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21/06/2005
Green Guide to Specification
BRE Materials Industry Briefing Note 3a: Characterisation
Purpose of this note
To develop characterisation factors to comprehensively cover the range of
environmental impacts caused by the manufacture, use and disposal of construction
materials, using well respected methodologies, following ISO, and without double
counting.
Background
Environmental impacts are assessed by looking at appropriate environmental impact
categories. Characterisation measures the level of environmental impact caused by
a product or functional unit studied in an LCA. Characterised results are calculated
for each impact category with findings presented in appropriate units (i.e. through use
of a reference substance such as kg CO2 equivalents for climate change).
Impacts in one category can be caused by many different substances, and one
substance can contribute to several impact categories. Characterisation is where all
the different substances contributing to each impact category are assessed relative
to one another to give an overall measure of the level of impact in each category.
Each impact category has a reference and the contribution of each substance to the
impact category is calculated by converting the amount of substance into the
equivalent amount of the reference substance or unit. This conversion is done using
characterisation factors. For example, for Climate Change, the reference substance
is CO2. So, the effects of 1 tonne of methane are converted into the amount of CO2
needed to cause the same effect over a 100-year timescale - as methane is 23 times
more damaging than CO2; the climate change characterisation factor for methane is
23.
The BRE Environmental Profiles methodology currently uses 12 environmental
impact categories:
Impact Category Name
Climate Change
Acid Deposition
Ozone Depletion
Human Toxicity to air and water
Summer Smog
Ecotoxicity
Eutrophication
Fossil Fuel Depletion
Minerals Extraction
Water Extraction
Waste Disposal
Source of characterisation factors
CML 19921, updated with IPCC 19952
CML 1992
CML 1992, updated with UNEP 19993
CML 1992
CML 1992
CML 1992
CML 1992
BRE 19994
BRE 1999
BRE 1999
BRE 1999
1
Heijungs et al, Environmental Life Cycle Assessment of products. Guide-October 1992.
Centrum voor Milieukunde - Institute for Environment, Leiden University, 1992.
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CML is internationally recognised for its expertise and experience in this field The
CML characterisation factors were largely based on work undertaken by other expert
groups or researchers, eg the IPCC (Intergovernmental Panel on Climate Change).
In 2000, CML published an updated characterisation methodology 5, again based
largely on the work of expert groups and researchers. The new methodology
includes new impact categories and revises and updates existing categories.
Suggested Route
Adopt the updated characterisation method developed by CML in 2000, and develop
any other relevant impact categories to ensure that a full range of environmental
impacts is included, without double counting.
The CML 2000 method is based on the problem-oriented (midpoint) approach. The
method covers a core baseline range of impact categories, broadly based on the
earlier CML 1992 Method, which BRE used as the basis for their original
Environmental Profiles Impact Assessment Methodology. CML have also developed
a number of other impact categories, not included within the baseline, which may be
appropriate to particular projects.
One new baseline category has been developed - Abiotic Resource Depletion, and
significant changes in methodology have been made to both the Ecotoxicity and
Human Toxicity categories since the earlier method. Further information on the CML
method can be found on their website at http://www.leidenuniv.nl/cml/ssp/index.html.
BRE feel that four areas of environmental impact are not covered by the CML
baseline indicators, and therefore intend to add categories relating to Solid Waste
Disposal, Radioactivity, Minerals Extraction and Water Extraction.
In adopting this approach the updated Environmental Profiling Methodology will
consist of 13 environmental impact categories.
Category
Abiotic depletion
Global warming (GWP100)
Ozone layer depletion (ODP)
Human toxicity
Fresh water aquatic ecotoxicity.
Terrestrial ecotoxicity
Photochemical oxidation
Acidification
Unit
kg Sb eq.
kg CO2 eq. (100 yr)
kg CFC-11 eq.
kg ,4-DB eq.
kg1,4-DB eq.
kg 1,4-DB eq.
kg C2H4eq.
kg SO2 eq.
2
Houghton et al, Climate Change 1995: The Science of Climate Change, Contribution of WGI
to the 2nd assessment report of the Intergovernmental Panel on Climate Change. IPCC,
1995
3
Ozone Secretariat, Production and Consumption of Ozone Depleting Substances 19861998. UNEP 1999.
