The impact of building materials on climate change is a major challenge for the construction sector, as they are responsible for more than 50% of a building's greenhouse gas emissions over its entire life cycle. In a sustainable development approach, it is therefore preferable today to develop local supply chains for biosourced materials, which have many economic and ecological advantages. However, despite the abundance of these materials, particularly in regions with hot climates, the development of these sectors often comes up against the harsh reality of the construction sector's habits: this is what Bernard Boyeux, director of C&B Constructions et Bioressources, explains.
What are the main advantages of biosourced materials or local supply chains in tropical or hot climates?
In both cases, beyond the environmental impact, we can mention the creation of non-relocatable jobs with high added value, as well as the revitalization effect of territories through the development of local resources and know-how. Biosourced materials are a way to limit the building's environmental footprint, due to their ability to store atmospheric carbon, their renewable nature and their low grey energy.
Through my work in Reunion Island, where I participated with the Nomadéis firm in the identification of local resources in order to develop sectors, or around Typha in Senegal, I was able to observe the sufficiency, even the abundance of local materials. Nevertheless, their use is almost non-existent!
What types of materials can be found?
The choice is vast and I do not pretend to draw up an exhaustive list. For example, in Reunion Island, one of the first candidates identified was wood that can be recovered from imported pallets. It can either be recycled and used for other wooden constructions or used to make plant-based concrete.
Another material found in most hot countries is bagasse. It is the fibrous residue of sugar cane, which is widely present in tropical and equatorial climates. It is used to produce vegetable concretes.
I would also like to mention bamboo, which many people consider to be the building material of the future. It is rapidly renewed with low energy consumption and has interesting mechanical properties. Simón Velez in Colombia and Vo Trong Nghia in Thailand have successfully adapted it to the needs of modern construction.
Finally, typha, which is a harmful and invasive aquatic plant, can potentially be an ecological asset to reduce greenhouse gas emissions thanks to its thermal insulation capacity. It is mainly present in West Africa. »
Are there any permanent supply chains?
This is very variable. Despite the ecological interest of exploiting these resources, building materials remain largely imported into these countries. The same is true in France in the DROMs and COMs. For instance, Reunion Island does not have any companies capable of recycling pallets in large quantities. However, this is economically viable since in metropolitan France, Alkern manufactures concrete blocks from end-of-life pallets. The problem is the same for the exploitation of bagasse and other local materials.
The biosourced materials or recycling sectors are very poorly developed for two reasons:
-Setting up such a network is complicated because it is a fairly long chain: not only must you have the right material, but also a commercial network, architects, companies to implement projects, customers interested in these materials in the process of development. The various sectors of activity in the chain (industry, agriculture, construction, etc.) are also sometimes not used to interact and develop common projects, due in particular to cultural differences but also to the differences in scale that exist between agricultural producers, industrialists, actors in project management and contracting, etc. The poor coordination between the actors of the sector is certainly one reason for its failure.
- Beyond these wishes and the relevance of the local approach, the development of these sectors must face the requirements of the construction sector - in particular regulatory and normative - which are not adapted to the diversity and size of these sectors.
What solutions do you think are available to overcome these difficulties?
To remedy this, producers of biosourced materials from local circuits must multiply actions aimed at structuring the sectors: in other words, federate and provide the sectors with a tool that brings a collective strategy to the national level.
It is also necessary to industrialize the sectors, which implies the ability of professionals to satisfy the technical and economic requirements of the market. The aim is therefore for the sectors to activate the drivers of industrialisation, in particular evaluation and certification (suitability for use, functional and environmental performance), the drafting of professional rules and, more generally, a quality approach.
On the other hand, innovation must be intensified. This consists in creating favourable conditions, based in particular on scientific knowledge from R&D programmes.
These actions certainly require more subsidies: local sectors face recurrent difficulties in this kind of situation:
Severe restrictions on access to the resource, linked to regulatory changes and the need to modernise equipment,
Expensive investments that are difficult for small structures to support.
In order to be competitive with large European and international companies that import building materials, it is essential to have a price that is lower or equal. For example, it is more economical for Reunion Islanders to import bamboo from China than to use the bamboo present on their territory! This is due to the characteristics of bamboos, but not only. The poor organisation of the supply chain and the lack of spatial planning (roads, few distributors of materials and therefore long distances to be covered for delivery, etc.) are also major factors.
This is also true in metropolitan France where the development of biosourced sectors is a real challenge. Beyond the economic aspect, we are also walking on our heads about the carbon footprint: Chinese boats carrying containers to the metropolis emit as much or even less greenhouse gases than trucks that travel halfway across the country.
Returning to the development of sectors, I think that investment is clearly worth it. However, it is an important choice to make:
Either we use local materials and contribute to the creation of local jobs, but the cost of construction can be more expensive.
Either we choose to build cheaper, whatever it costs in terms of other aspects than the purely economic plan.
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Consult the previous article:: #5 Biomimetism: a solution for building in hot climates?