Electric, Hydrogen, Or Biofuel Cars: Which Will Help Save Our Planet?
Comparing the land use, carbon, and water footprint of renewable alternatives to fossil fuel-based cars
Climate change is accelerated by us burning fossil fuels in large amounts. This is because burning fossil fuels causes CO2 emissions. CO2 is a greenhouse gas that holds on to heat radiated by the earth’s surface. This causes our planet to warm up.
This warming up is partly caused by the transport sector, as it uses a lot of fossil fuels for diesel and gasoline, which is responsible for up to a quarter of the total globally emitted CO2 emissions. Around three-quarters of these emissions come from road transport. This means that about 19% of all yearly CO2 comes from road transport. As this is a lot and the number of cars keeps increasing, it is important to find more environmentally friendly alternatives to cars based on fossil fuels.
Some more environmentally friendly alternatives are cars powered by renewable fuels such as biofuel, electricity, and hydrogen. These are renewable because they can be replenished within a relatively short period. For example:
- biofuels can be made from microalgae, which can be grown continuously and consume CO2 during growth (learn more: How Microalgae Can be Used As A Great Alternative To Fossil Fuels)
- electricity can be created using solar energy, which is available every day (learn more: How Solar Energy Technology Is Becoming More Efficient)
- electricity can be created using wave energy, which is available almost continuously (learn more: How Electricity Can Be Generated From Ocean Waves)
- hydrogen can be made from water, which is highly available when made from salt water.
The number of cars powered by, for example, electricity and hydrogen is rising, but still less than 0.5% of the 1.2 billion cars on our planet. As the transition from fossil fuel to renewable energy-based cars is happening, and we have more than one alternative, it is important to compare and understand how these alternatives impact our environment.
Comparing the environmental footprint of these alternatives is possible by looking at different environmental impacts, for example:
- land footprint, which involves the direct and indirect usage of land as a resource
- carbon footprint, which involves the greenhouse gas emissions produced by the car’s supply chain
- water footprint, which involves 1) gray water use: recycled water), 2) green water use: rainwater, and 3) blue water use: surface and groundwater.
These are the environmental footprints of different renewable alternatives for cars (all numbers are summarized in Table 1 in the scientific article):
Electricity
The first — currently most often discussed — alternative to fossil fuel for cars is electricity. Cars driving on electricity are called electric vehicles, often abbreviated to EVs. Electricity as a renewable energy source for cars has an environmental footprint multiple times lower than those of cars using conventional gasoline. Two examples of renewable electricity sources are:
- bioelectricity, which is generated from burning sugarcane’s biomass
- solar electricity, which is generated by photovoltaic solar panels
Different electricity sources have different environmental footprints. For example, for these two electricity sources (computed for 2019 Honda Clarity EV and 2019 Nissan Leaf electric cars):
- The land footprint is 280 cm2 per kilometer (69 square inches per mile) for bioelectricity and 9.1 cm2 (2.24 square inches per mile) per kilometer for solar electricity. This is the same as 280 and 9 fingernails per kilometer (about 448 or 15 fingernails per mile). To compare, the gasoline’s land footprint of 0 cm2 per kilometer (0 square inches per mile).
- The carbon footprint of bioelectricity-powered cars is 7.3 grams of CO2eq per kilometer (0.4 ounces per mile), while solar electricity-powered cars don’t emit greenhouse gases during driving. CO2eq stands for CO2equivalent, a measure for greenhouse gas emissions, not only CO2. The carbon footprint is calculated for these energy sources by measuring the nitrous oxide and methane emissions during combustion, but also nitrogen fertilizer production and soil management. To compare, the carbon footprint of conventional gasoline is 165 grams of CO2eq per kilometer (9.3 ounces per mile). This means that the carbon footprint of gasoline is about 23 times higher than when using bioelectricity as energy source, and even higher when compared to solar panels.
- The water footprint is 40 liters per kilometer for bioelectricity and 0.12 liters per kilometer (about 6.4 oz per mile) for solar-powered cars. To compare, the water footprint of gasoline is 0.25 liter per kilometer (about 13.5 oz per mile).
So, when comparing these electric vehicle footprints to the footprint of conventional gasoline, it becomes clear that the land use of electric vehicles is higher, the carbon footprint is lower, and the water footprint is lower or higher depending on whether the sun or biomass is the energy source.
