Impact Categories (LCA) – Overview5 min read

Learn what impact categories are useful for and which impact categories there are.

Luc Hillege

Environmental Specialist at Ecochain

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Impact categories help us make actionable statements about how emissions influence the environment.

Actionable is a very important aspect here. Environmental 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)

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, a large amount of emission data is collected: emissions from energy production, the waste produced, the raw material production, etc.

Role of Impact categories in an LCA

These emissions come in different shapes and formats, since the emissions from harvesting raw materials are very different from the emissions from producing 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 unit 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. These are taken from the EN15804 standard for LCAs in the construction sector. Other impact assessment methods exist as well, which use slightly different categories.

Environmental impacts

Impact category / Indicator Unit Description
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
Human toxicity 1,4-DCB-eq Impact on humans of toxic substances emitted to the environment (Dutch version of EN15804 only)
Fresh water aquatic ecotoxicity 1,4-DCB-eq Impact on freshwater organisms of toxic substances emitted to the environment (Dutch version of EN15804 only)
Marine aquatic ecotoxicity 1,4-DCB-eq/sup> Impact on sea water organisms of toxic substances emitted to the environment (Dutch version of EN15804 only)
Terrestrial ecotoxicity 1,4-DCB-eq Impact on land organisms of toxic substances emitted to the environment (Dutch version of EN15804 only)
Water pollution m3 Indicator of the amount of water required to dilute toxic elements emitted into water or soil (french version of EN15804 only)
Air pollution m3 Indicator of the amount of air required to dilute toxic elements emitted into air (French version of EN15804 only)

Resources used

Impact category / Indicator Unit Description
Primary renewable energy (materials) MJ Use of renewable primary energy resources as raw materials
Primary renewable energy (energy) 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 (materials) MJ Use of non-renewable primary energy resources as raw materials
Primary non-renewable energy (energy) 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

Waste type

Impact category / Indicator Unit Description
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

Output flows

Impact category / Indicator Unit Description
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.

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