Impact categories help us make actionable statements about how emissions influence the environment.
Actionable is a very important aspect here. Climate sciences are immensely complex. Thus, when companies try to become more sustainable, they have to define what they mean with that.
Definition: What are impact categories?
An impact category groups different emissions into one effect on the environment.
However, to fully understand impact categories, we need to have a basic understanding of Life Cycle Assessments.
Quick recap: Life-Cycle Assessment (LCA)
A Life Cycle Assessment (short LCA) is the standardized method of calculating the impact of, for example, a product on the environment.
During the course of the LCA, different kinds of emissions are collected: Emissions from the energy used, the water wasted, the raw material production, etc.
Role of Impact categories in an LCA
These emissions come in different shapes and formats, since the emissions of harvesting raw materials are very different from the emissions of electricity.
Here is where impact categories come into place. During the Life Cycle Impact Assessment (LCIA) of an LCA, we try to unite these different emissions into actionable numbers. That means that they are converted into one measurement that translates into one impact category.
KPI for the environment
You are probably familiar with the concept of Key Performance Indicators, or KPI, that measure the success of a business.
Impact categories can serve a similar function. They group complex data into accessible numbers – numbers that give a concrete picture of what the impact actually is.
A good example for accessible numbers like these is the Environmental Cost Indicator (ECI). The ECI aggregates all the impact categories into one monetary value that can be compared throughout industries.
All the impact categories (overview)
The following table gives you an overview of the relevant impact categories, which unit they are measured in and what they describe.
|Global warming||kg CO2-eq||Indicator of potential global warming due to emissions of greenhouse gases to air|
|Ozone depletion||kg CFC-11-eq||Indicator of emissions to air that cause the destruction of the stratospheric ozone layer|
|Acidification of soil and water||kg SO2-eq||Indicator of the potential acidification of soils and water due to the release of gases such as nitrogen oxides and sulphur oxides|
|Eutrophication||kg PO4 3−-eq||indicator of the enrichment of the aquatic ecosystem with nutritional elements, due to the emission of nitrogen or phosphor containing compounds|
|Photochemical ozone creation||kg ethene-eq||Indicator of emissions of gases that affect the creation of photochemical ozone in the lower atmosphere (smog) catalysed by sunlight.|
|Depletion of abiotic resources – elements||kg Sb-eq||Indicator of the depletion of natural non-fossil resources|
|Depletion of abiotic resources – fossil fuels||MJ||Indicator of the depletion of natural fossil fuel resources|
|Water pollution||m3||Indicator of the amount of water required to dilute toxic elements emitted into water or soil|
|Air pollution||m3||Indicator of the amount of air required to dilute toxic elements emitted into air|
|Primary renewable energy (resource)||MJ||Use of renewable primary energy resources as raw materials|
|Primary renewable energy (material)||MJ||Use of renewable primary energy, excluding renewable primary energy resources used as raw materials|
|Primary renewable energy (total)||MJ||Sum of the two values above|
|Primary non-renewable energy (resource)||MJ||Use of non-renewable primary energy resources as raw materials|
|Primary non-renewable energy (material)||MJ||Use of non-renewable primary energy, excluding renewable primary energy resources used as raw materials|
|Primary non-renewable energy (total)||MJ||Sum of the two values above|
|Use of secondary material||kg||Material recovered from previous use or from waste which substitutes primary materials|
|Use of fresh water||m3||Freshwater use|
|Use of renewable secondary fuels||MJ||Renewable fuel recovered from previous use or from waste which substitutes primary fuels|
|Use of non-renewable secondary fuels||MJ||Non-renewable fuel recovered from previous use or from waste which substitutes primary fuels|
|Hazardous waste disposed||kg||Hazardous waste has a certain degree of toxicity that necessitates special treatment|
|Non-hazardous waste disposed||kg||Non-hazardous waste is non-toxic and similar to household waste. It consists of inert waste and ordinary household waste|
|Radioactive waste disposed||kg||Radioactive waste mainly originates from nuclear energy reactors|
|Components for re-use||kg||Material or components leaving the modelled system boundary which is destined for reuse|
|Materials for recycling||kg||Material leaving the modelled system boundary which is destined for recycling|
|Materials for energy recovery||kg||Material leaving the modelled system boundary which is destined for use in power stations using secondary fuels (minimum energy efficiency 60% or 65% for installations opened after 2008)|
|Energy production||J||Energy exported from waste incineration and landfill|
Environmental Cost Indicator: One indicator for all impacts
Impact categories are not the be-all and end-all of measuring environmental impacts. In many cases, it makes sense to translate them into one aggregated metric, that makes the data comparable.
One popular metric for this is the Environmental Cost Indicator (ECI). You can learn more about ECI in our article about it.