Incorporating methane into ecological footprint analysis: A case study of Ireland

Carbon dioxide (CO₂) accounting is important to global ecological footprint analysis. However methane (CH₄), with a global warming potential (GWP) 25 times that of CO₂, should not be neglected as an environmental indicator for informed environmental management. While this is a significant component, the CH₄ associated with imported embodied energy should also be included in national greenhouse gas (GHG) inventories. This study proposes an initial method for incorporating methane into ecological footprint analyses and hopes to inform future debate on its inclusion. In order to account for differences in methane intensities from exporting countries, methane intensities for OECD countries were calculated using emission and energy consumption estimates taken directly from National Inventory Reports (NIR), published in conjunction with the Intergovernmental Panel on Climate Change (IPCC). For other countries the methane intensities were estimated using energy balances published by the International Energy Association (IEA) and IPCC default emission factors. In order to estimate embodied organic methane, material imports and exports were translated into units (such as live animals) capable of conversion into methane emissions. A significant increase in Ireland's footprint results from the inclusion of the GWP of methane is included within the footprint calculation.