Life cycle assessment: a getting started guide
Sustainability is widely debated; putting it into practice is harder. After an investigation, declarations and actions need to follow quickly if environmental damage is to be reduced and previous efforts improved on. Three conditions have to be met: an action must be available to take, the alternatives must be ranked, and the best practice must be chosen with cost, environmental impact, and economic constraints all in view.
Life Cycle Assessment (LCA) is the decision-making tool that helps select and optimize among the technology solutions or products available to meet that demand. The question is not how to solve a particular case of tight money — engineering already handles that. The question is how to set priorities, because no one can afford to fund everything. LCA shows which procedures most need to change.
From a sustainability standpoint, LCA matters because it covers the whole lifecycle of a product or service. That prevents a local improvement from simply moving the environmental burden somewhere else. Strategies for evaluating ecological performance, raw material use, and pollutant emissions all depend on the purpose of the system or item under study — which was not the case with earlier environmental assessments.
What is life cycle assessment?
LCA is a methodology for assessing the environmental impacts of a product or system across its whole life cycle, from cradle to grave. It identifies and quantifies the ecological effects of that system so decision-makers can choose more sustainably. It is used on cars, buildings, and food systems alike, and it considers every step: obtaining the raw materials, making the product, using it, and disposing of it.
LCA is a detailed and often complex process, commonly used to compare the environmental impacts of products and services. It can be applied at any level, from local to global. Several assessment methods and approaches exist; the important thing is choosing the method and procedure appropriate to the product or system in question.
LCA considers:
- Extraction of raw materials
- Production of the product
- Use of the product
- Transportation and energy use
- Waste management
How an LCA is carried out
An LCA is performed by a trained analyst who collects data across all stages of a product’s life cycle, enters that data into software, and models the system. It can be done by hand, but the calculation is slow; LCA software accelerates the process considerably.
The analyst then examines how each life cycle stage affects the environment and assigns each a weight, based on the nature of the effect and how much that stage contributes to the product’s overall impact. The output is an environmental profile of the product, together with recommendations for reducing its impacts.
What LCA is used for
- Identifying and reducing the environmental impacts of a business
- Identifying sustainable business practices
- Developing greener technologies, products, and systems
- Understanding the impacts of climate change on the environment and on health, and assessing approaches to address it
- Comparing products, technologies, or future scenarios against a baseline — the current situation, for example
- Improving the environmental performance of technologies
- Answering broad environmental and sustainability questions, particularly when combined with other assessment methods
- Identifying weak points in products, technologies, and services
- Helping consumers make informed decisions about what they buy
Types of LCA study
Screening LCA
Estimates how environmentally sound a product, service, or manufacturing process is. Drawing on a Life Cycle Inventory (LCI) database covering thousands of processes and sectors, it calculates several impacts — eutrophication, acidification, human toxicity, climate change — to give an overall picture of environmental load. It is useful for understanding whether choosing a particular product will improve or worsen a company’s environmental profile.
Product LCA
Examines the environmental performance of a product or technology from conception to disposal, covering every stage of the production cycle from extraction onward, including the disposal route and its consequences — pollution from landfilling, incineration, or hazardous waste handling.
Comparative LCA
Accounts for the impacts of every stage across two or more alternatives. The common case is comparing one product or technology against another, but the same approach applies to comparing development routes or scenarios.
LCA versus environmental impact assessment (EIA)
Comparing LCA and EIA across their respective time and geographical scales shows the two instruments to be complementary rather than competing. An LCA evaluates a product or service from extraction (cradle) through to End-of-Life (grave), typically on a global scale.
An EIA, by contrast, examines a single location. Site-specific EIAs weigh variables particular to that place — the number of people living nearby, the distance between the site and residential districts, and the presence of specific ecosystems.
Extraction of raw materials
Extracting natural resources means removing materials from the earth to be manufactured or sold as commodities — coal, oil, gas, metals. The process can be hazardous and damaging to the environment when not done responsibly.
Oil and gas are extracted by drilling into the earth and pumping the fuel out, either by conventional methods or by fracking, which uses high-pressure water to break up rock and release the fuel. Coal extraction involves removing the earth above the deposits, or drilling into the ground.
Metals are typically extracted through mining: the earth is dug away from the metal deposits, specialised tools pull out the metal, and it is then cleaned and processed to remove impurities before being transported to a manufacturing plant or refinery.
Raw material extraction accounts for a significant share of the total environmental load of a system or product, so this phase needs careful treatment in any LCA. It is also complex in data terms — the system boundaries of the evaluation, the sub-processes involved, and the energy used all have to be resolved.
This phase is the “cradle.” The final disposal of a product made from those raw materials is the “grave” — also called the End-of-Life (EoL) or waste management phase.
The phases of an LCA
An LCA is a listing and analysis of the environmental effects of a product or service across its entire life cycle — obtaining the raw materials, making the product, packaging it, distributing it, using it, and disposing of it. The method has been in use for over thirty years, and the International Organization for Standardization (ISO) published the governing standards in the 1990s. It is now a well-established part of product and environmental assessment, and can be applied at any stage of product development.
LCA supports work to:
- Evaluate the environmental impacts of products and services
- Identify and measure their ecological benefits and costs
- Assess their environmental performance
- Identify their significant ecological aspects
- Support decision-making about them
General steps in conducting an LCA
- Establish the boundaries and scope of the study
- Select the product or service to be assessed
- Identify and characterize the environmental impact categories
- Develop a methodology for estimating ecological impacts
- Estimate the environmental impacts
- Prepare the LCA report and communicate the results
Life cycle impact assessment (LCIA)
LCIA is an essential step of any LCA. Methodologies such as CML, ReCiPe, and TRACI have been developed to carry out the evaluation, and they operate at two levels: Mid-Point and End-Point.
