A frequently heard cliché in the airport industry is that “an airport is like a small city.” Denver International Airport (DEN), the fifth-busiest airport in the United States, is more like a medium-sized city with almost 200,000 passengers and employees using the facility each day. The parallels between a city and an airport are especially compelling as they relate to sustainability. Airports build facilities, use energy, generate waste, and set guidelines that influence the work of hundreds of business partners. An airport’s scale and function as a community gathering space provides unique opportunities for both leading by example and education through customer-facing activities such as recycling and composting, electric vehicle charging, and reusable water bottle filling stations. In all these areas and more, DEN acts with a focus on sustainability.
DEN opened in February 1995 as the first major airport built in the United States in decades, and many of the forward-thinking sustainability decisions during airport design helped set its present course of success. The current 53-square mile site northeast of downtown Denver was selected to accommodate airport growth that has ballooned from 32 million passengers in 1996 to over 61 million passengers in 2017 as Denver’s economy and cultural profile have expanded.1 At the same time, DEN’s contribution to the State of Colorado’s economic sustainability has continued to grow, totaling $26.3 billion in 2013.2 Denver was previously served by Stapleton International Airport, which has been transformed into a pedestrian-oriented new urbanist neighborhood that symbolically connects Denver’s former airport site to its new airport’s sustainable identity.
DEN’s sustainability work starts with the airport-wide Strategic Plan. Among the seven top-level objectives identified as critical to achieving the mission of becoming “America’s favorite connecting hub, where the Rocky Mountains meet the world” is a focus on “Investing for Sustainability.” This prominence within the Strategic Plan – alongside such typical airport goals as customer service, operational excellence, and financial performance – underlines DEN’s intention to consider sustainability in all airport decisions.
One of the ways that DEN operationalizes sustainability is through a new policy that was adopted in 2017 to formally define its sustainability values.3 The primary focus is the airport’s critical role in strengthening surrounding communities through responsible operations that consider social, environmental, and economic impacts. From connecting passengers to managing the impacts of aircraft noise, what sets DEN apart is the degree to which it prioritizes sustainability when making key decisions to maintain its “social license to operate.”
Key Sustainability Programs
For as much time as people spend in airports, there are many unique and easily unnoticed aspects of transporting passengers that can impact sustainability. Take aircraft deicing – as a cold-weather airport, effective deicing is critical to maintaining airport safety, efficiency, and reliability during the winter months.
The main component of aircraft deicing fluid used in the United States is a chemical called propylene glycol. While propylene glycol has low toxicity and is found in many household products, its high Biochemical Oxygen Demand means that it consumes oxygen while biodegrading and has the potential to negatively impact receiving waters and aquatic life. To mitigate these risks, DEN maintains an industry-leading stormwater management system that collects an average of 70 percent of the deicing fluid applied to aircraft during each winter season. This is even more impressive because Type IV “anti-icing” fluid applied during certain storm conditions is challenging to recover as it is engineered to adhere to the wing during aircraft ascent to prevent the build-up of snow and ice.
Once collected, DEN has an on-site glycol recycling plant that uses concentration and distillation systems to reclaim spent deicing fluid as 99 percent recycled propylene glycol to be sold back to industrial markets. What could have been a significant environmental liability is recycled into a commodity that saves the airport millions of dollars annually, reduces capital infrastructure costs, and improves water quality for our downstream neighbors – a true triple-bottom line success story!
Another aspect of air travel that is often overlooked by passengers is aircraft routing. Most people assume that when you get on a plane, you naturally fly a straight course to your destination. But for years, ground-based radar systems required aircraft to fly over specific waypoints, even if those waypoints took the plane off the most direct route.
Today, with the transition to satellite-based GPS navigation systems (referred to generally as “NextGen”), aircraft can fly significantly more precise routes. Working with the Federal Aviation Administration and regional partners, DEN was a leader in NextGen deployment as the first commercial airport to design a comprehensive plan that allows each NextGen procedure to reach its full potential.4 In addition to increased precision that dramatically reduces fuel burn and emissions (up to 900 pounds of fuel per trip), passengers experience the benefit of the time saved in the air. What’s more, a key part of NextGen allows for “Optimized Profile Descents” – rather than the traditional “stair-step” aircraft approaches that were required to maintain safety separations, arrivals into DEN can glide in on final approach without thrust, further reducing fuel burn and noise impacts while creating a smoother trip for passengers.
DEN is well-known for its commitment to renewable energy. In 2008, it became one of the first airports to host a large-scale solar photovoltaic array, a highly visible two megawatt (MW) system on Peña Boulevard, the main access road to the airport. Since then, four other solar projects have been built on DEN property, totaling 11.6 MW of generation with a design capacity of over 18 million kilowatt-hours per year.
The last solar project DEN participated in may be the most exciting – partnering with Xcel Energy, Panasonic, and L.C. Fulenwider Inc. to build a 1.6 MW solar canopy over a DEN-owned parking lot at the Peña Station NEXT transit-oriented development site. This array, in conjunction with a one megawatt/two megawatt-hour battery energy storage system, is part of a microgrid demonstration project serving the development.
DEN has worked to diversify its energy portfolio, including two recently constructed two megawatt “Community Solar Gardens.” DEN will be a major subscriber to these facilities that will also be open to individual and organizational subscribers from within the community. In addition, DEN is subscribing to four other off-site solar gardens and is participating in a new renewable energy purchasing program that will allow it to purchase additional emissions-free solar power directly from the local utility. In addition to the direct economic and sustainability benefits, these projects and programs will help support regional clean energy development.
In 2015, DEN became one of the first airports in North America to be certified to the international Airport Carbon Accreditation standard after completing a greenhouse gas emissions inventory that was verified by a third-party auditor, developing a carbon management program, and demonstrating a year-over-year emissions reduction.5 In 2018, it was certified to the next level of the program based on continued reductions and its work to engage business partners in greenhouse gas emissions reduction activities.
