7 Emission Factors

For some categories, emission factors vary over time. A good category to demonstrate this with is #749 “Agricultural Land Preparation”.

Here, annualize_DB_emission_factors() does the work of carrying emission factors forward in time. This means that for each value of year, the “most recent” emission factor, as of that year, is stored in ef_qty.

BY2011_ag_land_prep_ef_data <-
  BY(2011) %>%
  DB_area_source_emission_factors(
    verbose = TRUE) %>%
  filter_categories(
    "#749 Agricultural Land Prep" = 749) %>%
  annualize_DB_emission_factors(
    years = CY(1990:2030),
    verbose = TRUE)

In practice, chart_annual_emission_factors_by() is almost exactly identical to chart_annual_emissions_by(). The only real difference is in the default formatting of the values displayed directly in the chart by flag_years.

BY2011_ag_land_prep_ef_data %>%
  chart_annual_emission_factors(
    flag_years = CY(2011),
    title = "Agricultural Land Preparation",
    subtitle = "Emission factors pulled from DataBank (t1326).") 

In DataBank, emission factors are stored in units of “pounds per unit of throughput”. If you change the value of ef_unit (and alter the values in ef_qty accordingly), that will be reflected in the output of chart_annual_emission_factors().