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Hydrogen-powered aviation

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The transportation sector is responsible for about a quarter of human-generated greenhouse gas emissions.  Most of the energy used by transport systems comes from fossil fuels.  The transition to electric vehicles – cars, trucks, and buses – is making a real difference.  However, the emissions from the aviation industry have continued to grow faster than those of other forms of transportation.  There have been increased efforts to develop hydrogen-powered aircraft, but the challenges are substantial.

Hydrogen can be used for aviation both as a directly combusted fuel, or to power electric fuel cells.  Its advantages are that its use produces no carbon dioxide, and, in fact, hydrogen produces more energy per pound than jet fuel.

A study by researchers at MIT looked at the prospects for hydrogen use in aircraft and what needs to be done to make it practical.  The biggest issue is that the extra bulk of a hydrogen fuel tank and fuel cells in a plane would have to be offset by weight reductions elsewhere, such as reducing payload (cargo or passengers).  This would mean there would need to be more flights, thereby reducing the gains made.  The researchers argued that improvements in fuel cell power and more weight efficient fuel systems could eliminate the need for additional flights.

The bigger challenge is the infrastructure for generating and distributing hydrogen.  There needs to be green hydrogen – hydrogen produced without carbon emissions – and the infrastructure for getting it to planes where it is needed has to also not produce substantial emissions.

The study suggests that the rollout of hydrogen-based aviation should start at locations that have favorable conditions for hydrogen production.

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Fueling greener aviation with hydrogen

Photo, posted December 20, 2016, courtesy of Dylan Agbagni via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Electric planes: Fantasy or reality?

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Airplanes have been around for over a century, but the idea of powering them with electricity rather than with liquid fuels has been little more than a fantasy.  Over the years, billions of dollars have been invested trying to make electric planes practical.  In recent times, progress on battery technology has provided a much-needed boost for the field.

Electric planes are nowhere near becoming competitive with long distance commercial aircraft.  The weight and power requirements for such craft are far beyond what electric plane technology can do.  But electric planes could offer a very practical solution for transporting relatively small numbers of passengers over relatively short distances.

A plane built by the well-funded private company Beta Technologies has flown as far as 386 miles on a single battery charge.  The company envisions such planes to be mostly used for trips of 100 to 150 miles.  These planes could open new opportunities, like better connecting rural areas that have little or no direct air service.

Their latest model was tested on a trip between Burlington, Vermont and Florida, making multiple stops and flying through congested airspace over Boston, New York, and Washington.

Commercial versions of the planes will likely have lift rotors to take off and land like helicopters, making them deployable in a wide range of places.  Many companies are working on electric aviation, and they have backers like major automakers, major airlines, and large investment firms. 

Electric planes are not likely to replace conventional aircraft but are likely to have a meaningful impact how we move goods and services and reconnect rural parts of the country.

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Electric Planes, Once a Fantasy, Start to Take to the Skies

Photo courtesy of Beta Technologies.

Earth Wise is a production of WAMC Northeast Public Radio

Electric Motors For Aviation | Earth Wise

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Aviation contributes about 3% of global greenhouse gas emissions.  Its carbon footprint is one of the more difficult ones to reduce.  Electrifying planes would shrink that footprint considerably, but it represents a significant technical challenge.  To date, only small all-electric planes have gotten off the ground.  The electric motors in those planes generate hundreds of kilowatts of power.  To power large planes, like commercial airliners, megawatt-scale motors are required.

A team of MIT engineers is developing a 1-megawatt motor that could be a key step towards electrifying commercial aircraft.  They have designed and tested major components of the motor and have calculated how the completed design could generate one megawatt of power at a weight and size competitive with existing small aircraft engines.

To be suitable for aircraft use, motors have to be compact and lightweight.  The more power electric motors generate, the bigger they are and the more heat they produce.  Cooling motors requires additional components that take up space and add significant weight.  The MIT motor design and associated power electronics are each about the size of a typical checked suitcase and weigh less than an adult passenger.

