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 LCA in short

 

LCA IN SHORT

The following chapter provides an introduction to LCA methodology as well as the standards developed and applied.

 
2.1 Introduction to LCA methodology
 
 
The concept of LCA can be understood as stated by Baumann and Tillman (2004): It means that a product is followed from its ‘cradle’ where raw materials are extracted from natural resources through production and use to its ‘grave’, the disposal.
 
LCA addresses the environmental aspects and potential impacts in this context and the general categories of environmental impacts needing consideration include resource use, human health, and ecological consequences (ISO 14040:2006).
 
There are four phases in an LCA study as illustrated in Figure 2.1.

 


LCA aims to assess the environmental impact of products, product systems such as a transportation system or a road, and services. The methodology has been developed to be able to capture the inflows and outflows from activities in all life cycle stages associated with a product or product system and all environmental impacts related to these inflows and outflows. It considers the entire technical system related to a product from ‘cradle to grave’, i.e. from raw material acquisition to final waste treatment of waste products.
 
One of the greatest advantages of LCA is the ability to avoid so-called “problem shifts” or partial optimization, both with respect to life cycle stages and to environmental impacts:
 
1.    It captures all life cycle stages where impact occurs in order to identify the important stages and associated processes such as production processes, traffic or maintenance.
2.    It captures several environmental impacts simultaneously to identify the important environmental issues.

From several examples presented in the current literature, it may be seen that even when studying the same kind of construction works or building materials, LCA results may differ significantly. It can be shown in Figure 2.2 where four different calculation tools for LCA of infrastructure projects were used (A-D). Each point represents result from different LCA study for the same product.

 


How can this be explained? Performing LCA analyses of construction products, buildings or other civil engineering works requires methodological considerations on several dimensions, leading to a variety of explanations of differences in results. It can be seen in Figure 2.3 that some of the deviation of the results originate from incoherent way of modelling the working phases in the calculation tools.




There are a number of methodological options that may potentially influence the results from the LCA: the definition of scope, including the choice of functional unit (the defining reference for the analysis to be performed) and the system boundaries, data selection and data quality, impact assessment methods.


2.2 Standards for LCA of civil engineering works



2.2.1 Suite of standards


The purpose of the European Standards developed for LCA of civil engineering works is to enable comparability of the results of assessments. The series of standards are given in Figure 2.4. The green colored standards are environmental related standards for building, while red refers to social performance and blue to economic performance of buildings.  The light blue boxes represent civil engineering works and include all three pillars of performances.




Figure 2.4        Suites of European standards. Source: CEN/TC 350.


For civil engineering works the framework for sustainability assessment was published in 2017. The standard is EN 15643-5:2017: Sustainability of construction works - Sustainability assessment of buildings and civil engineering works - Part 5: Framework on specific principles and requirement for civil engineering works. And it provides specific principles and requirements for the assessment of environmental, social and economic performance of civil engineering works taking into account its technical characteristics and functionality.


There is also parallel work to EN 15643-5:2017 going on in the ISO-organization. ISO is in a process to finalize the parallel standard ISO/FDIS 21931-2:2018 Sustainability in buildings and civil engineering works -Framework for methods of assessment of the sustainability performance of construction works - Part 2: Civil engineering works.


This document will use requirements and principles form EN 15643-5:2017 (civil engineering works) and EN 15978 (building level assessment) as bases for recommendations.

 

2.2.2 Environmental assessment at civil engineering works level

 


The framework standard EN 15643-5:2017 gives principles for designing the LCA. It follows the same principles as for buildings.

LCA of civil engineering works requires information related to different activities along the life cycle of infrastructure. Thus,  Figure 2.5 shows the information modules the life cycle is covered by. Resource use, emissions and environmental impacts that are caused by a given activity are assigned to the respective information module.

 
Figure 2.5 Information modules applied in the assessment of environmental, social and economic performance of a civil engineering works (EN 15643-5:2017).
 

This structure differs slightly from the one used for EPD and LCA for buildings. A pre-construction phase is introduced - A0. In addition, use phase is introduced. Here impacts and aspects caused by the user’s utilization of the civil engineering works can be included, e.g. the fuel consumed by the vehicles use of a road. For roads this will include e.g. traffic, operation and maintenance. The standards are developing and there will be a new information module "C5 Re-landscaping" introduced in the revision of ISO 21931-2 which is the ISO framework standard for civil engineering works.


