Many decisions are made during the life cycle of a product, e.g., whether to replace a product or to keep using it. To pinpoint the “greener” choice, the consequential environmental effects of each choice should be estimated. Hereto, only activities occurring after the decision should be considered and, thus, not necessarily the complete product life cycle. Decisions are taken at different levels in the economy, ranging from small scale (e.g., few individual purchases) to large scale (e.g., policies). In this article, we introduce a framework that mainly focuses on the small-scale decision of replacement of a product in usage, illustrated in case of a petrol versus an electric car. For a fixed time span of usage (functional unit), the product system composition varies based on the selected time of replacement. Many market mechanisms occur within the cause-effect chain, for which argued presumptions are necessary. For example, the purchase of the alternative product is reasoned to possibly induce an additional product supply. Moreover, if the product is not obsolete after initial usage, it is sold in the secondhand market and will thus displace the average market mix. The developed framework for this small-scale replacement decision is different from the alternative consequential approach of ecoinvent that covers a different decision, namely, a marginal increase in demand, e.g., of car usage, at market level. In our framework, a ratio for the amount of newly car produced per purchase is introduced. For the case study, the global warming potential over 100 years is estimated, this using general data from databases and time-varying market mix (in composition), car technology, and electricity mix. A set of equations is introduced that serves as a first simplified framework. Bearing in mind limitations, if the petrol car is disposed of as waste after initial usage whereas the electric car resold, it is estimated that a replacement of the petrol car by the electric car at any time lowers the impact on climate change. A better characterization of impact over time and market and agent-based modeling should be at the core of further efforts, especially when upscaling to large-scale decisions. Framework and insights are provided on the modeling of the environmental effects of a replacement decision. Finally, this article may serve as a stepping-stone towards an integrated consequential modeling of sustainability impact of product-related decisions, looking beyond a normative consideration of a fixed product life cycle.

中文翻译：

---

何时更换产品以减少对环境的影响？——一个相应的 LCA 框架和汽车更换案例研究

许多决定是在产品的生命周期内做出的，例如，是更换产品还是继续使用它。为了确定“更环保”的选择，应该估计每个选择的相应环境影响。因此，只应考虑在决策之后发生的活动，因此不一定是完整的产品生命周期。决策是在经济的不同层面做出的，从小规模（例如，很少有个人购买）到大规模（例如，政策）。在本文中，我们介绍了一个主要关注更换使用中产品的小规模决策的框架，以汽油车与电动车为例。对于固定的使用时间跨度（功能单元），产品系统构成根据选择的更换时间而变化。许多市场机制发生在因果链中，为此需要有争论的假设。例如，购买替代产品被认为可能会导致额外的产品供应。此外，如果产品在初次使用后没有过时，它会在二手市场上出售，从而取代平均市场组合。这种小规模更换决策的开发框架不同于ecoinvent 的替代结果方法，后者涵盖了不同的决策，即市场水平上需求的边际增加，例如汽车使用量。在我们的框架中，引入了每次购买新汽车数量的比率。对于案例研究，估计了 100 年的全球变暖潜力，这使用来自数据库和随时间变化的市场组合（组成）、汽车技术和电力组合的一般数据。引入了一组方程作为第一个简化框架。考虑到局限性，如果汽油车在初次使用后作为废物处理而电动汽车转售，估计随时以电动汽车代替汽油车可以降低对气候变化的影响。更好地表征随时间和市场的影响以及基于代理的建模应该是进一步努力的核心，尤其是在升级到大规模决策时。提供了关于替代决策的环境影响建模的框架和见解。最后，