Once the MIT team can demonstrate an entire functional motor, the design could be used to power regional aircraft and could be the enabling element of hybrid-electric propulsion systems for jet aircraft.  Possible future configurations could make use of multiple one-megawatt motors powering multiple fans distributed along aircraft wings.

Electrification of aircraft is a slow but steady area of development and technologies such as that being developed at MIT could end up meeting the practical needs of the aircraft of the future.

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Megawatt electrical motor designed by MIT engineers could help electrify aviation

Photo, posted September 14, 2019, courtesy of Dylan Agbagni via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Airplane Turbulence And Climate Change | Earth Wise

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If you’ve ever been on an airplane, chances are pretty good that you’ve experienced turbulence.  As the busy summer travel season kicks off, travelers are being encouraged to brace themselves for a bumpier-than-usual ride. 

There has been a major increase in the number of severe turbulence cases on both domestic and international flights.  According to a new study by researchers from the University of Reading in the U.K., climate change is leading to this increase in turbulence, driving up costs (via wear and tear on aircrafts), and increasing the risks for passengers and flight attendants.  In the United States alone, turbulence costs the airline industry $150-$500 million annually. 

The study, which was recently published in the journal Geophysical Research Letters, found that warmer air, caused by carbon emissions, is creating bumpier flights around the world.  In fact, the study found that severe turbulence in the North Atlantic is up by 55% since 1979. 

The changing climate is affecting air travel in other ways as well.  A faster jet stream across the Atlantic is altering travel times.  Rising temperatures are reducing the weight that aircraft can carry.  Rising seas are threatening low-lying coastal airports around the world. 

But carbon emissions from aviation are also a significant driver of the climate crisis.  Air travel accounts for approximately 3% of global greenhouse gas emissions, and is one of the fastest growing sources of emissions. According to the International Civil Aviation Organization, emissions from international air travel are expected to triple by 2050.

The future is shaping up to be a bumpy ride.

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Climate crisis leading to more turbulence during flights, says study

Evidence for Large Increases in Clear-Air Turbulence Over the Past Four Decades

Climate Scientist Explains Increase In Airplane Turbulence

Airports and Rising Seas

Photo, posted May 9, 2018, courtesy of Steve Lynes via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Living in a Carbon Bubble | Earth Wise

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The earth’s atmosphere is a little over 0.04% carbon dioxide, currently about 420 parts per million.  That’s more than it’s been in millions of years and is changing our climate.  But these levels of CO2 are not enough to directly affect people.

However, people are sensitive to the amount of carbon dioxide they are breathing.  It is actually an indoor pollutant.  High concentrations have been shown to reduce our cognitive performance, our health, and our comfort.  For example, a study in 2012 showed that performance in a variety of cognitive function tests was reduced by 12% when CO2 levels reached 1,000 parts per million and by 51% at 2,500 ppm.

How common are high levels of carbon dioxide?  Pretty common.  Offices often have CO2 levels of 600 ppm or higher, but 5% of US offices have average concentration about 1000 ppm and some conference rooms can reach 1900 ppm.  Classrooms often reach average levels above 1000 ppm.  Passenger aircraft have average levels around 1400 ppm during flight, and can peak over 4,000 ppm.  Cars with one occupant with the windows closed and the air recirculating have levels above 4,000 ppm. 

Where does it all come from?  From us.  We exhale CO2 and if we are in enclosed spaces with insufficient air circulation and ventilation, we end up living in a carbon dioxide bubble.  Most of us live with high CO2 levels – all day and every day.  It is a form of indoor pollution that has not gotten enough attention.

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I’m living in a carbon bubble. Literally.

Photo, posted October 24, 2013, courtesy of Cory W. Watts via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Cleaning Up Diesel With Bacteria | Earth Wise

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Mothballed military outposts with piles of rusting oil drums are not an unusual sight in Greenland.  There are about 30 abandoned military installations in Greenland and diesel that was once used to operate generators and other machinery has, in many cases, seeped into the ground.

Removing tons of contaminated soil from these sites is incredibly resource-intensive involving the use of aircraft and ships, so it has not really been practical.  As a result, Danish Defense and the engineering company NIRAS instead conducted a five-year experiment to optimize the conditions for naturally occurring soil bacteria to break down the contaminating diesel.

