Bio-based materials and compostability

The SB&WRC project is part of the Programme Interreg VA France (Channel) England and benefits from financial support from the ERDF.

The end of life of biobased materials remains poorly understood, due to the fact that this type of materials has only recently been deployed for construction. However, a study carried out by the French Agency for Environment and Energy Management, ADEME[1], estimates the arrival of the first bio-based insulation products in the end-of-life sectors around 2020. Within the waste recovery and valorisation industry, manufacturers are looking for simple, practical and economically viable solutions.

In parallell to the LCA, UniLaSalle will take advantage of its expertise in materials' biodegradability in order to study the composting opportunities for bio-based prototypes of the SB&WRC project. Composting is an industrial process that already exists, and which represents a solution for the sustainable management of agricultural residues. It is one of the fastest ways to transform biowaste into a kind of humus, a stable matter, that may then be returned to the soil as an organic amendment, thus completing the cycle of organic matter and bringing a beneficial effect taken into account in the LCA, related to the ecosystem service (biodegradation) rendered by microorganisms which degrade materials.

The compostability of a material is defined by a standard test performed[2] in laboratory (Figure 1), which measures the amount of CO2 produced (mineralisation phase) by microorganisms during the biodegradation process within a compost medium.

Figure 1: Biodegradability test chamber

Many research projects study the behaviour of different crop[3] residues, such as those studied in the SB&WRC project (wheat, rapeseed and maize straws), and reveal their compostability as well as their agronomic value.

Figure 2: Results from a crop reside study (Xiu-Lang and al., 2016)

For both prototype 1, made from corn marrow, and prototype 3 made from wheat straw, we can rely on the bibliographical elements displayed in Figure 2 above to confirm their compostability potential and the interest to continue the studies on the development of a composting stream for the end of life of these materials. However, it is important to also verify that the implementation process that has been chosen for the material has no effect on its biodegradation. Research recently carried out at UniLaSalle shows that the thermocompression process used to manufacture prototype 1, does not impact the biodegradation of the material obtained[4] when the material directly returns to the soil.

This type of approach would make it possible, to close the carbon cycle for these types of material, in a circular economy approach, by the degradation of the carbon sources contained within the agricultural resources or by-products. By including a deconstruction and an adapted sorting, this approach, already used for some products such as packaging labelled OK compost[5], although still experimental in the building sector, could open new perspectives.