Linear Approaches to Characterization of Delayed Emissions of Methane

It is becoming more common to include the effects of delayed greenhouse gas emissions as an additional aspect in carbon footprinting. Although full dynamic assessment is the only accurate option to calculate those effects, the linear approach as outlined in, for example, the International Reference Life Cycle Data System (ILCD) Handbook, which is a popular reference. This approach overestimates the benefits of delayed emissions in all cases, but, for methane, the deviation is orders of magnitude. An alternative linear approach is proposed that does not start at t = 0. When using a time horizon of 100years, an initial no-accounting period of 75years is found to be appropriate for delayed emissions of methane, in most cases. The difference between the two approaches, when applying the concept of temporary carbon storage or delayed emissions to landfill, is considerable.