What is life cycle assessment (LCA)?

Stroll through any aisle in the grocery store today and it won’t take long to find products that claim to be sustainable. Some brands might profess how much energy was offset to make a product, while others may point to recycled content or natural ingredients.

But what do assertions by a business like these mean in real terms? How exactly is sustainability measured?

One of the most common methodologies for quantifying sustainability is life cycle assessment (LCA). An LCA is a systematic analysis of environmental impact over the course of the entire life cycle of a product, material, process, or other measurable activity. LCA models the environmental implications of the many interacting systems that make up industrial production. When accurately performed, it can provide valuable data that decision-makers can use in support of sustainability initiatives.

Read on for a basic introduction to LCA: What it is, how one is performed, and why it helps businesses, policymakers, and consumers make more informed decisions when it comes to supporting sustainability.

What are the benefits of doing an LCA?

The results of an LCA can help businesses, policymakers, and other organizations make more informed decisions to advance towards sustainability. It provides critical data that can support the following:

process and product-design improvement
marketing (e.g., backing up environmental claims or meeting consumer demand for green products)
hot-spot analysis to facilitate continuous improvement
third-party verification or certification
method for quantifying key environmental impacts (e.g., greenhouse gas, carbon emissions, water use, and energy consumption)
goal-setting for climate-change and other sustainability policies

What is life cycle thinking?

Understanding what an LCA is and how it works means thinking about industrial products and activities in terms of a life cycle.

It might seem odd to think about inanimate objects like a toaster or how a factory uses water as having a life cycle, but that’s exactly what LCA requires us to do. Every product, whether something as simple as a plastic cup or a highly designed electric car, is “born,” lives a “life,” and, when it is no longer useful, its life ends.

The linear production model

The life cycle that describes most manufacturing today is as follows:

material extraction
production
packaging and distribution
use
end of use
waste treatment or recovery

A product’s life cycle is not unlike a living thing’s: Natural resources (energy, materials, and water) are used while wasted material, energy, and emissions are created. This happens at different points throughout an entire lifespan, resulting in environmental impacts, all ranging in severity.

The life cycle above reflects a linear model of production, also known as a cradle-to-grave life cycle. An LCA can also account for other models of life cycles, such as cradle-to-cradle. This describes a circular economy, where the end-of-life phase feeds directly into a new life cycle, often through a value retention process like remanufacturing.

The circular production model

Whatever the economic model, an LCA is a tool for identifying or comparing the environmental impacts of a product or industrial activity by quantifying all material flows and assessing how they interact with the natural environment.

Life cycle stages. Source: U.S. Environmental Protection Agency (1993)

How is environmental impact measured?

Sustainability can seem like an abstract idea. An LCA helps to make it concrete and actionable through the scientific measurement of environmental impacts.

Industrial activity interacts with the environment in many ways. Some of these are immediate, while others may occur far from the company’s actual location, thanks to the reach of global supply chains. Industry, in all its varieties, draws upon many activities and processes—diverse resources are consumed along the way as different substances are emitted. An LCA helps to determine to what extent these material exchanges with the environment are detrimental to both natural ecosystems and human health.

When an LCA is performed, a practitioner will set metrics to quantify the different inputs (e.g., energy, water, resources, land) and outputs (e.g., emissions, wastes, products) that occur throughout the life cycle of an industrial process, technology, or commodity. It allows an assessor to map flows of energy, resources, and materials in and out of a system. These are objective measurements, tracking distinct quantities like volume, mass, or weight. They are collected as part of the life cycle inventory (LCI).

The LCI data is interpreted later in the study, during the life cycle inventory assessment (LCIA), to represent actual impacts on the environment or human health. For example, a certain volume of petroleum may be used to produce one plastic fork. This is recorded in the LCI. In the LCIA, this measurement is used to calculate how much this contributes to global warming.

