Argument: Natural gas supply chain emits substantial greenhouse gases
Overall results. BHP adequately estimated emissions of greenhouse gases arising from the start-up and operation of the proposed Cabrillo Deepwater Port, the energy and emissions from the unloading of ~2.2 LNG carrier berthings per week, emissions from fuel used by the Cabrillo receiving terminal’s tugs, tenders, and crew boats, and the main emissions source at Cabrillo: natural gas used in the FSRU’s re-gasification units. BHP’s estimate totals 261 tonnes of CO2 per year, including a small amount of methane from incomplete fuel combustion.6
BHP’s estimate of emissions from the Cabrillo Deepwater Port operations represents 1.5 percent of the supply chain emissions as estimated by Climate Mitigation Services (Table 1). Emissions from Cabrillo operations are significant, especially in terms of local air quality if not global warming, but clearly pale in comparison (by a factor of 66 to 1) to emissions from the other elements of the supply chain required for gas delivery to southern California. The major component is, not surprisingly, combustion of the delivered fuel. Compared to the emissions from end-use combustion of the gas — which is a common measure of the global warming contribution of natural gas — the rest of the supply chain emits an additional 44 percent.8 Methane is 6.1 percent of the total. The energy-intensive liquefaction plant and the LNG carrier “pipeline” across the Pacific emit ~twelve and nine percent of total emissions, respectively.