Under the federal Clean Air Act, Kentucky is required to keep haze air pollution under control in Mammoth Cave National Park.

Critics said the state's current plan falls short. Coal-fired power plants are the driving cause of air pollution impairing visibility in the Commonwealth, according to the National Parks Conservation Association.

Ashley Wilmes, executive director of the Kentucky Resources Council, said the state's current Draft Regional Haze State Implementation Plan only considers two facilities as significant pollution emitters, despite evidence there are more.

"There has to be a detailed analysis of additional major polluters in Kentucky that are contributing to this haze," Wilmes asserted. "They did not do this analysis for other major coal plants, including Ghent and Mill Creek, Trimble Station and others."

The Kentucky Energy and Environment Cabinet hears virtual public comments on the plan tomorrow at 10 a.m. ET.

Ulla Reeves, clean air program director for the National Parks Conservation Association, said several major polluters in the region are contributing to poor air quality.

"We see in Kentucky that Mammoth Cave is actually one of the most polluted national parks in the entire country," Reeves pointed out. "It is surrounded by polluting facilities."

Bryon Gary, program attorney for the council, said advocates are asking the state to include additional pollutants and facilities, and address environmental justice impacts to surrounding communities. He added residents' input will be considered by the Environmental Protection Agency.

"The public will have the opportunity to give those comments," Gary noted. "Then at some later point, the Energy Environment Cabinet will develop a written response to comments that will be submitted to EPA, along with their final state implementation plan."

Exposure to the air pollution particles triggering haze can cause breathing problems, lung cancer, heart attacks and low birth weight in newborn babies, according to the Centers for Disease Control and Prevention.

A new study shows trees in mid-city Los Angeles absorb up to 60% of carbon dioxide emissions during spring and summer when the trees are most active.

In 2021, researchers from the University of Southern California placed 12 sensors in central L.A. to monitor carbon dioxide levels.

Will Berelson, professor of earth sciences, environmental studies and spatial sciences at the University of Southern California-Dornsife, said trees are surprisingly effective at lowering carbon dioxide levels in the air.

"The input of CO2 from cars is predicted to be a certain level," Berelson explained. "But when we look for CO2, we find much less. This difference is due to uptake of CO2 by trees."

Berelson pointed out emissions are like passengers on a train, as wind moves pollution through the city, where some get picked up and dropped off. The sensors measure the pollution in real time. The research published in the journal Environmental Science and Technology found trees absorb about 30% of carbon dioxide, averaged over 24-hour periods over a year. So clean energy, improved public transit and broader emissions reductions are still needed.

Berelson noted the sensors, called a Carbon Census Array, will track carbon dioxide levels for years to come.

"The City of L.A. is always committed to reducing emissions and it isn't clear how they're going to keep track of whether their emissions have actually lowered or not," Berelson observed. "But we've got a way to now track emissions and quantify emissions."

The sensor network is now being expanded, with 12 additional sensors reaching out to Santa Monica on the west side of the city.

The negative effects on air quality from industrialized animal facilities in North Carolina stick around for a long time, according to a new study.

The research showed the effects are felt most by communities of color.

Sally Pusede, associate professor of environmental science at the University of Virginia and lead author of the study, said her team used satellite measurements of ammonia pollution associated with industrialized swine operations in eastern North Carolina.

"Those ammonia air quality impacts are disproportionately experienced by residents in eastern North Carolina who are Black and African American, Hispanic and Latino, and Indigenous," Pusede reported.

Compared to white communities, the study found ammonia concentrations were 27% higher for Black communities, 35% higher for Hispanic communities and 49% higher for indigenous communities between 2016 and 2021. Pusede noted satellite data from 2008 to 2013 showed the trends have largely remained unchanged.

Weather conditions can also increase the effects of ammonia pollution, with warm conditions and calm winds amplifying disparities. Pusede pointed out contrary to claims industrial swine operations only affect nearby communities, ammonia in warm conditions can travel quite far.

"Ammonia is emitted into the atmosphere, it travels downwind and then eventually that ammonia will deposit," Pusede explained. "The next day when the sun comes up, the air temperature warms, that ammonia can be reevaporated or revolatized into the atmosphere, and then can be transported even further downwind."

Pusede added broadly speaking, there are no protections from the air quality effects of industrial agriculture, not just ammonia but other pollutants as well.

"In North Carolina, there's a history of people not being protected by the state regulatory agencies," Pusede observed. "There's also not been regulations at the federal level from the EPA, and so that's a problem."


