The renewable energies we know
We are now used to recognizing renewable energy resources, compared to fossil ones and not at risk of exhaustion.
Solar energy, exploited to produce electricity through photovoltaic conversion and to produce domestic hot water, through panels. Wind energy, which converts the motion of the winds to produce electricity, through individual plants or onshore or offshore wind farms, but also mini plants on buildings. Hydroelectric energy is not only relegated to large power plants that exploit the fall of water from dams to generate electricity, but is also extended to mini, micro and pico water systems in rivers, streams, lakes and the sea, in the presence of wave motion, water currents and natural and induced waterfalls. Geothermal energy, which can convert subsoil heat for thermal purposes, as a source of heating homes or even for electricity production, using pressurized water vapor to move turbines. Energy derived from biomass, i.e. that which exploits the combustion of waste plants from forestry and agriculture, including wood, to produce biogas for traction and heating. Aerothermal energy, captured from the ambient air through heat pumps.
What about renewable materials?
What about renewable materials?
Speaking of constructions, even in the context of the aforementioned EPBD directive, the reference to construction materials is not as specific as for energy, which is a much more sensitive topic; much less is the reference to renewable construction materials so frequent, which are identified as those coming from nature, which regenerate spontaneously or through anthropic intervention, which are rapidly replaceable, recyclable and which offer a very low environmental impact, not generating unmanageable waste.
But then how many do we find with these characteristics? In reality these are reduced to a few categories, or rather to three categories: materials of vegetal origin, those of animal origin and those of marine origin; but there are those who add a fourth category, namely those of mineral derivation, on which however it is necessary to open a separate chapter.
Which materials can be considered truly renewable
So what are they? Undoubtedly the best known renewable material is wood and its many derivatives, used for the entire static construction, for floors, for covering the roof pitches and for cladding, but also for the insulation of the casing. It is a material derived from the processing of some plants which, spontaneously or with human contribution, can regrow and regenerate.
Various other materials are then obtained from plants with which high-performance thermo-acoustic insulating panels are produced, such as cork, obtained from the bark of some oak trees; hemp which finds multiple applications as a thermo-acoustic insulator, but also as an element to lighten plaster and complete bricks (lime-hemp); straw, derived from the non-digestible part of grasses, agricultural waste material that can be given new life to create insulating blocks in the form of bales, or in insulating panels after pressing in aggregation with particular binders; bamboo, a very rapidly growing plant, whose stem (or culm) has very high mechanical resistance, ideal for static constructions and the creation of thermo-acoustic panels; but also cellulose, jute, coconut fibre, linen and cotton fibres, grass fiber and rice processing waste, just to name a few.
Two insulating materials of notable quality are obtained from animal nature: goose down and sheep’s wool, the first used as a filling material and the second in the form of insulating wall panels.
From the sea, however, some algae and a very common plant, posidonia, are processed, the latter in the form of egagropilo.
Last but not least, there are those who also indicate clay as renewable, in the form of raw earth(1), an easily available mineral material, recyclable many times even for the same application – a rarity among quarry products – but which in reality is not renewable. In fact, clay cannot be replanted, cultivated and is not spontaneously regenerated by nature, except after a period that lasts a few geological eras, through a slow process of alteration and disintegration of the rocks caused by atmospheric agents. Its continuous removal can in fact cause irreversible impoverishment.
(1) It is important to specify the difference between clay and raw earth: clay is a pure mineral component, while raw earth is a composite material made up of clay which acts as a binding element, sand and natural fibres, such as straw or dry organic elements contained in the earth.
