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