4
Howard et al, BRE Methodology for Environmental Profiles of Construction Materials,
Components and Buildings. BRE 1999.
5
Guinée et al, Life cycle assessment: an operational guide to the ISO standards. CML,
Leiden University 2000.
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Eutrophication
Solid waste
Radioactivity
Minerals Extraction
Water Extraction
kg PO4 eq.
tonne solid waste
mm3 high level waste
tonne of minerals extracted
m3 water extracted
The characterisation process of each is now reviewed in detail.
1 Abiotic Resource Depletion
This impact category indicator is related to extraction of scarce minerals and fossil
fuels. The Abiotic Depletion Factor (ADF) is determined for each extraction of
minerals and fossil fuels based on the remaining reserves and rate of extraction. It is
based on using the equation, Production/(Ultimate Reserve)2 and comparing this to
the result for Antimony (Sb), which is used as the reference case. The reference unit
for abiotic depletion is therefore kg Sb equivalent.
2 Acidification
Acidic gases such as sulphur dioxide (SO2) react with water in the atmosphere to
form “acid rain”, which can cause ecosystem impairment. Acidification Potential (AP)
is expressed using the reference unit, kg SO2 equivalent. The revised method only
accounts for acidification caused by SO2 and NOx.
3 Climate Change
Climate change is caused by the release of “greenhouse gases” such as carbon
dioxide (CO2). The characterisation model as based on factors developed by the
UN’s Intergovernmental Panel on Climate Change (IPCC). Factors are expressed as
Global Warming Potential over the time horizon of 100 years (GWP100), measured
in the reference unit, kg CO2 equivalent.
4/5 Ecotoxicity to Freshwater and Land
The emission of some substances can have impacts on ecosystems. Ecotoxicity
Potentials are calculated with the USES-LCA6 which is based on EUSES7, the EU’s
toxicity model. This provides a method for describing fate, exposure and the effects
of toxic substances on the environment. Characterisation factors are expressed using
the reference unit, kg 1,4-dichlorobenzene equivalents (1,4-DB)/kg emission, and are
measured separately for impacts of toxic substances on:
• Fresh-water aquatic ecosystems
• Terrestrial ecosystems
Characterisation factors are also available for marine ecotoxicity, and ecotoxicity to
marine and fresh water sediments. The sedimentary ecotoxicity factors are not
included within the CML baseline characterisation factors and there are concerns
within the LCA community over the marine ecotoxicity category, with regard to the
impact of hydrogen fluoride and the normalisation figures. As a result we do not
propose to use these three categories.
6
Huijbregts MAJ, Priority Assessment of Toxic Substances in the Frame of LCA - The MultiMedia Fate, Exposure and Effect Model USES-LCA. Amsterdam: University of Amsterdam
(NL) 1999.
7
European Union System for the Evaluation of Substances. Version 1. Environment Institute,
European Chemical Bureau, Joint Research Centre, European Commission, 1997.
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6 Eutrophication
Nitrates and phosphates are essential for life but increased concentrations in water
can encourage excessive growth of algae, reducing the oxygen within the water and
damaging ecosystems. Eutrophication potential is based on the work of Heijungs
(1992), and is expressed using the reference unit, kg PO4 equivalents.
7 Human Toxicity
The emission of some substances can have impacts on human health.
Characterisation factors, expressed as Human Toxicity Potentials (HTP), are
calculated using USES-LCA, as with Ecotoxicity, which describes fate, exposure and
effects of toxic substances for an infinite time horizon. For each toxic substance
HTPs are expressed using the reference unit, kg 1,4-dichlorobenzene (1,4-DB)
equivalents.
Indoor air quality and its effect on human health is not covered by this category.
8 Photochemical Ozone Creation (Summer Smog)
In atmospheres containing nitrogen oxides (NOx, a common pollutant) and volatile
organic compounds (VOCs), ozone can be created in the presence of sunlight.
Although ozone is critical in the high atmosphere to protect against ultraviolet (UV)
light, at low level it is implicated in impacts as diverse as crop damage and increased
incidence of asthma. Photochemical Ozone Creation Potential (POCP, also known
as summer smog) for emission of substances to air is calculated with the United
Nations Economic Commission for Europe (UNECE) trajectory model (including fate),
and expressed using the reference unit, kg ethene (C2H4) equivalents/kg emission.
