A closer look at bio-based plastics
By Maaike Rijk
Bio-based raw materials are booming. Among these developments are plastics made from sugar cane. What makes this alternative raw material worth considering?
There are many uses for polyethylene (PE). It is the most commonly used plastic and is obtained from the polymerisation of ethene, also known as ethylene. Until only a few years ago, PE was mainly obtained from petroleum and natural gas. However, since oil reserves are steadily decreasing, more and more alternative sources emerge for plastic production. Sugar cane is one of these. Braskem annually produces 200,000 tons of polyethylene from sugar cane which makes it one of the largest bio-polymer producers in the world. Marco Jansen, Commercial Director for Renewable Chemicals, told us more about this relatively “young” raw material.
CO2 reduction by using sugar cane
“The most important reasons for choosing a bio alternative are a reduced carbon footprint, increasing pressure on CO2 emissions and depleted oil reserves,” said Marco. “Sugar, extracted from sugar cane, has a high calorific value. This makes it an extremely efficient product. Another advantage compared to oil is that sugar cane absorbs carbon dioxide from the atmosphere when it grows. This causes a reduction in CO2. Furthermore, the product brings a variety of additional benefits during processing and cultivation.
An efficient process
“In order to extract polyethylene from sugar cane, the plant is cut down and pressed. Sugar cane saps are released during this process, which creates ethanol after fermentation and distillation. The ethanol is then hydrated and ethylene is obtained from this. The residual fibres of the plant are burnt, which generates bio energy. The energy released is used by the factory and the remainder is sold. When everything is added up, the difference in CO2 reduction compared to traditional sources is around 4 kg for each kg of PE produced.”
No loss of rain forest
Bio fuel produced from plants is often controversial. There is the fear that primeval forests have to give way to plantations. What is the situation with sugar cane? “Fortunately the forests in Brazil are now well protected. Anyhow, the rain forest region is not suitable due to its heavy rainfalls. Sugar cane needs a lot of sunshine and only a little water. In addition to this, the soil type is not suitable for the cultivation of sugar cane. The ideal region for growing sugar cane is located around the state of São Paulo. Brazil currently uses only 20% of its available farmland for cultivating crops. Less than 0.02% of this land is used for the production of bio-polyethylene. Unlike in Europe, this does not have a negative impact on food production. There is still great potential here”, said Marco.
Bio-based does not mean biodegradable
What is the lifespan of a bio-based product made from sugar cane? Marco: “The shelf life of these products is similar to oil-based products. Bio-based does not necessarily mean biodegradable. Polythene made from sugar cane can be recycled, but does not decompose any faster than polyethylene made from oil or gas.”
More and more companies are discovering the possibilities of bio-based products. This alternative raw material is slowly gaining acceptance in the food industry which is extra careful about migration. Tetra Pak® already uses 100% bio-based high density polyethylene (HDPE) for its bottle caps. They have recently decided to deploy bio-based materials for the protective layer in their drink packaging as well. “In terms of migration, bio-based materials are just as safe as materials from traditional sources”, said Marco.
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