This paper presents an improved methodological approach for studying life cycle impacts (especially global warming) from changes in crop production practices. The paper seeks to improve the quantitative assessment via better tools and it seeks to break down results in categories that are logically separate and thereby easy to explain to farmers and other relevant stakeholder groups. The methodological framework is illustrated by a concrete study of a phosphate inoculant introduced in US corn production.
The framework considers a shift from an initial agricultural practice (reference system) to an alternative practice (alternative system) on an area of cropland A. To ensure system equivalence (same functional output), the alternative system is expanded with displaced or induced crop production elsewhere to level out potential changes in crop output from the area A. Upstream effects are analyzed in terms of changes in agricultural inputs to the area A. The yield effect is quantified by assessing the impacts from changes in crop production elsewhere. The field effect from potential changes in direct emissions from the field is quantified via biogeochemical modeling. Downstream effects are assessed as impacts from potential changes in post-harvest treatment, e.g., changes in drying requirements (if crop moisture changes).
An inoculant with the soil fungus Penicillium bilaiae has been shown to increase corn yields in Minnesota by 0.44 Mg ha−1 (~ 4%). For global warming, the upstream effect (inoculant production) was 0.4 kg CO2e per hectare treated. The field effect (estimated via the biogeochemical model DayCent) was − 250 kg CO2e ha−1 (increased soil carbon and reduced N2O emissions) and the yield effect (estimated by simple system expansion) was − 140 kg CO2e ha−1 (corn production displaced elsewhere). There were no downstream effects. The total change per Mg dried corn produced was − 36 kg CO2e corresponding to a 14% decrease in global warming impacts. Combining more advanced methods indicates that results may vary from − 27 to − 40 kg CO2e per Mg corn.
The present paper illustrates how environmental impacts from changes in agricultural practices can be logically categorized according to where in the life cycle they occur. The paper also illustrates how changes in emissions directly from the field (the field effect) can be assessed by biogeochemical modeling, thereby improving life cycle inventory modeling and addressing concerns in the literature. It is recommended to use the presented approach in any LCA of changes in agricultural practices.
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This position paper provides an LCA perspective on the development, adoption, and implementation of CE, while pointing out strengths and challenges in LCA as an assessment technique for CE strategies.
Life cycle interpretation is the fourth and last phase of life cycle assessment (LCA). Being a “pivot” phase linking all other phases and the conclusions and recommendations from an LCA study, it represents a challenging task for practitioners, who miss harmonized guidelines that are sufficiently complete, detailed, and practical to conduct its different steps effectively. Here, we aim to bridge this gap. We review available literature describing the life cycle interpretation phase, including standards, LCA books, technical reports, and relevant scientific literature. On this basis, we evaluate and clarify the definition and purposes of the interpretation phase and propose an array of methods supporting its conduct in LCA practice. The five steps of interpretation defined in ISO 14040–44 are proposed to be reorganized around a framework that offers a more pragmatic approach to interpretation. It orders the steps as follows: (i) completeness check, (ii) consistency check, (iii) sensitivity check, (iv) identification of significant issues, and (v) conclusions, limitations, and recommendations. We provide toolboxes, consisting of methods and procedures supporting the analyses, computations, points to evaluate or check, and reflective processes for each of these steps. All methods are succinctly discussed with relevant referencing for further details of their applications. This proposed framework, substantiated with the large variety of methods, is envisioned to help LCA practitioners increase the relevance of their interpretation and the soundness of their conclusions and recommendations. It is a first step toward a more comprehensive and harmonized LCA practice to improve the reliability and credibility of LCA studies.
Assessing impacts of abiotic resource use has been a topic of persistent debate among life cycle impact assessment (LCIA) method developers and a source of confusion for life cycle assessment (LCA) practitioners considering the different interpretations of the safeguard subject for mineral resources and the resulting variety of LCIA methods to choose from. Based on the review and assessment of 27 existing LCIA methods, accomplished in the first part of this paper series (Sonderegger et al. 2020), this paper provides recommendations regarding the application-dependent use of existing methods and areas for future method development.