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By Ethan Brown for The Sweaty Penguin.
Broadcast version by Mark Richardson for Colorado News Connection reporting for the Solutions Journalism Network-Public News Service Collaboration

It’s not every day that a journalist gets a request like this: instead of separate interviews, sources from three different organizations — Colorado’s Department of Transportation (CDOT), the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL), and the Alliance for Aviation Across America — wanted to hop on the same Zoom call. Together.

That alone made me curious. Government agencies aren’t exactly known for seamless collaboration or cutting-edge innovation. Yet here they were, not only working together but making real progress toward an ambitious goal: decarbonizing air travel. As CDOT Division of Aeronautics Director Dave Ulane quipped on the call, “We’ve got a great legacy of being very innovative and forward-looking. It’s what the folks of Colorado expect.”

It’s a daunting expectation to say the least. Air travel is responsible for about 2.5% of global carbon dioxide (CO2) emissions, the primary driver of global warming. That number is expected to triple by 2050. And decarbonizing the industry is notoriously difficult — electrifying planes poses steep technical challenges, and sustainable aviation fuels (SAFs) make up less than 1% of total jet fuel demand according to a 2019 report.

From preparing local airports for unprecedented spikes in electricity demand to ensuring United Airlines can use hydrogen aircraft in the state, Colorado’s partnership is showing how the aviation industry’s hardest problems might be solved — not through isolated efforts, but by working together. At a time when global leaders at COP29 are debating worldwide aviation taxes and activists are seemingly tracking Taylor Swift’s private jet around the clock, Colorado’s collaboration is offering a refreshing possibility: a sustainable future without sacrificing air travel.

A pilot study

The aviation sector connects over 27,000 city pairs worldwide, contributes $3.5 trillion to global GDP, and supports 87.7 million jobs. Yet, the environmental toll of aviation is significant. Combusting jet fuel releases CO2 along with water vapor, soot, and nitrogen oxides, intensifying warming at high altitudes through complex atmospheric reactions. These factors make aviation responsible for 3.5% of global climate impact, despite contributing only 2.5% of global CO2 emissions.

Colorado had other ideas. Believing aviation could become more sustainable, CDOT’s Division of Aeronautics launched a collaboration with NREL and its network of public-use airports and flight schools, creating what might be a first-of-its-kind approach to sustainable aviation.

“We were the first state aviation agency to actually partner with NREL and use their expertise to help us take a look at what these new technologies look like, when they might come into service, and really what sort of infrastructure needs might be needed at some of these airports to support them,” explained Ulane.

At its core, the partnership is about combining expertise. NREL brings cutting-edge research into potential sustainable aviation solutions such as SAFs, hydrogen, and electric-powered planes, while CDOT contributes the local understanding and coordination needed to ensure solutions can actually be executed. Colorado officially announced the collaboration in May 2023, with the Colorado Aeronautical Board approving a $400,000 budget to support NREL’s research efforts.

“We’re happy to have them do that [research] work for us,” said Ulane. “I think we’re a little more than halfway through, and look forward to getting an initial glimpse of what we need to start thinking about in our airports to get ready.”

“NREL is working across all different types of fuels, from sustainable aviation fuel, hydrogen power, electric hybrids,” added Brett Oakleaf, NREL’s Strategic Partnership Manager. “We’re really trying to understand the research and development needs in each of those across those different fuel platforms. But we’re also trying to give the airports the infrastructure, and understanding of what are those challenges and how do you optimize and de-risk those.”

The collaboration extends beyond the two government agencies. Ulane shared that all Colorado stakeholders, from airports to utilities to flight training programs, have been providing data for NREL’s reports and expressing interest in the outcome.

“Flight schools in particular see the issues around noise and leaded fuel as really kind of a threat to their operation,” Ulane noted. “So I think we’ve had really great participation and cooperation from the largest flight schools, most of which are centered here in the Denver area.”

“The collaboration between different sectors — all levels of government, the private sector, industry, research institutions and research universities — is really important,” added Devin Osting, Interim Executive Director of the Alliance for Aviation Across America, a nonprofit coalition advocating for the value of general aviation and local airports, particularly for rural communities. “It shows the proactivity of the industry.”

Preparing for takeoff

Decarbonizing aviation is not just a technology challenge, as Ulane and Oakleaf point out. For example, electric aircraft are a promising option for decarbonizing short-distance air travel, especially for trips under 500 miles. They come with clear advantages — quieter flights, lower maintenance costs, and reduced emissions. Models like electric vertical take-off and landing (eVTOL) aircraft offer entirely new designs almost reminiscent of a helicopter, and could expand access to smaller airports or even new vertiport locations, opening up new travel options for underserved areas. Several manufacturers are already testing these aircraft and working through FAA certification.

