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Calculations of climate effects from private luxury jets at Hanscom Field

Feb 24, 2023

There is considerable confusion about how the global warming effects of private jet travel are computed. This document explains the process.The global warming effects of emissions are the result of heat trapping effects. Carbon dioxide is a well-known source of heat trapping and the result of fossil fuel combustion. However, for jet travel, there are other effects of contrails, sulfur and other sources which add to the CO2 effect.

The global warming effect of jet emissions is expressed in carbon dioxide equivalent or CO2e, which includes both the CO2 contribution and the other effects. The contribution of CO2 is the direct result of burning fuel and is exactly 3.16 kg of CO2 for each kg of jet fuel burned. The other contributors to CO2e are the continuing subject of research, but various studies, including by the IPCC, have determined that the total effect is within 2 and 4 times that of CO2 alone (6.9 to 12.6 kg CO2e/kg). Papers suggest a consensus value of 7.8kg CO2e for each kg of jet fuel burned.

Therefore, burning fuel at high altitude in a jet plane is about twice as bad as would be expected from the carbon dioxide alone.

The global warming contribution of jet flights can therefore be directly computed from the fuel consumption: 7.8kg of CO2e for each kg of jet fuel. The contribution of a particular flight could be determined by measuring its fuel use, but this is not practical for a general analysis. Instead, there are generally available tables of fuel use for different aircraft, which describe how much fuel is consumed per hour. These tables are made based on averages across a flight, since fuel use varies during takeoff, cruising, and landing.

The fuel consumption of private jets ranges from 150 gallons per hour (very small Citation CJ3), to 500 gallons per hour (full size Gulfstream), depending on size and range of the airplane. A mixed fleet of private jets can be assumed to have a fuel consumption of 330 gallons per hour, which must be multiplied by 3.79 kg/gallon to get kg per hour.

The average flight duration from a specific airport could be found by tracking and averaging actual aircraft trips. For Hanscom Field, an average duration of 2.5 hours is a reasonable guess, although additional information could move this number up or down.With this information, the kg of CO2e of the average flight of the average private jet from Hanscom Field is computed at 24,399 kg of CO2e per flight, which is roughly 24 metric tons.

There are today 33,000 jet operations per year at Hanscom Field. Half are arrivals, and half are departures. The airport enables both of these operations, so we can consider both in the calculations of the effects. The 33,000 operations can be directly calculated to result in 805,000 tons of CO2e per year. If tripling the airport hangar capacity only caused an increase of 50%, the increase in CO2e would be 390,000 tons, for a total of about 1,200,000 tons per year.

The number of 1,200,000 tons of CO2e, without context, has very little value in describing the magnitude of the impact. Here are some facts which put it in perspective:

A typical car emits 5 tons per year.

A typical 5kw residential solar array offsets 2 tons per year (Massachusetts)

The total installed solar PV in Concord is 11.2MW offsetting 4,100 tons per year

A typical home is responsible for 25 tons per year.

All of these effects are orders of magnitude smaller than the effect of private jets. For example, a single private jet flight creates CO2e (24 tons) comparable to the contribution of a typical home (25 tons) in a year! This leads us to a number of remarkable facts regarding the magnitude of private jets at Hanscom Field. To offset the CO2e of the expected jet traffic at Hanscom field would require:

Removing 240,000 fossil cars from the road

Installing 3,200 megawatts of solar power

Converting 48,000 homes to net zero

Our communities are working hard to undertake significant climate-saving actions, which we had fully expected to reduce gloabal warming. Unfortunately our actions will only go towards cancelling a tiny amount of the greenhouse gas emmissions of the private luxury jet traffic operating from our town. As one commenter wrote: "How quaint that they drive their Tesla S to the runway—as if that makes up for the carbon output of flying directly from Hanscom to St. Bart or the Super Bowl (true examples)."

These values correspond to the impact with hangar expansion. Two thirds of this impact is already occuring. The new project to triple hangar capacity is conservatively estimated to be responsible for one third, but could result in much more. These estimates may be adjusted up or down if the airport releases additional information.

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