As shown by Denis Delestrac in a very compelling documentary (Le sable, Arte), sand is counter intuitively becoming a rare resource, notably because desert sand is useless for construction (it is simply too round and cannot aggregate). Sand is currently mainly extracted from the sea, as land sediments and rivers have already been scraped to the ground. This has a dramatic impact on the entire ecology of the ocean, and visible topographical consequences even start to be visible along the coast line. The scarcity of sand and aggregate is very well known in the building industry, and several initiatives have taken off to find new ways to build in a sand-less world.
The BFF (“Biomass For the Future”) project illustrates this trend, while addressing several other environmental and social concerns locally. Coordinated by Herman Höfte (INRA) together with several partners from the industry, local communities and academy, this project aims at developing non-food biomass to take the next step in ecological transition.
In particular, in a subproject called “Coeur vert” (for green heart), the giant grass miscanthus has been chosen to decontaminate soils that were unsuited for agriculture, after years of heavy and reckless industrial and agricultural pollution in the west suburbs of Paris (Chanteloup-les-Vignes).
Miscanthus is highly productive, does not require extra nutrients and is very resistant to diseases. While this crop cannot be used for food usage, its stems can be broken up and turned into a natural mulching film in fields, to prevent the development of weeds without the usage of herbicides. Miscanthus is also rich in cellulose, which is as stiff as steel when pure.
Recently, these stems have been successfully converted to a green concrete by a local cement company, which has developed the relevant technology. Such bricks are of course not as mechanically strong as sand-based concrete, but small houses can be built on site.
Being local, this also avoids any ecological cost due to transport. Interestingly too, the thermal insulation potential of such bricks is much higher than sand-based concrete, thus in line with the aim to generalize the development of zero energy homes in the future. This example illustrates how using our knowledge on plants can have a visible and positive impact on local communities, while providing an alternative to the shortage of resources, notably by shifting the “mine mind” dead end to the “plant plant”, with renewable and local plant-based initiatives.
30 mai 2014