Technologically, batteries remain heavy and limited in range, and the industry is still years away from mass adoption. But Scott Cary, who leads the ports and airports program within the Energy Systems Integration directorate of NREL, zeroed in on the implementation challenge.

“You have flight schools that are saying, hey, we want to buy these [electric aircraft]. And I heard I need some electricity. Can somebody help me with that?” said Cary. “Being able to come up with a good estimate of what they can go talk to their utility about and how to make it as cost-effective as possible is probably one of the big things that comes out of this.”

That’s where this collaboration proves essential. If electric aircraft went mainstream tomorrow, Colorado’s airports — really, all airports — would lack the electric capacity to charge those planes, let alone with clean energy. NREL’s research will identify gaps in local airport infrastructure, as well as which Colorado airports might be best suited to adopt the technology first, particularly for flight training.

“In many cases, these are small communities that struggle with reliable power because they’re at the end of the line,” said Cary. “And so we’re bringing power closer to the end of the line through the transportation system, and potentially helping the community for the majority of the time when those [charging systems] aren’t being used.”

NREL and CDOT are tackling similar challenges with hydrogen. Hydrogen-powered aircraft offer another promising pathway to decarbonize aviation, particularly for longer flights where batteries fall short. Hydrogen has a higher energy-to-weight ratio than batteries, making it a strong contender for powering aircraft over greater distances. Moreover, refueling hydrogen can be as fast as traditional jet fuel, it emits little to no carbon when produced cleanly, and it has the potential to reduce noise levels from engine operations.

On the technology side, hydrogen currently remains expensive, reliant on fossil fuels for production, and difficult to store. But as others work to tackle these challenges, NREL and CDOT are looking a few steps ahead. “United Airlines has a hub here in Denver, and they’ve got an order for 100 hydrogen hybrid regional aircraft,” said Ulane. “They fly to 14 other cities in Colorado. So how can we help one of our biggest airlines leverage this new technology in our state?”

Implementing hydrogen technology can’t happen overnight, according to Ulane. It will require rethinking airport infrastructure, from refueling stations to storage facilities to safety regulations. By working with NREL, Ulane’s team can find answers to these questions sooner rather than later, giving the Centennial State the head start it needs to integrate hydrogen aircraft when they arrive.

“How [do we] get hydrogen airports? What does that look like? How do the airports use it? Down the road, we’re going to have to look at a whole variety of other things, like storage and aircraft rescue, firefighting requirements that might be different for a hydrogen-powered aircraft versus a fossil fuel airplane.”

Navigating headwinds

Of course, the collaboration is not without its limitations. While the technologies themselves are in their infancy, this collaboration can’t necessarily change that reality — optimistic as they may be. With that in mind, researchers are working with projections rather than current data.

“We are trying to project what people are going to need before the vehicles are ever built,” said Cary. “That is a challenge.”

It’s not enough to project that airports will need a lot more electricity, for example. Cary pointed out that these infrastructure upgrades are expensive, and stakeholders rely on NREL to accurately predict their future electricity needs. An underestimate would be operationally problematic, while an overestimate would be financially burdensome.

“The easy answer is to oversize [the future electric load]. That may not be the cost-effective answer for these small businesses that are trying to leverage these new technologies.”

Sky’s the limit

While this particular project centers on Colorado, Ulane expressed hope that it can serve as a model for other states pursuing a sustainable aviation future.

“Aviation doesn’t end at the border of Colorado,” said Ulane. “We really want to help pave the way and show other state agencies and other airports and other groups how you can do this and take the lead.”

“I think it’s really going to inform a lot of other states and regions throughout the U.S.,” Oakleaf added. “We’re hoping this is the tip of the iceberg to inform a lot of decision-makers.”

In 2021, the International Business Aviation Council doubled down on its climate goals, floating the prospect of carbon-neutral aviation by 2050. Their declaration notes the need for all stakeholders — governments, fuel producers and suppliers, manufacturers, air navigation service providers, and airports and ground-handling service providers — to commit their participation and support. The Biden White House, for its part, set a goal to produce 3 billion gallons of sustainable aviation fuel per year by 2030 and 35 billion gallons by 2050, enough to supply 100% of domestic demand.

According to Osting, these goals are realistic. But it will take a team effort, emblematic of CDOT and NREL’s partnership, to achieve them.

“The commitments that have been made, net zero by 2050 — both by the general aviation community and by the broader aviation community internationally — are really important. These collaborative efforts are really what it’s going to take to get us there.”


Ethan Brown wrote this article for The Sweaty Penguin.


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