2.2.3 Environmental assessment at construction products level (EPD and PCR)

 

An EPD is an executive summary of an LCA of a construction product or service. The EPD is an “information carrier”, similar to the content of nutrients on a package of food, and provides data input to support building and civil engineering works environmental assessment. Information from an EPD regarding information modules A1-A3 (cradle-to-gate information for the product) is the information used at building level for the different construction products that represent the building. Then the EPD may contain information regarding how the construction product is transported to construction site (A4), how it should be installed in a given context (A5), how often it needs to be replaced and how this could be done (B4), and how the scenarios for waste processing for both the replaced product (B4) and for the product after end-of-life of the building (C1-C4) may look. As a construction product may be used for several purposes, the end of life scenarios will always be based on assumptions. 


ISO 14040 and ISO 14044 give rules for how to perform LCA for all products and services. ISO 14025 is the corresponding standard that established the principles and specifies the procedures for developing EPD for all products and services, while EN 15804 or ISO 21930, both give core rules for ‘all’ construction products and services. They include rules for all stages until the end of ‘cradle-to-gate’ (A1-A3) that apply to all construction materials, and guidelines for the creation of scenarios in the construction phase, use phase and end-of-life (A4-C4, see Figure 2.5). The latter must be detailed specific for each product category; e.g.; asphalt, or concrete product, by so called product category rules (PCR). PCR define the rules and requirements for the EPDs of a certain product category. PCRs developed for infrastructure include CPC 53210, 53211 and 53212.

It is mandatory that EPDs provide information on ‘cradle-to-gate’ (information modules A1-A3) for construction products as well as modules C and D. A1-A3 is minimum based on the previous version of EN15804. The revised EN15804 has included more mandatory modules (C and D). PCRs can also define extended mandatory modules. In addition, an EPD program operator can in their General Program Instructions (GPI) define more mandatory modules. An example is A4 that is included in Norway. EPDs for construction materials must be in accordance with EN 15804. They must also be 3rd party verified, and approved/published by an EPD Program Operator. Due to a transition period between the previous and the current version of EN 15804, EPDs published during this time may differ in their scope and the modules included.

As illustrated in Figure 2.6, several EPDs and other information will be ’added up’ to make the full LCA of the civil engineering works. 

 
Figure 2.6 Link between product level information and building level assessment (Rønning, 2017).



Essential for material and product data exchange are digital EPD’s. BuildingSMART develops standards for Product Data Templates (PDT) for building materials and products (EN ISO 23387). The environmental properties are handled in the same way as other properties of the product in a digital product template. Templates will enable data exchange through the life cycle of the product, using the same data structure, terminology and GUIDs, thus making the data machine-readable.


2.3 Comparison Between Projects and for sub-construction works

 

 Comparisons between alternatives at early planning stages can provide valuable input in deciding what the best infrastructure solution would be for a specific project. Applying LCA methodology for the purpose of comparing between LCA studies has several limitations related to the specific parameters defined at project level. Direct comparisons between projects that have different parameters and serve different traffic flows are of limited use and cannot provide a useful result. Details on the parameters that have to be considered when defining the LCA study are addressed in detail in chapters 4 and 5 of this document.

EN 15804 specifies that comparisons are possible at the sub-construction works level, e.g. for assembled systems, components or services for one or more life cycle stages. In all cases of comparing construction products, the principle that the basis for comparison of the assessment is the construction works level shall be maintained by ensuring that the same functional requirements are met and:

  • the same functional requirements as defined by legislation or in the client’s brief are met, 
  • the environmental performance and technical performance of any assembled systems, components, or products excluded are the same, 
  • the amounts of any material excluded are the same, 
  • excluded processes or life cycle stages are the same, 
  • the influence of the product systems on the operational aspects and impacts of the civil engineering works level are taken into account.
To ensure comparability, it is important that construction products within the same product group or products that solve a specific function, have used the same ‘calculation rules’ and assumptions


Oprettet
15-05-2020.
Senest opdateret
02-11-2020.