The enormous environmental impact of construction is becoming increasingly apparent and unacceptable to many structural engineers, whose designs typically account for the majority of a building’s embodied carbon. It is timely, therefore, that consensus is forming around a methodology for calculating embodied carbon. This encourages the inclusion of all life cycle stages, from material production and construction, through use and eventual demolition, disposal and reuse. In practice, however, end-of-life processes are fraught with uncertainty and often ignored, despite the potentially large associated carbon fluxes. Further uncertainty exists when considering bio-based construction materials, which store carbon during use. There are no widely-accepted means of accounting for timing of these carbon fluxes, despite the long service life of most buildings. Could we consider whole-life carbon in a more holistic and climate-focused way?

This article uses dynamic life cycle assessment to convert greenhouse gas emission histories to key climate impacts using a simple dynamic model. The implications for structural design decisions are explored by comparing concrete, steel and timber options for a typical medium-rise building structure. Concrete is found to have a higher impact than steel, with the climate response of both options dominated by the large initial emissions of material production and construction. Timber has the smallest impact, for this example, under a typical scenario with sustainable forest management and re-emission of sequestered carbon at end-of-life. The analysis takes a forward-looking approach to sequestration, with timing corresponding to the growth of replanted trees. An optimistic timber scenario, whereby future carbon-capture technology avoids most end-of-life emissions, demonstrates the possibility of structures with small long-term climate cooling effects. Conversely, in a hypothetical worst-case scenario where no replanting or subsequent sequestration occurs, the long-term warming effect of the timber structure is increased by the net emission of biogenic carbon.

Although end-of-life processes are important in the long-term, particularly for timber, the analysis also highlights the importance of the initial emissions from material production and construction. These cause high rates of short-term temperature increase and prolonged accumulation of radiative heat for all the buildings, but the impacts are again lowest for timber.

Most importantly, the investigation shows how dynamic life cycle assessment can be used to explore climate impacts in a comprehensive, graphical and unbiased way. As a simple extension to established methodologies for calculating embodied carbon, it is a powerful decision making tool in the climate emergency.

对于建筑的巨大环境影响正变得越来越明显，并且对于许多结构工程师来说，这种影响是无法接受的，他们的设计通常占建筑物内含碳量的大部分。因此，及时地围绕计算含碳量的方法论形成共识。这鼓励从材料生产和构造到使用和最终拆卸，处置和再利用的所有生命周期阶段包括在内。然而，实际上，尽管潜在的相关碳通量很大，但报废过程充满不确定性，常常被忽略。考虑使用生物基建筑材料时会存在更多不确定性，这些材料在使用过程中会积碳。没有广泛接受的方法来解释这些碳通量的时间，尽管大多数建筑物使用寿命长。我们能否以更全面，更注重气候的方式考虑整个生命的碳排放？

本文使用动态生命周期评估，通过一个简单的动态模型将温室气体排放历史转换为关键的气候影响。通过比较典型的中层建筑结构的混凝土，钢材和木材选择，探索了对结构设计决策的影响。人们发现混凝土的影响比钢铁要强，这两种选择的气候响应主要是材料生产和建筑的大量初始排放。在此示例中，木材的影响最小，在这种情况下，具有可持续的森林管理和寿命终止时的固存碳再排放。该分析采用前瞻性方法进行固存，其时机与重新种植的树木的生长相对应。乐观的木材情况，从而使未来的碳捕获技术避免了大多数使用寿命终止的排放，证明了具有长期长期气候冷却效应的结构的可能性。相反，在假设的最坏情况下，没有发生重新种植或随后的隔离的情况，生物碳净排放会增加木材结构的长期变暖效果。

尽管报废过程从长远来看很重要，特别是对于木材而言，但分析还强调了材料生产和建筑产生的初始排放的重要性。这些会导致所有建筑物的短期温度升高幅度很高，并且辐射热量会长时间积累，但对木材的影响仍然是最低的。

最重要的是，调查显示了如何使用动态生命周期评估以全面，图形化和无偏见的方式探索气候影响。作为已建立的计算内在碳计算方法的简单扩展，它是气候紧急情况下的强大决策工具。