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What is life-cycle assessment?How is LCA used to contribute to a sustainable bioeconomy?What are the limitations? I Case studies

What is life-cycle assessment?

Life-Cycle Assessment (LCA) focuses on the material flows and related environmental pressures of products or services at the level of product systems. In a full life cycle assessment, modelling starts from the extraction of the resources needed to produce the product from the environment to its disposal after product use or to a point where co-products, by-products or waste for recycling cross the system boundary, i.e. the product system. This approach is also referred to as "cradle to grave". Most commonly, an LCA is used to compare the environmental performance of different but functionally identical systems. In the case of biomass systems, for example, this would be the comparison with a fossil system. The reference flow in this comparison is the functional unit, which is defined as the quantified benefit of a product system.

The LCA is a structured, comprehensive and internationally standardised methodology. The ISO standards 14040:2006 and 14044:2006 (ISO 2006a; b) are relevant for this methodology. It defines the fundamental phases of the LCA: 1.) goal and scope definition; 2.) inventory analysis; 3.) impact assessment; 4.) interpretation.

For Impact assessment, a a whole bouquet of methods exists, but the resource footprints for energy, land, material and water have been shown to be sufficient to cover over 80 % of the variance in the total environmental impacts associated with a product [1]. Supplemented by the climate footprint, this results in a footprint set that is suitable for a comprehensive assessment of environmental impacts. While for the energy and land footprint we use standard LCA methods [2], the methodology for the product carbon footprint (PCF) is based on the LCA method, just being limited to the one impact category Global Warming (ISO DIN EN ISO 14067). The product material footprint (PMF) represents a central instrument to assess the potential environmental impacts of products based on their life-cycle-wide material use [3]. The water scarity footprint (WSF) is a set of indicators to assess quantitative and qualitative water use along the supply chain of a product with respect to regional water availability [4].

How is LCA used to contribute to a sustainable bioeconomy?

LCA is used to compare products and assess their relative sustainability. In this way it can compare the substitution potential of products produced from biomass to those from non-renewable sources. For example,  Verkerk et al. (2021) reviewed 64 studies to find that  “use of wood and wood-based products is generally associated with lower fossil and process-based emissions when compared to non-wood, functionally equivalent products” [5]. Three-quarters of the reviewed studies focused on the construction sector and most refer to products in North America and Europe.

LCA can also be used to assess the absolute sustainability of products [6]. The material footprint uses two indicators to measure the biotic part: The RMI biotic measures the used biotic raw materials related to the production activities in the economy and the TMR biotic measures the extracted biotic primary materials related to the intervention in nature, including deposition. The RMI biotic could be used, e.g., to assess the primary timber biomass used for wooden products related to the net annual increment (NAI) of forests in the spatial scope area of the analysis. The NAI measures the regrowth of forests in terms of the timber harvest potential; for agricultural harvests, the total agricultural production could be used as a proxy reference. The TMR biotic could be related to the actual net primary production (NPP) or the hypothetical natural net primary production in the area corresponding to the spatial scope of the analysis.

The product related context is also referred to as the micro level. The reference to higher-level material flows, on the other hand, such as total wood consumption in Germany, is referred to as the macro level. The two approaches are complementary in some respects. While at the macro level, for example, information is obtained on macroeconomic systems, the micro level provides granular information on the drivers of environmental impacts (and thus also starting points for optimisation) or also decision-making bases for product policy measures.

As various studies show, however, it is quite common to use the LCA method for the assessment of higher-level material flows. For example, it can already be found in the life cycle assessment of graphic papers published on behalf of the Federal Environment Agency in 2000. In more recent studies, aspects such as the cascading use of biogenic raw materials [7] [8] or the identification of priority use paths of biomass in the context of national environmental goals [8] are increasingly being investigated.

What are the limitations?

For all its versatility and wide-ranging applications, LCA cannot entirely cover every type of environmental impact. At the same time, the flexibility of the instrument means that results must always be interpreted in the light of the specific question, depend on the definition of the specific individual case and general findings are often difficult to generalise. This allows the LCA to conduct precise case analyses with a high level of detail. At the level of large material flows, however, this level of detail can be a constraint. For these cases, gross simplifications are necessary, which counteract the actual strength of LCA. Thus, the LCA approach for the macro level is too granular in terms of its basic life cycle principle and can therefore hardly be applied meaningfully, or only with either great effort or extreme simplification.

It must also be emphasised that the standardisation of LCA is limited despite all efforts, which means: the concrete method (e.g. type of system boundary definition, selection of an attributive or consequential approach, selection of impact categories, interpretation approaches) must always be explained anew.

Case studies

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Notes and references

  1. Steinmann et al. (2016). How Many Environmental Impact Indicators Are Needed in the Evaluation of Product Life Cycles? Environ. Sci. Technol. doi: 10.1021/acs.est.5b05179.
  2. Schomberg et al. (2022). Spatially explicit life cycle assessments reveal hotspots of environmental impacts from renewable electricity generation. Commun. Earth Environ. doi: 10.1038/s43247-022-00521-7.
  3. Mostert and Bringezu (2019). Measuring Product Material Footprint as New Life Cycle Impact Assessment Method: Indicators and Abiotic Characterization Factors. Resources. doi:10.3390/resources8020061.
  4. Schomberg et al. (2021). Extended life cycle assessment reveals the spatially-explicit water scarcity footprint of a lithium-ion battery storage.  Commun Earth Environ. doi: 10.1038/s43247-020-00080-9.
  5. Verkerk et al. (2021). The role of forest products in the global bioeconomy – Enabling substitution by wood-based products and contributing to the Sustainable Development Goals FAO. doi: 10.4060/cb7274en.
  6. Mostert and Bringezu (2022). Biotic Part of the Product Material Footprint: Comparison of Indicators Regarding Their Interpretation and Applicability. Resources. doi: 10.3390/resources11060056.
  7. Fehrenbach et al. (2017): Biomassekaskaden: Mehr Ressourceneffizienz durch stoffliche Kaskadennutzung von Biomasse – von der Theorie zur Praxis. UBA. Available at: https://www.umweltbundesamt.de/publikationen/biomassekaskaden-mehr-ressourceneffizienz-durch
  8. Mehr et al. (2018). Environmentally optimal wood use in Switzerland - Investigating the relevance of material cascades. Resourc., Conservat. & Recycl. doi: 10.1016/j.resconrec.2017.12.026.