Towards a Carbon-Neutral Gathering

As part of our effort to reduce global climate change, Transition US asks each participant in the 2017 Gathering to minimize your carbon footprint for travel. Wouldn’t it be great to be carbon-neutral?

The key to reducing climate disruption is to greatly reduce emissions of greenhouse gases, which are those molecules that don’t let the Earth cool off each day.

Everything we do requires energy, and most of our energy comes directly or indirectly from fossil fuels - if you are coming to the Gathering, you cannot avoid the resulting greenhouse gas emissions.

So, we ask that you work with your local Transition group, other groups, friends, and family so that they can help offset the “carbon cost” of your travel by changing their behavior.

Greenhouse Gases

One of the most important greenhouse gases is carbon dioxide (CO2) and burning fossil fuels (coal, oil, and natural gas) accounts for the vast majority of anthropogenic (our) CO2 emissions.

US GHG Emissions

Other greenhouse gases, like methane and nitrous oxide, are present in much smaller concentrations, but are much more effective in trapping heat than CO2. Other combustion products (water and nitrogen oxides) also trap heat or contribute in other ways to global warming. All those effects usually are added up as equivalents to CO2, so the total impact of fossil fuel use is expressed as CO2 equivalents (CO2e).

To know how much carbon offset you need, you have to calculate it. The next section makes this easy. Each example is an estimate for a 1,000-mile round-trip. Simply multiply the CO2e shown by your miles, and then divide by 1,000 miles. For example, if your round-trip in a 40 mpg gasoline car will be 500 miles, your footprint will be 258 kg CO2e X 500 / 1000 = 129 kg CO2e.

The following calculations are approximate, because baseline data were drawn from sources that were not strictly consistent in what they included.

CO2e Emissions from Travel

There are many carbon footprint calculators online that will estimate the CO2e for your travel. Here, however, are some general guidelines you may use.

To keep this simple, we focus only on the “marginal” footprint due to fossil fuel use per person. Here, the estimates include the energy needed to acquire, refine, transport, and combust the fuels, but not the energy required to make the vehicle, build and maintain roads, tracks, airports, and so on.

Transport GHG Emissions

Personal Vehicles

If you travel to Macalester College by car or motorcycle powered by liquid fuel, you need to know the distance, the fuel type (gasoline or diesel), and miles per gallon the vehicle actually achieves on the trip. We’ll restrict this to gasoline, which generates 8.89 kg CO2e per gallon in direct emissions and 1.55 kg CO2e/gal in indirect emissions before you buy it. Therefore, 10.34 kg CO2e are emitted for each gallon of gasoline you use.

In a car that gets 25 mpg, your vehicle emits 0.413 kg CO2e/mile (10.34 kg CO2e/gal divided by 25 miles/gal); one that goes 40 miles with a gallon emits 0.258 kg CO2e/mile. If you travel alone, and the round trip is 1000 miles, your 25 mpg car will emit 413 kg CO2e, whereas the more fuel efficient 40 mpg car will emit 258 kg CO2e.

The story with electric vehicles is more complicated. Like those that use liquid fuel, they vary in the amount of fuel (electricity) they need per mile. The website of DOE and EPA lists all personal electric vehicles and shows a range from 0.83 miles/kWh to 4 miles/kWh (121 to 25 kWh/100 mi).

Furthermore, the carbon footprint of electricity varies with the fuel sources used to produce it. There are essentially no CO2e emissions caused by charging the battery with electricity produced only by renewable sources. But finding these charging stations is difficult, so usually you have charge at a station using power from the regional grid. Different regional electrical grids have different emission factors, as seen in the eGRID map below.

eGrid Subregions Map

The average emission factor for those states and areas outlined in green is the lowest, 0.30 kg CO2e/kWh. The highest emission factor for electricity generation, 0.71 kg CO2e/kWh, is in the central states, outlined in red. The band of states from southern Nevada to Florida and Virginia has an intermediate emission factor, 0.50 kg CO2e/kWh.

