Over the last two years, we grew from a small team of just over 100 to one with over 400 employees…and our carbon footprint grew, too. In 2016 and 2017 alone, we flew over 8 million miles, rode over 86,000 miles in rideshares, used over 217.05 MWh of energy to power our offices, and a significant amount for our servers. To balance out our impact, we purchase carbon offsets and renewable energy credits from Terrapass, a company that funds projects that help reduce greenhouse gases. Terrapass funds projects that expand wind farms and build anaerobic digesters to transform methane into electricity.

Pulling carbon emissions data together isn’t easy — I needed to spend some time crunching the numbers to figure out our exact carbon footprint. In the end, it proved to be a mixture of science, hard data, art, and classic “good-enough” estimates. Here’s a look at how we did it.

Step 1: Gather data from your vendors

First, I gathered as much data as possible on travel bookings, car share, office electricity, and server usage.

We use Egencia to book corporate travel, and their administrative dashboard can produce a report on our total mileage — 4.5 million air miles in 2017. We have two large offices in DC and SF (nearly 40% of our miles werebetween these cities), and smaller offices around the world. It’s important that we spend a lot of time meeting our customers and user community, so we travel a lot. Our CEO traveled over 300,000 miles last year.

For carshare, we have both Lyft and Uber corporate accounts for the team’s business travel. Uber currently provides total mileage, but Lyft does not.

With four offices we run ourselves, all with different electricity providers and billing systems, and several co-working spaces, gathering our electricity usage in megawatt hours (MWh) wasn’t straightforward. For some offices, I gathered our bills for the entire year; and for others, I could only get a single bill for the entire building, including other tenants.

Step 2: Make estimates

This is where the art comes in. I made some assumptions to help us get our estimated emissions close enough for the purpose of offsetting.

From the vendor calculations, I could only access 2017 information (not 2016 information), creating a big data gap. I opted to make an estimate based on growth of people at the company. At end of 2016, Mapbox had 193 people in total, and by Dec 31, 2017, we grew to 325. So for flights, assuming a similar number of miles flown per employee, I used this ratio to approximate our air miles in 2016. Total: 8,083,967.6.

I didn’t have Lyft mileage, but I did know the total money spent on both carshare companies. So I made the assumption that there was a similar $/mile ratio as Uber, and took the ratio of the dollar amounts we spend to estimate Lyft miles.

In our SF office, I only received electrical use information for one billing period, for the entire building. I divided by the number of floors to get an approximation, and then multiplied by 12 to calculate the entire year’s of energy usage.

Step 3: Calculate carbon dioxide emissions

To estimate the amount of carbon dioxide emitted (C02e) for flights and rideshare, I used the straightforward Terrapass carbon footprint calculator.

For flights, I entered the total air miles traveled, with an even split of short, medium, and long-haul flights, which Terrapass then uses to calculate metric tons of C02e — 1,383 for Mapbox flights. There are numerous factors you’d need to get a precise amount, if ever possible: the type of aircraft and condition of the engines, the exact route taken, atmospheric conditions, the number of seats filled on the flight. Short haul flights are less efficient than long-haul flights, due to greater fuel usage on takeoff and landing. All of which is to say, the 1,383 metric tons of estimated CO2 emissions is an art, but I’m confident it is close enough to meet our commitment.

For carshare, I used the Terrapass fleet calculator. The 86,364.16 miles driven by carshare, emitted 33 mT. Assumed that these trips were in standard gasoline vehicles, and submitted the distance as total mileage on one vehicle. The exact amount would have varied based on the vehicle type and condition, traffic speeds, and other factors.

Step 4: Purchase offsets

The most straightforward step. There are lots of options for purchasing offsets and renewable energy credits. Armed with our total numbers of C02e and MWh, we decided to purchase from Terrapass, who won us over with their online calculator, DIY purchase interface, certification system, and great reviews.

Make the commitment!

It requires a bit of work, but we encourage other businesses to aim to be carbon neutral, and calculate and offset your carbon emissions. Find support in networks like ClimateAction.tech, who wrote the excellent field guide to sustainability for employees. Reach out to our community team @mapbox on Twitter with your story of going carbon neutral.

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