Everyday equivalents of a quantity of CO2-equivalent

Converts grams of CO2-equivalent into two everyday comparisons: kilometres driven in an average European passenger car (175 gCO2/km) and tree-months of carbon sequestration (917 gCO2 per tree per month), the two comparisons the Green Algorithms calculator prints, with their sources. Use it to make the co2e_g of compute_footprint easier to read in a report.

Usage

footprint_equivalents(co2e_g)

Arguments

co2e_g

Numeric scalar, grams of CO2-equivalent; finite and non-negative (for example the co2e_g element of a compute_footprint result).

Value

A list with car_km (numeric, kilometres), tree_months (numeric) and sources (named character vector, car and tree, naming each factor's source).

Details

The conversions are plain divisions: \(\mathrm{km} = g / 175\) and \(\mathrm{tree\ months} = g / 917\). Both factors are averages and the comparisons are illustrations, not offsets: a tree-month is the carbon one mature tree takes up in a month, not a promise that planting one cancels the emission. Errors when co2e_g is not a single finite, non-negative number.

References

Green Algorithms data v3.1, context.csv: car factor from Helmers et al. (2019) Atmospheric Environment and UK BEIS 2019 conversion factors; tree sequestration from Bernal et al. (2018) via the same file.

See also

compute_footprint

Examples

footprint_equivalents(1200)
#> $car_km
#> [1] 6.857143
#> 
#> $tree_months
#> [1] 1.308615
#> 
#> $sources
#>                                                                  car 
#> "175 gCO2/km, European passenger car (Green Algorithms context.csv)" 
#>                                                                 tree 
#>             "917 gCO2 per tree-month (Green Algorithms context.csv)" 
#> 

# the footprint of a small computation, in everyday terms
fp <- compute_footprint(sum(sqrt(seq_len(2e5))), location = "CA-ON",
                        cpu_power_w = 45, memory_gb = 8)
unlist(footprint_equivalents(fp$co2e_g)[c("car_km", "tree_months")])
#>       car_km  tree_months 
#> 4.109534e-09 7.842621e-10 

# a vector is refused: convert one total at a time
try(footprint_equivalents(c(10, 20)))
#> Error : `co2e_g` must be a single non-negative number