The three most popular 2017 models of fully electric vehicles and their fuel efficiencies are shown below. Assuming the same 1000-mile round trip to Saint Paul was within the central state region described above, the total energy required (kWh) is shown as are the total CO2e emissions:

  • Chevrolet Bolt: 3.57 mi/kWh 280 kWh 199 kg CO2e
  • Nissan Leaf: 3.33 mi/kWh 300 kWh 213 kg CO2e
  • Tesla Model S: 2.94 mi/kWh 340 kWh 241 kg CO2e

The calculation is simple for an EV traveling across two grid regions: divide the total mileage within each grid region by the fuel efficiency, multiply each by the emission factor for the region, then add those results for the two grids.

Regardless of the fuel source, the more people there are in the car, the less energy use per person, so divide the total travel footprint by the number of folks in the car to estimate your personal footprint. (Of course, there is slightly more energy needed to move more weight, but the general concept holds.)


The previous point about people per vehicle is why buses generate far less GHG per person. For commercial bus service, a good estimate is 0.061 kg CO2e per mile, only 24% as much as one person driving in a 40-mpg car and less than one-third as much as the Chevy Bolt. If your round trip travel is 1,000 miles, the carbon footprint is 1,000 times 0.061, or 61 kg CO2e. With 4 people in the 40-mpg car, the GHG emissions would be nearly equal to riding in the bus (providing you don’t let the car engine idle during all the bathroom breaks…).


If you travel by train to Saint Paul, we can use the general estimate of 0.18 kg CO2e/mile, according to Amtrak. Your thousand-mile trip results in 180 kg CO2e emissions. This value is a weighted average for coach, roomette, and bedroom, but it should serve as a reasonable estimate. This estimate from Amtrak is for all long-distance routes, which vary in the relative number of seats of each type. It is instructive that their footprint is 0.40 kg CO2e for shorter routes (e.g., Boston to DC).


Air travel generally requires more energy per passenger than other transportation modes, with takeoff, landing, and taxiing requiring extra fuel. This means that, unless the size of the plane changes, direct flights usually are more efficient that flights with multiple stops.

A useful average emission rate per mile flown is 0.38 kg CO2e per passenger mile, and this includes one takeoff and landing. If your trip involves multiple stops, add 270 kg CO2e per additional airport.

For the 1,000-mile round trip example, your personal footprint would be 380 kg CO2e for direct flights plus 270 kg for each additional stop both directions (and the same total flying distance). As in the case for Amtrak, coach seats have smaller GHG footprints than business or first class.

A Few Ways to Offset Your Travel Emissions

There are many companies and organizations that offer offsets that promote sustainable, low carbon development. The Swiss-based is one of these and uses the Gold Standard to assure compliance and sustainability.

However, even better is to ask your friends, family, and colleagues to contribute to covering your “carbon debt.” After all, we have some direct control over two-thirds of the total energy and greenhouse gases emitted in the US per capita.

Discretionary Trips

Paper Airplanes Logo

Many of us have grown accustomed to traveling long distances for fun, relaxation, learning, and visiting. It is time we ask ourselves: is it really necessary to “vacate” for vacation? Is the business trip really necessary? If we still need to go, is there a conveyance that has a lower footprint?

An obvious tactic for our local support group is to avoid a flight. This might mean not going at all, substituting a heartfelt letter for a visit, attending the meeting via an internet link, or experiencing the Great Barrier Reef through someone else’s video rather than through our own goggles.


Drop a Car Logo

Let’s say you flew nonstop 500 miles to come to the Gathering and will fly back the same way. Your carbon debt would be 380 kg CO2e. If five of your support group each reduce their gasoline use by 5 gallons, they will have covered your debt - and they may have discovered they like to walk or bike instead of drive for those trips, or that they really didn’t need to go in the first place! (The calculation is 380 kg CO2e divided by 15.38 kg CO2e/gal gasoline, divided by 5 people = 4.94 gallons of gasoline/person.)

For those with access to public transit, who can bike or walk for short trips, or where a car can be rented or borrowed for necessary trips, your entire travel to the Gathering could be covered if only one person reduced the household fleet by one vehicle, if they use at least 25 gallons of gasoline less afterward. Think of the savings on maintenance and insurance!

