Introduction
Electric bicycles not only provide users with an easy way to exercise outdoors, enjoy fresh air, and conquer various terrains, but also have a positive impact on the environment. They not only help reduce carbon footprint, but also do not release hazardous chemicals into the air like cars. Which stages of the lifecycle of an electric bicycle emit the most carbon? What are the main greenhouse gas emission links? Can the carbon footprint of electric bicycles be reduced?
Overview:
The electric bicycle market in Europe is rapidly expanding. By 2030, electric bicycles will account for approximately 55% of total bicycle sales in Europe.
Electric bicycles are a low-carbon mode of transportation: they emit an average of 13 grams of carbon dioxide equivalent per kilometer of travel. New energy vehicles emit up to 60 to 75 grams of carbon dioxide equivalent per kilometer.
During the entire lifecycle of electric bicycles, the majority of greenhouse gas emissions come from the manufacturing process (94%), especially the production of aluminum frames.
The conversion of second-hand bicycles into electric bicycles is the most environmentally friendly solution, as it eliminates the need for frame production.
If you want to further reduce the carbon emissions of electric bicycles, you can consider replacing aluminum with other materials, or using sodium ion, solid electrolyte batteries, etc.
01
In Europe, sales of electric bicycles have surged in recent years: in 2020, 20% (4.5 million units) of bicycles sold in Europe were electric bicycles, and it is expected that this number will rise to 55% by 2030. Will electric bicycles exacerbate global warming?
Compared to many other modes of transportation, electric bicycles are already very green! In France, the carbon emissions from electric bicycles traveling 20000 kilometers are an average of 13g CO2e (carbon dioxide equivalent) per kilometer, which includes the entire lifecycle of emissions - from manufacturing, use, maintenance to disposal. The carbon emissions of pedal bicycles are 10-12g CO2e/km, which is almost on par with electric bicycles.
Image source: Anne De Bortoil, based on data updated in November 2023: https://doi.org/10.1016/j.trd.2021.102743 Note: The carbon footprint of electric bicycles in France (blue) and Germany (red) is compared, with a left column measuring 20000 kilometers and a right column measuring 15000 kilometers.
Taking into account environmental factors, electric bicycles are one of the most environmentally friendly modes of transportation. In France, the carbon emissions of electric trains are about 35g CO2e/km per passenger, while those of new energy small cars for urban commuting are 60-75g CO2e/km. Both fuel powered cars and airplanes exceed 100g CO2e/km, with only walking (1-2g CO2e/km) and Paris metro and suburban train RER (8-10g CO2e/km) being lower in carbon emissions than cycling. It is estimated that in France, an electric bicycle with a mileage of over 1000 kilometers can have a lower carbon footprint than a gasoline powered car used for urban commuting.
02
Should the low emissions of electric bicycles in France be attributed to its low-carbon power generation industry?
When I was researching this topic seven years ago, I found that the carbon footprint of electric bicycles in China was three times higher than that in France. However, now that China's power structure has undergone a green transformation, the gap has narrowed. The greenhouse gas emissions from electricity generation in Germany are currently 10 times that of France, and the carbon emissions from electric bicycles traveling 20000 kilometers in Germany are 17g CO2/km. However, overall, the total carbon emissions of electric bicycles will not be very high, as the power consumption during use is already low, and most of the greenhouse gas emissions throughout the entire lifecycle occur during the manufacturing process.
03
Why is the manufacturing process the most emission intensive part of the entire lifecycle of an electric bicycle?
For an electric bicycle with a mileage of 20000 kilometers in France, the manufacturing process accounts for 94% of its total carbon emissions. Electric bicycles made in China emit 181kg CO2e from each 20kg aluminum frame (excluding the drive system) during the production process; Each battery emits 20kg CO2e; Each motor emits 37kg CO2e. From this, it can be seen that the emissions from manufacturing chassis are the highest, and all of this is attributed to aluminum smelting. China is a major aluminum refining country in the world, with aluminum production accounting for about half of the global total. Despite efforts to reduce carbon emissions from power generation, the greenhouse gas emissions from aluminum refining itself remain high, thereby increasing the emissions of electric bicycles throughout their entire lifecycle. Because of this, even if the assembly process of electric bicycles is transferred to France, it still has no effect on reducing emissions.
Compared to aluminum smelting, the emissions from batteries are almost negligible. Due to the popularity of new energy vehicles, the environmental footprint of batteries has been widely reported. But a car can carry hundreds of kilograms of batteries, while electric bicycles only have a few kilograms of batteries, so the emissions cannot be too high.
The displacement of the battery is difficult to accurately evaluate. We analyzed over thirty academic papers on lithium-ion batteries and found significant differences in carbon emissions per kilowatt hour, up to 10 times higher. After all, it is not easy to obtain industrial data on the mining and extraction conditions of minerals required for batteries. But in any case, the fact that the production displacement of the frame is the highest will not change. For this, it can be considered to install an electric power system on existing pedal bicycles to avoid additional emissions caused by producing new frames.
04
What are the main greenhouse gas emission stages throughout the lifecycle of electric bicycles?
The specifics vary by country. In France, maintenance accounts for about 8% of the total displacement of an electric bicycle throughout its entire lifecycle; The average power consumption per 100 kilometers is 1kWh, equivalent to 0.5g CO2e/km (approximately 4% of the total emissions). In Germany, 5g CO2e is emitted for every 1 kilometer driven (approximately 29% of the total emissions). Of course, the data will vary depending on the specific situation of each bicycle and user, as well as the terrain and power generation structure of the driving area.
In terms of scrapping, recycling batteries and materials in France can reduce the carbon emissions of electric bicycles by 6%. Unfortunately, currently less than 8% of batteries are recycled.
05
Can the carbon footprint of electric bicycles be reduced?
Sure, for example, through bicycle modification and battery and material recycling as mentioned earlier. The longer the service life of a car, the smaller the carbon emissions per kilometer traveled.
Due to the fact that the frame accounts for the largest proportion of emissions, it should be a key focus of attention. In the future, more environmentally friendly materials such as steel and wood can be considered to replace aluminum. In addition, we have conducted extensive research on batteries to evaluate the impact of other types of batteries such as sodium ions and solid electrolytes on carbon emissions from electric vehicles, and the results are very encouraging.
