast majority of transcontinental voice and data traffic. The high capacity and bandwidth of these cables make it possible to transfer large amounts of data around the globe almost instantaneously. Yet, little is known about the potential environmental impacts of a submarine cable from a life cycle perspective. This study applies Life Cycle Assessment (LCA) methodology to collect and analyse the potential environmental impacts of a submarine cable system within a single consistent framework. The system boundary is drawn at the limits of the terminal station where the signal is transferred to, or from, the terrestrial network. All significant components and processes within the system boundary have been modelled to account for the flow of resources, energy, wastes and emissions. Data quality analysis is performed on certain variables to evaluate the effect of data uncertainties, data gaps and methodological choices. The results highlight those activities in the life cycle of a submarine cable that have the largest potential environmental impact; namely, electricity use at the terminal station and cable maintenance by purpose-built ship. For example, the results show that 7 grams of carbon dioxide equivalents (CO 2 eq.) are potentially released for every ten thousand gigabit kilometres (10,000Gb·km), given current estimations of used capacity. The potential environmental impacts are directly linked to capacity and system usage, thus, increasing data traffic improves the environmental performance of the submarine cable system per unit of data. A focus area for further improvements is the emissions from ships, where the greatest gains in environmental performance are likely to be made through reduced emissions. This study is perhaps the first tentative step in linking together research into the environmental impact of terrestrial ICT networks. Keywords: Life cycle assessment, LCA, submarine cables, fibre optics. ii Twenty thousand leagues under the sea: A life cycle assessment o f fibre optic submarine cable systems Executive Summary Submarine cables carry over 97 percent of our transcontinental voice and data traffic. The world map of submarine cable networks shows that Europe, North America and Asia are well connected with many cable systems. Yet, little is known about the potential impacts of submarine cable systems from a life cycle perspective. This study applies Life Cycle Assessment (LCA) methodology to collect and analyse the potential environmental impacts of a submarine cable system within a single consistent framework. A “cradle-to-grave” approach is considered, which begins with the extraction of raw materials from the natural environment and ends with the return of wastes back to the environment. The goal of this study is to undertake an LCA of a fibre optic submarine cable system in order to assess the potential environmental impact of sending data over the cable network. To evaluate these impacts, the modelled flows within the system must be related to a quantifiable function of the system, described as the functional unit . The environmental impacts are described as “potential impacts” as they are not fixed in time and space and are often related to an arbitrary functional unit. In this study the functional unit is given as Ten thousand gigabit kilometres (10,000Gb.km), which is a scalable unit and can be interpreted as, for example, 1.25Gb of data sent over 8,000km of submarine cable. The technological system boundary is defined as the limits of the land terminal station where the signal is received from, or transmitted to, the terrestrial network and includes the submarine cable, submarine repeaters and all significant components within the terminal station. The temporal boundary is based on a commercial service lifetime of 13 years and the geographical boundary based on a generic system in a global perspective. Detailed data of the flows within, and crossing, the system boundary has been collected during the inventory stage of this study. Key processes are the production of electricity and the production and combustion of marine fuel. A total of 127 gigawatt hours (GWh) of electricity are used, given the lifetime of 13 years, with 90 percent of this being consumed during the use & maintenance phase. Ship operations represent the other key activity requiring a total of 179 ship days per 1000 kilometres of cable, resulting in the combustion of a total of 1515 tonnes of fuel. A total of 54 percent of the fuel is consumed during the use & maintenance phase, with 19 percent consumed during the installation and end-of-life recovery phases. The end-of-life decommissioning scenario considers that the cable is recovered by purpose-built ship and recycled for the mechanical materials, such as plastic, steel and copper. Recycling of these particular mechanical materials is highly efficient and a “closed-loop” recycling process is modelled, which assumes that 90 percent of the virgin material input is offset by the recycled materials. Impact assessment is undertaken on the modelled flows based on characterisation databases. This process assigns each flow to ten baseline impact categories based on an impact factor in relation to a single indicator, for example, carbon dioxide equivalents (CO 2 eq.) as an indicator of climate change. The ten impact categories used in this study are; abiotic resource depletion potential, acidification potential, ecotoxicity potential to freshwater, seawater and land, global warming potential, photochemical ozone creation potential, ozone depletion potential, eutrophication potential, human toxicity potential. The results show that the use & maintenance phase clearly dominates all impact categories at an average of 66 percent. By comparison, the raw materials and design & manufacturing phases account for, on average, only 6 percent of the total potential impact. This clearly highlights that the greatest impact over the life cycle of a submarine cable system comes from the use & maintenance activities. Namely, electricity use at the terminal to power the terminal equipment and the combustion of marine fuel during cable maintenance with purpose-built ships. These are two key activities relating to the environmental performance of the cable system. Analysis of the use & maintenance phase shows that the emissions of CO 2 equivalents are equally shared between electricity use at the terminal (47 percent) and maintenance of the cable by purpose-built ship consuming marine fuel (53 percent). However, further analysis shows that iii Twenty thousand leagues under the sea: A life cycle assessment o f fibre optic submarine cable systems the impact, per unit of primary energy input, from the combustion of marine fuel oil has a far greater impact on climate change than the impact from electricity use. This reflects the disparity in the environmental impacts of electricity and fossil fuel consumption. Focusing on climate change, the results show that a total of 7 grams of carbon dioxide equivalents (CO 2 eq.) are released for every 10,000Gb.km. This result can be applied to, for example, a telepresence conferencing system. Consider a conference between Stockholm and New York with a distance of 8000km and a bandwidth usage of 18Mbps, then 0.1 grams of CO 2 equivalents would potentially be released every second, which results in a potential release of 355 grams of CO 2 equivalents per hour. By comparison, this equates to only 3 kilometres of air travel for a single person or 2.2 kilometres road travel by the average EU passenger car. Expanding this example, a 2 day meeting could utilise the telepresence system for 16 hours resulting in a potential release of 5.7kg of CO 2 equivalents. By comparison, this same 2 day meeting in a face-to-face setting would require 16,000km of air travel, resulting in a release of 1920kg of CO 2. It should be noted that this example considers only the impact of sending data via the submarine cable system and not the telepresence system as a whole. The function of the system is based on usage, or the actual used bandwidth, as opposed to the lit capacity, or the present technological limitations (at the terminal) of any system. Research shows that bandwidth usage is approximately 25 percent of current lit capacity. If this gap between usage and lit capacity was reduced, notwithstanding technical and commercial limitations, then a subsequent gain in environmental performance per data unit would be achieved. However, it should be noted that the overall environmental impact over the system lifetime remains unchanged. Similarly, increased system usage, in this case increased total data traffic, reduces the resulting potential environmental impacts per unit of data. The sensitivity analysis (described below) supports this conclusion and shows that increasing system usage over the 25 year technical lifetime of a submarine cable system reduces the potential environmental impact per unit of data. From a life cycle perspective, the longer a cable remains in service, the superior the environmental performance per unit of data. Used capacity and service life therefore have a significant effect on determining the results. The limitations of the study affect the final result, therefore, as recommended by the ISO 14040 series guidelines, a sensitivity analysis has been undertaken to estimate the effect of data gaps, assumptions and methodological choices. The submarine repeaters and terminal components are two sub-models affected significantly by data gaps and assumptions. However, by changing parameters within these sub-models, the sensitivity analysis shows that they have little effect on the final result. This indicates that the LCA model is relatively unaffected by the greatest uncertainties and is thus, robust.