lca _environmental profiles methodology

8/14/2019 LCA _Environmental Profiles Methodology

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CONTENTS

EXECUTIVE SUMMARY

1 INTRODUCTION.................................................................................................................42 GENERAL PRINCIPLES ....................................................................................................53 GOAL AND SCOPE............................................................................................................5

3.1 Goal .................................................................................................................................53.2 Scope of the study...........................................................................................................63.3 Scope of data for impact assessment ............................................................................93.4 Data sources ...................................................................................................................9

4 INVENTORY DATA COLLECTION..................................................................................104.1 Defining the process .....................................................................................................104.2 Outputs ..........................................................................................................................114.3 Inputs.............................................................................................................................114.4 Emissions and discharges ............................................................................................12

5 INVENTORY DATA HANDLING:- ALLOCATION............................................................14

5.1 Explanation of allocation rules ......................................................................................145.2 Summary of rules for allocation.....................................................................................206 FURTHER INVENTORY DATA HANDLING....................................................................21

6.1 Rules and conventions..................................................................................................216.2 Creating the generic Profile...........................................................................................216.3 Transport .......................................................................................................................236.4 Fuel................................................................................................................................236.5 Carbon cycle .................................................................................................................256.6 Adjusting carbon dioxide emissions for re-carbonation................................................266.7 Emissions ......................................................................................................................266.8 Imports...........................................................................................................................27

7 IMPACT ASSESSMENT...................................................................................................28

7.1 Presentation of results: the Environmental Profiles......................................................287.2 The impact assessment process ..................................................................................287.3 Explanation of impacts on the characterised and normalised Profile ..........................29

8 REFERENCES .................................................................................................................339 ANNEXES.........................................................................................................................34

A1 AVERAGE GROSS CALORIFIC VALUES FOR UK FUELS - 1996..............................34A2 FUEL USED IN ELECTRICITY GENERATION 1996 ....................................................34A3 TOTAL AND UPSTREAM FUEL EMISSION FACTORS 1996......................................35A4 PRIMARY ENERGY RATIOS FOR UK DELIVERED ENERGY - 1996 .......................35A5 GROSS v NET CALORIFIC VALUES............................................................................36A6 STANDARD CONVERSION FACTORS AND UNITS....................................................36A7 CARBONATION CALCULATIONS.................................................................................37

A8 TRANSPORT METHODOLOGY FOR CALCULATING FUEL USE..............................38A9 SOURCES OF LCA DATA..............................................................................................41A10 THE STANDARD QUESTIONNAIRE FOR INVENTORY DATA COLLECTION. .......42A11 CHARACTERISATION FACTORS ..............................................................................49A12 AN OVERVIEW OF THE ENVIRONMENTAL PROFILES DATABASE......................61A13 INVENTORY PROFILE FORMAT ................................................................................63A14 CHARACTERISED AND NORMALISED DATA PROFILE FORMAT .........................65


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THE BRE METHODOLOGY FOR ENVIRONMENTAL PROFILES OF CONSTRUCTIONMATERIALS, COMPONENTS AND BUILDINGS

This document is the result of over 3 years work in collaboration with representatives of theConstruction Materials sector through a DETR Partners in Technology project. The followingorganisations have participated in the steering group for this project. It is the view of themajority of the members of this steering group that the methodology set out in this documentis a practical, consistent and comprehensive method for the life cycle assessment of alltypes of building materials and components.

Aluminium FederationBrick Development AssociationBritish Cement AssociationBritish Lime AssociationBritish Plastics FederationBritish Non-ferrous Metals Federation

British Precast Concrete FederationBritish Wood Preserving and Damp-proofingAssociationBritish Woodworking FederationCementitious Slag Makers AssociationCelotex Ltd.Clay Pipe Development Association

EurisolForestry CommissionGypsum Products Development AssociationNational Council of Building MaterialsProducersNickel Development Institute

Quarry Products AssociationReinforced Concrete CouncilSteel Construction InstituteStone Federation of Great BritainTimber Trade FederationUK Forest Products AssociationWood Panel Industries Federation

PEER REVIEW STATEMENT

The following experts in Life Cycle Assessment and Building have undertaken a peer reviewof this methodology:

Sverre Fossdal, Senior Researcher, Norwegian Building Research Institute.Tarja Hakkinen, Chief Research Scientist, VTT Building Technology, Finland.Jean Luc Chevalier, Head of the Environment and Durability Division, Materials DepartmentCSTB (Centre Scientifique et Technique du Batiment), France.Wayne Trusty, Wayne B Trusty and Associates Ltd, Canada.

They have confirmed that the choices used in this methodology conform with InternationalStandard Organisation Guidelines ISO14041.


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EXECUTIVE SUMMARY

Environmental Profiles are the result of over three years work undertaken in collaborationwith representatives of the Construction Materials sector through a DETR Partners inTechnology project.The work has been conducted to enable architects, specifiers andclients to make informed decisions about construction materials and components, bydeveloping a method for providing independent, "level playing field" information about therelative environmental impacts of different design options. BRE believe that the collaborationbetween UK materials industries and BRE has resulted in a methodology that is uniqueworldwide in its consistent application of the LCA approach. UK materials producers shouldreap competitive benefits from the method, which sets a new standard for delivering thisincreasingly important aspect of product information.

The work has achieved two significant results: this methodology document and a UKnational database providing access to Environmental Profiles generated by the industry.

The BRE Methodology for Environmental Profiles of Construction Materials and

Components.The development of this set of common rules and guidelines for applying LCA to UKconstruction products enables materials producers in the UK to produce LCA data in theform of Environmental Profiles. Conformity with this methodology means that materials userscan have confidence in the "level playing field" status of Environmental Profiles, for everymaterial type.

The Methodology document has been produced to ensure transparency of the methodsemployed in creating Environmental Profiles. This document describes in detail theconsistent approach to the identification and assessment of the impacts of all constructionmaterials and components over their life cycle, including:

Standard goal and scope, Inventory data collection procedures,

Preferred data sources,

Consistent treatment of transport, Calculation of emissions from fuel use,

Allocating impacts to products from multiple product lines,

Adjusting Profiles for recycled content,

Impact assessment procedures-for classification, characterisation and normalisation,

Formats for Environmental Profiles.

Environmental Profiles of Construction Materials and Components.

Profiles may be calculated for materials, components and building elements. The buildingelements Profiles can be presented "as built" or over a nominal life.

Materials are presented as "cradle to gate" Profiles, on a per tonnebasis.

Installed elements are presented on a "cradle to site" basis and are calculated "persquare metre" of element.

Sixty year life elements are presented as a "cradle to grave" Profile, taking account oftheir maintenance, replacement and disposal rates for a sixty year life. These are alsocalculated on a "per square metre" basis.

Profiles which have been created over the life of the project are held in the UK Database ofEnvironmental Profiles of Construction Materials and Components, which is available via an

Internet service. Materials producers can add new Profiles for additional products at any timeand the database will be regularly updated.


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BRE METHODOLOGY FOR ENVIRONMENTAL PROFILES OF CONSTRUCTIONMATERIALS, COMPONENTS AND BUILDINGS

1 INTRODUCTION

Reliable and independent environmental information about building materials andcomponents is in high demand. Environmental Profiles provide a useful way of providing thisinformation. To be of help to the working architect, client or building specifier, this informationmust be produced according to an agreed methodology. This is a standardised way ofidentifying and assessing the environmental effects of building materials over their entire lifecycle, through their extraction, processing, construction, use and maintenance and theireventual demolition and disposal.

The reason for producing the agreed methodology is to ensure consistent assessment ofdifferent types of building materials, elements and whole buildings and to help the user byreducing the number of confusing claims about the environmental properties of alternative

building products.

This document is provided to ensure transparency of the method applied to create the datain the Environmental Profiles Database. It records the rationale and methodological rulesthat have been adopted by BRE to create a standard UK method of applying LCA toconstruction products and components. There is no single "right" answer for applying LCAbut it is has been agreed by the majority of the building materials producers representativesin the project that this methodology represents a suitable approach to deal with allbuildingmaterials. It is recognised that different approaches to LCA which can be applied to buildingmaterials may be equally valid and also meet ISO criteria. The BRE methodology has beendevised with the particular aim of assisting decision makers to make comparisons betweenall types of building material from a "level playing field" perspective.