The experiment was performed at Station 9117 Mestersvig, an abandoned military airfield on the coast of East Greenland.  Forty tons of diesel fuel contaminated the soil there.

The remediation method using bacteria is known as landfarming and has most often been applied in warmer climates around the world.  This was the first large-scale test under Arctic conditions.

Landfarming works by distributing contaminated soil in a thin layer, which is then plowed, fertilized, and oxygenated every year to optimize conditions for bacteria to degrade hydrocarbons.

The site was monitored by scientists from the University of Copenhagen, and they found that after five years, the bacteria had bioremediated as much as 82 percent of the 5,000 tons of contaminated soil on the site. 

Based on these results, it appears to be feasible for naturally occurring bacteria to be used to remediate contamination in all of the 30 deserted military installations in Greenland as well as in other Arctic sites contaminated by diesel pollution.

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Bacteria used to clean diesel-polluted soil in Greenland

Photo, posted September 6, 2013, courtesy of Maj. Matthew J. Sala/The U.S. Air National Guard via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Private Jets and CO2 Emissions | Earth Wise

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During the heart of the Covid-19 pandemic, private jet use saw record levels because chartered aircraft were estimated to have 30 times lower risk for covid than flying commercial.  By August 2020, while commercial flights were down 60% year-over-year, private jet traffic was actually up.  From an environmental perspective, however, flying on a private jet is about the worst thing one can do for the environment.

Private jets are 10 times more carbon intensive than airlines on average and 50 times more polluting than trains.  A four-hour private flight emits as much as the average person does in a year.

In Europe, 7 out of the 10 most polluting routes taken by private aircraft lie in the UK-France-Switzerland-Italy axis, with jets departing the UK and France being the biggest source of pollution.  One in 10 flights departing France are private jets, half of which travelled less than 300 miles.

A study by the research group Transport & Environment points out that wealthy private jet owners are ideally suited to aid in the decarbonization of the aviation sector.  Private jet short hops are prime targets for replacement by clean technologies like electric and hydrogen aircraft.  European policy makers could ban the use of fossil-fuel private jets for flights under 600 miles by 2030.  Until such a ban, jet fuel and flight taxes could be imposed on private jets to account for their disproportionate climate impact and support technology development.  And companies and individuals could commit to substantial reductions in private jet use when alternatives exist that do not unreasonably increase travel time.

The super-rich could be part of the solution instead of part of the problem.

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Private Jet Use Rising, Sending CO2 Emissions Soaring

Photo, posted September 9, 2020, courtesy of Mackenzie Cole via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Marine Debris | Earth Wise

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Marine debris is a troubling issue around the world.  For most people, it is unsightly and perhaps inconvenient, but for many it is a critical problem that has serious impacts on many aspects of life.  This is especially the case for indigenous communities for whom the natural environment around the ocean is central to subsistence, recreation, culture, and economic opportunities.

The National Oceanic and Atmospheric Administration sponsors a Marine Debris Program that supports multiple projects.  In Alaska’s Pribilof Islands, the indigenous communities of St. George and St. Paul Islands conduct regular cleanups to protect and steward the natural resources that they depend on.  They make use of unmanned aircraft system surveys to target removal and monitoring efforts.

Another NOAA-sponsored program works to clean up the Maybeso Estuary in Alaska’s Prince of Wales Islands.  The project has removed 35,000 pounds of debris, freeing the flow of the salmon stream and restoring the area as a prime hotspot for fishing, boating, and outdoor recreation.

In Washington State’s Olympic Coast, the Makah Tribe has a project to locate and remove derelict crab pots and fishing lines from 80 miles of fishing area and marine sanctuary.  Derelict fishing gear can trap and entangle animals, degrade habitat, imperil navigation, and interfere with fishing.  The project team is working with tribal stakeholders on promoting marine debris awareness.

All of these communities have cared for the environment for generations, but marine debris poses perilous threats to their territories and community action is needed to preserve and protect these remarkable places.

