Terminology

• Suberin: waxy compound in cork cell walls, about 40 percent
• Virgin cork: lower-quality cork from the first harvest at 25 to 30 years
• Corkboard: insulation board of agglomerated cork
• Cork-cement composite: cork granules in cement, 400 to 1,500 kg/m³
• Phellem: the bark layer

History and demand

Sourcing

• Portugal produces about half to 55 percent of the world's cork, of about 300,000 to 340,000 tonnes a year; Spain about 29 to 30 percent, Morocco about 6 percent, and Algeria about 5 percent (APCOR and Amorim)
• Cork oak forest covers about 2.12 million hectares: Portugal 34 percent, Spain 27, Morocco 18, Algeria 11 (APCOR)

Demand trend

• Natural cork closures are used for about 80 percent of the roughly 20 billion wine bottles produced each year; cork use declined after synthetic alternatives appeared in the mid-1990s and recovered to about 60 percent of wine stoppers by 2016; stoppers are about 60 percent of cork-based production

Composition and production

Raw materials

• Suberin about 40 percent, lignin 22 percent, polysaccharides 18 percent, extractables 15 percent
• Cork oak forests cover about 2.2 million hectares; annual production about 300,000 tons; Portugal 49.6 percent, Spain 30.5 percent, Morocco 5.8 percent, Algeria 4.9 percent, Tunisia 3.5 percent, Italy 3.1 percent, France 2.6 percent

Manufacturing process

• Harvested only from early May to late August; first harvest at about 25 to 30 years, then roughly every nine years (up to thirteen)

Properties

Mechanical

• Gas-filled cells act like pads and recover after compression; almost zero Poisson ratio, so the radius barely changes when squeezed or pulled

Fire behavior

• Natural fire retardancy

Uses in buildings

Building elements

• Resilient Flooring: varnished cork flooring, an alternative to linoleum, stone, or ceramic tile
• Floor Underlayment: cork underlayment beneath floor finishes
• Wall Cladding: cork wall and facade cladding
• Wall and Roof Insulation: corkboard and cork granule insulation
• Acoustic Wall and Ceiling Panels: acoustic insulation

Pros and cons

Pros

• Impermeable and buoyant
• Recovers after compression
• Non-allergenic, petrochemical-free insulation alternative

Cons

• Supply concentrated in southwest Europe and northwest Africa (Portugal about half)
• Harvest only every nine years or more

Manufacturing and cost

Main manufacturers and suppliers

• Wicanders (Amorim)

Sources

• Wikipedia: Cork (material), https://en.wikipedia.org/wiki/Cork_(material)
• Wikimedia Commons: Cork p1160013.jpg, photo by David Monniaux (CC BY-SA 3.0), https://commons.wikimedia.org/wiki/File:Cork_p1160013.jpg
• BKWine: Portugal dominates cork production, https://www.bkwine.com/news/portugal-dominates-cork-production/
• Amorim: cork oak forest, https://amorim.com/en/cork/cork-oak-forest