Life Cycle Assessment (LCA) requires the collection of an inventory of data on all the inputs

and outputs of a process, i.e. the environmental burdens*and their subsequent conversion

into defined environmental impacts.

This document provides a description of the basic principles that are applied in the creationof Environmental Profiles and is then structured around the different LCA stages that areundertaken to produce the Environmental Profiles. For each stage in the process adescription of the work undertaken is provided. More information on LCA may be found inGuidelines1.from SETAC, the Society for Ecological Toxicology and Chemistry (SETAC),which is a leading authority in life cycle analysis development,

The different stages of LCA are:

Defining the Goal and Scope

Inventory Data Collection and Analysis Impact Assessment: Classification

CharacterisationNormalisationWeighting

*The inputs and outputs to a system are called "interventions" under International Standard

Organisation convention. In this document the term environmental "burdens" is usedbecause we consider it to have more meaning for the user.


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2 GENERAL PRINCIPLES

The following principles are fundamental to every stage of BRE's application of LCA tobuilding materials, components and buildings and encapsulate the philosophy and logicbehind the method to be adopted:

BRE's methodology aims to be consistent, scientifically robust and to ensure thatburdens and impacts are completely accounted for without any double counting orundercounting.

BRE's methodology aims to be consistent for all stages of the life cycle across allmaterial classes i.e. the winning of raw materials and fuels, energy conversion, chemicalprocesses, manufacture, fabrication, transport, operation and use, repair and maintenance,refurbishment, demolition, reuse or recycling, disposal.

BREs methodology must be permitted to evolve as our understanding becomes morerefined. The field of environmental assessment is evolving rapidly and methods need to be

updated at an appropriate rate.

These principles represent the ideal and are often not reflected in existing databases, due tothe difficulties of achieving them in practice. In BRE's work every endeavour has been madeto comply with these principles. For practical reasons however, it is necessary in somecases to use data that is unknown with respect to these objectives. In such cases it must beensured that the results are not sensitive to this data.

3 GOAL AND SCOPE

Whenever a life cycle assessment is performed, it is necessary to define why the study is

being made and for whom. This is the goal. It is then necessary to define what will beincluded within the parameters of the study and what it is not possible or desirable toinclude. This is the scope.

3.1 Goal

Reason for carrying out the studyTo gather and assess comprehensive and reliable information regarding the positive andnegative environmental impacts of construction materials used in defined applications, whichare generated over a defined lifetime.

Target audienceDesigners, specifiers and their clients and those involved in the production of LCAs forbuildings.

Intended useThe data is intended to be used to improve the environmental performance of buildingdesigns, by allowing the designer to understand the impacts from different building elementsand optimise the overall impact of a building design.


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3.2 Scope of the study

BoundariesMaterials and components can be considered to have a lifetime from cradle to grave.

The BRE method accounts for burdens and impacts on a cradle to gravebasis. In otherwords, from the point when man exploits resources from the environment to the point atwhich the goods and services used become redundant and the materials and other effectsreturn to the environment.

In application, BRE results are also presented for some intermediate stages i.e. cradle togateand cradle to site. If the scope of the assessment is declared cradle to gate, theinvestigation must trace production right back to the winning of all of the raw materials butdoes not include impacts beyond the factory gate. If the scope is declared as cradle tograve, then all of the processes from the winning of raw material through production, throughuse, reuse and recycling until eventual disposal within the environment need to beaccounted for.

"Gate to gate assessments" incorporate only one part of the production process and areconsidered to be potentially misleading because they may omit many of the largest impactphases of production. For example, the fabrication of a component might involve very highimpact materials, but only incur modest impacts from a gate to gate assessment of thefabrication process alone. This type of scope would be useful for manufacturers wishing toseek process improvements. This is not a goal of the work described in this project but therules

A cradle to grave assessment appears at first sight to be the most complete andcomprehensive and hence most justifiable. However, in making a cradle to graveassessment, large numbers of assumptions must be made about the use phase of the

materials and products over typically very long timescales for buildings. For example, forinsulation materials, their insulating properties will be far more important over the life ofapplication than the impacts from the material production. In addition, scenarios ofmaintenance, repair and replacement must also be assumed and these can also have manytimes more effect on the life cycle performance than the initial production, especially overlong life buildings.

Different boundaries of assessment will be useful to different decision makers at differenttimes and the methodology has been created to reflect these varied needs. The boundariesapplied in this methodology are explained below for the different units of assessmentavailable in the Environmental Profiles Database.

Functional UnitsTo understand the life cycle of a product, it is essential that it is considered in the context ofits application - i.e. in its functional unit.

Whilst materials and components can be considered to have a lifetime from cradle to grave,it is not possible to assign a life to a pile of bricks or tonne of insulation - they only have atrue "life" when considered in the context in which they are used, e.g. as a wall. As a wall, orany other type of building element, building components do assume a life and they will fulfilvarious functions for a set amount of time, they will have maintenance requirements and willhave to be dismantled at the end of their role in the building. Different materials can then becompared on a like-for-like basis, as components that fulfil the same or very similarfunctions. This means that important variables such as the mass of a material required tofulfil a particular function are therefore taken into account. For example, the results of adirect comparison between 1 tonne of steel and 1 tonne concrete would be misleading to a


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building designer. Instead the quantity of steel, and the other components, required toproduce a square metre of steel wall should be compared with the quantity of concrete, andother components, required to make a concrete wall with a comparable function.

The functional unit for construction materials has been chosen to be their typical as-builtelemental form, over a service life of sixty years.

Material and component dataOther units of assessment may be useful for purposes other than that stated as the goal ofproducing Environmental Profiles. Per tonnedata with a cradle to factory gate scope maybe used for comparisons between identical products arising from different methods, orroutes to production, or different feedstocks. It is also used to build up the Profiles ofelements.

The preparation of the per tonneinventory involves tracing all raw materials back to theirextraction, describing the mode of transport and distance travelled to the processing site andthe processing activities carried out there. The inputs and outputs to these processes are

then identified. For some products, transport to a second site may need to be included aswell as further manufacturing activity.

Per tonnedata is calculated for materials and components, for example manufacture of onetonne of Portland cement. This data comprises of information about the inputs and outputsinvolved in extracting, processing or making the input materials. These, plus theenvironmental burdens of actually making the cement itself, must be added together toachieve the full picture for a tonne of cement. Per tonneinformation provides the basic"building blocks" of Environmental Profiles and hence the database. When materials areconsidered per tonnehowever, they are not a functional unit and therefore they do not havea life cycle associated with them.

For per tonne data, the boundary is defined as cradle to gate, therefore transport data toconstruction site is not included in per tonnedata.

Building element dataIn this project, Environmental Profiles for building elements will be created for a squaremetre of element. Data currently comes from the Profiles project, with supplementary dataadded where necessary Profiles are missing from the database. Two types of elementaldata may be calculated:

Installed elements

Per installed element data has a boundary of cradle to installation on site. This type of

Profile allows the user to see the overall burdens of different components in specific functionbut require the user to apply their own life time factors.

Sixty year elements

The functional units must have an anticipated lifetime and maintenance programme ifreplacement and maintenance factors are to be taken into account. Environmental Profilesfor per sixty year building elements will again be for a square metre of element, as forinstalled elements, but determined for the life of the element in a typical building of 60 years.

This data has a scope defined as cradle to site over a 60 year life. The lifetime includesconsideration of environmental aspects from gate to grave, within the limitations of currentknowledge. For this methodology, a BRE study into information available2 has resulted inthe following boundaries for cradle to grave Profiles which affect the collection of data


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between the factory gate and the end of life. These assumptions will be investigated infurther research.

Boundary assumption 1: Construction impactsThis first edition of the methodology does not include construction impacts. This is becausethe documentation of impacts arising on site is very poor and more studies are required toprovide meaningful information. The energy used in construction is estimated to be 0.5% ofthe UK national energy use which can be compared to the small but significant proportion ofannual national energy used to generate building materials for new buildings, which isestimated to be between 5 - 6%3.

