Building a Better Future: How We Offset Our 2025 Emissions

Ayers Saint Gross has long been committed to excellence in sustainability through our projects, our office culture, and our operations. I’m proud to share that, as of this month, we have completed and offset our firm’s operational greenhouse gas (GHG) emissions for 2025, which include emissions related to our office spaces, flights, train travels, commuting, and ground transit (including mileage from cars, taxis, rental cars, and other rideshare options).

In case the weeds don’t interest you, the punchline is that our 2025 Ayers Saint Gross GHG Emissions Footprint looks like this, totaling 900 MT CO₂e.

We worked with Tradewater to offset the carbon footprint of our firm’s Scope 1 and Scope 2 emissions (related to energy use in our primary offices) as well as select Scope 3 emissions (commuting and travel emissions). Prior to arriving at this partnership, we vetted eight carbon offset vendors recommended by peer organizations. We found Tradewater to have the best alignment with our firm’s values and characteristics:

• Because we value integrity, we wanted a highly reputable carbon offset partner.
• Because our firm has existed for 114 years, we wanted a carbon offset partner with a long tenure.
• Because we maintain a Just Disclosure bi-annually, we wanted a carbon offset partner who was similarly transparent about its business operations.
• Because we’re headquartered in Baltimore, we wanted to support U.S.-based projects through a U.S.-based carbon offset partner.

Tradewater met all those criteria for us. Headquartered in Chicago, they deliver high-impact, verified projects in the United States, have a long tenure in the carbon offset market, and are B Corp certified.

The United States alone has over 141,000 documented orphaned oil and gas wells (OOG) — and likely more that are undocumented — but no regulation compels their cleanup. Left unchecked, OOG wells leak methane and other pollutants that fuel climate change and threaten ecosystems and public health. Methane has significantly higher Global Warming Potential than carbon dioxide, so plugging these wells is a high-impact practice.

While there is some government money available to states to take on this challenge, it is woefully insufficient to tackle the problem. Our offsets help close that funding gap and prevent ongoing emissions by enabling Tradewater to plug these wells as part of their OOG1 project.

Tradewater’s OOG1 project plugged three former gas wells in Indiana. These three were prioritized because they were actively leaking methane, had damage to the above-ground equipment, were emitting toxic gases in addition to methane, were not on the state’s plugging plan, and were in areas that presented real hazards to the local community.

This project is important and relevant to us here at Ayers Saint Gross because we have clients in Indiana — Purdue University among others — and many others more broadly across the Midwest. This project also earned an “A” rating from MSCI which signals high confidence that each credit we bought really does deliver CO₂ reductions along with positive social and environmental outcomes. Learn more here about the OOG1 project here.

I tend to like weeds, so let’s dive into our carbon accounting in hopes that it helps others estimate their emissions.

Tradewater has an online carbon calculator that can help organizations estimate their emissions from a variety of sources. Just like other calculators, it requires certain input data to tabulate a MT CO₂e estimate. We found that much of our best available input data didn’t fit neatly into Tradewater’s calculator, so we leaned on the research we’d done across carbon offset vendors to find a calculator that could work with our data. CNaught is a carbon offset vendor that came highly recommended to us. While we ultimately did not select them, we found their online carbon calculator tools to be a great fit for the data we had available.

Office Space. Our Arizona, Baltimore, and D.C. offices total 36,980 SF. Using CNaught’s online carbon calculator, this pretty quickly equates to 318.03 MT CO₂e. Per CNaught, “Area is multiplied by the average carbon intensity of office space of 7.0 kg CO₂e per square foot per year as provided by the Energy Information Administration CBECS survey. This estimate includes the impact of the average usage of electricity, natural gas, and fuel oil for U.S. commercial buildings.” This estimate is likely a little higher than the actual GHG emissions associated with our office space because Arizona, D.C., and Maryland are all in cleaner-than-national-average electricity grids. That said, we also didn’t specifically include any square footage for our fully remote employees, so it’s a “good enough” estimate even if it’s not perfectly accurate.

Flights. Our flight data comes from two sources: our firm’s 2025 SWABIZ report and expense reports. The SWABIZ data lists the departure and arrival airport for every trip linked to SWABIZ as well as airfare costs. That made it easy to search trip mileage and calculate carbon emissions for everything in SWABIZ. The expense report data was messier because we don’t universally list departure and arrival airports, but this is a practice we hope to evolve this year to support our 2026 accounting. Because the cleanest flight data from expense reports is cost, we used the SWABIZ data as a “ruler” to convert the expense report cost data to mileage.

Trains. Our train data is measured in dollars spent per year, as reported on expense reports. We assumed that most of our train travel is between our DC and Baltimore offices (or vice versa) on either Amtrak ($15 to 30 one-way) or MARC ($9 one-way). To make the math easier, we estimated a one-way trip between DC and Baltimore costs on average $20 and each one-way trip is 35 miles. That helped us convert dollars per year in expense reports to annual mileage. After using CNaught’s calculator, we translated that to MT CO₂e.

Commuting. 2025 survey responses from a representative sample of our employee-owners demonstrated that our firm members commute in a variety of ways, including driving alone, carpools, trains, and Baltimore’s water taxi in addition to walking, bicycling, and telecommuting. Based on those findings, we used a variety of methodologies to estimate carbon emissions. The distribution of our typical commutes looks like:

Ground Transit – Mileage. Our mileage data comes from expense reports in dollars reimbursed per year. We divided the total reimbursed costs by the IRS-set reimbursement rate of $.70 per mile and then entered that number into CNaught’s calculator assuming the passenger car, van, or SUV vehicle type.

Ground Transit – Taxis / Ubers / Lyfts. Our data here comes from our corporate Uber account and expense reports. The corporate Uber account captures trip mileage directly for conversion to CO₂e emissions as well as fares with and without tips. The expense report data was messier because we didn’t capture mileage for taxis, Ubers, or Lyfts as part of the data — we hope to evolve this practice in 2026 to support better carbon accounting. The cleanest expense report data on this category is cost so we used the Uber account data as a “ruler” to convert the expense report cost data to mileage which was later entered into CNaught’s calculator to get to MT CO₂e.

Ground Transit – Rental Cars. Our rental car data comes from expense reports in dollars spent per year. There was no easy way to determine mileage without going through a ton of receipts. Sometimes team members might only drive a rental car 10 total miles over three workshop days, while other teams might drive more than 60 miles from an airport to a more remote campus. Using either the IRS reimbursement rate or the Uber account data gave significantly different mileage results, which we averaged together to estimate. As a result, this data has pretty big error margins, but it’s likely close enough. Once we determined a mileage estimate, that too was converted in CNaught’s calculator.

Other. Some expense report charges didn’t fit the categories above. We applied the 2025 IRS rate to the dollars that ended up in this bucket to get to a mileage and then converted it using CNaught’s calculator.

In our experience, the first time we do anything is often a heavy lift. It was certainly challenging, at times, to determine the emissions totals across all of these distinct categories. We expect that, as with many things, this process will become easier with practice.

We are proud to have completed this first carbon accounting and offset our impact. As we continue to push our projects toward our AIA 2030 carbon neutrality goals, we look forward to continuing this practice and offsetting our own emissions as well.

Allison Wilson is the sustainability director for Ayers Saint Gross.