Life Cycle Assessment
Life Cycle Assessment (aka 'LCA' or 'Life Cycle Analysis') is a tool for assessing the environmental impacts of a product or material from its origin through to disposal ie across its entire lifecycle. All activities or processes during the lifecycle of a product result in environmental impacts due to consumption of resources, emissions of substances into the environment as well as other exchanges.
ISO 14040 is the international benchmark of LCAs and the standard to which most LCAs are carried out or generally follow.
LCAs and EPDs
LCAs are usually experienced by specifiers as one part of an Environmental Product Declaration. EPDs are a method of delivering meaningful and consistent information about the environmental impact of a product. In the UK LCAs are typically encountered as part of a BRE 'Environmental Profile' of a construction product.
Environmental impacts covered
LCAs are not, by any means, identical in their structure, though they usually broadly cover the following impact areas:
• Climate change
• Ecosystem quality
• Human health
The BRE's 'Environmental Profile' methodology, a typical LCA. examines the following impacts in detail:
• Climate change: Global warming or greenhouse gases
• Acid deposition: Gases causing acid rain etc.
• Ozone depletion: Gases destroying the ozone layer
• Human toxicity to air: Pollutants toxic to humans
• Human toxicity to water: Pollutants toxic to humans
• Summer smog: Air pollutants causing respiratory problems
• Ecotoxicity: Pollutants toxic to the ecosystem
• Eutrophication: Water pollutants promoting algal blooms etc.
• Fossil fuel depletion: Coal, oil and gas consumption
• Minerals extraction: Metal ores, minerals and aggregates
• Water extraction: Mains, surface and ground water consumption
• Waste disposal: Material sent to landfill or incineration
• Freight transport: Distance and mass of freight moved
The Life Cycle
What comes in and what goes out: the Inventory
The inventory is the process of mapping and measuring the flow of inputs and outputs throughout the life cycle of the product or material. The inventory relies on accurate and well-defined data collection. Identifying which data is collected and which is omitted is defined in advance by the 'system boundary'.
Making sense of the data
The collected data is evaluated or 'characterised' for its contributions to each of the impact categories. It is usual that the impacts are then stated in terms of a unit common to other LCAs. This process of 'normalisation' enables environmental impacts to be compared across a range of LCAs. For example, LCAs normalise the category 'Human toxicity' in terms of 'kg of dichlorobenzene - equivalent' an organic compound pesticide that is also toxic to humans; 'Photochemical ozone creation potential' is cited in terms of 'kg of ethylene - equivalent', one of a number of gaseous organic compounds that when oxidised forms 'smog'.