Countries/regions
1.2 Carbon footprint (CF)
The main goal of this project is to provide the best possible estimate of Denmark’s consumption‐related
“carbon footprint”. By carbon footprint is meant GHG‐emissions, expressed as carbon dioxide equivalents
(CO2‐eq.). Consumption‐related is defined as GHG‐emissions from the Danish economy including imports,
while emissions associated with exports are excluded. In this respect, the limitations of the traditional geographical approach to account for national emissions are addressed by taking into account the full life cycle of imported products to Danish economy. Data on production, imports, and exports of goods and services are obtained from environmentally‐extended input‐output (IO) tables.
An additional goal of the project is to provide an overview of the products and services imported to and exported from Denmark, and their embedded GHG‐emissions.
A detailed description of the data and methods used in the calculations is provided. This involves clear descriptions of choices and assumptions made to determine the GHG intensity of products and services produced in Denmark and in other countries. In addition to the GHG‐emissions typically included in official national emission reports and common input‐output models, the current study also includes contributions from land use induced land use changes and special radiative forcing from operation of aircrafts at high altitudes.
This document reports the project and its results, and has been carried out by 2.‐0 LCA consultants from October to December 2013.
1.2 Carbon footprint (CF)
The concept ‘carbon footprint (CF)’ emerged and became a buzzword in the last half of the first decade of the 2000s (Weidema et al. 2008). The concept is very similar to the global warming potential (GWP) impact category in life cycle assessment. In 2013, a technical specification (ISO/TS 14067) on carbon footprint was published. The requirements on methods are almost fully identical to ISO 14040 and 14044 on life cycle assessment.
In ISO/TS 14067 (2013, p 1) a carbon footprint of a product is defined as “sum of greenhouse gas emissions
… and removals … in a product system …, expressed as CO2 equivalents … and based on a life cycle assessment … using the single impact category … of climate change”.
Expressing climate change as a single impact category measured in CO2 equivalents means that all GHG‐
emissions associated with a product are turned into one indicator. In ISO/TS 14067, this indicator is
calculated using the so‐called global warming potential (GWP), where different emissions’ radiative forcing
32
during a 100 year time horizon is expressed relative to the radiative forcing of CO2 in the same time horizon. This means that the contribution to climate change from different greenhouse gasses can be expressed in CO2 equivalents. Of the so‐called long‐lived greenhouse gasses10 CO2, CH4 and N2O accounts for approximately 96% of the GWP100 from global emissions in 2000 (IPCC 2007, p 2006). The last 4%
comes from several halocarbons such as CFCs, SF6, PFCs, HFCs, and HCFCs.
Table 1.1: Global warming potentials for the three major greenhouse gasses (IPCC 2007, p 212).
GHG‐emission Global warming potential (GWP100) Carbon dioxide (CO2) 1 kg CO2‐eq./kg
Methane (CH4) 25 kg CO2‐eq./kg Nitrous oxide (N2O) 298 kg CO2‐eq./kg
In the current study biogenic emissions have generally been excluded, i.e. contributions to GWP from CO2‐ uptake from plant growth (negative GWP) as well as CO2‐emissions from decay or combustion of plant material are not included. However, there is one exception; emissions from land use changes are included despite these emissions have biogenic origin. The GWP from land use changes/deforestation is modelled in a special way taking into account the effect from temporal issues. This is further described in section 3.5.
The life cycle assessment approach referred to in ISO/TS 14067 means that all GHG‐emissions in the life cycle of the product under study are accounted for. This implies that emissions from raw material extraction, processing, transport, use and end‐of‐life of the product are included in the inventory.
Results of carbon footprints and life cycle assessments are always shown relative to a so‐called functional unit. The functional unit is a “quantified performance of a product system for use as a reference unit” (ISO 14040), i.e. a specification of what all emissions and results are related to. For products, a distinction between functional units which includes ‘cradle to grave’ and ‘cradle to gate’ emissions is often used. The latter does not include the use and disposal stage while this is included in ‘cradle to grave’ studies. For life cycle studies at the societal level the ‘cradle to grave’ perspective is typically used for studies focusing on consumption, while studies on export typically only focus on emissions related to the production of products to the point where they are exported (i.e. the ‘gate’ in a ‘cradle to gate’ study).
Carbon footprints and LCAs are not necessarily limited to focusing on products, but the same concept can be applied to assess life cycle emissions at other levels as well, see Table 1.2.
10 CO2, CH4, N2O, and halocarbons (IPCC 2007).
Table 1.2: Different application levels of carbon footprint (or life cycle assessment).
Level Focus/functional unit
Product or service Focusses on the emissions throughout a product’s or service’s life cycle.
Organisation Focusses on the emissions related to typically one year of operation of a company. This includes directly emitted emissions from the company (typically from combustion of fuels), emissions related to purchased electricity and hot water/steam, and other upstream emissions related to the production and distribution of purchased goods and services by the company. Most often downstream effects from products supplied by the company are not included.
Project, programme or policy This focus is closely related to environmental impact assessments (EIA) of projects and strategic environmental assessments (SEA) of programmes and policies. The main difference is that carbon footprints include all upstream (and sometimes downstream) implications of the project, programme and policy, where the typical focus is EIA and SEA is primarily on direct effects and not so much on entire product systems.
Society A society can be e.g. a municipality, nation, regional or the whole world. The focus is on the life cycle emissions related to consumption by the society’s citizens, the production by the society’s industries as well as life cycle emissions related to imported and exported products.
The current study belongs to carbon footprint studies applied to the societal level in Table 1.2.