Beyond net-zero: Buildings materials as carbon-sinks
Buildings are responsible for 37% of carbon emissions in 2020. Striving for zero energy in buildings aims to achieve carbon neutrality for the sector. Net-zero usually focuses on the operational energy: the emissions from day-to-day use. More extended definitions use a life cycle approach and include emissions from construction energy.
However, as carbon emissions keep rising, a new approach is to make buildings carbon negative. By using carbon-negative materials, buildings can become carbon sinks. Carbon-negative materials already exist, but there is a drive to increase this trend.
An example is Solidia (2), a company that already makes a carbon-negative concrete:
-Cures in 24h instead of the usual 28 days;
-Uses CO2 for the cure instead of water (water used in production can be recycled, not end trapped on the concrete, as currently happens);
-Wither in color (it uses CO2 biding with calcium, resulting in a lighter hue).
But the US Department of Energy is keen to accelerate this trend. In 2022 alone, three different research grants focused on research for carbon-negative buildings (3),(4) and (5): Solidia was also recipient of one of these grants.
There are also efforts to substitute insulation materials for biological-based equivalents, like cork, hemp, wood or straw. When switching to biomaterials, some new issues arise. Building envelopes will need more depth since biobased materials have lower R values.
In addition, biomaterials proprieties vary more than their fossil-based counterparts, which can lead to over-specification. Nevertheless, straw production in Europe can meet the region’s building insulation demands, while creating a new source of income for farmers(6).