Solar-based hydrogen
The second alternative to fossil fuel for cars is solar-based hydrogen. Hydrogen as a fuel is a gas that can be produced via electrolysis of water. Electrolysis means sending an electric current through the water.
For cars powered by hydrogen that is produced using electricity from solar panels (computed for 2019 Honda Clarity):
- the land footprint is 23 m2 per kilometer (396 square feet per mile). To compare, the land footprint for gasoline 0 m2 per kilometer (0 square feet per mile).
- the carbon footprint is 0 grams of CO2eq per kilometer (0 ounce per mile). To compare, the carbon footprint of conventional gasoline is 165 grams of CO2eq per kilometer (9.3 ounces per mile).
- the water footprint is 0.39 liters per kilometer (21 oz per mile). To compare, the water footprint of gasoline is 0.25 liter per kilometer (about 13.5 oz per mile).
So, when comparing hydrogen car footprints to the footprint of conventional gasoline, it becomes clear that the land use and water footprints of electric vehicles are higher, and the carbon footprint is lower.
Biofuel blends
The third alternative to fossil fuel for cars is biofuel blends. Biofuel blends are mixtures of biofuel and fossil fuel. The environmental footprint of biofuel blends for cars is the highest compared to electricity and hydrogen. Two examples of biofuel blends are:
- B20: a blend of 20% biodiesel from rapeseed and 80% of diesel
- E85: a blend of 85% bioethanol from sugar beet and 15% of gasoline
Different biofuel blends have different environmental footprints. For example, for these two blends (comparing a 2019 Chevrolet Cruise Hatchback with B20 and a 2016 Mercedes Benz with E85):
- the land footprint is 0.37 m2 per kilometer (6.4 square feet per mile) driven for B20-fueled cars and 0.21 m2 (3.6 square feet per mile) for E85-fueled cars. This means that to produce B20, about three-quarters more land is needed than to produce E85. To compare, the land footprint of conventional gasoline is 0 m2 per kilometer (0 square feet per mile).
- the carbon footprint is 185 grams of CO2eq per kilometer (10.4 ounces per mile) for B20-fueled cars and 80.2 grams of CO2eq per kilometer (4.5 ounces per mile) for E85-fueled cars. B20 causes more than 2 times as many greenhouse gas emissions as E85. To compare, the carbon footprint of conventional gasoline is 165 grams of CO2eq per kilometer (9.3 ounces per mile), which is less than B20 but more than E85.
- the water footprint is similar for B20- and E85-fueled cars: 170 liters per kilometer (9197 oz per mile) for B20-fueled cars and 163 liters (8819 oz per mile) for E85-fueled cars. To compare, the water footprint of conventional gasoline is 0.25 liter per kilometer (about 13.5 oz per mile).
So, when comparing these biofuel blend footprints to the footprint of conventional gasoline, it becomes clear that the land and water use of biofuel blends is a lot higher and that the carbon footprint of biofuel blends is a little higher or lower depending on the blend.
Conclusion
So, the environmental footprints of cars using renewable energy sources differ depending on whether land use, carbon, or water footprints are considered. Overall, the environmental footprint is the smallest for electric vehicles powered by solar energy, followed by solar-based hydrogen cars. Biofuel as a combination of diesel and biodiesel from rapeseed oil has the worst environmental footprint.
How we can take action
Here are practical ideas of what you and I can do to make driving a car more environmentally friendly:
- Buying an electric or hydrogen-powered car
- Charge electric vehicles with solar power
- Driving at a constant speed
- Turning off the motor at standstill
- Taking foot from accelerator pedal instead of braking
- Driving a smaller rather than larger car
Do you have further ideas of what you and I could do? Thank you in advance for leaving them in a comment to this question for us all to get inspired.
About the author
Dr. Erlijn van Genuchten is a an internationally recognized environmental sustainability expert. She is a science communicator, helpings scientists in the fields of nature and sustainability increase the outreach of their results and allowing us all to put scientific insights into practice and contribute to a sustainable future. Erlijn has inspired thousands of people around the world — for example — by supporting the United Nations with her expertise, her book “A Guide to A Healthier Planet” published by Springer Nature, and her posts on social media.
- More about her book “A Guide to a Healthier Planet”
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