Environmental impact categories

Every LCA sets out specific environmental impact categories that guide the direction of the LCIA. There are many different LCA methods and each utilizes a unique set of categories. However, there are general types found across all methods, though different wording and metrics may be used.

climate change (contribution to global warming)
acidification (contribution to the occurrence of acid rain)
energy (cumulative energy demand and loss throughout a life cycle)
eutrophication (the release of nitrogen and phosphorous, which leads to algal blooms)
radiation
land use
air pollution
resource depletion
water use
ecotoxicity (the release of toxins that are harmful to life)

Hotspots

While evaluating the environmental impacts of a product or industrial activity, an LCA serves to identify hotspots. These are points in the life cycle that have significant negative impact on the environment. Most often, resolving hotspots becomes the cornerstone of the sustainability plan based on a complete LCA.

Who performs an LCA?

An LCA may be done by a certified professional (LCACP), but certification is not required. Many engineers within different industrial sectors regularly perform LCAs and related modeling to further sustainability efforts. In the United States, LCACP certification is awarded by the American Center for Life Cycle Assessment (ACLCA).

How is an LCA performed?

The four key steps of LCA

The approach that would become LCA first emerged in the 1960s and 1970s, though there was little consistency in how such analysis was practiced. However, by the 1990s, the international scientific community made steps to standardize LCA. This led to a commitment by the International Organization for Standardization (ISO) in 1994 to create today’s LCA standards including guidelines and the principles and framework.

In 2002, the United Nations Environmental Programme (UNEP) and the Society for Environmental Toxicology and Chemistry (SETAC) moved to advance LCA through the creation of the Life Cycle Initiative. By 2005, the European Union, the United States Environmental Protection Agency, and many other government bodies had implemented policies promoting the use of LCA as part of sustainability initiatives.

Today, LCA is a methodology used by scientists, policymakers, and business leaders to set sustainability goals. It is often used in conjunction with other well-known tools, like material-flow analysis (MFA).

The ISO standards describe the principles and full framework for conducting an LCA. The assessment is broken down into the following four phases:

goal and scope definition
life cycle inventory analysis (LCI)
life cycle impact assessment (LCIA)
interpretation

Each step is described in greater detail below. Highlights from an actual LCA performed by the New York State Pollution Prevention Institute (NYSP2I) are also included in order to better illustrate each phase of the study.

Step 1: Goal and scope definition

Accounting for all the many potential impacts of an entire manufacturing process would require an incredible amount of time, data, knowledge, and resources—there are limits to the breadth and data quality of any analysis, after all. An LCA analyst makes this task manageable by first clearly defining an LCA’s goal and scope.

Functional units, system boundaries, and limits to the analysis are set to outline where in the life cycle the study begins and where it ends, and to identify what processes within the technical system will be assessed. A functional unit is the basis for the study. It is a measurement of production or output against which impact indicator metrics are normalized.

The scope of an LCA is determined by the number of life cycle stages and impact categories that will be assessed. One assessment might take in just one life cycle stage and one impact, making it very targeted and focused. Another might be far more comprehensive in scope, addressing an entire life cycle across many impact categories. Between these two poles stand many possibilities.

A business is more likely to prefer an LCA that is narrow in scope—it requires far less time and resources to perform, and it’s more likely to lead to actionable results. However, its limited range often means turning to supplemental data sources and estimated measurements to fill in gaps. A truly comprehensive study, as an attempt to model all of a manufacturer’s activities, would generate a complex set of data that would not lend itself as easily to practical interpretation. Yet this richer data is attractive to researchers and policymakers because it can help them understand real-world conditions more accurately.

Designing the assessment

Urban Mining Northeast (UMNE) manufactures a novel pozzolanic material (Pozzotive) that uses post-consumer glass to increase the sustainability of concrete. It does this by replacing a portion of Portland cement, a common concrete ingredient with a big environmental footprint. To gain a more objective understanding of how their product contributes to more sustainable building material, UMNE’s leadership partnered with the NYSP2I to conduct an LCA.

The LCA was performed as part of a larger trend towards sustainability within the cement industry. The production of cement consumes about ten times the national average ratio of energy to the gross output of goods and services, and contributes nearly 5% of global anthropogenic carbon dioxide emissions (CO₂) each year. In response to this, the International Energy Agency (IEA) and the World Business Council for Sustainable Development (WBCSD) Cement Sustainability Initiative (CSI) launched a technology roadmap for reducing the CO₂ intensity of cement manufacturing. A central goal of the plan was to find sustainable substitutes for cement clinker, like Pozzotive™.

