Between 2013 and 2018, I flew over 500,000 miles for business, enough to circle the globe 21 times. At the time, I regarded the output of this travel in frequent flyer miles and the growing count of countries I had visited, but I failed to seriously reckon with the literal exhaust: 75 metric tons of CO2 in my wake.
A Past Due Carbon Accounting
Thanks to TripIt and other travel records, I was able to compile a complete record of five year’s worth of business travel by a combination of plane and Amtrak representing 75 tons of CO2¹.
For reference, the average American generates 16.5 metric tons of CO2 each year². Over that five year period, I was effectively living enough for two lives: equivalent to two Americans-worth of heating, lighting, driving, Netflix-binging, and all other carbon-generating activities over 365 days.
At standard temperature and pressure, 75 metric tons of CO2 fills over 38,000 cubic meters, which is equivalent to a cubic volume 33.7 meters on each side, a 23-foot deep pool the size of a football field, or the volume of the U.S. Capitol rotunda³. The carbon alone could form a diamond 18cm on each side.
Off hand, this actually feels small given the tremendous weight, but evidently volumes of gas are heavier than common experience suggests.
But consider instead what activities would generate an equivalent amount of CO2 emissions:
- Burn 29 short tons of anthracite coal or 1.3 million standard cubic feet of natural gas⁴.
- Burn gasoline to drive 16 average U.S. cars for a year⁵, or drive one Hummer H3 over 153,000 miles⁶ (98 days of continuous highway driving) or one Mitsubishi Mirage (the most fuel efficient all-gasoline vehicle today) for 365,000 miles⁷.
- Generate and deliver 106,000 kilowatt-hours of electricity⁸ to power 10.2 U.S. homes completely for a year⁹, drive a Tesla Model 3 427,000 miles¹⁰, or power a 60W light bulb for 200 years.
Paying Down This Carbon Debt
Having incurred this alarmingly large climate cost, how can a person begin to re-balance the scales? Convert to CFL bulbs, occasionally bike to work instead of drive?
Let’s consider lifestyle changes that would prevent an equivalent amount of emissions going forward:
- Switch from car commuting in the Atlanta MSA (which is home to the longest average commute among U.S. “large metro areas” — 12.8 miles one way¹¹) to bike commuting every work day for 28 years.
- Switch from a high meat diet to a vegetarian diet for 61 years (or convert 61 people for one year)¹².
- Install 5 kW of roof-top solar capacity in a suitable geography to offset grid-based electricity for 12 years¹³.
Alternatively, I could seek to recapture that volume of CO2 that I’ve let into the atmosphere. The most accessible method is planting trees, but I would have to plant 120 fast-growing conifers (e.g., ponderosa, red, white pines) that each survive at least 40 years¹⁴.
Offsetting Carbon and Conscience
Lastly, we can consider the easiest but most unappealing path: paying someone else to clean up my mess through carbon offsets.
Why is this unappealing? Not only does this absolve me of any role in solving the problem I created, but more importantly, carbon offsets are not clean fixes either environmentally or socially. In order to fully count environmentally, offsets must be additional, permanent, and without leakage¹⁵. This means, for instance, that protecting a forest that wasn’t at risk of disappearing doesn’t count, nor does simply shifting a logging operation a mile down the road.
More troubling though, are the potential human costs. In her powerful book, This Changes Everything, Naomi Klein details examples of social harm following from carbon offset markets run-amok: powerless communities in developing countries cut off from ancestral forests that provided literal and spiritual sustenance, and over which they have exercised thoughtful stewardship for generations.
Fortunately, there are credible certification schemes that help ensure these environmental and social standards are met by offset vendors. Two such certified vendors are TerraPass and Carbonfund.org¹⁶ which allow buyers to offset CO2 amounts for $11 and $10 per metric ton, respectively, using bundled portfolios of green projects.
Ultimately, I chose to buy offsets through the slightly more expensive GoldStandard.org which is also credibly certified, but furthermore allows buyers to obtain offsets from specific green projects (reminiscent of Kiva’s donation shopping workflow). For $12/ton I can contribute to a clean water project in Laos that offsets 40,000 tons of CO2e per year. $18/ton will help reforest degraded farm land in Panama.
I will be offsetting 25 tons per month for the next three months.
This is ultimately such a small drop in the atmospheric bucket. I had set out to calculate the PPM increase that this amount of CO2 represents, but quickly abandoned the effort among so many zeroes to the right of the decimal. But at the same time, I am one of seven billion people, and moreover, one of the privileged few whose impact is vastly outsized compared to the average.
Just as my personal history of intensive emissions is a microcosm of the climatic problem, so too might my reflection here be a microcosm of a larger global discussion that is rising in importance as our society undertakes its journey from carbon-intensive industrial past to a hopefully cleaner future.
: Estimated route-specific plane emissions were obtained from the UN’s International Civil Aviation Organization’s carbon calculator and EPA standard emission factors were used to calculate emissions from long-distance train travel.
: Per standard emission factors, referenced above.
: Assuming U.S. average CO2/kWh, which varies regionally by source mix; https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references
: https://link.springer.com/article/10.1007/s10584-014-1169-1 (includes CO2-equivalents such as methane)
: https://www.solarreviews.com/blog/average-residential-solar-panels-cost-and-savings-arizona-2018; Exact duration varies by region, however, given varying mix in CO2-intensiveness of electrical power generation. See https://www.eia.gov/electricity/state/