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The global challenge of large-scale climate change mitigation requires action also in the building and construction sector. From a life cycle perspective, and considering the mitigation timeframe, the issue of reducing embodied GHG emissions is gaining attention. Effective ways to reduce embodied GHG emissions have been proposed by the use of fast-growing, bio-based materials, due to carbon sequestered in the biomass. Another promising, yet largely under-explored option is to harness the environmental potentials and low embodied GHG emissions of earth-based materials for building construction. Earth construction dates back from 10,000 to 8000 BC and has been derived in many vernacular construction techniques. More recently, some earthen techniques have been modified, using stabilizers, mainly cement and lime, to increase strength and water stability. The objective of this article is to compare existing literature performed on the LCAs applied to various earthen construction techniques and seek for key factors. Transports as well as binder stabilizations are very influent on the results. Climate, nature of local soil, and geographical context are very influent on functionalities of buildings, mix design and transports, themselves influencing environmental impacts. According to design choices and local context, earthen construction is not always better than concrete. This means that no universal solution can be recommended with the LCA of an earthen wall. The solution has to be adapted to the local context. All references comparing walls material to conventional materials at the building scale, find better environmental performances of earthen walls compared to fired brick walls. However, a full comparison between earthen construction and conventional materials should account for the use phase: combining LCA models with thermal and durability models is a key research issue. Finally, it certainly would be useful to seek for solutions with best environmental performances in a local context, accounting for the nature of soil, the building's functional requirements as well as geographical and cultural specificities. Such an approach would ensure to lower environmental impacts but represents a drastic change in current construction practices. Whereas today building materials are standardized in order to fit with construction working practices, this paradigm shift would require to adapt construction working practices to the local material and context. As earthen construction is today, in many countries of the world, a re-emerging technique, and new professional practices are yet to be established, it seems possible to make this paradigm shift happen. Certainly, in the current context of the need to substantially reduce building-related GHG emissions, there is still strong potential in earth construction techniques for both research and building practice.

The need for a vast quantity of new buildings to address the increase in population and living standards is opposed to the need for tackling global warming and the decline in biodiversity. To overcome this twofold challenge, there is a need to move towards a more circular economy by widely using a combination of alternative low-carbon construction materials, alternative technologies and practices. Soils or earth were widely used by builders before World War II, as a primary resource to manufacture materials and structures of vernacular architecture. Centuries of empirical practices have led to a variety of techniques to implement earth, known as rammed earth, cob and adobe masonry among others. Earth refers to local soil with a variable composition but at least containing a small percentage of clay that would simply solidify by drying without any baking. This paper discusses why and how earth naturally embeds high-tech properties for sustainable construction. Then the potential of earth to contribute to addressing the global challenge of modern architecture and the need to re-think building practices is also explored. The current obstacles against the development of earthen architecture are examined through a survey of current earth building practitioners in Western Europe. A literature review revealed that, surprisingly, only technical barriers are being addressed by the scientific community; two-thirds of the actual barriers identified by the interviewees are not within the technical field and are almost entirely neglected in the scientific literature, which may explain why earthen architecture is still a niche market despite embodying all the attributes of the best construction material to tackle the current climate and economic crisis. This article is part of the theme issue ‘The role of soils in delivering Nature's Contributions to People’.

Bio-based materials are subject to a growing interest since the nineties to reduce the environmental impacts of the building sector. Light earth is a low impact insulation material. Light earth building methods are based on the use of earth slip, a mix of clayed earth and water, and aggregates or fibers. The earth slip is characterized on site by mason by different means. This study aims to compare different rheological measurements methods in laboratory conditions, and then to define simple and robust tests adapted to any conditions. The study is based on six soil samples. Geotechnical characterizations show that these soils cover a wide range of natural variabilities. Their cohesive behaviors were investigated by measuring the yield stress with a rheometer, a spread test, a dipping test and a rough wall cone test, both developed for the study, and a Marsh cone test. Accuracy and the validity range of each test are presented alongside the needs for light earth applications.