Life Cycle Assessment




Historically geared toward and used by the private sector, Life Cycle Assessment (LCA) is a systems analysis tool which was designed specifically to measure the environmental sustainability of products and services through all components of the value chain. LCA is an input-output tool, measuring resource use and emissions that can be allocated to a particular product. In addition to its use by the private sector, LCA has also been very successfully used as a national and even international policy tool, and is imbedded in many laws in the EU, Japan, Malaysia, Australia, and elsewhere. LCAs can be set to analyze environmental impacts at many different scales (e.g. watersheds, counties, or countries). Properly done, an LCA allows companies and other interested parties (including consumers) to make comparisons among products and services. LCA is a decision-support tool that has primarily been used for three kinds of decisions:

  • Engineering decisions for product/ process improvement: Also called design for environment or eco-efficient manufacturing, this allows companies to identify opportunities for environmental improvement/optimization and measure the improvement along the entire supply chain. With LCA practice, this is often linked to hotspot analysis or identifying which parts of the product life cycle have the greatest environmental impacts.
  • Policy decisions at the company or governmental level: This allows companies to develop a more rational and holistic view of the environmental impacts of their activities. In this context, economic input-output life cycle analysis—though actually not applied at the company level—has proven to be a very useful economy-wide tool, permitting one (typically government entities) to calculate estimates of the impacts of marginal production in the different economic sectors. Use of LCA in the context of national rulemaking is countenanced within the World Trade Organization as not creating a technical barrier to trade, providing that the relevant international standards are followed.
  • Environmental purchase and sales decisions: This occurs either as a support for environmental claims or as the supporting information for LCA-based ecolabels. Use of LCA in communicating environmental issues with external stakeholders is discussed in detail in Section VII. Environmentally preferable purchasing programs often make use of LCA as a decision-support tool.


Water and LCA

Hundreds of thousands of LCA studies have been published in the last 40 years. The field of agricultural LCA has been especially prolific, and several international conferences have been devoted to the LCA of foods. However, traditionally, water use has not been accounted for within this method in any sort of detailed or comprehensive fashion. If measured at all, water use has typically been accounted for strictly as an inventory of a product’s total water withdrawal (rather than consumption) that is neither locally specific nor features any impact assessment. However, given companies’ growing concerns over water scarcity in the last decade, the development of better ways of accounting for water use within LCA has become a priority. Further, consensus appears to have been reached among LCA practitioners on the importance of better differentiating between consumptive and non-consumptives water uses in LCA studies. Also recognized is the need to understand and specify the geographic location of water use, the sources of the water (e.g., lake/river, groundwater, rainwater) and whether those sources are renewable or non-renewable.

There is currently an abundance of research on water scarcity and life cycle impact assessment modeling of the resource, along with the health effects and ecosystem damage associated with water scarcity. LCA practitioners have put forward different ways of characterizing the impacts of water use, though these have varied from study to study. Some of the impact categories proposed in these methods include water sufficiency for different users, ecosystem quality, resource consumption, and human health, among others. LCA’s approach to impact assessment is discussed in detail in Impacts.


Scope, structure, and outputs

Unlike water footprinting, which focuses on a single environmental resource (i.e., water), LCA was designed as a method that enables cross-media evaluations and comparisons across many different types of environmental resources, emissions, and their impacts. Indeed, the ability to assess impacts across a range of environmental categories is LCA’s core function and value. These analyses require a much more comprehensive process than the strict water-related measurements seen in water footprinting. LCAs are typically comprised of four basic stages:

  • Goal and scope: The goals and scope of study in relation to the intended application are specified. This includes establishing the boundaries of the system being assessed (i.e., determining what is being measured) and defining the functional unit of the product for the purpose of the study, a measure of the product or service being assessed.
  • Life cycle inventory: Environmental inputs and outputs (e.g., water use, GHG emissions) that may have subsequent impacts are measured. In respect to water, this is the stage where the volume; timing; type (i.e., stocks, flows); location of use; and the volume/ mass of contaminants released to waterways (among other things) may be captured.
  • Life cycle impact assessment: The environmental inputs and outputs measured are translated into impacts (e.g., contribution to global warming, fresh water depletion, human health concerns). Emissions and resource uses from a variety of different sources are collected and assigned into their relevant impact categories, then characterized by the relevant impact factors developed through resource management and fate and transport models.
  • Interpretation: The final stage further translates the quantification of impacts determined in the previous stage into meaningful conclusions and recommendations to improve the environmental performance of the product or service.

As discussed, LCA provides information on different types of environmental activities and different impact categories which those flows can affect. This allows LCA to quantify and compare the multiple types of impacts caused by one type of use or emission, as well as the various resource uses or emissions that contribute to one type of impact (e.g., the various business activities that contribute to eutrophication of water bodies). Typically, life cycle inventory data reflects the volume of water used at a given unit process. The challenge for evaluating the impact of water use is that often one does not know where that unit process occurs.

Unilever recently conducted two case studies that piloted the accounting and impact assessment components of both water footprinting and LCA for two of its products: tea and margarine. It aimed to compare the two accounting approaches in terms of functionality, determine how the results can be practically implemented, test impact assessment methods, and contribute to methods development.

The WF study measured the blue, green, and gray water footprints, while separating them into supply chain and operational components. Though impact assessment is typically not included in WFs, this study attempted to assess impacts by mapping areas of significant water use on a water stress index (i.e., ratio of water withdrawals to water availability) map. This was not used to calculate impact indexes (or “scores”) but rather simply to identify hotspots.

The LCA study used a variety of different data inputs. It used WF calculations (i.e., evaporative uses of blue and green water) as the basis for its crop water use measurements, Unilever data as the basis for its manufactureand end use phases measurements, and databases from the Ecoinvent Centre for data on background processes. The main differences between the two methods for this stage were that WF does not include energyrelated water use and LCA tended to overestimate certain water uses because it looked at abstracted water instead of consumed water. Like the WF study, the LCA study used a water stress index using the ratio of withdrawals to availability to determine impacts. However, unlike the WF study, the LCA study calculated impacts in order to get a quantified assessment of impacts across different production processes. The LCA study also included an assessment of impacts on eutrophication and ecotoxicity resulting from pollution caused by the products. Despite some differences, Unilever found that the methods were ultimately quite similar in the hotspots they identified.

Freshwater ecosystem impacts in Lipton Yellow Tea Production


Financial and personnel requirements

LCAs vary in time and cost depending on whether the assessment uses more database data (i.e., a screening LCA) or more actual production data (i.e., full LCA), as well as whether the study looks at a wide range of indicators (e.g., GHG emissions, human health, ecosystem health, energy use) in addition to water use, or whether it is water-specific. A screening LCA typically takes roughly ten person days spread across one month to fully complete, while a full LCA takes 35 person days over 3-4 months. A LCA study considering only a company’s water use and its impacts across its product portfolio takes roughly 260 person days over the span of a year consisting of ad hoc support from 5-8 employees (Milà i Canals, 2010).

Like WFN water footprints, companies usually conduct LCAs with assistance from an external organization with expertise in the field. Unlike water footprints, there is an extensive community of practitioners that provide such assistance. These external organizations typically charge 10,000-30,000USD for screening LCAs and 50,000-100,000USD for full LCAs when looking at a comprehensive set of indicators. These costs are typically cut in half (i.e., 5,000-15,000USD for a screening LCA and 25,000-50,000USD) when only considering water use and its associated impacts (Humbert, 2010).

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