Under the Methane & Other Gases slider in En-ROADS, you can simulate the reduction in non-CO2 greenhouse gases in your scenario. The "Agricultural and waste emissions (CH4 and N2O)" slider represents policies such as modifying agricultural practices to decrease the use of fertilizer, decreasing meat consumption, and increasing the capture of methane from landfills. The "Energy and industry emissions (CH4, N2O, and F-gases)" slider represents policies such as decreasing methane leakage from oil and gas industries and research and development into substitutions for F-gases in industrial processes. 

 

Reducing the "Agricultural and waste emissions" slider causes non-CO2 greenhouse gas emissions to fall relatively quickly:

 

 

Whereas reducing the "Energy and industry emissions" slider takes much longer (notice where the blue line of the current scenario departs from the black line of the Baseline scenario):

 

 

This is because energy and industry emissions are affected by the same capital stock turnover dynamics that affect the energy supply. These energy and industry emissions are only reduced when the equipment causing those emissions is replaced or retrofitted. For example, the average lifespan of an air conditioning unit in the U.S. is 15-20 years. An air conditioner that was installed in 2015 might continue to leak hydrofluorocarbons (HFCs), a type of F-gas, until 2035.  If you introduce a policy in 2021 to reduce the use of F-gases in air conditioning, only the new air conditioning units bought in 2021 and afterward will be affected. The amount of emissions released each year by air conditioning units will slowly start to decline, but it takes a while for the stock to turn over and the old units be replaced with new ones. 


In contrast, agricultural and waste emissions can be reduced on a shorter time frame because many of the sources of these emissions are not capital stock equipment that must be replaced. Reducing these emissions involves actions such as properly capping landfills; educating farmers about the optimal amount of fertilizer to spread on fields; and changing consumer food preferences. That does not necessarily mean that reducing agricultural and waste emissions is easier, but it is not subject to some of the delays of energy and industry.