Measuring the environmental impact

Introduction

Most material choices on BedZED have been made on the basis of clear environmental benefits. Reclaimed steel is much better than new. UK grown FSC certified timber is better than imported non-FSC timber. When such choices can be made cost-neutrally, there is no need for sophisticated analysis. When there is a cost premium or a life cycle implication, it can be helpful to have some method of quantifying the comparative environmental benefits of the alternatives in order to put the issue in context and make an informed decision.

In this report, three different assessment methods have been used to quantify environmental benefits.

Embodied energy and embodied CO₂

The embodied energy of a material is the energy required the abstract, process, manufacture and deliver it, measured in GU/tonne.

The embodied energy of a material needs to be considered over the lifespan of the material, for example aluminium is a highly durable material with a long lifespan of 60 years and is therefore an appropriate solution in some cases, despite its high embodied energy.

Energy consumption itself does not constitute an environmental burden. It is often more useful to consider a material in terms of its embodied CO₂ rather than embodied energy. As it is the CO₂ emissions that contribute to greenhouse gases and lead to global warming.

Embodied CO₂ is not directly proportional to embodied energy. It depends on the specific energy sources of a process. Processes that require high grade electrical energy will result in higher CO₂ emissions than those that run on low grade heat energy. It also depends on the energy source for that particular process. In Scandinavia, most of the power used in the aluminium industry comes from hydro-electric schemes and therefore has no embodied CO₂ in its manufacture.

The embodied energy and CO₂ data used in this report are supplied by the BRE 3 and are based on UK national averages.

This method quantifies the specific impact of CO₂ emissions, widely considered to be the most urgent current environmental issue.

This method takes no account of toxic emissions, habitat loss or any other environmental issues

BRE Environmental Profiling

BRE Environmental Profiling uses Life Cycle Assessment methodology and complies with an internationally established approach for analysing impacts of products and processes. It measures environmental performance throughout a product's life, through manufacture, operational use in a building and in demolition. The system has been developed by the BRE and it measures a material's impacts in 12 areas:

1 Climate change
2 Fossil fuel depletion
3 Ozone depletion
4 Human toxicity to air
5 Human toxicity to water
6 Waste disposal
7 Water extraction
8 Acid deposition
9 Ecotoxicity
10 Eutrophication
11 Summer smog
12 Minerals extraction

The impact of the material in each area is compared with the average impact of each UK citizen and given a "score" known as an Ecopoint score.

This method provides a comprehensive method for comparing materials and combinations of materials. It usefully combines a wide range of environmental issues and brings them together into one figure.

The relative weightings of the 12 impact areas are subjective and only represent perceived importance. This method makes no reference to what ecopoint score is actually sustainable given the earth's finite capacity. Despite a significant weighting in the BRE's consultation exercise, wildlife and habitat loss has not been incorporated into this system due to difficulties in measuring impacts.

Eco-footprinting

Ecological Footprint analysis is an accounting tool that represents the environmental impacts of a process or a person's lifestyle as an area of land. It measures the area of biologically productive land that is required to meet the needs of a given product or population. It compares this area with the actual available area on earth and informs as to whether we are living within the earth's capacity.

A person's ecological footprint is made up of the footprints of all their activities, products consumed and waste produced. It includes the area of forest required to absorb the CO₂ emissions attributable to that person. It includes a share of the area taken up by infrastructure, food and timber growing and fishing. A person's energy consumption has an eco-footprint, as does their food consumption, transport, work activities and leisure activities. Each consumer product has an eco-footprint as does each construction material.

This method relates what we do to the actual sustainable carrying capacity of the earth.
Eco-footprinting does not rely on any subjective weightings.

This is a relatively new tool and there is not always data available on the impacts of a product.
Eco-footprinting has not yet been developed sufficiently to take toxic pollution impacts into account.

Further information

• The full report can be obtained from Bioregional: www.bioregional.com