The short answer: Activate “Use detailed settings” in the Methane & Other Gases advanced view, and then set the “Energy and industry emissions” slider to -25%.


Natural gas is mostly methane. Somewhere between 2 and 9% of natural gas leaks into the atmosphere somewhere along the flow from extraction to use.  17% of all human-caused methane emissions are due to natural gas leakage, or about 10% of non-CO2 greenhouse gases (EPA 2019; Howarth 2011). Other sources of methane include coal and oil mining, refining, and transport; industrial processes; agriculture; and waste.


We group methane and other non-CO2 gases together because the efforts to curb their release are similar or could be based on similar agreements and regulations. For most users, this coordinated action is simple and adequate — the main slider reduces emissions of all non-CO2 gases. Other users will want the added control gained by clicking the “Use detailed settings” switch. This activates controls to do several things:

  • Set different percent action for “Agriculture and waste” versus “Energy and industry” emissions;
  • Specify a start year for action on other greenhouse gases; and
  • Set a year to begin phasing out hydrofluorocarbons (HFCs).


We have written about simulating changes to the food system using the “Agriculture and waste” slider here: https://www.climateinteractive.org/blog/how-to-talk-about-food-in-en-roads/.


If you want an estimate of what would happen if you took the isolated action of fixing the leaks in natural gas infrastructure, use the detailed settings and set the “Energy and industry emissions” slider to -25%.


The math behind this is: natural gas leaks represent 10% of all non-CO2 GHG emissions (EPA 2019). In 2060, non-CO2 emissions in the Baseline scenario in En-ROADS are 21.5 GtCO2eq/year, so natural gas leaks would be about 2.1 GtCO2eq/year. If action can bring the leak rate from 3%  to 1% , emissions would fall by 2/3, or about 1.4 GtCO2eq/year.  That emissions reduction corresponds to 25% on the “Energy and industry emissions” slider. This “Energy and industry” slider controls more than methane from leaking natural gas facilities, but a 25% reduction using this slider is a reasonable estimation of leaking pipelines given that reductions of the gases is calculated using CO2 equivalents. The inclusion of more gases than just methane does not change the policy implications and insights


To see the results of your policy, show the graph “Non-CO2 Greenhouse Gas Emissions.” Note that even 100% action on both the “Agriculture and waste emissions” and the “Energy and industry emissions” sliders do not reduce emissions to zero – we calibrate the sliders to maximum achievable reductions since some of these emissions are thought to be unavoidable. 25% on the “Energy and industry emissions” slider, appropriate for a “fix the leaks” effort, does lower emissions compared to the baseline, but makes less than 0.1 degree C difference in temperature change by 2100.

 

** En-ROADS formerly had a separate slider for the leak rate of natural gas. There was some overlap between using that slider and the sliders under Methane & Other Gases, which could confuse users. The Methane and Other Gases sector now cover all the leaks and emissions from methane, including from natural gas.


References:

EPA 2019 https://cfpub.epa.gov/ghgdata/nonco2/reports

Howarth et al 2011 https://link.springer.com/article/10.1007/s10584-011-0061-5