Car Manufacture Energy

Introduction

Fig. 1: Diagram of Blast Furnace. Input iron ore, coke, and limestone. Output pig iron which is combined with carbon, some recycled steel, and other elements in the steel-making process. Note that this is only one step in the process and a Blast Furnace will not produce steel alone. [1] (Source: A. Mensah)

All factors matter. Electric Vehicles (EVs) that completely run on electricity have zero tailpipe emissions of CO₂. Whereas gas-powered vehicles with internal combustion engines (ICE) do emit CO₂ during their isolated operation. Cars and light trucks emitted 0.9 billion metric tons of CO₂ or 16% of the total U.S. greenhouse gas emissions in 2020. Gasoline releases 19.4 pounds of CO₂ per gallon when burned, compared to 22.5 pounds per gallon for diesel. [1] However, many factors go into the overall perception of the carbon footprint of the two types of personal transportation. Some factors include the source of electricity for EV charging, the shipping emissions of the vehicle, the mining of the materials for the batteries, as well as the carbon emissions of the steel production process. All these factors matter. The fact remains that EVs are more environmentally friendly when used in a country that has a high proportion of electricity production from renewable sources. However, the difference is significantly smaller in countries that generate electricity mostly from fossil fuels. [2] Of the roughly 30,000 kgs CO₂ emitted over the lifetime of an internal combustion engine car (assuming 93,000 miles driven), 84% come from the use phase. [1]

The important note is that there is a significant loss in the environmental advantage solely due to electricity production sources as well a significant (about 16%) portion of total emissions from the lifetime of a car coming from outside of its use. With these factors, this report will dive into the energy used to manufacture personal transportation vehicles with respect to steel production. This will also allow me to draw a distinction between the manufacturing carbon footprint of EVs versus gas-powered vehicles and estimate how many EVs will offset this footprint.

Steel Production

The production of steel is essential to the production of cars. According to the World Steel Association, a car is comprised of 55% steel by weight. In 2007, a car weighed on average 1089 kg. [3] This means we can assume the "car" we will be calculating the emissions for has about:

Steel is one of the world's most important materials. It is an alloy of iron that is made by removing oxygen and other impurities from the iron ore. Then the iron is combined with carbon, some recycled steel, and other elements for it to become steel. The dominant way of making iron is in a blast furnace (BF) which is a very energy-intensive process (see Fig. 1). The process consumes fossil fuels and because of that, the BF process is responsible for about 7% of the anthropogenic CO₂ emissions. BF uses coal whereas other parts of the process use natural gas, oil, and electricity. [1] The specific emissions of world steel are currently at 1.8 ton CO₂/ton steel. [4] This means that the steel of car production emits CO₂ in the amount:

Through the modernization of production and energy systems and the adoption of new methods, the specific emissions of world steel could be reduced to 0.4 - 0.5 CO₂/ton steel. [4] If we take the upper bound of this assumption we find that the steel of car production would emit CO₂ in the amount:

Conclusion

As previously stated, roughly 30,000 kg of CO₂ are emitted over the lifetime of an internal combustion engine car (assuming 93,000 miles driven). [1] Now we can compare the amount of CO² emitted in the production of steel of the vehicle vs the emissions over a lifetime:

With the new technology this value becomes:

Here we see that currently, an electric vehicle has an environmental advantage in direct emissions of about 28 internal combustion engine cars. This could increase to 101 cars if new technologies are improved for steel production. Through this analysis, we see that there is a sizeable benefit to EVs given they are consuming electricity from renewable sources. An extension of this analysis would be to see how significant the emissions change based on the lifetime of an EV running on fossil fuel sources.

© Anthony Mensah. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

References

[1] "Carbon Footprint Factsheet," Center for Sustainable Systems, University of Michigan, Pub. No. CSS09-05, September 2022.

[2] R. Muha and A. Peroša, "Energy Consumption and Carbon Footprint of an Electric Vehicle and a Vehicle With an Internal Combustion Engine," Transp. Probl. 13, 49 (2018).

[3] "Energy Use in the Steel Industry," World Steel Association, April 2021.

[4] L. Holappa, "A General Vision for Reduction of Energy Consumption and CO₂ Emissions from the Steel Industry," Metals 10, 1117 (2020).