Within the “global guidance for LCIA indicators and methods” project of the Life Cycle Initiative hosted by UN Environment, 62 members of the “task force mineral resources” representing different stakeholders discussed the strengths and limitations of existing LCIA methods and developed initial conclusions. These were used by a subgroup of eight members at the Pellston Workshop® held in Valencia, Spain, to derive recommendations on the application-dependent use and future development of impact assessment methods.
First, the safeguard subject for mineral resources within the area of protection (AoP) natural resources was defined. Subsequently, seven key questions regarding the consequences of mineral resource use were formulated, grouped into “inside-out” related questions (i.e., current resource use leading to changes in opportunities for future users to use resources) and “outside-in” related questions (i.e., potential restrictions of resource availability for current resource users). Existing LCIA methods were assigned to these questions, and seven methods (ADPultimate reserves, SOPURR, LIME2endpoint, CEENE, ADPeconomic reserves, ESSENZ, and GeoPolRisk) are recommended for use in current LCA studies at different levels of recommendation. All 27 identified LCIA methods were tested on an LCA case study of an electric vehicle, and yielded divergent results due to their modeling of impact mechanisms that address different questions related to mineral resource use. Besides method-specific recommendations, we recommend that all methods increase the number of minerals covered, regularly update their characterization factors, and consider the inclusion of secondary resources and anthropogenic stocks. Furthermore, the concept of dissipative resource use should be defined and integrated in future method developments.
In an international consensus-finding process, the current challenges of assessing impacts of resource use in LCA have been addressed by defining the safeguard subject for mineral resources, formulating key questions related to this safeguard subject, recommending existing LCIA methods in relation to these questions, and highlighting areas for future method development.
The safeguard subject of the Area of Protection “natural Resources,” particularly regarding mineral resources, has long been debated. Consequently, a variety of life cycle impact assessment methods based on different concepts are available. The Life Cycle Initiative, hosted by the UN Environment, established an expert task force on “Mineral Resources” to review existing methods (this article) and provide guidance for application-dependent use of the methods and recommendations for further methodological development (Berger et al. in Int J Life Cycle Assess, 2020).
Starting in 2017, the task force developed a white paper, which served as its main input to a SETAC Pellston Workshop® in June 2018, in which a sub-group of the task force members developed recommendations for assessing impacts of mineral resource use in LCA. This article, based mainly on the white paper and pre-workshop discussions, presents a thorough review of 27 different life cycle impact assessment methods for mineral resource use in the “natural resources” area of protection. The methods are categorized according to their basic impact mechanisms, described and compared, and assessed against a comprehensive set of criteria.
Four method categories have been identified and their underlying concepts are described based on existing literature: depletion methods, future efforts methods, thermodynamic accounting methods, and supply risk methods. While we consider depletion and future efforts methods more “traditional” life cycle impact assessment methods, thermodynamic accounting and supply risk methods are rather providing complementary information. Within each method category, differences between methods are discussed in detail, which allows for further sub-categorization and better understanding of what the methods actually assess.
We provide a thorough review of existing life cycle impact assessment methods addressing impacts of mineral resource use, covering a broad overview of basic impact mechanisms to a detailed discussion of method-specific modeling. This supports a better understanding of what the methods actually assess and highlights their strengths and limitations. Building on these insights, Berger et al. (Int J Life Cycle Assess, 2020) provide recommendations for application-dependent use of the methods, along with recommendations for further methodological development.
System incompleteness is an outstanding issue in footprint studies, causing systemic truncation errors and misestimation of results. This issue has many implications for analysts, from misleading conclusions in comparative assessments to hampering effective data exchange and comparability between models. A key element of system incompleteness is the treatment of services and capital, which are, respectively, often misrepresented in life cycle assessment (LCA, due to being largely missing in process-based databases) and input–output analysis (IOA, due to being exogenous to the intermediate uses). To gain insight into both the magnitude of such truncation errors and how to mitigate these, this paper analyses the impact of systematically including both services and capital in the system descriptions used in footprint analysis.
