Energy requirements and CO2 emission for polymers

As recently highlighted on the Bioplastics markets conference in Guangzou , China bio-based plastics use renewable or biogenic carbon as a building block. This biogenic carbon is captured from the atmosphere by plants during the growth process and converted into the required raw materials. When the product is being incinerated at the end of its useful life, the biogenic carbon is returned to the atmosphere - or in other words, cycled in a closed biogenic loop, referred to as being �carbon-neutral'.

On the Plastics Europe website - on which one can find a Life Cycle Analysis (LCA) for most polymers and also a number of end products - a method is offered to compare the eco-profiles of different end products. This website also provides information regarding the kg CO2 emission per ton polymer, for the traditional polymers in those mentioned end applications. Based on an internal LCA from Purac Biochem for a lactide based PLA polymer and internal Synbra figures for the processing of BioFoam� it is possible to make a comparison with traditional polymers. These figures will be incorporated in a formal BioFoam� LCA, to be finalized in the very near future.

PLA has a different production process than most other polymers. This polymer is derived from in the production of sugar cane, which is being refined to sugar, then fermented to lactic acid, from which lactide is being made. Lactide is finally polymerised to PLA. Of course for a number of these steps fossil fuel is also needed. The most important steps are sugar production, production of lactide, transportation and the polymerisation of lactide to PLA. An important difference with the fossil fuel based polymers is that the raw material is originating from biomass, namely sugar cane, see figure 1.

Figure 1 CO2 emission

The most important gain lays in the fact that during the growth of the plants nett CO2 is absorbed. The sugar cane plants stores CO2 by forming sugar under the influence of the sunlight. This energy represents a large part of the energy needed of the end product and does not come from oil. During the production of lactide based PLA, which in the end will lead to moulded BioFoam, on the average only 30-40% of CO2 will be emitted compared to the production of other polymers, which is a reduction of 60-70%. In some cases it can even be higher.

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