lifecycle

The U.S. Military And Climate Change

July 9, 2019 By EarthWise Leave a Comment

According to new research by scientists from Durham University and Lancaster University, the United States military is one of the largest climate polluters. The U.S. military consumes more liquid fuels and emits more greenhouse gases than most countries.

The study, published in Transactions of the Institute of British Geographers, finds that if the U.S. military were a country, it would be the 47^th largest emitter of greenhouse gases in the world, falling between Peru and Portugal. And this only takes into account the emissions from its liquid fuel consumption. For this study, the U.S. military’s 2015 consumption was compared with the 2014 World Bank country liquid fuel consumption.

In 2017, the U.S. military purchased more than 269,000 barrels of oil a day, emitting more than 25,000 kt- CO2e by burning those fuels. The Air Force accounted for $4.9 billion worth of this fuel, followed by the Navy at $2.8 billion, the Army at $947 million, and the Marines at $36 million.

The Air Force and the Navy are not only the U.S. military’s largest purchasers of fuel, they also use the most polluting types of fuel. The Air Force is the largest emitter of greenhouse gases at more than 13,000 kt CO2e, nearly double that of the Navy’s 7,800 kt CO2e.

Despite this study’s findings and a general uptick in awareness, it’s unlikely that the U.S. military’s dependence on fossil fuels will change. That’s because the military continues to pursue open-ended operations around the globe, and the lifecycle of its existing military equipment insures dependence on hydrocarbons for many years to come.

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U.S. military consumes more hydrocarbons than most countries — massive hidden impact on climate

Photo, posted July 8, 2016, courtesy of Alan Wilson via 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.

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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.

Emissions From Electric Buses

September 12, 2018 By EarthWise Leave a Comment

Municipalities and transit agencies are gradually replacing conventional diesel buses with cleaner alternatives such as natural-gas-powered, diesel-electric hybrid, or fully electric buses. The goal is to reduce the substantial carbon emissions associated with buses as well as reducing unhealthy air pollution. Diesel buses on average get less than 5 miles per gallon as they transport passengers around, so there is plenty of motivation to find more efficient ways to power them.

Indirect Greenhouse Gas Emissions

February 15, 2018 By EarthWise Leave a Comment

When considering the greenhouse gas emissions associated with any energy source, it is important to look at the total life cycle emissions both from the direct use of the energy source and from the indirect emissions associated with building the system, producing and transporting fuels and other supplies and, ultimately, decommissioning the system. Taking all of this into consideration is necessary in order to have a full accounting of the carbon impact of power sources.