The NYSP2I LCA analyst’s first step was to determine the scope of the project.

A functional unit was set as one metric ton of cement. The system boundary was determined as a cradle-to-gate analysis, which means the LCA evaluated material supply, transportation of materials, and related manufacturing processes.

Since the study was not a cradle-to-grave analysis, certain phases in the life cycle of Pozzotive™ were set as “out of bounds” in the interest of practicality and feasibility. Whenever possible, an analyst will look to authoritative sources, like standards or certifications, to define the parameters of a study in order to make it as accurate and objective as possible. The boundaries of the UMNE assessment were set in accordance with an ASTM International standard. Before any work began, the scope was agreed to between the NYSP2I analyst and UMNE.

Step 2: Inventory analysis

Once the boundaries of an LCA have been drawn, a LCA analyst is ready to begin collecting data. This is the LCI phase, when an industrial system’s inputs and outputs are measured and recorded (according to the functional unit). By the end of this phase, an inventory list is created that details all input/output data for the system under study.

Collecting the data

The LCA that NYSP2I performed for UMNE reviewed three main life cycle stages: raw material supply, transportation, and product manufacturing.

The raw material stage, as an example, accounted for all materials that go into UMNE's production process: post-consumer glass, cement, and concrete. Using the LCA's functional unit, one metric tonne of cement, the analyst observed each of UMNE’s manufacturing processes firsthand over the course of a day in order to quantify how much material and energy were used.

Each stage was assessed in a similar way. The results were documented in the inventory list.

In addition to gathering data directly from a facility during a specific time period, existing data can be referenced as needed. The results of UMNE's LCA could be compared against existing LCA data for traditional Portland cement in order to track differences within specific impact categories.

Step 3: Impact assessment

Once all relevant data has been collected, the LCIA phase begins. The LCA analyst, at this point, evaluates the inventory of data that has been collected in order to make it meaningful in the context of potential damage to the environment or human health. For example, knowing that a process emits 10 megatons of carbon dioxide (CO₂) and 17 megatons of methane (CH₄) does not, in itself, describe a contribution to climate change. An LCIA translates these measurements into meaningful information for expressing their impact. The raw data is characterized to communicate the relative potency of materials, emissions, or other factors. So, in the case of CO₂ and CH₄, an LCIA allows us to say that the latter contributes 25-30 more to climate change than the former.

An LCIA is how the data collected in Step 2 is made meaningful, actionable. It is when actual environmental impacts are calculated, drawing on the life cycle inventory. The U.S. Environmental Protection Agency breaks down an LCIA into the following steps:

selection and definition of impact categories
classification
characterization
normalization
grouping
weighting
evaluating and reporting LCIA results

Defining impact

The inventory of data NYSP2I staff collected from UMNE’s operations was used to determine environmental impacts in the following categories, set out in the ASTM product category rules for cement:

global warming
acidification
eutrophication
smog creation
ozone depletion
total primary-energy consumption

ASTM’s guidance specifies the use of USEPA TRACI, a tool that normalizes impacts and does not include weighting or addition. See how TRACI defines the specified environmental impacts used in the UMNE LCA:

TRACI defines the specified environmental impacts used in the UMNE LCA

A large amount of energy is required to produce “clinker,” a key ingredient of Portland cement. UMNE’s Pozzotive™ would decrease how much clinker is needed in cement, lowering its overall energy usage. To quantify this improvement, cumulative energy demand (CED) was calculated.

CED is an indicator that represents the total quantity of primary energy (renewable and non-renewable) used during the whole of a product’s life cycle. CED is useful as part of an LCA because it can function as a proxy for greenhouse gas emissions and other environmental impacts caused by energy use. See the CED methodology used in the UMNE LCA:

Step 4: Interpretation, critical review, and reporting

The final phase of the LCA—when the study’s results are interpreted alongside its original goals and scope—may be the most important of all when it comes to turning what was learned into actionable tasks.

If a business hires an LCA analyst to perform the assessment, the results are most often put into a report format that is as informative and accessible as possible. Included in this report are key priorities for mitigating environmental impact as well as any suggested opportunities for improving the sustainability of a product or process. However, such reporting is typical only to an LCA performed for a business by an external body. Many LCAs do not result in reports.

