Agriculture and Environment: Rubber

Environmental Impacts of Production: Pollution from Processing Rubber

One of the main environmental concerns with rubber production is the effluent from the initial stages of processing that most often occur in or near the plantations.

The volume of effluent from rubber processing is 25 to 40 times greater than the volume of rubber that is produced.

Deadly when discharged in water bodies
There are two main types of effluents - the serum from the coagulation process and the water used to wash the rubber. The serum contains dissolved organic solids that readily oxidise and so create a significant biochemical oxygen demand (BOD) when they are dumped into water bodies.

The washing effluent contains proteins, sugars, and other organic materials as well as inorganic chemicals. It also has high BOD, which can cause fish kills and harm other aquatic species in rivers and streams.

In addition, some of the chemicals that remain in the sap after the latex is coagulated can be toxic (which is not surprising, as some serve the role of protecting the tree from pests).

Vulcanisation, a highly toxic process
The vulcanisation of rubber is considered by people in the industry to be one of the most toxic industrial processes on the planet. Either lead or zinc oxide is used in the vulcanising process.

Heavy metal pollution
Even though zinc is probably the least toxic of the heavy metals, it is still quite toxic (even in very small doses) to invertebrates and many freshwater and marine species. These heavy metals can contaminate water bodies if the effluent is dumped into streams, and they are also released as rubber products are used or as they degrade.

At this time, there is no way to reduce the heavy metals either in production effluents or in degraded products. Many people believe that the reason sneaker manufactures moved to Southeast Asia is because of lower labour costs. In fact, it is probably equally important that the countries where shoes are now manufactured do not have stringent pollution control or worker health and safety measures.

The extent of heavy metal pollution from the degradation of rubber products is more than one might expect. It is estimated that ore than 3,000 metric tons of zinc are released into the environment per year from tire wear alone. This represents about 25% of the anthropogenic release of zinc into surface waters (Chapman 2002).

The European Union uses about 100,000 metric tons of zinc per year in the manufacture of rubber products. In order to reduce pollution from this manufacturing, the European Union has proposed standards of 1 to 3 milligrams per litre of zinc in effluent and 0.5 milligrams per cubic metre in stack emissions (Chapman 2002).