This article is also available in Italian / Questo articolo è disponibile anche in italiano

A few years ago, I remember reading about houses on a Danish island thatched with thick layers of seagrass, poignantly referred to as the country’s “300-year-old homes of the future”. The houses on Læsø are something out of a fairy tale: curiously “alive” looking and as if a stout little forest witch may step out at any moment. In true human fashion, these 17th century roofs were borne out of necessity, when the island’s last trees had been burnt to feed its salt kilns in support of its flourishing saltworks industry.

While not much has changed since then − we’re still deforesting land at unprecedented rates to feed industry − bio-based materials have dropped drastically as a fraction of total material use as societies turned to metals and minerals to build up infrastructure and fuel production. Now, they seem to be coming back into vogue, moving from fringe acceptance amongst “conscious” consumers (growing up in the Pacific Northwest, I was no stranger to hemp clothing) to somewhat broader integration across industries, from timber buildings to sugarcane packaging. But biomass being renewable doesn’t make it inherently sustainable or circular: its extraction is a huge driver of emissions of ecosystem degradation, and caution shouldn’t be forgone in proceeding full-speed ahead with the bio-based transition.

The recently launched Circularity Gap Report Textiles illustrates this finding − perhaps counter-intuitively − that a large-scale shift away from synthetics to “natural” fibres including cotton, linen, and viscose would have negative impacts on a range of environmental aspects. These materials require far more land inputs than synthetic alternatives, although the latter tend to be more carbon- and material-intensive.

Bioplastics can be similarly problematic: they are often produced from crops cultivated specifically for this purpose, with large-scale production relying on dedicated agricultural land that competes with food production. At the same time, they have become a greenwashing nightmare, with titans like Coca-Cola launching a “PlantBottle” that is, to no one’s surprise, only 30% bioplastic: this share is made of sugarcane, linked to odd behavioural changes in the fish exposed to it in addition to good old fashioned deforestation and soil degradation.

Timber used for construction may pose similar concerns, with the World Resources Institute recently remarking that any move to “mass timber” would have substantial negative effects on the world’s forests – precious carbon sinks and goldmines of biodiversity − and cautioning against any initiatives that spur demand for land and its outputs. So where do we go from here? The 17th century Danes may have been heading down the right path: if land is in short supply, turn to the sea. Their seagrass roofs were fire-, rot- and pest-resistant, breathable but with insulation properties comparable to mineral wool, incredibly long-lasting, and relatively low-impact. When harvested and used locally, various types of seaweed are carbon neutral, as well as quick-growing and not fertiliser-dependent.

And if you dislike the image of whimsical thatched roofs topping modern glass tower blocks, worry not − Læsø’s seagrass is now being developed into prefab panels that can be used as insulation for facades and rooftops. While incredible uses are being found for seaweed across sectors − from animal feed and packaging to pharmaceuticals, textiles, and biofuels − using residual products or “waste” appears promising, too, with fruit peels and corn husks already being processed into biodegradable packaging materials and textiles.

But even these aren’t perfect solutions, and scaling will be challenging: extensive seaweed harvesting could negatively impact marine ecosystems’ biodiversity if responsible practices aren’t soon mandated, and bio-waste isn’t available at volumes large enough to meet demand for mass production. Funnelling all waste into new products could also compete with the natural decomposition processes necessary for healthy soils.

The bio-based transition isn’t a panacea, and its actualisation must be framed within the circular economy model, where renewable resources are sustainably managed, renewable energy is used for processing and production, and bio-based materials can be effectively returned to the earth at their end-of-life. The ultimate lesson? There won’t be a miracle material to save us without first drastically reducing consumption.

DOWLOAD AND READ THE NEW ISSUE OF RENEWABLE MATTER: MATERIALS

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