In many regions and at the planetary scale, human pressures on the environment exceed levels that natural systems can sustain. These pressures are caused by networks of human activities, which often extend across countries and continents due to global trade. This has led to an increasing requirement for methods that enable absolute environmental sustainability assessment (AESA) of anthropogenic systems and which have a basis in life cycle assessment (LCA). Such methods enable the comparison of environmental impacts of products, companies, nations, etc, with an assigned share of environmental carrying capacity for various impact categories. This study is the first systematic review of LCA-based AESA methods and their applications. After developing a framework for LCA-based AESA methods, we identified 45 relevant studies through an initial survey, database searches and citation analysis. We characterized these studies according to their intended application, impact categories, basis of carrying capacity estimates, spatial differentiation of environmental model and principles for assigning carrying capacity. We then characterized all method applications and synthesized their results. Based on this assessment, we present recommendations to practitioners on the selection and use of existing LCA-based AESA methods, as well as ways to perform assessments and communicate results to decision-makers. Furthermore, we identify future research priorities intended to extend coverage of all components of the proposed method framework, improve modeling and increase the applicability of methods.

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Target values for creating carbon budgets for buildings are important for developing climateneutral building stocks. A lack of clarity currently exists for defining carbon budgets for buildings and what constitutes a unit of assessment-particularly the distinction between production-and consumption-based accounting. These different perspectives on the system and the function that is assessed hinder a clear and commonly agreed definition of 'carbon budgets' for building construction and operation. This paper explores the processes for establishing a carbon budget for residential and non-residential buildings. A detailed review of current approaches to budget allocation is presented. The temporal and spatial scales of evaluation are considered as well as the distribution rules for sharing the budget between parties or activities. This analysis highlights the crucial need to define the temporal scale, the roles of buildings as physical artefacts and their economic activities. A framework is proposed to accommodate these different perspectives and spatio-temporal scales towards harmonised and comparable cross-sectoral budget definitions. Policy relevance The potential to develop, implement and monitor greenhouse gas-related policies and strategies for buildings will depend on the provision of clear targets. Based on global limits, a carbon budget can establish system boundaries and scalable targets. An operational framework is presented that clarifies greenhouse gas targets for buildings in the different parts of the world that is adaptable to the context and circumstances of a particular place. A carbon budget can enable national regulators to set feasible and legally binding requirements. This will assist the many different stakeholders responsible for decisions on buildings to coordinate and incorporate their specific responsibility at one specific level or scale of activity to ensure overall compliance. Therefore, determining a task specific carbon budget requires an appropriate management of the global carbon budget to ensure that specific budgets overlap, but that the sum of them is equal to the available global budget without double-counting.

Given the increasing environmental impacts associated with global agri-food systems, operating and developing these systems within the so-called absolute environmental boundaries has become crucial, and hence the absolute environmental sustainability concept is particularly relevant. This study introduces an approach called absolute sustainability-based life cycle assessment (ASLCA) that informs the climate impacts of an agri-food system (on any economic level) in absolute terms. First, a global carbon budget was calculated that is sufficient to limit global warming to below 2°C. Next, a share of the carbon budget available to the global agri-food sector was estimated, and then it was shared between agri-food systems on multiple economic levels using four alternative methods. Third, the climate impacts of those systems were calculated using life cycle assessment methodology and were benchmarked against those carbon budget shares. This approach was used to assess a number of New Zealand agri-food systems (agri-food sector, horticulture industries and products) to investigate how these systems operated relative to their carbon budget shares. The results showed that, in 2013, the New Zealand agri-food systems were within their carbon budget shares for one of the four methods, and illustrated the scale of change required for agri-food systems to perform within their carbon budget shares. This method can potentially be extended to consider other environmental impacts with global boundaries; however, further development of the ASLCA is necessary to account for other environmental impacts whose boundaries are only meaningful when defined at a regional or local level. Keywords:absolute environmental sustainability agri-food carbon budget climate change industrial ecology life cycle assessment Supporting information is linked to this article on the JIE website