Boundary assumption 2: Life Time Use: MaintenancePainting and varnishing maintenance is included, by considering the quantities of materialsused, but not the associated transport for achieving the maintenance. Cleaning and otherforms of maintenance are not included in this edition of the methodology.

Boundary assumption 3: Life Time Use: Replacement

A set of replacement factors has been calculated based on best information sourcesavailable today. This pragmatic approach is intended as the basis for the factorial service lifeprediction techniques in progress by ISO. It means that, for our 60 year office building, if anelement has a service life of only thirty years, then all the impacts are doubled. No allowanceis made for materials that will last, say, forty years and then have an "excess" service life oftwenty years from the point of replacement, over the designated sixty years. If a componentin an element is expected to fail before sixty years and can be replaced without removing therest of the element, then only the impacts associated with that particular component will bereplaced. If other components of the element, or the entire element, must be replacedbecause of the shorter lived components, then their cradle to grave impacts will be multipliedby the replacement, even if the materials removed have a potentially longer lifetime.

Boundary assumption 4: Life Time Use: Contribution to Lifetime Energy Use in aBuilding

All buildings are built to meet building regulations and achieve the minimum U-value. All theelement specifications have been chosen because they achieve this requirement. Thisallows the designer to consider the overall impact from quantities of different materialsrequired to produce different building solutions. For example, the merit of more insulativewall materials is made explicit because less insulation material is included in the preparedelement, which has been designed to meet the desired U-value.

Boundary assumption 5: DemolitionThis first edition of the methodology does not include demolition impacts or waste removalimpacts.

Boundary assumption 6: DisposalThe boundary ends at the point at which the quantity of materials sent to disposal - to landfillor incineration - is calculated. The mass of any materials known to be reused or recycled isexcluded from these waste burdens. Only the CO2 and methane emissions from incinerationand landfill can be included in the Profile at the present time. Where appropriate, thereduction in volume from incineration, but including the volumes of ash produced, is includedin the quantity of waste to landfill. If appropriate, following further research work at BRE in1999/2000, a new method of attributing per tonnewaste disposal environmental burdens willbe added to the Profile of the building element.


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3.3 Scope of data for impact assessment

The long term aim of this work is to comprehensively account for all of the key parameters ofenvironmental, economic and social impact including land use, resource consumption,energy, labour, capital, the consequential pollution to air, water and land and the resultingecotoxicity and human toxic impacts, the wastes arising for disposal and their potential forreuse and recycling. Currently, the work is restricted to environmental impacts from:

Energy, Minerals and Water consumption, Waste, Air and Water emissions.

These are generally considered to be the burdens most relevant for construction materials.Land use and biodiversity issues are important omissions from this list. These and othersmay be added into future editions as the methodology evolves. The list of issues and theirmeasurement units will need to develop and be updated progressively as knowledgeand methods improve.

3.4 Data sources

Preferred sources1. Detailed process information obtained directly from a reasonable sample of

manufacturers of UK building materials, products and components.2. Industry-generated average figures without data separately identified from individual

companies. Where industries supply data collected as part of a previous LCA study, fulldetails of the rules and conventions used in the study have been sought and the BREmethodology applied.

3. For substances and products which have a significant input to a process but for whichdata cannot be readily obtained from the suppliers, data has been obtained from existingcommercial databases (sources used are fully referenced in Annex 9).

Data qualityData in Environmental Profiles is accompanied by descriptors relating to sources andcollection methods. See Profile format, Annex 13 and 14.

BRE will endeavour to make random checks on data providers to verify the sources andestimation methods used to derive data. Ultimately, however, the database relies upon thequality of data provided by industry.


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4 INVENTORY DATA COLLECTION

This chapter contains the guidelines for compiling the inventory. To compile the inventory,the boundaries of the process must be defined and then data about inputs and outputs to theprocess collected.

4.1 Defining the process

For all data provided for the UK National database, a comprehensive process treeshould be provided including any major transportation stages with a clearly markedsystem boundary to indicate the included from the excluded processes. The resultinginventory should balance in mass terms and in energy terms(taking due account of anyphase change processes like evaporation in order to be thermodynamically correct. Theonly exception is nuclear processes where mass and energy must collectively balance). Inother words, the total energy or mass flowing into the system boundary must be accountedfor with an equivalent mass or energy flow out of the system boundary. Figure 1 provides a

standard format for creating a process tree.

Figure 1Generic Process Tree

Annex 10 gives a standard questionnaire suitable for data collection when creatingEnvironmental Profiles.

The inventory comprises the following items:

Inputs: MaterialsTransport FuelProcess FuelWater

Outputs: Emissions to airDischarge to waterEmissions to land

InputsPROCESS

1

tr

tr

OUTPUTSInputs

PROCESS

3(ETC)

OUTPUTS

INCLUDINGFINALPRODUCT

OUTPUTS

PROCESS2Inputs

tr Transport


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Guidelines for the collection of data for each inventory item are given below. Details of howthe data should then be manipulated to provide the per tonneinventory are given in section5, "Inventory Data Handling"

4.2 Outputs

Information on all outputs from the process, including any co-products, by-products andmaterials sent for re-cycling/re-use/re-processing should be provided. This includes anyoutput which is sold, recycled or re-used in any way, such as waste oil, packaging sent forreuse and by-products such as slag from iron production.

Where data on inputs or emissions have been given which apply to more than the productbeing considered for the Profiles project, e.g. total factory output or product and co-product,then effort should be made to identify the emissions associated with the product underconsideration. If this is not possible, the methodology requires that the burdens ofproduction are allocated to the products according to economic value. Relative values of the

product to all relevant outputs should therefore be provided where necessary. Information onthe allocation procedure is given in greater detail in Chapter 5.

4.3 Inputs

Inputs to the process that are measured in the inventory include the materials associatedwith the manufacture of a product and also the consumption of fuel and water.

a) MaterialsThe inventory process gathers all the inputs to the plant that are associated with a product,including product ingredients, packaging materials and consumable items.

Criteria for significance

For many processes, a large number of substances and materials are used in very smallquantities and it would be unrealistic to gather data on all of these. However, it is importantthat significant environmental effects are not omitted by ignoring these low masssubstances. Sensitivity analysis may later reveal that these substances do not significantlyaffect the overall result but it is important that data is provided to enable this conclusion to bedrawn. To achieve this, the following conventions are applied:

Data should be included for 98% of all inputs by mass.

Data should be included on all materials with a mass greater than 2% of the output

from the process. Information should also be provided for materials which contribute lessthan 2% by mass, but possibly have:

significant effects in their extraction, their use or disposal, or

are highly toxic, or

classed as hazardous waste.

Materials with a low mass input but which contribute a significant proportion of the energyinput should also be included. For example, the adhesives which are used in themanufacture of window frames are integral to the product and should be included eventhough they account for less than 2% of the output (by mass).


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b) Transport of materials to the plantData on transport to site should be collected for all the input materials, including fuelsdelivered to the site (excluding electricity and pipelines). This may be achieved by more thanone mode of transport. These should be listed, including size and type, along with theaverage distance travelled, the number of deliveries per year, average delivery weight, andwhat is carried on the return journey (or percentage part load). Where more than onesupplier is used, estimates of the tonnage from each should be made and informationprovided about each one.

c) Direct consumption of fuelThe inventory requires the total quantity of each fuel used by the plant for one year, includingfuels used for heating and lighting in buildings. To ensure all fuels are included, the purposefor using each fuel should be recorded. Space heating and office fuel use should beincluded. Only vehicle fuels used for transport on site should be included. Fuel from off sitetransport is calculated separately.

If electricity is not purchased from the national supply, its source should be given.