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Lives and Livelihoods Disrupted by Marine Debris

Photo, posted September 11, 2015, courtesy of NOAA’s National Ocean Service via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Aircraft Emissions And Climate Change | Earth Wise

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The aviation industry accounts for about 2.4% of global carbon dioxide emissions.  If the aviation industry was a country, it would place sixth in emissions, between Japan and Germany.

According to scientists at the University of Reading in the United Kingdom, aviation industry emissions could be reduced by simply better surfing the wind.  The researchers found that commercial flights between New York and London could have used up to 16% less fuel if they had made better use of the fast-moving winds at altitude.

The study, which was recently published in the journal Environmental Research Letters, analyzed approximately 35,000 flights in both directions between New York and London last winter.  The researchers compared how much fuel was burned during these flights to how much less fuel would have been burned by flying into or around the eastward jet stream air currents. 

They found that taking better advantage of the winds would have saved about 125 miles worth of fuel per flight on average.  The fuel saving per flight was 1.7% when flying west to New York, and 2.5% when flying east to London. 

New satellites will soon allow transatlantic flights to be tracked more accurately.  This should afford aircraft more flexibility in their flight paths, allowing them to better follow tailwinds and avoid headwinds. 

Upgrading aircraft or switching to greener fuels are two other ways that the aviation industry can reduce emissions, but those things are costly and take time to implement.  Optimizing flight paths is cheaper and offers immediate benefits.  

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Aircraft could cut emissions by better surfing the wind

Photo, posted May 16, 2011, courtesy of Cory W. Watts via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Toughest Beetle Of Them All | Earth Wise

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In 2015, UC Riverside materials scientists placed a mottled black beetle in a parking lot and ran it over with a Toyota Camry.  Twice.  Crushed beneath the wheels of a 3,500-pound sedan, the inch-long insect made it through without a scratch.

For the past five years, a group of scientists have been studying this remarkable bug, which has the splendid name of the diabolical ironclad beetle. Using a combination of advanced microscopy, mechanical testing, and computer simulations, the researchers have figured out the secret of this beetle’s crush resistance.

The beetle’s super-toughness lies in two armorlike structures called elytra that meet in a line, called a suture, running the length of the abdomen.  The suture acts like a jigsaw puzzle.  It connects various exoskeletal blades – the puzzle pieces – in the abdomen under the elytra.   These structural components can act in different ways.  The interconnecting blades lock to prevent themselves from pulling out of the suture.  The suture and blades delaminate, leading to a graceful deformation rather than catastrophic failure.  These strategies dissipate energy to circumvent fracturing.

The researchers found that the diabolical ironclad beetle – just had to say that name again – can take on an applied force of about 150 newtons, a load at least 39,000 times its body weight.  (That’s the equivalent of a 150-pound person resisting the crush of about 25 blue whales).

An ongoing challenge for structural engineering is how to join together different materials without limiting their ability to support loads.  The strategies evolved in these beetles may be applicable in gas turbines of aircraft, for example, where metals and composite materials are joined together with mechanical fasteners.   We can learn things from the toughest beetle of them all.

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Diabolical ironclad beetles inspire tougher joints for engineering applications

Photo, posted April 9, 2017, courtesy of Vahe Martirosyan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Contrails And Climate Change

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The white wispy trails of condensation produced by the exhaust from aircraft engines have been the subject of a popular conspiracy theory for quite a while.  The story goes that the long-lasting condensation trails are actually “chemtrails” composed of chemical or biological agents left in the sky by aircraft and are intentionally sprayed for a variety of nefarious purposes undisclosed to the general public.  This story, of course, is nonsense.

But while contrails are not deliberate efforts to modify weather, control population, manipulate psychology, or any of the other bizarre things attributed to them, it turns out that they are having unfortunate effects on the climate.

It turns out that contrails are creating an often-invisible thermal blanket of cloud across the planet that has a significant effect on atmospheric temperatures.  Contrails are essentially human-made clouds that form above 25,000 feet where the air is moist and colder than -40 degrees Celsius.  At times, contrails stick around in the sky, either as tight, white lines like chalk marks, or by spreading to create thin layers of ice clouds.  At any one time, contrail-created clouds cover more than half a percent of global skies.

