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Sustainable Solutions: The Energy Balance
Sustainability of Mirel Bioplastics produced by microbial fermentation

An important consideration in the broader application of Mirels is the energy efficiency of the overall production process. Metabolix has developed highly efficient production strains that produce Bioplastics at higher yield and productivity than strains used in the past. In addition, Metabolix has achieved significant simplifications in the recovery process that have resulted in additional energy savings. Bioplastics are now definitely more sustainable in their energy consumption than many of the important synthetic materials in widespread use today. Comparative energy consumption figures are indicated in the accompanying chart.

As has occurred with synthetic materials over the years, further improvements in yield and efficiency are possible, and Metabolix is already working to realize these. The energy requirements for microbially produced Bioplastics will then be further reduced as indicated in the chart.

Carbon dioxide is a major green house gas and production of energy, chemicals, and polymers from non-renewable fossil fuel resources is the major human contributor to these emissions. Metabolix's Mirel Bioplastic production process achieves a very significant reduction in net carbon dioxide generation, in large part because the carbon contained in Mirels is derived from atmospheric carbon dioxide.

Sustainability of Mirel Bioplastics produced directly in plants

While Mirel Bioplastics produced by fermentation are more sustainable and require less energy input for their production than most synthetic polymers, Mirels produced directly in plants, when coupled with use of the energy content of the remaining plant biomass will contribute, rather than consume, energy. A thorough analysis (1) has been presented by Kurdikar et al., in the Journal of Industrial Ecology in which the authors concluded that, "an integrated system, wherein biomass energy from corn stover provides energy for polymer processing, would result in a better greenhouse gas profile for Mirel than for polyethylene." Bioplastics produced in switchgrass would be expected to be even more favorable than in corn stover (although the technology to transform switchgrass did not yet exist at the time of that study).

1. Kurdikar et al., "Greenhouse Gas Profile of a Plastic Material Derived from a Genetically Modified Plant", Journal of Industrial Ecology, Vol. 4, No. 3. 2002.