Issue 02/2017

Agriculture/Horticulture
PLA branches
into agriculture
New root trainers for rubber plants
are biodegradable
Fig. 1: Young rubbers planted in root trainers
Fig. 2: Young rubbers planted in soil with root trainers
Natural rubber is a key economic commodity for the
countries of Southeast Asia. It is used in many different
industries, ranging from auto manufacturing and
sports to medical and marine applications, and consumer
products. A biopolymer, natural rubber is derived from latex, a
milky fluid that is tapped from the rubber tree (Hevea brasilliensis)
and subsequently coagulates into rubber. In addition
to natural rubber, synthetic rubbers have also been developed
that are produced from petrochemicals. For the majority of
applications, including tires, compounds of natural and synthetic
rubbers are used.
In 2016, demand for both natural and synthetic rubbers
reached approximately 25 million tons. As only 12 million
tonnes of natural rubber were produced, this meant that the
shortfall had to be made up by synthetic rubbers. Nonetheless,
demand for natural rubber continues to rise, not only because
of its biobased origins, but also because of its superior quality,
which makes it the material of choice in high-performance
products such as aircraft tires. The natural rubber supply,
however, is limited by the suitability of both land and climate
for rubber production.
Natural rubbers are exported mainly from the four
Southeast Asian countries of Thailand, Indonesia, Malaysia
and Vietnam. Combined, these four countries produce some
70 % of the world’s natural rubber supply. Thailand is the
biggest producer, accounting for 40 % of global production.
These four natural rubber-producing countries implement
massive replanting programs on a yearly basis. Rubber trees
have a service life of 25 years, after which the latex yield
becomes too low and they are cut down. The farmers then
replant with higher-yielding clones. Each year, the trees that
have reached the end of their economic life are taken out and
replaced. Replanting involves cultivating the young rubber
seedlings in nurseries for about six months before outplanting
in the plantations. The rubber seedlings in the nurseries are
grown in plastic bags or in plastic cones called root trainers.
Rubber trees grown from root trainers have service lives that
are about 5 years longer than those grown in bags; in other
words, the productive life of the tree is extended to 30 years.
Farmers not only enjoy the benefits of 5 additional years of
productivity, the costs of replanting are also reduced.
In the past, root trainers were made from polypropylene,
which does not biodegrade in soil. This meant that the farmers
were required to extract the young trees from the root trainer
in order to replant these in the plantation, resulting in damage
to the root systems and, consequently, a higher rate of dead
trees. This disadvantage jeopardized the benefit provided by
the added years of productivity. As the country with the largest
replanting program - a program in which 70-90 million new
Fig. 3: Root trainers degraded after 4 months in soil
24 bioplastics MAGAZINE [02/17] Vol. 12