9 Stratospheric Ozone depletion
Damage to the ozone layer by chlorinated and brominated chemicals increases the
amount of harmful UV light hitting the earth’s surface. The characterisation model
has been developed by the World Meteorological Organisation (WMO) and defines
ozone depletion potential of different gases relative to the reference susbstance
chlorofluorocarbon-11 (CFC-11), expressed in kg CFC-11 equivalent.
Additional Characterisation Issues
In addition to the above BRE feel that solid waste disposal, radioactivity, minerals
and water extraction are of significant environmental importance and are not
adequately accounted for in the impact categories reviewed above. We therefore
propose to include the following categories within the updated Environmental Profiles
Methodology.
10 Solid Waste
The updated Environmental Profiles Methodology will take into account the impact
from emissions and infrastructure associated with waste disposal, for example, the
emissions associated with landfill, incineration and composting. However, this will
not cover other environmental issues associated with landfilling such as dust, noise
and odour, and the loss of resource implied by the final disposal of waste. We feel
these issues must be accounted for within the Methodology. Other characterisation
methodologies, for example the Dutch EcoIndicator and the Swiss Ecopoints, use the
mass of solid waste as a category, and BRE intend to use this as the basis for the
characterisation factor for the category.
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Any waste that is finally disposed of in landfill will be measured. Waste that is
incinerated will not be included within this category, but any resulting waste (eg ash)
that needs to be landfilled will be included. No differentiation will be made between
hazardous, inert or organic wastes, though different impacts from these routes will be
included within the waste treatment models (landfill, incineration and composting) for
these wastes.
11 Radioactivity
Radioactivity can cause serious damage to human health, and as yet, no treatment
or secure storage location exists for higher level radioactive wastes, such as that
generated by the nuclear power industry and from decommissioning nuclear power
stations. Such wastes need to be stored for periods of up to 1,000 years before their
radioactivity reaches safe levels. The World Nuclear Association states that higher
level nuclear waste (high and intermediate level waste) accounts for a very low
percentage of nuclear waste, around 10% by volume, but 99% of its radioactivity 8.
Other characterisation methods, such as the Swiss Ecopoints, use the volume of
highly active radioactive waste as a category, and BRE intend to use this as the
basis for the characterisation factor for the category, measured in m3 of spent fuel,
high and intermediate level radioactive waste.
12 Minerals Extraction.
Although the Abiotic Resource Depletion category covers mineral ores extracted from
the ground, minerals such as sand, limestone and granite are such widely available
resources that, even at the high current levels of extraction, there is not an issue of
scarcity of resource.
However, we feel that there are considerable environmental impacts associated with
minerals extraction not covered by the resource depletion issue. This view is shared
by the UK government, which has introduced an aggregates levy, which is a tax on
primary sand, gravel and rock that has been extracted from the ground and dredged
from the sea. We suggest this impact category to address the environmental damage
caused by these activities in the form of noise, dust and loss of biodiversity.
We, therefore, propose that, as with the existing Environmental Profiles Methodology,
an impact category for minerals extraction is included. This would be based on each
tonne of mineral extracted (including overburden) and would be a proxy for the noise,
dust and biodiversity impacts, and problems with subsidence and spoil associated
with quarrying and mining.
As the extraction of scarce minerals with abiotic resource depletion factors also
causes quarrying impacts, this minerals extraction impact will also apply to them but
this is not double counting as two distinct environmental impacts are being
considered.
13 Water extraction
Around the world, water is becoming an increasingly scarce resource, due to
increased demand, and changes in patterns of rainfall. To recognise the value of
water as a resource, and the damage that over extraction from rivers and aquifers
can cause, BRE propose to refine their existing water extraction category.
8
http://www.world-nuclear.org/education/wast.htm
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The category would therefore include all water extraction, except:
• Sea water
• Water extracted for cooling or power generation and then returned to the
same source with no change in water quality (water lost through evaporation
would be included in the category)
• Water stored in holding lakes on site for recirculation (top-up water from other
sources would be included)
• Rainwater collected for storage on site
The category would be measured using m3 of water extracted.
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