Life Cycle Assessments as a tool for making environmentally friendly decisions
© plainpicture / Tom Chance
It is easy to make statements about environmental benefits such as 'Combustion engines are more environmentally friendly because battery production for electric vehicles is so resource-intensive' or 'Plastic bottles are more environmentally friendly than glass bottles because they are lighter and washing glass bottles consumes a lot of energy'. However, providing proper justification and defending them against objective criticism is difficult. Well-founded and reliable statements about the environmental impact of products, particularly when compared to other products, are now almost always based on life cycle assessments.
An influential ISO standard
The ISO 14040 and 14044 standards set out how to carry out life cycle assessments. The first version of this standard was published in the late 1990s. Since then, it has undergone continuous development, but its basic principles have remained unchanged for almost 30 years. It stipulates that a life cycle assessment must consider all stages of the product's life cycle and its impact on the natural environment, human health and resources. Therefore, it is not permissible to derive a general environmental benefit solely from the production or use phases. Similarly, studies that quantify greenhouse gas emissions only are not life cycle assessments, as they disregard impacts on resources. ISO-compliant studies must also be critically reviewed by external, independent experts. With this basic framework, life cycle assessment has become a pioneering method of environmental assessment. It is highly regarded due to its transparency, scientific approach, and broad applicability. Further methods, such as the Product Carbon Footprint and the Environmental Footprint, have been developed on this basis.
Four phases of life cycle assessment
Life cycle assessments comprise the following four phases:
- Defining the objective and scope of the study: The underlying question is specified and several methodological details are established. The scope of the assessment and the reference unit, also known as the functional unit, are defined.
- Life Cycle Inventory: The material and energy inputs and outputs are compiled: How much electricity and heat are consumed? What materials are required? Where possible, the data should be derived from representative measurements. Things become tricky when a process produces multiple products, such as milk and meat from livestock farming. In such cases, the environmental impact must be allocated to the products, e.g. by using physical or economic criteria.
- Life Cycle Impact Assessment: The inputs and outputs are assigned to environmental problems and their contribution to these is quantified. A well-known example of this is the conversion of one kilogram of methane into approx. 30 kg of CO₂ equivalents (based on the global warming potential over 100 years). In practice, this is usually carried out with just one click, since the life cycle assessment software stores data on all substances, showing how much each one contributes to environmental problems compared to a reference substance. Usually, between five and twenty environmental problems or indicators are evaluated, such as greenhouse gas emissions, the eutrophication and acidification of the environment, land use, the generation of particulate matter, and energy, water and metal/mineral consumption.
- Interpretation: Which processes contribute the most to the environmental impact? Is this plausible? How robust is the result if certain parameters change? These questions frequently necessitate further refinement during phases 1 to 3. If carried out carefully, the underlying question can usually be answered.
The example of battery recycling
In Phase 1, the scope of the investigation is defined in concrete terms, e.g. the recycling of nickel-cobalt-manganese (NCM) car batteries. The underlying question is also formulated: 'What are the environmental advantages and disadvantages of recycling lithium-ion batteries of the defined type (NCM), particularly compared to the primary production of the metals they contain?' The core of the system under analysis is the recycling processes (transport and unloading, dismantling, shredding and pyrometallurgical and/or hydrometallurgical processing), but the primary production of metals such as nickel, cobalt and lithium and the upstream and downstream steps are also considered.
In Phase 2, the recycling company provides data on energy and material consumption. Quality factors also play a role, such as whether the recovered nickel is as pure as primary nickel and if it can be reused immediately in new batteries. The environmental impacts of primary metals are obtained from life cycle assessment databases.
This diagram shows how Phase 2 of a life cycle assessment is carried out. The inputs and outputs of all the processes within the system boundary are compiled. For processes in the foreground system, measurements can usually be used for this purpose. The remaining data is taken from life cycle assessment databases.
Phase 3 reveals the environmental advantages and disadvantages. By replacing primary production, recycling saves large quantities of greenhouse gases but also releases a considerable amount of additional emissions. A typical emission hotspot is hydrometallurgical processing, which uses large quantities of chemicals. The greatest greenhouse gas savings result from recycling the casing (mostly aluminium) and the active materials (in this case, nickel, cobalt, and lithium). Overall, the savings outweigh the emissions. The savings are even more pronounced for other indicators, such as metal and mineral consumption, than they are for greenhouse gas emissions.