Natural Gas

Natural gas is primarily methane and is widely used for home heating, cooking, water heating, and drying laundry in many areas of the US. It produces about 6.6 kg CO2e/therm, including the upstream emissions, so 380 kg CO2e is equal to 62.2 therms of natural gas.

Divided equally, your 5 friends, family, and colleagues could start saving their 12.4 therms each by doing laundry in cold, rather than hot water, taking shorter showers, hanging up the laundry to dry instead of using the gas dryer, reducing the home thermostat setting in winter, and turning down the gas water heater thermostat. Of course, the amount of heat to accomplish each of these depends on system efficiency. But considering a reasonably efficient water heater, if the family uses 50 gallons of hot water per day, lowering the water heater temperature from 130° to 120°F can save about 15 therms per year.


Eat Less Meat Logo

Beef is a popular food in the US, but it has the second highest GHG footprint of common sources of protein, about 12.3 kg CO2e/pound of meat. To offset your carbon debt of 380 kg CO2e, your friends back home would need to avoid eating 30.8 pounds of beef. That means that 5 people would have to give up one quarter-pound hamburger every week this summer. Not difficult for some, but pretty hard for others, eh?

Grow Food Logo

How about growing vegetables at home versus buying them at the store? Many of the folks you know may already be doing this, but maybe you can convince others to begin or expand their gardens. One report concluded that GHG emissions were reduced by 0.95 kg CO2e/pound of veggies grown at home. That means getting your local group to substitute about 400 pounds of store-bought veggies with locally-grown veggies would offset your travel footprint. It’s a bit more work than the two examples above, but it’s pretty easy to produce 1 pound of veggies in 1 square foot of garden, and each of the 5 supporters could do that in two 4-foot by 10-foot garden beds.

Our appreciation to Pat Thompson of Transition Town - All St. Anthony Park, Saint Paul, MN, for the black and white logos.

Purchasing Your Offset

This option is the easiest, and it can be reliable, but the impact is generally much slower than behavior change can achieve. Can we really afford to wait to reduce greenhouse gas emissions?

Furthermore, purchasing your offset will not change the behavior of others in the US, and may not motivate you to take further steps to reduce your carbon footprint.

If you choose to go this route, go to their contribution website, make sure that USD is selected in the currency line, enter 0.380 tons (380 kg) of emissions (or whatever your travel footprint is), select “Contribute," and proceed through to checkout. 

myclimate Screenshot

During the past three generations, we’ve become accustomed to flying. It’s relatively convenient and reliable, can take us places quickly, and opens up opportunities to travel anywhere on the globe. But, flying is tough on the environment - in one trip, it is easy to “burn up” all the carbon you’ve conserved last year by driving less, eating less meat, changing light bulbs, using a push mower, and doing all the other things you do to reduce global climate change.

Two of us recently visited elderly parents in Europe. The footprint of that single round-trip flight for two (5800 kg CO2e) was nearly twice the couple’s GHG emissions for living in their home for a year. They decided to purchase an offset for the trip, and have decided to purchase offsets for the rest of their GHG emissions, while they work to reduce their GHG footprint further.


Cleveland, D.A., N. Phares, K.D. Nightingale, R.L. Weatherby, W. Radis, J. Ballard, M. Campagne, D. Kurtz, K. Livingston, G. Riechers, and K. Wilkins. 2017. The potential for urban household vegetable gardens to reduce greenhouse gas emissions (GHGE). Landscape and Urban Planning. 157:365-374.

Hammerschlag, K. 2011. Meat Eater’s Guide to Climate Change + Health. Environmental Working Group. (no date) Calculation principles.

National Academy of Sciences. 2015. Comparison of Passenger Rail Energy Consumption with Competing Modes. National Cooperative Rail Research Program. Report No. 3.

Parker, D.S. P.W. Fairey, and J.D. Lutz. 2015. Estimating daily domestic hot-water use in North American Homes. Florida Solar Energy Center.

US DOE and US EPA. 2017. Fuel Economy. Office of Transportation and Air Quality.

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Wilson, L. (no date) Shrink That Footprint 4: Calculate your carbon footprint.

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