Research has shown that when contrails are around, nighttime temperatures can go up appreciably.  After 9/11, when all U.S. flights were grounded for three days, the difference between daytime and nighttime temperatures actually increased by about 3 degrees Fahrenheit because nights were cooler.

The effects of aviation on climate, both from the CO2 emissions from aircraft engines and from these contrail effects are becoming an increasingly important issue. To complicate matters further, as aircraft engines become more efficient, they will create more, whiter, and longer-lasting contrails.

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How Airplane Contrails Are Helping Make the Planet Warmer

Photo, posted May 15, 2012, courtesy of Mike Lewinski via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Hybrid-Electric Aircraft

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The commercial aviation industry is a major source of carbon dioxide emissions and, as other industries try to move towards decarbonization, its share is getting larger.  But reducing emissions from aircraft is challenging because powering planes without burning fossil fuel is hard to do.

The biggest problem is that powering aircraft with electric motors instead of fossil fuel motors requires so much energy that the batteries needed to supply it become impractically heavy.  While research goes on to develop lighter-weight batteries, an interim concept may pay dividends.

Just as hybrid cars represent a stepping stone towards full electrification, hybrid-electric aircraft may be a way to obtain substantial reductions in aircraft emissions.  The idea is to use battery-powered electric motors to power planes, but to greatly reduce the capacity requirements of the batteries by having an on-board fossil-fuel generator to charge the batteries and supply additional needed power.

A study by the University of Illinois looked at the potential emissions reductions for hybrid-electric aircraft taking into account the emissions associated with generating the electricity that charges the batteries in the plane.  The requirements in the study were that the plane needs to be able to carry the same number of passengers and travel the same distance as current aircraft. 

The results were that a drivetrain that gets 50% of its power from battery charge reduced emissions by about 50% over the full lifecycle of the plane.

As batteries get lighter and the electric grid gets greener, the possibility of making major reductions in aircraft carbon emissions looks increasingly realistic.  But there is a long way to go.

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Study Examines Commercial Hybrid-Electric Aircraft, Reduced Carbon Emissions

Photo, posted September 26, 2014, courtesy of Jeff Turner via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Traffic Jams In The Jet Stream

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Many extreme weather events are associated with unusual behavior by the jet stream.   Jet streams are the global air currents that circle the earth.  The meandering and speed changes in the jet stream affect weather and also play a big role in how long it takes aircraft to make their way across the country.  The behavior that leads to extreme weather events is known as “blocking” in which the meandering jet stream stops weather systems from moving eastward.

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An All-Electric Plane

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The British discount airline EasyJet recently announced a partnership with American company Wright Electric to develop an all-electric commercial airplane that they said could be flying within 10 years.  The goal of the partnership is to develop aircraft with a maximum range of 335 miles, which is long enough for many of the European routes that EasyJet flies from its hub in England.

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Wind Farms And Ordinary Farms

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Farmers in many places have found additional sources of income by allowing wind turbines to be built on their land.  One example is the Amazon Wind Farm, which is a massive project of over 100 turbines near Elizabeth City, North Carolina.  The 494-foot tall turbine towers scattered over 34 square miles are rising up above farms that grow corn, wheat and soybeans.  It is the first utility-scale wind farm in the Southeast.

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Finding Methane Leaks

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The boom in natural gas drilling by conventional methods and by fracking has led to a spike in methane emissions from pipelines, storage tanks, processing facilities, and other parts of the natural gas system.   Natural gas is mostly composed of methane, so these emissions constitute waste and lost revenues.  But they also represent a serious environmental problem because methane is 25 times more effective in trapping atmospheric heat than carbon dioxide.

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Greener Friendly Skies

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In March, United Airlines began using a new biofuel for flights between Los Angeles and San Francisco.  The fuel is a renewable product called Honeywell Green Jet Fuel that can replace up to half of the petroleum jet fuel used in flight without any changes to the aircraft technology and it meets all current jet fuel specifications.  

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