The calorific value of fuels such as wood residues, secondary liquid fuels (SLF) and landfillgas should be included. Inherent fuels such as fletton clay and fuels obtained from recoveryprocesses such as blast furnace gas or waste wood should also be included. Informationabout the transport mode and distances to deliver fuels to site should be provided in b)"Transport of materials to plant."

d) Water useThe inventory must include the water brought into the plant each year in terms of the totalquantity used and, where possible, the quantity per tonneof product. It is useful todistinguish water purchased from water company and private supplies of surface and groundwater. It is also important to distinguish water use from water abstracted to ensure anyrecycling of water is recognised within the Profile. This will mean that the recycled water is

not given a burden for extraction every time it is used.

e) Capital equipmentAlthough it is a form of indirect energy input into the process, the contribution of capitalequipment is not normally considered in LCA and it is not included here. Maintenance ofequipment, including use of lubricants, is also not included in the LCA. Frequently"consumed" items such as saw blades and sanding paper and mould oil are included in theinventory.

4.4 Emissions and discharges

The inventory includes a record of the quantities of each substance of interest associatedwith the manufacture of one tonne of the material or product. Emissions from industriesconsidered in this methodology include those resulting directly from processes and thoseresulting from fuel use.

Some emissions are measured by the industry, others may be calculated in the preparationof the inventory from standardised conversion factors (see the next section). Others mayderive from assumptions made about the process, e.g. the CO2 produced by the heating ofcarbon containing minerals such as limestone, from theory based on chemical composition.If emissions are measured and calculated on an annual basis for Integrated Pollution Control(IPC) authorisation, then these values may be used and allocated appropriately. If suchvalues are not available, then the results of other measurements should be supplied.Estimates should be accompanied by a clear explanation of their origin.


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Emissions from a plant may be from more than one product. If emissions are known to arisefrom specific products, by causal relationship, then these should be provided together with adescription of the method used to identify the emissions. If this is not possible, emissions forthe whole plant should be provided. Accidental emissions are not included. Negativeemissions of substances, e.g. sequestration of CO2 by growing plants or re-carbonation oflime should be included (see sections 6.5 and 6.6.).

a) Emissions to AirIn theory, it is only necessary to record emissions to air resulting directly from the processand as a default, emissions arising from fuel usage will be calculated separately, usingstandard emission factors. It is important to note however, that emissions of NOx, CO andVOCs are dependent on the efficiency of combustion and emission control techniques mayhave been fitted for SOx and PM10 emissions. Therefore, if these emissions are measured ata plant, these measurements should be provided to give a more accurate inventory.

b) Discharges to WaterInventory information is collected on the total quantity of water discharged to both the sewer

and to surface water (fresh and marine) each year. Both average values and ranges shouldbe provided for the concentrations of BOD, COD and suspended solids discharged to bothsewer and surface water, as well as the sampling procedure used. Other measuredemissions should be provided.

c) Emissions to landWaste is defined in this project as a product of a manufacturing or processing stage whichthe manufacturer considers has no value and no purpose in that part of the process. Itincludes particulates collected from gas streams and de-watered sludge and solids fromtreated effluents. It is important to identify those materials that manufacturers consider to bewaste separately to those which they treat as co-products and by-products such as slag fromiron production and bark from wood processing.

Information is required on the categories, quantities and final destination of both controlledwastes and those which are not controlled, e.g. mine overburden waste from mining andextraction operations and furnace slag, ash, bark and sawdust which is not reused or sold onfrom processing operations. Information on controlled waste can be collected from 'Duty ofCare' transfer notes.

It is important toprovide as much detailed information as possible about the content and thedestination of waste. Information should be provided on the quantities produced per year ofthe three main categories - Controlled Commercial, Controlled Industrial, Controlled Special- as well as a list of the main materials in the description of the wastes produced. For rawmaterials extraction, there is an additional category, mine and quarry waste, which should be

used. For special waste, the National Waste Classification Codes and Hazard PropertyCodes 4 should be given where possible. Data should be provided on the route(s) fordisposal which are in current use. The potentialrecyclability of a product is not consideredat the data collection stage - see Chapter 5.


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5 INVENTORY DATA HANDLING:- ALLOCATION

5.1 Explanation of allocation rules

Allocation for Linked Processes

Figure 2

Al loca t i on p r i nc ip les

Process P

W H Y T H E P R O C E S S E X I S T S

Ca p i t a l I n v e s t m e n t C

P r o d u c t 1 w o r t h v 1 . t 1

Inputs

Wastes

Recyc led was te v3 .t 3

t1

P r o d u c t 2 w o r t h v 2 . t 2

t2

R e c y c l e d w a s t e 0 . t4

R E T U R N v.t

Al locateP.v

1.t

1/ v. t

t3

t4

P.v2 .t 2/ v. t

P.v3 .t 3/ v. t

P.0.t 1 / v. t

A unit process is supplied with inputs and generates output products, by-products andrecyclable wastes all of which might find application in further processes, together withwastes which must be disposed of and pollution which must be carried by the environment.An allocation rule is needed to assign the burdens appropriately between the co-productsand reusable or recyclable wastes. ISO 14040 recommends a series of priorities forallocation as follows:

Avoid, by division of a single process into sub-processesBy system expansion to avoid allocation.By physical property (e.g. mass or calorific value)By product value

BRE has used the following, in order of preference:

Avoid, by division of a single process into sub-processesBy physical propertyBy product value

BRE recognises the desirability of avoiding allocation and therefore separates processesinto sub-processes to avoid allocation wherever possible. To achieve the goal of the BREstudy it is necessary to have a standard method of LCA for all materials. To achieve acommon approach to allocation, wherever physical data is available to divide between twoprocesses, then this information will be used to allocate between multi-product processes.However, where physical data is not known there is a requirement for a further method that

can be applied to all materials. It is not possible to use system expansion for all materialsbecause alternative products must be available for which the by products from a system can


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be substituted and this does not apply to all materials. BRE consider economic value to bean effective and appropriate method of allocation which can be applied consistently to allmaterials where avoidance or allocation by physical property cannot be applied.

Where two product streams come from a single process (or inseparable parallelprocesses), and physical data is not available, BRE will allocate burdens according tothe proportion of product revenue earned from the two product streams. This rule isconsidered to be justified because the producer has invested in setting up the process(es)and expects to earn revenues from the product streams. Accordingly the value of theproduct streams is considered the most appropriate basis for allocation since it assigns theburdens in proportion to the product streams contribution to profits arising from theprocess(es). See Figure 2. The price that is used to make the allocation is the average threeyear market price of the relevant materials.

If process 1 and 2 are sequential processes, with all product 1 used as an input for product2, all of the inputs, wastes and pollution for both processes can be added together, product 1can be ignored and all of the burdens can be assigned to product 2. This is called expanding

the system boundary so that the two processes can be treated like a single process. Forsequential processes, it is acceptable to expand the system boundary to account forthem collectively. See Figure 3.

Figure 3

Sequential processes

Process

1Input 1 Process 2Process 2

Expand boundary so all Inputs for Product 2 = Input 1 and Input 2

Input2

Product 2Product 1

If only part of the output from product 1 goes into process 2 then only the appropriate

proportion by mass of the burdens going into process 2 should be passed on toprocess 2 and assigned to the production of product 2. The remainder of theseburdens should remain with the balance of product 1.

Figure 4 shows that if process 1 and 2 are operated in parallel in a single productionfacility, they should as far as possible be treated as separate processes and theinputs, outputs, wastes and pollution calculated separately for the two processes. Inpractice, however, it may often not be possible to distinguish the processes, especiallywhere they share common feedstock or fuel sources that are not separately metered. Incases where the data cannot be separated for the two processes, the systemboundary can be expanded to encompass both processes, and allocation by productstream value will be used to allocate burdens between the products.


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Figure 4

Two processes in parallel

Process 1 Product 1 worth

v1.t1Inputs

t1

Product 2 worthv

2.t

2

t2Process 2

1. Try to separate the processes and determine their profiles.2. ONLY IF 1 IS NOT POSSIBLE combine the profiles for the processes and use allocationby value.

Allocate

P.v1.t1 / v.t

P.v2.t2/ v.t

Recycling and allocationIn assessing recycling, three issues need to be addressed: -

1. To avoid double or undercounting, the method mustEITHER distinguish recycled, reused and primary products to todays decision takerOR combine recycled, reused and primary over a materials cradle to grave multi-life-cycle

(which may comprise a succession of different products).

