Consumption-as-usual instead of ceteris paribus assumption for demand

Abstract

Background, aims, and scope Life cycle assessment (LCA) according to ISO 14040 standard (ISO-LCA) is applied to assess the environmental impact per functional unit of new or modified products. However, new or modified products can also induce demand changes-socalled rebound effects. If overall environmental impact is of interest, there is a need to assess the potential magnitude of such rebound effects and to allow recommendations on how to mitigate these effects. To do so, this study proposes to complement the constant demand assumption (implicitly assumed by the ISO-LCA), commonly known as the ceteris paribus assumption, with a consumption-as-usual assumption allowing a systematic stepwise inclusion of rebound effects. Materials and methods We base our results on a formal description of household consumption. To indicate the relevance of the proposed integration of rebound effects, different comparative LCAs are reviewed and the concept is applied to mobility as illustrative examples. Results Based on a description of household demand and consumption feedback loops, we propose the consumptionas-usual concept, which in contrast to the constant demand assumption assumes that (1) the use of household resources for consumption does not change and (2) preferences remain the same. Household resources for example are purchasing power (we assume that households do not work less), time, and living space. We outline how this concept allows integrating potential rebound effects into ISO-LCA by considering three different cases of reallocating freed household resources. To illustrate the use of the consumption-as-usual concept, we draw implications for different comparative LCAs from the literature and illustrate cases with income and time rebound for different personal travel modes. Discussion The consumption-as-usual concept is applicable to a broad range of product modifications and allows an important complementation of the LCA regarding rebound effects. For products with various changes in the need for household resources, the assessment becomes however a challenging task. The limits of the consumption-as-usual concept are mainly given by its two underlying assumptions. Therefore, new or modified products with the potential to change consumer preferences or even the amount of household resources used for consumption go beyond this concept. Conclusions The integration of rebound effects is feasible for many comparative LCAs. It helps in increasing the reliability of the assessment of overall environmental impact reduction through new or modified products. In addition, a basis is provided with which to mitigate rebound effects and give appropriate recommendations to product users. Recommendations and perspectives Potential rebound effects should be included in LCA in order to guide consumers and policy towards sustainable consumption. We recommend the consumption-as-usual concept for this purpose. To predict rebound effects under consumption as usual instead of outlining potential amplitudes, further research on househo...

Life Cycle Sustainability Assessment: What Is It and What Are Its Challenges?

“…However, we feel that deepening discussions are very important as part of maturing LCSA approaches. We illustrate this by the example of modelling rebound effects in a life cycle perspective, which has been addressed by several authors (Hertwich 2005 ;Hofstetter et al 2006 ;Thiesen et al 2008 ;Girod et al 2011 ;Druckman et al 2011 ;Font Vivanco and Voet 2014 ). Hertwich ( 2005 ) defi nes the rebound effect as 'a behavioural or other systemic response to a measure taken to reduce environmental impacts that offsets the effect of the measure.…”

From Sustainable Production to Sustainable Consumption

“…The following consumption-induced secondary consequences and aspects that modify them can be differentiated (compiled from Becker 1976;Eyerer and Wolf 2000;Hofstetter et al 2006;Weidema 2008;Girod et al 2010, with additions):…”

“…"More of the same function or need fulfilment" (originally termed "More of similar" by Girod et al (2010)) means that e.g. saved time due to a faster car will be used to generally increase travelling, also with other transport means.…”

“…by Girod et al 2010) for lacking to capture the various secondary consequences of consumption decisions, including due to changes in the available income, time, and other household resources. 2 In this chapter, instead of asking for changing product LCA, the authors follow a different approach, namely that of proposing differentiated life cycle modelling methods for the two fundamentally different perspectives: the product perspective and the consumption perspective, resulting in dedicated approaches for different actors and applications (Lundie et al 2007;European Commission 2010;: different applications imply a different purpose and scope of supported decisions and hence require a differentiated guidance.…”

“…This draws on the works of Hofstetter et al (2006), Weidema (2008), Girod et al (2010) and others, and ends in an outlook of recommended next steps to further develop, differentiate, and deploy LCA as a tool that equally well supports efforts towards sustainable consumption as it already supports decisions on sustainable production and products.…”