The Practical Challenges of Carbon Footprinting

What is the carbon footprint of the things we use every day? This is a question Suzanne Greene, leader of ESI’s Metals, Minerals & the Environment Program and manager of the MIT Sustainable Supply Chains Initiative, continues to ask. By looking at the carbon emissions companies report (or in some cases, don’t report), we can better understand entire industries’ and economies’ climate impacts, and set a “carbon budget” to reduce them.

Greene recently published two studies that dive deep into two sectors that make a big difference for our everyday life—mining and oil. Making up a lion’s share of industrial carbon emissions, both sectors are key to making society work, but also key to reaching the Paris Agreement climate goals. By looking at these “elemental” commodities, we can start at the base of global supply chains, understanding where and how emissions occur and targeting efforts to address them.

In “Responsible or reckless? A critical review of the environmental and climate assessments of mineral supply chains,” published in Environmental Research Letters, Greene and her co-authors look at the methods major mining companies use to calculate their annual carbon emissions. They found that reporting was often incomplete, and differences in methodologies employed by companies made a significant difference in the final numbers. These inconsistencies inhibit investors and consumers from being able to compare and contrast corporate emissions and progress towards climate goals.

In the second paper, “Well-to-tank carbon emissions from crude oil maritime transportation,” published in Transportation Research, Greene and her co-authors used information on more than 28,000 shipments of crude oil to understand the carbon emissions from the sea transport of oil. The results show that there are significant differences in the carbon footprint of oil transport depending on the oil’s origin and destination—underlining the point that all fuel has a carbon footprint above and beyond the emissions associated with burning it. Understanding these upstream emissions will become even more relevant as putatively low-carbon fuels like biofuel and hydrogen hit the market, for which most emissions lie upstream.

Greene continues to extend these research efforts as part of the Coalition on Materials Emissions Transparency (COMET), a multi-institutional effort to create a universal framework for direct comparison of greenhouse gas emissions in diverse industrial supply chains. Tracking global carbon emissions is a challenging prospect, but one society needs to master if we are to meet our 2050 climate goals. The advancement of consistent methodologies, application of satellite tracking, and setting of science-based targets are all pieces of the puzzle that we can work to advance.