2. How to allocate impacts between recycled, reused and primary product from processscrap, home scrap or end use scrap or wastes.

3. Whether to reward a product today for its recyclability over very long building timescales(perhaps over hundreds of years for several recycles) OR focus upon only todaysdecision-making and current recycling and recycled content.

BRE have chosen to resolve these issues by adopting the following rules in theEnvironmental Profiles methodology.

Distinguishing recycled, reused and primary products

Of the two approaches described in 1) above, distinguishing recycled, reused andprimary products to todays decision taker is the preferred approach by BRE in that itdistinguishes the recycled and reused products in the market place and allows usersto show a preference for (and presumably pay a premium price for) the lowerenvironmental impact product. However, it is recognised that the second approach isuseful for comparing products made from comprehensively recycled materials such asmetals with those made from inherently non-recyclable materials. Hence, BRE accept thatfor particular comparisons, it may be appropriate to use the second method, but where allconstruction products are being assessed to a common methodology, as for the

Environmental Profiles, the first method is preferred.


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Allocation for recycling and reuse

Expanding the system boundary is an appropriate way to account for closed looprecycling in sequential processes. If material is recycled between sequential processstages (as in Figure 5 - closed loop recycling or recycling into the same process), thenexpanding the system boundary to incorporate the recycling processes is considered thebest way of accounting for this.

Figure 5

R e c y c l i n g i n t o s a m e p r o c e s s

P r o c e s s Ptp . v p U s e

P r i m a r y p r o d u c t i o n =

P ( 1 - y ( v r/ v p ) ) + y (v r/ vp ) ) = P

^ a d d e d f r o m r e c y c l e d

^ d e d u c t e d f r o m p r i m a r y f o r r e c y c l e d .

y i e l d y

t r .v r

However, if (as in Figure 6) material is taken out of the system boundary, then therecycled material has to be treated separately. Where scrap arises from postconsumer use (old scrap), it is not considered appropriate to expand the systemboundary to take account of scrap arising. To do so requires a comprehensive scenario

of use, repair, maintenance, dereliction and reuse and recycling to be assumed over verylong timescales. It would be difficult to be confident that all parties in the chain of decisionmaking would consistently comply with the assumptions made, especially over such longperiods. A similar approach to Figure 6 is therefore taken as if a separate recycling processis undertaken to recycle material, rather than adding this material as an input to the primaryproduction (Figure 7).

Figure 6

Recyc l ing in to ano ther use

P r o c e s s

PInputs

tp. v p U s e 1 R e cy c l e

R

P r i m a r y p r o d u c t i o n=P (1 - ( tr .v r) /( tp. vp ) ) o r

P (1 -y (v r/v p ) )

^deduc ted f rompr i ma ry fo r recyc l ed .

y ie ld y

t r. vr

R ecyc l ed p roduc t i on =

R + P ( ( y . v r/v p )^sha re o f p r i ma ry i n 1s t recyc l e

I f the recyc l ed ma te r i a l has nova l ue , then none o f the i mpac ts

f rom the f i r s t p rocess a re

at t r ibu tab le to the recyc led product .

U s e 2


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Figure 7

Separate recycling process

Process PInputstp .vp Use Recycle R

R1, R

2..R

n

Primary production =

P(1-(tr.v r)/(tp. vp)) or

P(1-y(v r/v p ))

^deducted from

primary for recycled.yield y

t r.vr

Recycled production =

R(1- (y.v r/v p)n) + P((y.v r/v p)

n - (y.vr/v p)(n+1))

^share of primary in n recycles

^share of recycled in future recycles

For infinite numbers of recycles = R

Wastes or recycled products from open loop recycling will be allocated burdensbased on the residual value of the waste stream compared to the value of the processproduct (and waste) streams.The same approach can be applied to allocating burdens to wastes or recycled productsfrom open loop recycling as between products and co-products based on the value of thewaste stream. This approach allocates a proportion of the impacts from production to the

wastes that arise, in proportion to the residual value of those wastes compared to the valueof the original products (and wastes). In this way, the burdens assigned to the product areeffectively assigned to the use of the product over its life. At the end of the useful life of theproduct, it becomes a redundant liability unless it retains some inherent value. The burdensassigned to a valueless waste stream would be zero, but if a product retains some valuethen it ought to carry some of the burdens of its production onto the recycling or reusephases.

The proportion of burdens carried by a waste into the future are then subtracted fromthe burdens assigned to the primary product. Mathematically, this is completelyconsistent with the closed loop recycling principles and expanding the system boundarybecause any burdens retained by closed loop recycled product (which are subtracted from

the primary production) are added again when the scrap returns to the process. The methodalso works for waste recycled into new construction materials production. If the waste has amarket value, then it should attract a proportion of the burdens from the process. These arein turn subtracted from the burdens for producing the other products. This approach appearsto give very sensible results. Producers that consume PFA from power stations would attractless than 0.02% of the burdens from electricity production because PFA is of such smallvalue compared to the electricity as the main product . The PFA that is sold receives aproportion of the impacts of electricity generation, including a proportion of the burden ofPFA sent to landfill, according to its market value.

Hence, all of the materials arising from a process that have a financial value attract aproportion of the burdens associated with the production processes. This approach is

entirely consistent, avoids double or undercounting and assigns burdens in proportion to thevalue paid and therefore perceived by society for the materials and products.


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Figure 8 demonstrates an important feature of the recycling methodology. "Home scrap" isscrap which arises from further fabrication processes but is not "post consumer" scrap,otherwise known as "old scrap". In this methodology, home scrap is considered to arisewithin the expanded boundary of the production process. Only old scrap is considered tohave left the system and is thus available to reduce the impacts of the production processthrough recycling.

Figure 8

Recycling home and new scrap

Process

P1Inputs

Process

P2

Recycle R

Use

For home scrap and for new scrap, expand the system boundary.Only old scrap should attract any recycling discount from the production

processes.

home scrap--> new scrap--> old scrap-->

3 Recyclability or Recycled ContentBRE will base its consideration of the recycling or reuse properties of a material or producton current recycling achievement. The rationale for this approach is as follows:Traditionally, we have thought about recycling as something that happens at the end of thelife of a material or product. If we take account of recyclability, we must rely on decisiontakers in the future responding to our predictions and on markets wanting to use thesematerials into the future. For many high value materials, there is a strong historic precedentfor justifying this assumption. However, for many newer materials e.g. plastics, it has beendifficult to establish and sustain markets for recycled product and for some materials orproducts there are questions about degrading quality and performance. In addition, many

materials or products are recycled into different materials and products for later uses. Finally,because buildings last for so long, it is impossible to imagine what innovations in recyclingtechniques, in building products which use recycled material and the changes in marketvalues for different scrap materials and wastes. Hence, there is very large uncertainty aboutthe real scenarios for recyclability.

An alternative view of recycling is to consider it as the first stage in the production of arecycled product and starts right now with the effective mining of raw material from wastestreams and results in a product that can be distinguished in todays market place for itsrecycled content. This view of recycling is entirely contemporary and doesnt rely on asuccession of decision takers to deliver consistent action for possibly hundreds of years intothe future. The performance of todays products can be reflected to todays decision taker

acting in known market places with known recyclability performance. This approach also


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has advantages in that it can consistently use the same allocation rules based on the valueof product or waste streams without the complications of discounting for future values.

BRE will use recycledcontent as the basis for its methodology together withconsistent allocation rules based on the value of current waste streams. In mostcases, recycled material will attract no burdens from earlier phases of production.Recyclability cannot be considered consistently with this approach.

5.2 Summary of rules for allocation

Allocation for products and co-products Allocation rules are needed to assign the burdens appropriately between products, co-

products and reusable or recyclable wastes from a process.

Where two product streams come from a single process (or inseparable parallelprocesses), burdens are allocated according to the proportion of product revenue earnedfrom the two product streams.

For sequential processes, it is acceptable to expand the system boundary to account forthem collectively.

If only part of the output from a product 1 goes into a process 2 then only the appropriateproportion by mass of the burdens going into process 2 should be passed on to process2 and assigned to the production of product 2. The remainder of these burdens shouldremain with the balance of product 1.

