Carbon Budget: There are 550 Gigatons of carbon left to emit to stay under 1.7 degrees Celsius. US emissions make up 11% of world emissions, transportation makes up 29% of US emissions, and freight trucking makes up 24% of those emissions. This yields 550*.11*.29*.24 = 4.21 Gigatons budget for US trucking.
Carbon per Truck per Year: CO2 emissions for diesel trucks are estimated at 1700 g/mile. The average annual distance per truck is estimated at 62751 vehicle miles. This makes 1700 g/mile * 62751 miles/truck/year = 106676700 g/truck/year. Converting to metric tons, that’s about 107 metric tons CO2/truck/year.
Emissions until 2025: It is estimated that 54,000 trucks will be converted by 2025.
Assuming this is done in a linear fashion, the number of remaining diesel trucks can be modeled by the following curve (shown until 2026 to represent the end of 2025):
Integrating for the area under this curve, we get (2,900,000 trucks – 27,000 trucks) * 5 years = 14,365,000 truck years. Now, multiply by carbon per truck per year to get 1.5 Gigatons of emissions by the end of 2025.
Given a maximum rate of conversion of 180,000 trucks per year, based on truck sales, emissions during the conversion period can now be calculated. We will assume that the conversion period begins with (2,900,000 – 54,000) = 2,846,000 diesel trucks and ends with none left on the road. Then, this will take 2,846,000 trucks / 180,000 trucks/year = 15.8 years. On a graph:
Now, integrating for the area under the curve yields 0.5 * 15.8 years * 2,846,000 trucks = 22,499,211 truck years. Multiplying by carbon per truck per year, that’s about 2.4 Gigatons of CO2 emissions during the transition phase.
Finally, these amounts can be subtracted from the initial carbon budget. 4.21 Gigatons – 1.5 Gigatons – 2.4 Gigatons = 0.31 Gigatons left to emit. Calculating emissions in 1 year with 2,846,000 diesel trucks yields 2,846,000 truck years * 107 Gigatons/truck/year = 3.05 Gigatons of emissions. This allows roughly one buffer year between the end of 2025 and the starting year for the conversion period. Therefore, it is estimated that, to remain under 1.7 degrees of warming, all truck sales would need to be electric by the end of 2026.