In Phase 3 of a life cycle assessment, the various environmental advantages and disadvantages are presented, including those relating to greenhouse gas emissions (Global Warming Potential).
Phase 4 examines whether the results of the life cycle assessment remain consistent when relevant parameters are varied. For example, are greenhouse gas savings still achieved when batteries containing lower levels of cobalt and higher levels of nickel are recycled? What impact would it have on the life cycle assessment if part of the environmental impact arising from the original manufacture of the batteries were also attributed to battery recycling? While the specific life cycle assessment can inform a discussion about whether such an approach is reasonable, fair and meaningful, it cannot provide a definitive answer.
Weaknesses of the life cycle assessment method
Although life cycle assessments fundamentally aim to provide a complete picture of the environmental impacts of processes and products, some environmental aspects are difficult or impossible to capture using this method. This is partly because the input-output model is generally static, meaning it does not cover temporal aspects and barely covers spatial ones. This undermines its meaningfulness, given that the location of particulate matter emissions, for example, plays a major role in their impact. In general, local environmental impacts, such as those on soil, water and air, are difficult to capture accurately using a life cycle assessment. These include microplastics, noise, toxic effects, littering and aspects of traditional nature conservation. In the case of wind turbines, for example, site-specific effects such as bird strikes or habitat fragmentation are not realistically captured, nor are the specific impacts on sensitive ecosystems such as moors or offshore habitats. To obtain a complete picture of sustainability impacts, the life cycle assessment must be supplemented by further analyses that shed light on social and economic aspects.
Life-cycle assessments allow for a great deal of interpretation. This can result in two studies that address the same question reaching different conclusions. For example, should electric vehicles, which are expected to flood the market in the years ahead, be permitted to claim green electricity? Or, in such cases involving high levels of power consumption, should other, more flexible sources of electricity be assigned, such as those from natural gas power plants? One argument is that renewable energies are already operating at full capacity and are needed to meet existing demand. Such questions give rise to repeated discussions about limiting the scope for interpretation in life-cycle assessments and harmonising key methodological specifications for specific questions instead.
Two approaches determine the use of life cycle assessments
For some years now, two fundamental applications for life cycle assessments have emerged:
- Attributional approach:
- Focus on established processes and products
- Regularly occurring environmental impacts are compiled and allocated to the products.
- Consequential approach:
- Focus on innovations
- Potential future impacts and savings likely to arise from new or different process or product variants compared to established market products are examined.
In this context, questions about what the increasingly decarbonised global economy of the future will look like, and which indicators will be the most helpful once carbon footprints become less significant, are becoming ever more important.
Current developments and challenges
Additionally, several other interesting developments and challenges are currently being observed within the life cycle assessment community. These include:
- The location at which emissions or resource consumption occur should be reflected more accurately in life cycle assessments. This already works well for water consumption, for example, as it makes a significant difference whether water is extracted in an arid region or in a country with high water availability.
- With regard to the greenhouse gas impact of flights, there is currently no consensus on how to convert contrails, water vapour, nitrogen oxides and soot into ‘CO₂ equivalents.
- Life cycle assessment databases collect information on the environmental impact of materials and processes. These databases are constantly growing and are kept as up to date as possible. They can be compared to Wikipedia, where knowledge is shared and grows continuously on a global scale.
- Unfortunately, life cycle assessments have increasingly been equated with carbon footprints and greenhouse gas balances for some years now. This 'carbon tunnel' overlooks many environmental, social and economic aspects.
- It remains to be seen in the years ahead whether AI tools such as One Click LCA will make it easier to carry out life cycle assessments and contribute to cost reductions, or whether the quality and, consequently, the high level of acceptance of such studies worldwide will suffer.
Life cycle assessments as a catalyst
Life cycle assessments are a well-established scientific tool for the systematic and transparent evaluation of environmental impacts. They provide politics, business and society with a robust foundation for decision-making. At the same time, they are well-suited to the transparent articulation of uncertainties and conflicting objectives. Consequently, life cycle assessments are not intended to offer a definitive conclusion; rather, they are an invitation to engage in discourse and contribute to shaping the transition towards a sustainable and climate-neutral society in a fact-based manner.
Tobias Wagner frequently uses life cycle assessments in his research and works in Oeko-Institut’s Resources & Transport Division in Darmstadt.
