Life cycle assessment of greenhouse gas emissions

Life cycle assessment (LCA) serves analyzing environmental burdens and impacts of products from resource extraction to waste disposal. Life cycle assessment methodology may also be applied to parts of the life cycle, for instance, “from cradle to (farm or factory) gate.” LCAs of greenhouse gas emissions are often part of wider environmental assessments, also covering other environmental burdens or impacts. Outcomes of life cycle assessments of greenhouse gas emissions are uncertain and variability thereof may originate in different choices regarding system boundaries, time horizons, and the allocation of emissions to outputs in multi-output processes and recycling. Life cycle assessments may include other interventions that can affect climate than the emission of greenhouse gases that become well-mixed in the atmosphere, such as changes in tropospheric ozone and aerosol concentrations, changes in albedo, turbulence and evapotranspiration, and the generation of contrails and cirrus clouds.

Life cycle assessments may be useful in the identification of life cycle stages that are major contributors to life cycle greenhouse gas emissions and of major emission reduction options, in optimization of products and verification of alleged climate benefits, and to establish major differences between competing products. In this chapter main findings from available life cycle assessments of greenhouse gas emissions are summarized for a wide range of products. Guidance for reducing greenhouse gas emissions is presented. Future directions in developing life cycle assessment and its application are indicated. These include better handling of indirect effects and uncertainty and improved comprehensiveness in dealing with climate change.