The following impact categories, as used by CML2.7 (2007) method, are described below (SimaPro, 2007):
- depletion of resources;
- global warming;
- stratospheric ozone depletion;
- human toxicity;
- freshwater aquatic ecotoxicity;
- marine ecotoxicity;
- terrestrial ecotoxicity;
- photo-oxidant formation;
- acidification; and
- Depletion of resources. This impact category is concerned with protection of human welfare, human health and ecosystem health. This impact category indictor is related to extraction of minerals and fossil fuels due to inputs into the system. The Abiotic Depletion Factor (ADF) is determined for each extraction of minerals and fossil fuels (kg antimony equivalents/kg extraction) based on concentration reserves and rate of de-accumulation. The geographic scope of this indicator is at a global scale.
- Global warming can result in adverse affects upon ecosystem health, human health and material welfare. Climate change is related to emissions of greenhouse gases to air. The characterisation model as developed by the Intergovernmental Panel on Climate Change (IPCC) is selected for development of characterisation factors. Factors are expressed as Global Warming Potential for time horizon 100 years (GWP100), in kg carbon dioxide/kg emission. The geographic scope of this indicator is at global scale.
- Stratospheric ozone depletion. Because of stratospheric ozone depletion, a larger fraction of UV-B radiation reaches the earth surface. This can have harmful effects upon human health, animal health, terrestrial and aquatic ecosystems, biochemical cycles and on materials. This category is output-related and at global scale. The characterisation model is developed by the World Meteorological Organisation (WMO) and defines ozone depletion potential of different gasses (kg CFC-11 equivalent/ kg emission). The geographic scope of this indicator is at global scale. The time span is infinite.
- Human toxicity. This category concerns effects of toxic substances on the human environment. Health risks of exposure in the working environment are not included. Characterisation factors, Human Toxicity Potentials (HTP), are calculated with USES-LCA, describing fate, exposure and effects of toxic substances for an infinite time horizon. For each toxic substance HTP’s are expressed as 1.4-dichlorobenzene equivalents/ kg emission. The geographic scope of this indicator determines on the fate of a substance and can vary between local and global scale.
- Freshwater aquatic ecotoxicity. This category indicator refers to the impact on fresh water ecosystems, as a result of emissions of toxic substances to air, water and soil. Ecotoxicity Potential (FAETP) are calculated with USES-LCA, describing fate, exposure and effects of toxic substances. The time horizon is infinite. Characterisation factors are expressed as 1,4-dichlorobenzene equivalents/kg emission. The indicator applies at global/continental/ regional and local scale.
- Marine ecotoxicity refers to impacts of toxic substances on marine ecosystems (see description freshwater toxicity).
- Terrestrial ecotoxicity. This category refers to impacts of toxic substances on terrestrial ecosystems (see description freshwater toxicity).
- Photo-oxidant formation is the formation of reactive substances (mainly ozone) which are injurious to human health and ecosystems and which also may damage crops. This problem is also indicated with “summer smog”. Winter smog is outside the scope of this category. Photochemical Ozone Creation Potential (POCP) for emission of substances to air is calculated with the UNECE Trajectory model (including fate), and expressed in kg ethylene equivalents/kg emission. The time span is 5 days and the geographical scale varies between local and continental scale.
- Acidification. Acidifying substances cause a wide range of impacts on soil, groundwater, surface water, organisms, ecosystems and materials (buildings). Acidification Potentials (AP) for emissions to air are calculated with the adapted RAINS 10 model, describing the fate and deposition of acidifying substances. AP is expressed as kg SO2 equivalents/ kg emission. The time span is eternity and the geographical scale varies between local scale and continental scale.
- Eutrophication (also known as nutrification) includes all impacts due to excessive levels of macro-nutrients in the environment caused by emissions of nutrients to air, water and soil. Nutrification potential (NP) is based on the stoichiometric procedure of Heijungs (1992), and expressed as kg PO4 equivalents/ kg emission. Fate and exposure is not included, time span is eternity, and the geographical scale varies between local and continental scale.
Please note the following adaptions made by ERM to the CML 2.7 method;
- VOC characterisation factor has been included. NMVOC & VOC are considered the same characterisation factor and included in GWP, human tox, fresh water tox, marine tox, terrestrial exotox and photochemical oxidation. Characterisation factors developed from speciation shown in "UK emissions of air pollutants 1970 - 2005" by UK emissions inventory team, Nov 2007, pg 67, table 2.13. Speciations were modelled and analysed using CML2001 method. This is based upon method suggested by leiden university. www.airquality.co.uk/archive/reports/cat07/0801140937_2005_Report_FINAL.... and www.leidenuniv.nl/cml/ssp/databases/cmlia/index.html
- Nitrogen oxides have been duplicated (by different naming convention) in CML 2.7 as they can be characterised under a number of different substances. All NOx is now characterised and added to Eutrophication and Photochemical oxidation categories.
- The characterisation factors for biogenic CO2 emissions and carbon dioxide removals from air are set to zero.
- Carbon dioxide for land transformation and carbon in organic matter and in soil were considered to be removed as probably biogenic but left in for now as further research needed into this. See paragraph below copied from methodology report.
A new elementary flow is introduced to account for the CO2 emissions due to land transformation, in particular due to clear cutting of primary forests. Carbon losses from soil and carbon dioxide released by burning wood residues from clear-cutting are classified as "Carbon dioxide, land transformation".
In line with the IPCC accounting rules, this elementary flow is treated like fossil CO2 emissions in life cycle impact assessment methods (see Jungbluth et al. 2007).
Additionally, the elementary flow (resource) "Carbon, in organic matter, in soil" is introduced. It balances the carbon dioxide emissions caused by soil degradation.