What is natural rubber?

The tree “Hevea Brasiliensis” is the source of natural latex, the precursor for all subsequent rubber products. It thrives in tropical latitudes, especially in South and Southeast Asia, as well as in West Africa and Central America.

In 2020, about 13 million tons of natural rubber (NR) (latex and solid rubber) were produced worldwide. About 40 million people are directly and indirectly dependent on the production of NR. Of particular note is the fact that approximately 90% of the total is produced by smallholder farmers and their families. This makes natural rubber an important factor in the economies of the producing countries, most of which are developing countries.

There are a number of arguments in favor of expanding production in the growing regions. However, before thinking about expanding production, our focus should be on the processing of natural latex in the producing countries.

Factories in tropical countries use machines that operate on a principle developed in the late 19th century. Consequently, energy consumption is high, and many greenhouse gases are produced during processing.

The tree produces latex with approx. 30 parts solid rubber and some 70 parts water.

During processing, part of the crop is concentrated by centrifugation and sold with about 60 parts solid rubber.

The other part is coagulated with acid and a small amount is dried with air or by burning wood with smoke and heat, so called Air Dried Sheets (ADS) and/or Ribbed Smoked Sheets (RSS) are produced. By far the largest quantity is dried in drying ovens by burning kerosene or diesel oil. Large quantities of fossil fuels are required. Solar energy is only used to a very small extent.

Exact figures are not available. Assuming that 11 million tons are produced as solid rubber, it can be estimated that approx. 1.8 – 2 million tons of water have to be evaporated. Since the fuels and drying systems used are very different, only theoretical numbers can be given. Drying natural rubber requires approx. 800 MJ per kg. Using the figures mentioned in the literature, 200,000 t of diesel oil would theoretically be required, a process which emits approx. 530,000 t of CO2 into the atmosphere when burned.

The trees need CO₂ to grow and produce natural latex. With an estimated cultivation area of about 14 million hectares worldwide, this results in a CO₂ consumption of about 180 million tons per year. In addition, this translates into a release of about 130 million tons of oxygen.

By contrast, the production of synthetic rubber from crude oil derivatives is polluting the environment with CO₂.

Cup lumps happen to be the result of natural coagulation of field latex in the tapping cup on the tree. The further processing of the cup lumps in developing countries is carried out in smaller or larger – mostly privately owned – factories.

The owners of these factories can only be persuaded to change the traditional system of rubber processing if they see the advantages based on a pilot project. Only then can precise values and data be collected that can later be used as a basis for scaling-up production.

In order to save energy and increase efficiency, modern machines are available that double the performance with the same power consumption. Introducing them is a priority. For the implementation of such a project – the conversion of an existing natural rubber factory, only a relatively small investment is required. The amount of such an investment depends largely on the local conditions and which machines need to be modernized.