If two processes are operated in parallel in a single production facility, they should as faras possible be treated as separate processes and the inputs, outputs, wastes andpollution calculated separately for the two processes.

In cases where the data cannot be separated for the two processes, the systemboundary can be expanded to encompass both processes, and allocation by productstream value will be used to allocate burdens between the products. This is the price atwhich the product is sold by the manufacturer and should be based on 3 year averageprices.

Allocation for recycling and reuse

Wastes or recycled products from open loop recycling are allocated burdens based onthe residual value of the waste stream compared to the value of the process product(and waste) streams.

The proportion of burdens carried by a waste into the future are then subtracted from theburdens assigned to the primary product.

Hence, all of the materials arising from a process that have a financial value attract aproportion of the burdens associated with the production processes.

Where repeated recycling occurs, for example for metals, the primary burden carriedforward through each recycling decreases until after an infinite number of recycles itreaches zero.


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6 FURTHER INVENTORY DATA HANDLING

6.1 Rules and conventions

Raw inventory data collected from manufacturers must be modified to produce standard datain an Environmental Profile. The process is as follows:

Data is converted to standard units, e.g. MJ for energy, Tonnes for inputs.

Conversion figures for transport, into emissions to air and fuel consumption will havebeen applied

Conversion figures for fuel will have been applied into emissions

Additional figures will have been incorporated to fill in missing data from plants (with theapproval of data providers) and to expand the data to include later stages in the life cycleof the product.

Allocation procedures will have been applied to obtain burdens for the main products andby-products etc.

Transport figures will be calculated to provide data on product delivery to site. Where appropriate, lifetime data on maintenance and replacement will be added, at first

using readily available information and professional rules of thumb. Additional informationwill be acquired from the further BRE study of life cycle impacts.

The data will have been normalised to per tonnelevels.

Generic UK figures will be calculated where individual site data have been provided.

The basic procedure to produce a per tonnedatasheet is:

Check data-using mass balance, process diagrams.

Process data to standard units [ given in Annex 6].

Apply Input and Output inventory handling procedures.

The checklist in Table 1 describes the inventory data handling procedures for convertingeach inventory item to per tonnedata items. This is followed by a more detailed explanationof how generic Profiles are produced.

6.2 Creating the generic Profile

Where data is available from a number of sites for a product group, the generic product forthe UK is arrived at by applying an average based on the proportional contribution of eachsite by mass to the total UK mix of the sites supplied, where known. In a small number of

cases the generic figure is derived from one site.

It has already been noted that upstream data, i.e. data about inputs into a process, has beenobtained from within the Profiles project where possible, but that important data gaps inmanufacturing data sets that we cannot fill from partners will be filled using data from bestavailable sources. These are primarily from IVAM, Pr, BUWAL, ETH and SBI data, listed inAnnex 9. Further data may also be found from other sources, using the most recent andgeographically applicable data as a preference. Wherever possible, all additional data isallocated according to the principles outlined in this document. Considerable effort has beenmade to check and compare the accuracy of additional data to UK production and othersources of data. Where possible, the UK fuel mix for electricity generation, together withassociated emissions have been applied to the additional data. A lack of transparency in the

inventory may prevent this.


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Table 1: Inventory data handling checklist

OUTPUTS

Output materials:1) Define Principal product for per tonneDatasheet

2) Include all other Products and By products3) Include all materials sent to recycling4) Divide outputs by product output in tonnes to obtain per tonnedata.

5) Obtain relative values of all OutputsUse relative values to allocate

--------------------------------------------------------------------------------------------------------------------------INPUTS

Transport:1) Check total inputs, loads, vehicle sizes and number of deliveries correspond.

2) Allocate to principal product.

3) Apply method for fuel consumption and emissions to air (see Annex 8).4) Divide by principal product output in tonnes to obtain per tonneData.

Fuel:

1) Convert quantities to MJ2) Allocate to principal product3) Divide by principal product output to obtain per tonnedata.

4) Use standard conversion factors to obtain Primary Energy value.5) Use standard conversion figures to obtain Fossil Fuel Depletion value.--------------------------------------------------------------------------------------------------------------------------------------

Water Use, Supply and Discharge:

1) Convert quantities to M3

2) Divide by product output to give per tonnedata. Note: use of recycled water is accounted for by

considering total water use and total output.--------------------------------------------------------------------------------------------------------------------------------------

EMISSIONS

Emissions to Water

1) Cross check with Chemical Release Inventory2) If concentration is given, multiply by water discharge to obtain mass3) Allocate to principal product.

4) Divide by principal output in tonnes to give per tonnedata--------------------------------------------------------------------------------------------------------------------------------------

Emissions to Air1) Calculate emission for each fuel using Standard Conversion factors.

2) Ensure process emissions are included.3) If chimney emissions have been given, check which fuels these apply to and ensure that there is

no discrepancy between calculated emissions and given emissions (taking account of efficiencies

and attenuation, e.g. FGDS) and substitute chimney emissions.4) Cross check with Chemical Release Inventory5) Allocate to principal product

6) Divide by product output in tonnes to obtain per tonnedata7) Aggregate data together with Emissions to Air arising from Transport.

-------------------------------------------------------------------------------------------------------------------------- Emissions to Land

1) Includes Solid and Liquid emissions to Landfill and Incinerators (and Mine and Quarry waste etc.)2) If incinerated on-site, give details of incineration emissions and any heat recovery.3) Allocate to principal products

4) Divide by product output to obtain Per tonnedata.


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6.3 Transport

Transport to factory gateThe environmental burdens arising from the transport of raw materials and other goods tomanufacturing sites are included within the unit process for that material or component. Forexample, the transport of clay to a brick manufacturing plant, or the transport of processedtimber to a window manufacturer are included. Transport fuel data is calculated using themix of transport modes used by an industry and the average loads and sizes of vehicles.The method incorporates mode, distance, vehicle size and return loads. See Annex 8 fordetails of calculating Road, Rail and Shipping fuel consumption.

Transport to siteStandard values will be assumed for each material or component. In life cycle software tools,it should be possible to change this "default" to take account of local conditions.

In the absence of better data, the standard values for transport to the construction site fromthe factory gate is based on "average" haulage journeys for each material in the UK, as

collated by DETR. It is assumed that there is an average loaded journey from the finalfabricator to the site and that the return journey is empty and of average length. Using fuelconsumption figures for different types of lorry, and the total distance travelled, the fuel usedand associated emissions can be calculated. The loaded distance travelled in order totransport 1 tonne of product gives tonnes kilometres. Transport to site is not associated withper tonnefigures. It is incorporated into the figures for installed and sixty year life elements.

6.4 Fuel

Primary and delivered energyFor any manufacturing, transportation or heating process, energy is supplied from a number

of different sources used as fuels, including waste materials. The data collected on thequantities of this energy used in a process provides a value for the delivered energy(called process energy in ISO). However, all fuels suffer losses and fuel expenditure in theirextraction, their refining, and their supply and transmission, and require energy expenditureto extract, refine and distribute them. So that the full impacts of manufacture and processingcan be assessed, the quantities of each form of delivered energy and fuel must be adjustedto take account of these losses. Values for delivered energy corrected to take account of theproduction and delivery losses and expenditure are known as primary energy. The factorswhich will be used by BRE for conversion of delivered energy values to primary energy aregiven in Annex 4. Values are also given for the current fuel mix used in the UK for thegeneration of electricity, Annex 1 and 2.

Fuels of no economic value, e.g. oil within fireclay and "town ash" are considered to have aprimary energy value because the energy to win these fuels is considered in the inventorywhen they are used. Their transport to the place of consumption, i.e. factory, contributes tothe energy consumption of the final product but is not included in the "primary energy" of thefuel, as for standard fuels.

Primary energy is provided as a data item in the Inventory Environmental Profile. Theprimary energy is equivalent to the "embodied energy" figure for a material orelement. The environmental impact of energy use arises from depletion of available fuelresources, or emissions from burning them. The emissions to air do not derive solely fromthe use of fuel, but fuel combustion is a major contributing factor. Energy use in thecharacterised Profile is also represented by Fossil Fuel Depletion. Fossil fuel depletion ismeasured in Tonnes of Oil equivalent (toe), which is an amount of energy equal to 41.83 GJ.It is calculated by converting the primary amount of fossil fuels, such as coal, oil and gas,


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used to provide the delivered energy into toe. Further details of this characterisation factorare given in section 7 and Annex 11.