The fundamental purpose of this final phase is to identify priorities in light of an LCA’s stated goals. So, if the goal was to mitigate waste, strategies for doing so will be highlighted following what was learned through the study.

The ISO standards for LCA dictate that this interpretation should

identify significant issues based on the LCI and LCIA phase;
evaluate the study itself, how complete it is, if it’s done sensitively and consistently, and account for uncertainty; and
provide conclusions, limitations, and recommendations.

Making the data meaningful

NYSP2I’s LCA analysis focused on how UMNE’s product variations compared to conventional Portland cement in terms of overall environmental impacts, in accordance with the IEA-WBCSD CSI roadmap. It is important to stress that no LCA is completely conclusive—its findings cannot be generalized too broadly and should be considered alongside similar studies. NYSP2I’s LCA was done within strict limits (described “Designing the assessment” above) and only contributes to a wider set of research investigating the environmental impacts of either Portland cement or Pozzotive™.

See the normalized results contrasting the impacts of concrete using UMNE’s product to concrete made with ordinary Portland cement. It follows the study’s defined impact categories:

Impacts of concrete using UMNE’s product vs. concrete made with ordinary Portland cement

LCA as a research methodology

This introduction to LCA focuses primarily on how the methodology can be applied to the needs of a business. But it is worth mentioning that LCA has a much broader usage, and serves as a fundamental scientific methodology used by researchers working within sustainability.

Some important ways in which researchers use LCA to generate findings that may inspire smarter, more effective sustainability policies include the following:

To enable the transition to a circular economy: LCA is useful for identifying practical opportunities for circularity within linear industrial systems.
To mitigate “burden shifting”: Burden shifting is what happens when one source of environmental impact is solved but another is created. LCA is a strategy for avoiding such unintended consequences because it offers a systems-level perspective, assessing multiple environmental impacts at once.
To objectively verify sustainability claims: Researchers may also use LCA to substantiate or disprove sometimes commonsense assumptions. Dr. Callie Babbitt, associate professor at the Golisano Institute for Sustainability (GIS) at Rochester Institute of Technology (RIT), made this point in a 2017 article in Clean Technology and Environmental Policy:
“Typically, it is taken as fact that a bio-based alternative would be greener compared to a nonrenewable resource, that a waste feedstock is preferable to a primary raw material, or that absence of a known hazard automatically ensures that a new technology is ‘clean.’ It is far less common to see systematic assessment of such assumptions, even on a qualitative basis, or a parallel investigation of both technical and environmental performances.”

LCA research at GIS: Integrating an industrial-ecology analysis

You’re likely to find far more electronic products in today’s average American household than you would have in one just a few decades ago. Even if each new product is much more sustainable when considered alone, the impact of multiple green electronics can add up. This cumulative impact may even outweigh that of an older, legacy item (like a cathode-ray tube television). And, as consumer electronics become more lightweight and affordable, their life cycle has shrunk over the past fifty years. Consumers tend to buy more electronics more often, but use them for less time before sending them into the waste stream. This net effect means that sustainable design does not, alone, reduce environmental impacts.

A traditional LCA, evaluating the environmental impacts of electronic products individually, may miss important observations like those above. So what happens when consumption trends and ownership patterns are taken into an assessment? When an LCA considers a series of electronics and their owners as part of an ecosystem, rather than each in isolation? These were questions that researchers from GIS put forward in a 2015 study.

The GIS researchers wanted to know how these dimensions—consumer behavior and ownership trends—could be meaningfully integrated into an LCA study. They saw a complex relationship between consumption and technological progress, and recognized limits to describing it through a conventional LCA. To create an LCA methodology with a wider frame, they turned to biological community ecology to develop a new concept, the product community. An adjusted methodology was introduced, the consumption-weighted LCA, which is designed to capture the shifts in net environmental impacts that follow a fast-evolving electronic product market.

In the study, the methodology was applied to common consumer electronics used in an average U.S. household over the course of a year (the functional unit), and analysis evaluated energy use and greenhouse-gas emissions (impact categories). However, its findings suggest that it could be applied more broadly to different sectors and product types.