The goal of defraEmissionsFactors is to make emissions factors provided by DEFRA more easily accessible and transparent.
The starting point is Greenhouse gas reporting: conversion factors 2018. The following code chunk downloads and extracts relevant data, in this case kg CO2 per km, for different car sizes:
source("code/defra-emissions.R")
knitr::kable(cars_size_co2, digits = 3)| type | co_2_petrol | co_2_diesel | co_2_hybrid | co_2_phev |
|---|---|---|---|---|
| Small car | 0.143 | 0.155 | 0.108 | 0.022 |
| Medium car | 0.172 | 0.193 | 0.114 | 0.071 |
| Large car | 0.213 | 0.283 | 0.160 | 0.077 |
| Average car | 0.176 | 0.183 | 0.124 | 0.071 |
This shows that cars typically emit around 180 g CO2/km, nearly double the EU’s 2021 target of 95 g CO2/km. We can convert these into energy use values based on the following conversion factors:
Burning diesel emits 73.6 gCO2/MJ
(source),
meaning that 1 KG of CO2 released from burning diesel is associated with
1 / 0.0726 (13.6) MJ of energy use. This figure, and the associated
value of 0.0728 for petrol, means we can calculate energy use of
different types of cars as follows:
cars_energy = cars_size_co2 %>%
mutate(energy_diesel = co_2_diesel / 0.0726) %>%
mutate(energy_petrol = co_2_petrol / 0.0728) %>%
select(type, matches("energy"))Crudely assuming an even petrol/diesel fuel mix, we can estimate the average energy use per km driven as follows:
(cars_energy$energy_diesel[4] + cars_energy$energy_petrol[4]) / 2
#> [1] 2.466373