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Glenn Ruskin, ACS GCI Contributor
Ever since humans harnessed fire over 1.5 million years ago, combustion has been at the heart of our energy creation. Fire from wood was first used by humans to cook meat, provide warmth and protection from wild animals. It wasn’t until the early 19th century, that fossil fuels (coal, oil and natural gas) replaced wood as the primary source of energy generation. Today the vast majority, over 80%, of energy is still generated by fossil fuels, with nuclear comprising 10% and other renewable sources making up the rest.
But the present dependence on fossil fuels, by an ever-growing world population, is contributing heavily to climate change and its increasingly devastating impacts on lives around the globe. And because fossil fuels are finite, alternatives must be found with adequate leeway to permit a seamless transition.
Chemistry, particularly sustainable and green chemistry, is leading the way to improve energy efficiency in the near term, and in the longer term making renewable and alternative forms of energy reliable, affordable and sustainable. Decarbonizing, or ceasing the burning of fossil fuels, will require a huge global effort. In a decarbonized world, electricity will be generated from renewable sources, such as solar and wind power. At present, oil, coal and natural gas fuel over 63% of global electricity generation. However, the challenge is increased when looking at the total global energy consumption (electricity generation, transport and heating) where over 84% comes from burning fossil fuels. Because this topic is so large and complex, this article will focus on the transportation sector, particularly light-duty vehicles, and examine where chemistry is leading the way to a greener and more sustainable future.
Transportation – In the US alone, transportation consumes 31% of fossil fuels, more than any other sector, with 96% being petroleum-based. The vast bulk of the energy consumed in this sector is by light-duty vehicles, with trucks and buses coming in second, although, trucks and buses primarily use diesel, not gasoline. Clearly, improvements made in this sector will benefit the move to decarbonization.
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Making Fossil Fueled Vehicles More Efficient – The US Department of Energy’s Vehicle Technologies Office (VTO) estimates that a 10% weight reduction can deliver an increase of nearly 8% in fuel efficiency.
Chemistry has paved the way for lighter and stronger materials to be used in vehicle construction, such as carbon fiber, polymer composites, magnesium and aluminum alloys. VTO estimates these materials can reduce vehicle body and frame weight by up to 50%. The VTO further estimates that combining these lightweight components and high-efficiency engines enabled by advanced materials in one-quarter of the U.S. fleet could save more than 5 billion gallons of fuel annually by 2030. (For more information visit the USDOE VTO website.)
A key aspect of making lighter materials is to focus on greener and more sustainable ways to do so. For example, green chemistry research is showing how renewable raw materials can be used for polymer composites as well as for carbon fiber manufacture. Not only are these developments less energy-intensive, they may also allow for easier recycling and reuse.
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Electric Vehicles – Electric vehicles have been around for over 100 years. Here in the US, chemist William Morrison introduced the first successful electric car in 1890, a six-passenger vehicle capable of a top speed of 14 miles per hour and 50 miles on a charge. Recharging took 12 hours, but the car was expensive – over $3000. Henry Ford’s low-cost, gas-powered, Model T eclipsed the electric car and gave birth to the modern gas car revolution.
Cut-away of a Nissan Leaf battery packClimate concerns reignited the interest in electric cars, and over the past decade, electric vehicles have become an increasing percentage of global vehicles. Much of that has come as a result of the combination of governmental purchase subsidies and technological increases, namely reliability, range and practicality.
Chemistry has always been at the heart of electric cars – batteries. With the resurgence of electric cars, Nickel Metal Hydride (Ni-MH) batteries were commonly used and have now largely been eclipsed by Lithium-ion (Li-ion) batteries. Li-ion batteries are lighter in weight, quicker to recharge, have no memory issues and generate less heat, making them highly popular.
Sales of Li-ion batteries was a $30 billion industry in 2017 and is expected to grow to $100 billion in 2025. But for all its technical advantages, Li-ion batteries present sustainability and safety challenges (Nature, 2021).
- Extracting lithium, depending on location/source, is water and energy intensive.
- 70% of cobalt for the battery electrode comes from the Democratic Republic of the Congo where child labor and safety issues are major concerns.
- Recycling Li-ion batteries also presents challenges between removal from the vehicle and regulatory requirements.
The search for even more superior batteries continues, with chemists and material scientists exploring the use of graphite and silicon anodes, solid-state batteries and other alternatives to increase durability, range and rapid recharge.
The Biggest Present Limitation
It is a fact that electric cars, over their lifetime, generate fewer greenhouse gases (GHGs) than gas-powered cars. Although, during production of electric cars and batteries, GHGs are higher than the GHGs from the production of a gas vehicle.
The biggest limitation to electric cars being close to a zero-emission vehicle is their need to recharge. The electricity needed to recharge the electric vehicle largely comes from power plants burning fossil fuels.
In the US, electric power generation is the second largest user of fossil fuels – 28%. And that is comprised of 59% natural gas, 40% coal and 1% petroleum (US Energy Information Administration, 2020).
Until renewables can provide the bulk of input to electric generation plants, the promise of electric cars and zero emissions will remain elusive. Outside the US, there are promising signs that renewables are establishing a foothold. Nuclear and renewables account for more than one-third (36.7%) of global electricity.
As world governments wrestle with how to adopt decarbonization and a zero-emission world, perhaps lessons learned from global government subsidies and incentives that successfully led to the large increase in the purchase of electric cars can be applied to revolutionize the electricity generation sector.
Just as fossil fuels edged out wood as the principal global energy combustion source, let’s encourage and support our talented chemists, scientists and research labs to continue their research to make the capture, storage and distribution of renewable energy the gold standard in the decade ahead and help meet UN SDG Goal 7.