Most LCIA procedures work at the Mid-Point level. A few, ReCiPe among them, provide End-Point evaluation. At End-Point, environmental themes such as Global Warming Potential (GWP), Human Toxicity Potential (HTP), Acidification Potential (AP), energy depletion, Eutrophication Potential (EP), and Ozone Layer Depletion (OLD) are aggregated into damage categories — damage to health, damage to ecosystems, and damage to natural resources. Eleven or more environmental themes collapse into three ecological indicators.
Choosing an appropriate LCIA approach is rarely straightforward. Reviewing industry reports and peer-reviewed academic studies is one practical route through that difficulty.
Environmental themes
Environmental themes — also called environmental loads or impact categories — are the results produced by the LCIA phase. Climate change (GWP) is the most familiar; HTP is another. The themes most often evaluated in LCA are below.
- Abiotic Depletion of Elements (ADE) — measured in kg Sb eq., the effect of natural resource exploitation: the difference between resources used across the life cycle and resource consumption.
- Abiotic Depletion of Fossil resources (ADF) — expressed in MJ, relating to depletion of energy and non-renewable resources such as natural gas.
- Acidification Potential (AP) — in kg SO₂ eq., the quantity of H⁺ ions created per kilogram of material relative to SO₂, representing the maximum acidification a material may induce.
- Eutrophication Potential (EP) — in kg phosphate eq., the potential for fertilizers to over-fertilize water and soil.
- Freshwater Aquatic Ecotoxicity Potential (FAETP) — in kg DCB eq., quantifying the harm of toxic chemicals to aquatic life.
- Global Warming Potential (GWP) — in kg CO₂ eq., the standard measure of climate change potential.
- Human Toxicity Potential (HTP) — in kg DCB eq., reflecting chemical emissions such as heavy metals to which humans are exposed.
- Terrestrial Ecotoxicity Potential (TETP) — in kg DCB eq., the impact of hazardous chemicals on terrestrial ecosystems.
LCA data
Despite the volume of secondary data available, some processes and materials are simply absent from LCA databases. Data gathering is the hardest part of any LCA. Depending on time and resources, missing data can be collected directly or estimated in several ways. Two categories are worth distinguishing:
- Foreground data — specialised data describing the particular production or product system being modeled.
- Background data — emission factor databases and literature covering generic materials, energy, transportation, and waste management.
Life cycle inventory (LCI)
LCI databases of emission factors represent the environmental impact of products and materials per functional unit across their life cycles. They hold information on the materials and energy used in production and the waste generated in use and disposal, allowing impact to be assessed at each stage from raw material extraction to final disposal. They also support comparison between products and materials, and help identify where impact can be reduced.
Examples of LCI databases
- ecoinvent — the leading global LCI database, with broad coverage of country-specific processes in industrial nations, plus extensive processes categorized as China-Data or Global Data. It provides detailed process data across thousands of processes.
- IDEA (Inventory Database for Environmental Analysis) — the leading LCA database in Japan, covering most of the country’s economic production activities. It holds around 3,800 processes based on the Japan Standard Commodity Classification, and is now accessible through SimaPro and openLCA.
IDEA holds roughly 3,800 processes; ecoinvent holds around 18,000 activities and is updated frequently with new approaches. Note that widely used LCI databases such as ecoinvent and GaBi Professional, along with their extensions, include country-specific datasets covering Japan among others.
The four iterative phases of LCA
Goal and scope definition
The study is outlined here, with its objectives and scope described. Several critical aspects are fixed at this point: the function of the system, the functional unit on which emissions and extractions will be based, and the system boundaries. Both the base scenario and the alternatives are set out.
The functional unit is the reference — the production of 1 kg of plastic, for instance, used to compare an alternative at the same 1 kg reference. Multiplying that unit impact by total production yields the net environmental impact of daily, monthly, or annual output.
Inventory analysis
Emissions to air, water, and soil, and extractions of renewable and non-renewable raw materials, are quantified. The resources the system needs to function are also determined at this stage.
Impact assessment
This phase determines the significance of the impacts identified in the inventory. Its steps are:
- Establishing impact categories, category indicators, and characterization factors
- Assessing environmental consequences — global warming, human toxicity, ecotoxicity, resource use, and others
- Classifying emissions that contribute to each impact category, with End-Point characterization weighting and aggregating them based on their Mid-Point values
- Damage characterization, combining impact categories into damage categories — human health, ecosystem quality, resources
- An optional normalization step, showing the studied product’s contribution as a fraction of the global impact in a given category
- An optional socially based weighting, accounting for relative importance or damage
Interpretation
The results are interpreted and the uncertainties assessed. Critical analysis tests the effect of the chosen boundaries and hypotheses, using sensitivity studies and uncertainty analysis — Monte Carlo simulation — to identify the main parameters and the alternatives for improvement. Environmental consequences can finally be weighed against economic or societal ones.
Evaluation levels
Within a system boundary, and within the dataset of a particular process, there are several levels of evaluation. What the dataset covers depends on its type — whether it is a gate-to-gate unit process, an aggregated process, or a process aggregated from cradle to grave.
- Gate to gate — all company or site-related operations, from material acquisition or procurement through every on-site manufacturing process up to the final steps before leaving the site gates.
- Cradle to gate — all operations from resource extraction through the final steps before exiting the site gates, including all energy and precursor production and on-site production.
- Gate to grave — extends operations from the gate through to final disposal.
- Cradle to grave — the whole life cycle: cradle-to-gate extended through the product’s use, maintenance, and End-of-Life, covering disposal, recycling, and reuse.
Conclusion
LCA is a practical tool for determining how products affect the environment and where that impact can be reduced. It helps companies lower the environmental burden of what they make, and make better decisions about how to design products and which materials to use.
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