Manufactured capital is endogenised into the input–output table (IOT) by using capital use information from growth and productivity accounts. Comprehensive service inputs are included in life cycle inventories (LCIs) by means of integrated hybrid LCA. For illustration purposes, the method is applied on two popular LCI and IOT databases—ecoinvent and EXIOBASE—and four common modelling applications of LCA and IOA: LCA- and IOA-based footprints, comparison between IOA and LCA footprints, and a case study using hybrid LCA.
The results suggest that the inclusion of both services and capital, either individually or in combination, leads to overall notable differences in footprint results, for example, median relative changes in carbon footprints of 41% and 12%, respectively, for IOA- and LCA-based footprints. Such differences can have notable implications, such as redefining environmental ‘hotspots’ and reversing the results of comparative analyses. Results, however, vary greatly across applications, impact categories and industry/product types, and so specific implications will depend on the research question and scope of analysis. Overall, endogenising capital has a larger impact than including missing services.
This exercise highlights two fundamental aspects for footprint modelling: the trade-offs between external and internal consistency and the facilitation of model integration. First, the proposed method increases system completeness of LCA (external consistency with the subject of study, namely economic systems) at the expense of internal inconsistencies stemming from ontological discrepancies between input–output and LCI systems (e.g. system completeness). This discrepancy can be mitigated by exploiting the potential of integrated hybrid LCA to create a highly interconnected hybrid system. Second, this approach shows how footprint models can complement each other towards more comprehensive and consistent descriptions of the socio-economic metabolism.
.... of Life Cycle Assessment: Theory and Practice, edited by Michael Z. Hauschild, Ralph K. Rosenbaum, and Stig Irving Olsen; Environmental Life Cycle Assessment, by Olivier Jolliet, Myriam Saadé-Sbeih, Shanna Shaked, Alexandre Jolliet, and Pierre Crettaz; and Life Cycle Assessment: Quantitative Approaches for Decisions That Matter, by H. Scott Matthews, Chris T. Hendrickson, and Deanna H. Matthews
This book review by Bo Weidema and Miguel Brandão is supplemented more detailed comments on each of the three textbooks, available from this link: https://ilca.es/news/review-of-three-recent-textbooks-on-lca/
Considering the general agreement in the literature that environmental labelling should be based on consequential modelling, while all actually implemented environmental labelling schemes are based on attributional modelling, we investigate the arguments for this situation as provided in the literature, and whether a dual label, representing on the same label the attributional and consequential results for the same product, can be a relevant solution or at least contribute to a more informed discussion.
We developed a dual label for three hypothetical, comparable products and presented this for a small test audience, asking three questions, namely “Which product would you choose?”, “Was the attributional information useful?” and “Would you accept to have only the attributional information?”
From this small pilot exercise, it appears that informed consumers may have a strong preference for consequential information and that the main problem in communicating consequential results is that they are perceived as less trustworthy and more uncertain due to the fact that the consequences are located in the future. It thus appears important to build into a consequential label some increased level of guarantee of future good behaviour.
We propose to apply the above questions to a more statistically representative audience to confirm or refute the findings of this little test exercise.
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A prerequisite to improving the sustainability of agriculture are reliable methods to identify and quantify types of environmental impact. This collection summarises current research on the use of life cycle assessment (LCA) and other modelling techniques to measure and improve the sustainability of agriculture.
Part 1 looks at current best practice and key methodological challenges in life cycle assessment. Part 2 reviews ways of modelling particular types of impact, from nutrient and carbon cycles to freshwater balances, energy use, pesticide use and biodiversity. Part 3 reviews the environmental assessment and optimization of sectors such as crops, ruminant and other livestock production as well as by-products.
Assessing the environmental impact of agriculture will be a standard reference for researchers in agricultural and environmental science concerned with understanding and mitigating the environmental impact of agriculture.