Calculation of energy-related emissionsCarbon dioxide, sulphur oxides and nitrogen oxides are produced by each type of deliveredenergy, e.g. electricity, coal, gas, before they are delivered to the process and, apart fromelectricity, during their combustion. BRE has calculated the emission factors for these fuelsper MJ of delivered energy. These are given in Annex 3. Combustion emissions from fuelsare calculated using UK emission rates supplied by NATCEN. Where factory chimneyemissions of specific gases are supplied, they are compared with the theoretical combustionemission values from the relevant fuels and substituted, with substantiation required for anydiscrepancies in the values. This process allows manufacturers using techniques thatminimise emissions, such as SO2 to benefit from their improved performance. Upstreamemissions from the extraction, processing and distribution of fuels have been calculated fromDUKES6 and the UK Greenhouse Gas Emissions Inventory7. Where factory chimneyemissions of specific gases have been supplied and substituted for theoretical combustionemissions (see section 4.4), the upstream emissions will still be added to the Profile.

Feedstock energyFeedstock energy is defined by ISO8as the combustion heat of raw material inputs, whichare not used as an energy source. BRE includes the feedstock energy of fossil fuels in itsprimary energy calculations but does not include feedstock energy of non-economic fuels,e.g. timber. Tillman9 has discussed the problems of accounting for inherent and feedstockenergy to avoid double counting.

Embodied energy and embodied carbon dioxideThere is no definition for embodied energy in the ISO Standards. The generally accepteddefinition is that produced by International Federation of Institutes of Advanced Studies(IFIAS) at a summer school on energy analysis in 1974: the total primary energy that has to

be sequestered from a stock within the earth in order to produce a product or service10

.

The energy used in the extraction and processing of a material is sometimes defined as itsinitialembodied energy to distinguish it from the energy used at other stages in the materiallife cycle.

Although values for initial embodied energy may be calculated on a mass basis as part ofthe unit process data, like other effects they must only be used within a system to makecomparisons of alternative functional units, i.e. designs of particular components, elementsor whole buildings with the same function. Once an element or building has been defined,then the whole life of the materials and products can be included in the embodied energyvalue - the energy used to extract, transport and process raw materials, to convert them into

manufactured products and components, to transport them to the construction site andincorporate them into a building.

The definition in this methodology to be used for the embodied energy of a material over thelife of a building is:

The total primary energy that has to be sequestered from a stock within the earth in order toproduce, transport, maintain and dispose of the materials within a specified product,component, element or building.

Many government initiatives are in place to reduce the energy use and CO2 emissions ofindustry. Carbon dioxide, or "embodied carbon dioxide" data needs to be considered asseparate value because, although a major proportion is the result of the use of fuels of all


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kinds, some processes in building material production release CO2 from carbonaceousmaterials.

Calculation of valuesThe definition of stock within the earth requires interpretation in order to determine whichinput data should be aggregated to calculate a single value for embodied energy.

The interpretation adopted by IFIAS when concerns were first raised about the use of fossilfuels required that only non-renewable hydrocarbons (and then confined to those which areextracted as economic fuels) are included in the estimate. Fuel and energy use is convertedfrom delivered to primary terms and then only the energy obtained from fossil fuels, and notthat produced from renewable sources, is included in the aggregated estimate.

The term embodied energy is effectively an accounting analysis and in no way refers to thephysical or chemical composition of the materials, and is not meant to imply that there is aninherent energy content that can be recovered. In the calculation of embodied energy orfossil fuel depletion, the energy of feedstocks is not included in the calculation apart from

that obtained from fossil hydrocarbons which are extracted as economic fuels e.g. oils. Thisview is shared by the authors of the guidelines for the Athena project11,12. The impacts of theuse of organic materials as feedstock are addressed within the inventory.

In this methodology, primary energy will be evaluated as the sum of:

1. the gross calorific value of economic fuels extracted from reservoirs within the UK orimported in crude form into the UK

2. the thermal energy generated in nuclear power stations calculated as the grosselectricity generated divided by the average thermal efficiency of nuclear stations

3. refined fuels and electricity imported into the UK, counted as having the same embodiedenergy per unit of fuel as those generated from primary stocks within the UK.

Non economic fuelsFuels defined as non economic fuels do not contribute to fossil fuel depletion. However, theydo contribute to the emission of CO2 and other combustion products. Precise emissionfactors for all fuels should be obtained and added to an Environmental Profile. Where this isnot possible, emission data from a similar material should be used. Renewable fuels areconsidered to be CO2 neutral where the emission of CO2 occurs less than 100 years fromthe sequestration of the CO2. See section 4.5 below. CO2 emissions from non-renewablefuels used in processing and transporting renewables are included where appropriate.

6.5 Carbon cycle

Carbon sequestration is considered over a timescale of 100 years (as are the impacts ofCO2 emissions in relation to their global warming potential). CO2 emissions arising fromCarbon sequestered after this date will not be considered, nor the carbon sequestrationassociated with the emission.

One common factor for timber-based fuels (wood, bark, chips, sawdust, shavings etc) is thatthe CO2 released when they are burnt has been absorbed (sequestered) from theatmosphere and stored in the tree during growth. Had it not been released when the woodwas used for energy production, it would have been released during the biologicalbreakdown of the wood that would have taken place instead. The CO2 emissions from timberthat is burnt are therefore assumed to be zero, since the use of wood as fuel does not


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contribute to the build up of CO2 in the atmosphere. For forestry, account is taken of theemissions of methane arising from pruning, trimming, site clearance and felling. Where siteclearance involves the release of CO2 from, e.g. peat bogs, sequestered more than 100years ago, this is also considered.

Timber cannot be assumed to be CO2 neutral according to the assumption above becausenot all timber is burnt at the end of its life. Based on current BRE statistics, BRE assumesthat 80% of timber from buildings goes to landfill, whilst 15% is reclaimed and 5% isincinerated. Of the timber that goes to landfill, it may be estimated from Municipal wastefigures13 that half of the timber decomposes over one hundred years and the other halfremains inert. Of the decomposed timber, it is assumed methane and carbon will beproduced in roughly equal quantities, with some of the methane being burnt and convertedto CO2.

6.6 Adjusting carbon dioxide emissions for re-carbonation.

In the case of cement and lime, CO2 will be "carbonised" back into the mortar/cement aftermanufacture. Again, this carbonation is considered over a 100 year timescale for the productas constructed.

Lime carbonation is counted within the per tonneproduct data because the assimilation ofCO2 is a function of how the product behaves and happens in a short timescale. The factorfor carbonation will therefore be used at 100%, i.e. 0.785 t/tonne, considered as a propertyof one tonne of lime at the factory gate. Further explanation is provided in Annex 7

For blocks, whilst the rate of carbonation is slower than for free lime, the rate of carbonationis sufficiently fast for it to be assumed that carbonation will also take place at 100% for theamount of free lime in one tonne of product and 65% of the cement content at the factory

gate.

For cement, carbonation is an unwelcome activity and one which happens slowly over thelife of the building. In this methodology, carbonation will only be considered for the wholebuilding element, because carbonation is greatest for the first 5 cm of concrete exposed tothe atmosphere. Thus the carbonation will be calculated for 5cm depth multiplied by thesurface area exposed for each concrete element over 60 years. Further explanation isprovided in Annex 7

6.7 Emissions

Emissions to airData for emissions to air derived from fuel use are based on the NATCEN conversion factorsprovided in Annex 3. These are added to emission figures from the process. Emissions to airare converted to kg of emission per tonneof product produced and presented individually.As much detail is retained as possible. For example, if emissions are known for"formaldehyde" and "VOCs" from a process, this is how they should be entered, even thoughformaldehyde is a VOC.