Although DEN does not produce or sell food directly, the organic waste generated by its many food and beverage concessions represents a significant diversion opportunity. Despite the airport’s efforts to promote waste reduction through expansive recycling and composting programs, airport security and access logistics have created challenges to diversion. With the knowledge that 30-40 percent of all prepared food goes to waste, DEN created an airport-specific solution to work with business partners to address the problem.6
Starting with a small pilot project in 2015, DEN began strategically locating coolers at the main airport loading dock and on a passenger concourse to capture healthy, safe food that otherwise may have been landfilled. Following a 2016 grant from the State of Colorado, the program expanded to restaurants on all three concourses, DEN’s on-site hotel, and airline flight kitchens. In 2017, 117,000 pounds of food were donated to Metro Caring, a leading Denver-based hunger-relief organization. The United States Environmental Protection Agency’s food-recovery hierarchy ranks food donation only below source reduction as an environmentally preferable strategy (even higher than composting).7 DEN’s award-winning program facilitates a reduction in landfilled waste, reduces tipping fee costs, provides a tax benefit to donors, and supports food-insecure Denver families. It’s a notable example of the role large organizations like airports can play in the community – even without donating directly, working with business partners to identify champions and influence behavior can have significant sustainability benefits.
DEN opened in 1995 as one of the most sustainable airports in United States and works hard to maintain that reputation 24 years later through a commitment to continuous improvement and innovation.
In 2004, DEN became the first commercial-service airport in the United States to develop an ISO 14001-certified Environmental Management System (EMS) that covers all airport operations. This system allows DEN to be proactive about environmental management – rather than being unprepared for environmental challenges, it has thoughtfully considered the potential impacts of operations, strategically ranked the risks, and developed processes and plans to prevent pollution and quickly respond to issues when they occur. One of the hallmarks of a successful EMS is a focus on continuous improvement. This attitude permeates DEN’s sustainability program, as it works to strategically understand the operational aspects that can affect sustainability and identify opportunities to get better each year.
DEN is not alone when it comes to sustainability leadership in the aviation industry. Although other airports – especially those of comparable size in the same geographic area – are in some sense “competitors,” sustainability is an area in which friendly competition leads to collaboration and mutual support. DEN is active in several aviation-focused sustainability groups that allow airports to discuss common issues and share best practices. While there is another common cliché that “if you’ve seen one airport, you’ve seen one airport,” many are collectively striving to reduce impacts and influence business partners to do the same. Different airports have unique priorities based on management goals, community priorities, or geographic requirements – including airports that are international leaders on climate change adaptation planning, sustainable aviation fuel development, and net-zero green building practices.
DEN’s recent growth and future passenger projections come with a significant responsibility to proactively plan for continued industry leadership. One of the aspects that makes DEN unique is the opportunities afforded by its extensive land area. Although DEN is already one of the most-traveled airports in the world, its master plan envisions an expansion from the current six runways to a full build-out of 12 to improve its ability to serve passengers. That expansion has already begun as DEN embarks on a multi-year 39-gate expansion effort. As with all DEN construction, the new gates will be designed and constructed to the United States Green Building Council’s Leadership in Energy and Environmental Design (LEED) Gold standard. These projects will join DEN’s existing high-performance building portfolio that includes a LEED Silver Data Center, LEED Gold Concourse C West expansion, LEED Gold Fire Station 35, and the LEED Platinum airport-owned Westin hotel, which sits directly above the “A Line” electric commuter rail that opened in 2016 and transports passengers to and from downtown Denver.
DEN is an active participant in the annual Sustainable Denver Summit and during the inaugural event in 2015, committed to reduce the airport’s scope one and two greenhouse gas emissions by an amount equal to the annual operating emissions of the new hotel. Based on a variety of lighting, HVAC, and controls projects and the general decarbonization of Denver’s electric grid, DEN achieved that goal ahead of schedule and has reduced overall greenhouse gas emissions more than 23 percent since 2013.
Beyond the growth in DEN’s aviation functions, its land mass also provides opportunities for commercial development. The airport is considering ambitious sustainability goals within the DEN Real Estate Strategic Development Plan to reduce long-term costs and environmental impacts, improve reliability and resiliency, and serve as a market differentiator that drives long-term land value.
As part of the City and County of Denver, DEN actively participates in citywide programs conceived under the leadership of Mayor Michael B. Hancock and supported by DEN’s progressive leadership team. The combination of top-down and bottom-up support puts the airport in a unique position to promote sustainability as a key business value that will drive airport success long into the future.
- Denver International Airport. Passenger Traffic Reports [online] https://www.flydenver.com/about/financials/passenger_traffic
- Denver International Airport. Study: Denver International Airport Grows to a $26.3 Billion Economic Engine for Colorado [online] https://www.flydenver.com/sites/default/files/downloads/DIAPR_131010y.pdf
- Denver International Airport. Sustainability Policy [online] https://www.flydenver.com/sites/default/files/environmental/den_SustainabilityPolicy.pdf
- Denver International Airport. Denver’s Blue Skies Turn Green with New Departure and Arrival Procedures [online] https://www.flydenver.com/sites/default/files/downloads/DIAPR_130620e.pdf
- ACI Europe. Accredited Airports Across the World [online] https://www.airportcarbonaccreditation.org/airport/participants/north-america.html
- United States Department of Agriculture Office of the Chief Economist. Frequently Asked Questions [online] https://www.usda.gov/oce/foodwaste/faqs.htm
- United States Environmental Protection Agency. Food Recovery Hierarchy [online] https://www.epa.gov/sustainable-management-food/food-recovery-hierarchy