airplane

Hydrogen-powered aviation

December 16, 2024 By EarthWise Leave a Comment

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.

**********

Web Links

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

Airplane Turbulence And Climate Change | Earth Wise

July 4, 2023 By EarthWise Leave a Comment

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.

**********

Web Links

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

Banning Short Plane Flights | Earth Wise

May 20, 2021 By EarthWise Leave a Comment

Almost everything we do ultimately results in greenhouse gases entering the atmosphere and therefore has an impact on the climate. But some activities have much more impact than others. The aviation industry is responsible for about 5% of global warming.

This doesn’t seem like that large a contribution, but only a very small percentage of the world’s population flies frequently and even in richer countries, only around half the population flew in any given year (at least before the pandemic.)

Flying is generally the only practical option for most long-haul trips and unless people give up on seeing the world or conducting global business in person, they are not going to give up taking air trips.

But shorter flights are a different story. If you are planning to take a reasonably short trip in France, a plane will soon no longer be an option. The French government says that flights will be banned on any route where the trip could be made on a train in 2.5 hours or less. The driving force is the reduction of CO2 emissions. A plane trip emits an average of 77 times more CO2 per passenger than taking a train on the same route.

The Netherlands and Belgium are also considering bans on short-haul flights and Austrian Airlines recently replaced its Vienna-to-Salzburg flights with train service.

Advocates of the flight bans say that not only does taking the train significantly reduce a traveler’s carbon footprint, but it can be cheaper and actually faster than a plane when factoring in the time spent getting to airports, standing in security lines, getting on and off planes, and so on. Europe’s extensive train system makes this approach broadly practical. Unfortunately, here in the U.S., it is not quite that easy.

**********

Web Links

France Will Ban Short Flights That Could Be Replaced By a Train Trip

Photo, posted December 17, 2016, courtesy of Dylan Agbagni via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Pandemic Lockdowns And Carbon Emissions | Earth Wise

November 25, 2020 By EarthWise Leave a Comment

The early months of the COVID-19 pandemic saw many human activities reduced to a fraction of what they were previously. Notably, air pollution in major cities was dramatically lower than it had been in decades. Now, a new study has looked at the effect of the pandemic shutdowns on carbon dioxide emissions.

An international team of climate scientists has published an assessment of carbon dioxide emissions by industry, transportation, and other sectors from January through June. According to their measurements, this year’s pandemic lockdowns resulted in a 9% decline in emissions from 2019 levels.

An earlier study reported a 17% drop in CO2 emissions, but the new study was more comprehensive and detailed.

The new data includes estimates of day-by-day, sector-specific and country-level differences in CO2 emissions derived from frequently updated data sources, some of which are nearly in real-time. It tracks the effects of COVID-19-related disruptions of human activities in China starting in February and in the United States and Europe in March through May.

The data revealed the resumption of emissions in many regions, such as in China, where they are now back to pre-pandemic levels. Emissions in the Americas and Europe have been slower to recover, especially in the US, where COVID-19 hotspots are continuing to emerge.

The reduction in carbon emissions has been due mostly to transportation with fewer people driving to work and traveling by air. Even by June, when lockdowns were easing, global emissions were still significantly reduced. In any case, a pandemic is a highly undesirable and unwelcome way to reduce carbon emissions, but the data from this year does show that it is effective.

**********

Web Links

Pandemic lockdowns caused steep and lasting carbon dioxide decline

Photo, posted August 7, 2020, courtesy of Michael Mueller via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Jet Fuel From Acetone | Earth Wise

February 25, 2020 By EarthWise Leave a Comment

Acetone is a common organic solvent. It is used to make plastic, fibers, drugs, and other chemicals. It is commonly used by consumers as nail polish remover. Acetone is a manufactured chemical, but it is also found naturally in the environment in plants, among other places. There are now companies that produce acetone entirely by fermentation of plant feedstocks, such as corn.

Researchers at Los Alamos National Laboratory have now developed a process by which acetone can be converted into a fuel additive that can improve the performance of petroleum-based jet fuel, providing both environmental and economic benefits.

The process takes biomass-derived acetone and converts it to isophorone, which they produce by a process called photochemical cycloaddition that creates more complex hydrocarbons. They then use ultraviolet light to convert the isophorone into cyclobutane, which is a type of hydrocarbon with high energy density that is suitable for aviation fuel applications.

Acetone itself is quite volatile and is unsuitable for fuel applications. It also cannot be added directly to any fuel supply since it can dissolve engine parts and o-rings. Cyclobutane, on the other hand, is a safer and more energy-dense fuel that can be a replacement for additives that require high-pressure hydrogen treatment in their synthesis. Currently, most hydrogen is produced by a process that generates carbon dioxide. The new conversion process does not result in carbon emissions.

According to the Los Alamos researchers, their process can result in a domestically generated product that will provide environmental benefits, create domestic jobs, improve U.S. energy security, and further U.S. global leadership in bioenergy technologies.

**********

Web Links

Acetone plus light creates a green jet fuel additive

Photo, posted December 18, 2007, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Hybrid-Electric Aircraft

May 20, 2019 By EarthWise Leave a Comment

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.

**********

Web Links

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.

Plant-Based Jet Fuels

May 9, 2019 By EarthWise Leave a Comment

The global aviation industry uses a whole lot of fuel: more than 5 million barrels a day. It is an incredibly energy-intensive industry and almost all of its energy comes from petroleum-based fuels.

While other large energy sectors such as electric power, ground transportation and commercial buildings have well-defined pathways to adopting renewable energy sources, the aviation industry does not have such a straightforward way to make a transition to sustainability. Electrifying planes using batteries or fuel cells is very challenging for a number of reasons, notably the weight restrictions on aircraft. So liquid biofuels as replacements for petroleum-based fuels remain the most promising approach.

A new study at the Lawrence Berkeley National Laboratory concludes that sustainable plant-based biofuels could provide a competitive alternative to conventional petroleum fuels if current development and scale-up initiatives are successful.

Multidisciplinary teams based at the Department of Energy’s Joint BioEnergy Institute are focused on optimizing each stage of the bio-jet fuel production process. This includes bioengineering ideal source plants and developing methods for efficiently isolating the carbohydrates in non-food biomass that bacteria can digest and bioconvert into fuel molecules.

The critical issue is cost. The theoretical cost of bio-jet fuel has come down dramatically in recent years but is still around $16 a gallon. The cost of standard jet fuel is about $2.50 a gallon. So, the real challenge is bridging that gap.

Reducing the cost of the fuel could come both from the material and process improvements that are underway as well as by finding ways to turn the leftover lignin residuals from the bioconversion process into valuable chemicals.

**********