The plantation is called Rio Frio. That means something like “cold river.” But it is rarely cold here in southern Portugal, not far from the mouth of the Tagus. This is good for cork oaks. “They like warm, hot climates,” says Nuno Oliveira. The forestry engineer has a central task in Río Frío. The aim is to make the local cork oak forest more productive, Montado in Portuguese.

Oliveira works for Corticeira Amorim. The Portuguese company is the largest producer of wine and champagne stoppers in the world, with sales of around one billion euros.

25 years until the first harvest

To date there is little experience in large-scale commercial cultivation of oaks. Because more than 90 percent of the current cork oak population has been planted. For owners, the cork industry is traditionally a secondary activity. They grazed their cows and cattle in the forests and carried out other activities.

It usually takes 25 years for the bark of young oaks to become thick enough to peel for the first time. From then on, it is possible to harvest every nine years. But only in the second harvest does the bark acquire the quality that natural corks need for high-quality wines. By then more than 40 years had passed since the planting.

Cork oak forests store a lot of CO2

Since cork production has been a tradition in Portugal for more than a hundred years, this long period of time has not yet hindered the supply of the cork industry. The trees can live 200 years and the total area in Portugal, Spain and other Mediterranean countries is large enough to guarantee industry supply.

Amorim usually buys cork from independent producers. General director Antonio de Ríos Amorim explains during a visit to a factory in Santa María de Lamas, near Porto, that the company is now entering the forestry sector with Rio Frio: “We want to reduce the time until the first harvest by half , ten or twelve years. Then do the math “The investment will improve after 30 years and will be interesting for institutional investors such as pension funds and insurance companies looking for investments in carbon storage.”

Since the cork oak is not felled, but can be harvested about twenty times during its life, the cork stores a lot of CO2. “And 73 tons per ton of cork,” calculates Antonio Amorim. A cork oak forest that could be exploited more quickly would be “profitable” and could satisfy the expected increase in demand.

Cork for SpaceX

In addition to its positive climate impact, cork is also of interest to many industries thanks to its numerous technical properties. For example, NASA space shuttles and SpaceX rockets use cork as a heat shield. Because the material is naturally non-flammable. During last summer's devastating wildfires, fires spread primarily through eucalyptus and pine trees. Cork oak forests, on the other hand, are barriers. And where cork oak forests grow, for example in North Africa, they slow down the expansion of the desert.

Amorim runs several factories in Portugal where the bark is dried and one-piece corks for expensive wines are made. What remains is transformed into cork granules: raw material for many other applications, such as floor coverings, insulation, shoe soles and seats for high-speed trains.

Versatile natural material

The reason for its versatility is the structure of the cork bark. It is made up of honeycombs with around 40 million cells per cubic centimeter. Each cell acts as a thermal insulator and dampens sound and shock. Chemically, cork is made up of 45 percent of the polymer suberin, which forms cell walls. In nature it is found almost exclusively in cork.

“There are no limits for cork,” says Antonio Amorim. “We have ten employees who are constantly working on new applications. This is how the idea of ​​using the insulating and vibration-damping properties of cork for power transformers came about.” Amorim believes that if electrification progresses as expected, demand will grow very strongly.

And this requires more productive forests like those planned in Río Frío. Forestry engineer Oliveira is convinced that this can work in what is probably the oldest and, at 5,000 hectares, the largest artificial cork oak plantation.

Simply let the cork oaks grow unhindered

One of the measures is to increase the number of trees from the current 100 to 400 per hectare. And then they should be allowed to grow. People traditionally prune trees so they can harvest more acorns and produce firewood. This inhibits their growth. The trunks were only two or three meters high. “If the seedlings are left practically alone, they will grow quickly and directly towards the sun,” Oliveira hopes. And it is most likely to reach a size of three to four meters.

The ecological advantages of extensive cork oak forests should be maintained despite closer planting. “Biodiversity is one of the most important aspects of the Montado,” says Oliveira. “It provides a habitat for a large number of species of flora and fauna. These include endangered species such as the Iberian lynx.” This is mainly because people can, to a large extent, leave the forest alone. Not much management will be necessary during the growth in Río Frio. Especially since the plant is undemanding, needs little water and can thrive in sandy soils.

Author: Oliver Ristau