Emissions to landEmissions to land are the solid wastes derived from the process. These are currentlymeasured only in terms of the tonnes of waste produced and greenhouse gases emittedfrom landfill and incineration. This position will be revised following further examination intothe impacts associated with the disposal of different materials in landfill and incinerators.


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Waste may currently be entered onto the inventory Profiles as a detailed description of thequantities of different waste types emitted.

Emissions to waterData on emissions to water requested on the questionnaire receive no further manipulationfor the creation of the Profile. Data is entered onto the inventory Profile according to thedetail provided in the questionnaire. For the characterised Profile, data is incorporated intothe eutrophication and ecotoxicity to water categories.

6.8 Imports

The inputs and outputs attributed to imports of materials and products should, whereverpossible, be based upon analyses appropriate to the country of origin and will include theenergy of transportation. Where data for the country of origin are not available, the input andoutput data should be based upon the closest domestically produced product with anaddition made for the transportation from the country of origin.

The exception to this is for imported refined fuels and electricity; these are attributed thesame environmental burdens as those generated from primary sources within the UK.

Delivered energy values (in GJ/tonne) represent the calorific value for the gross deliveredenergy of the appropriate fuel. Gross calorific values include the quantity of heat necessaryto evaporate water present in the fuel during the combustion process. This is also termedthe higher heating value (HHV). The UK energy statistics on which BRE bases itscalculations are presented gross whereas international statistics are presented net or interms of the lower heating value; if these values are used they will be adjusted using theconversion factors given in Annex 5.


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7 IMPACT ASSESSMENT

7.1 Presentation of results: the Environmental Profiles

Environmental Profile of inventory dataThe standard format for this Profile is shown in Annex 13. It may be applied to per tonne,installed elements and sixty year life elements. This is the data that has been treatedaccording to the inventory data handling procedure in chapters 5 and 6. No further impactassessment is carried out. Inventory Profiles are useful to see, transparently, the data thatrelates to the production of a product or building element. They are not very useful forunderstanding the environmental consequences of the product or element because noinformation is provided on how the inputs and emissions relate to environmental impacts.

Environmental Profile of characterised and normalised impact data.The standard format for this Profile is shown in Annex 14. Characterisation andnormalisation are important steps towards increasing the understanding of the impacts from

a product or element. They allow the user to see the contribution towards each impactcategory and relate this to the impacts of a person over one year. This stops short of a finalevaluation of the importance of each of the different impact categories, where weightingfactors would be applied.

7.2 The impact assessment process

All units of measurement must be recognised as proxies for both the activity that causes theimpacts and for the effects of an impact. In assessing environmental impacts, parametersinteract and there is no point at which cause starts and effects finish. Every effect becomesthe cause of additional impacts. Hence, the aim is to comprehensively account for all of the

burdens and impacts arising but avoid omissions or double counting. Many different impactassessment methodologies have been developed and are available for use. Much of theBRE methodology is based upon the work of Heijungs et alat CML, the University of Leidenin the Netherlands. This team have a significant input to the work of the Society forEcological Toxicology and Chemistry (SETAC), a leading authority in life cycle analysisdevelopment.

The three stages of impact assessment, classification, characterisation and normalisation,have been undertaken, as follows:

ClassificationClassification is the process of allocating different environmental burdens (interventions) to

categories of impact.BRE propose to follow international practice in the classification of inventory data into impactcategories. Data in the UK national database will be classified for its impacts on theenvironment according to the following scheme:

Climate changeAcid depositionOzone depletionPollution to air: Human toxicityPollution to air: Low level ozone depletionFossil fuel depletion and extractionPollution to water: Human toxicity

Pollution to water: EcotoxicityPollution to water: EutrophicationMinerals extractionWater extractionWaste disposalTransport pollution and congestion: Freight


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CharacterisationCharacterisation is the process of defining the contribution of an environmental burden(intervention) to a particular category of impact. For each category, there may be one burdenwhich makes a contribution which is considered to have a contribution to that impact, or'potency', of 1. Other burdens are provided with a potency factor relative to this.

Alternatively, the burden can be characterised by measuring it in a particular unit, such astonnes of oil equivalent (toe). BRE propose to follow international practice in thecharacterisation of inventory data for their potency within the different impact categories.

Annex 11 shows the methods to be adopted to characterise data from the UK nationaldatabase for the potency of impacts on the environment. Work is continuing internationallyto develop improved methods of characterisation methods and BRE will continue to adapt toappropriate international practice. Areas of particular weakness that have been identified arehuman toxicity, ecotoxicity and ecological diversity.

Normalisation

In common with many other groups internationally, BRE will use normalisation ofimpacts against the impacts arising from human activity. Normalisation entailscomparing the impacts arising from any activity (e.g. production of a tonne of material,production of a kWh of electricity, providing laundry services for a hospital for a year) withthose from a common unit of activity usually the impacts for an average citizen for a year.This step reduces each impact to a dimensionless ratio and eliminates the problem of unitsbeing widely variant between issues (e.g. kgCO2, tonnes of mineral extracted).

Normalisation will be based on impacts from an average UK citizen, calculated bytaking data on UK emissions, energy use etc, applying characterisation factors, and dividingby the population.

A table of the characterisation and normalisation factors used is provided in Annex 11.

The first set of sheets headed Characterisation Factors shows the parameters and valuesused to assess the relative potency of the different emissions and consumption in terms ofthe selected proxy measurement unit. The headings show the different issues addressed.

The second set of sheets headed Normalisation Factors shows how the total UKemissions/consumption divided by the UK population gives the total UK impact per person.These factors are then characterised to give the characterised impact for each impact perperson. The normalised impact is the characterised impact contributed by a materialexpressed as a percentage of the characterised impact contributed by a UK citizen in oneyear.

7.3 Explanation of impacts on the characterised and normalised ProfileEach of the categories in the characterised and normalised Profile is described below.

Climate change tonnes CO2 eq."Global warming" is associated with problems of increased desertification, rising sea levels,climatic disturbance and spread in disease. It has been the subject of major internationalactivity, and methods for measuring it have been presented by the Intergovernmental Panelon Climate Change (IPCC).

Gases recognised as having a "greenhouse" or radiative forcing effect include CFCs, HFCs,N2O and methane. Their relative global warming potential (GWP) has been calculated bycomparing their direct and indirect radiative forcing to the emission of the same mass of CO2


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after 100 years. E.g. CFC-11 is 3400 times more powerful as a greenhouse gas than CO 2and therefore one tonne of CFC-11 is equivalent to 3400 tonnes CO2. Global warmingpotential is measured in CO2 equivalents for each emission, which can be added and

entered into the Profile under Climate change as CO2 equivalents (100yrs).

A timescale is applied to the GWP figure because the GWP of different gases is related tothe amount of time they will spend in the atmosphere and the amount of radiative forcingthey will induce over that period. It is important to recognise how long the gases will last inthe atmosphere. For example, both carbon dioxide and CFC-11 are greenhouse gases butthey have different half lives in the atmosphere and they will thus have a different relativeeffect over different timescales. Three different scenarios are available for GWP: 20 years,100 years and 500 years. The 100 year scenario is most commonly used and has beenapplied here.

Fossil fuel depletion toe

This unit reflects the total quantity of fossil fuel energy depleted by consumption. It ismeasured in tonnes of oil equivalents- (toes), which is a unit of energy. The characterisation

method assumes that the energy content of all fossil fuels is equally valuable to total fossilfuel resources. This is measured from the perspective of their depletion with acharacterisation factor of 1 per tonne of oil equivalent for all fossil fuels. The characterisationfactor for all fossil fuels will then be the primary energy value of the fuel in toe.

Acid deposition Kg SO2eq.Acid deposition on landscapes causes ecosystem impairment of varying degree, dependingupon the nature of the landscape ecosystems.Gases are related to the acidification of one tonne of Sulphur Dioxide (SO2). They includeAmmonia, Hydrochloric acid, Hydrogen Fluoride, Nitrous Oxides and Sulphur Oxides. Theequivalents are calculated by dividing the contribution of protons (H+) to the ecosystem from

a compound with the contribution from SO2.

Ozone depletion Kg CFC11 eq.Ozone depleting gases cause damage to stato

lca _environmental profiles methodology

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