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bioplasticsMAGAZINE_1306

People Basics Biobased

People Basics Biobased carbon vs biomass ? Understanding terminology and value proposition in the bioplastics space – biobased vs biobased carbon vs biomass based There are a growing number of terms being used in the bioplastics space with the potential to confuse and mislead the various industry stake holders and the general audience - from regulators, to NGOs, to brand owners, to consumers, and the general public. In this article we will sort through the technical jargon of terminology usage and more importantly the relationship between these terms and to the ultimate value proposition bioplastics has to offer. Many of these terms are originating in the various International standards (ISO, EN, ASTM) being developed and under development. It is critical that the various bioplastics stakeholders including standards writers, certification organizations, and the representative trade organizations have a clear understanding of the terms and definitions and the linkages to each other. We begin with the basic terminology – bioplastics, biobased plastic, biodegradable-compostable plastics. The term bioplastics encompasses two separate but interlinked concepts: (a) biobased plastics representing the beginning of life of the plastic and (b) biodegradable-compostable plastic representing the end-of-life. Biobased plastics – plastics made from plant biomass/agricultural crops. These are photoautotrophs that convert (remove) CO 2 in the environment to organic materials (like carbohydrates, lipids, and proteins in plant biomass) using water and sunlight energy (photosynthesis). This is in contrast to plastics made from petro/fossil resources (like Oil, Coal, Natural gas) which are formed from plant biomass over millions of years. The rate and time scale of CO 2 conversion to organic materials in plant biomass is typically one year (an agricultural or biomass crop) or around 10 years (wood/ tree plantation). Therefore plastics made from plant biomass/agricultural crop is consistent with removal of CO 2 from the environment in a short time (1-10 years) and incorporating them into plastic polymer molecule. In the case of plastics made from fossil resources the carbon present has formed over a million year time frame and so cannot be credited with any CO 2 removal from the environment even over a 100 year time scale ( the time period used in measuring global warming potential, GWP100). Figure 1 illustrates this natural biological carbon cycle. By: Ramani Narayan Michigan State University, East Lansing, Michigan, USA To illustrate this carbon footprint reduction (CO 2 removal/sequestration from the environment), consider the manufacture of biobased polyethylene from sugarcane (plant biomass). Figure 2 shows the stoichiometric equations starting with CO 2 in the environment being converted to sugar (in sugarcane) by photosynthesis, fermentation of the sugar to ethanol; dehydration to ethylene, and polymerization of the ethylene to biobased polyethylene. Summing up, the net reaction is the removal of 88 kg of CO 2 in the atmosphere to manufacture 28 kg of biobased polyethylene – that is every kg of biobased PE manufactured results in 3.14 kg of CO 2 removal from the environment. This illustrates the clear, unambiguous, quantitative carbon foot print reductions achieved from switching to biobased carbon and that is the fundamental value proposition. Using similar basic stoichiometric, it can be shown that for every kg of 100% biobased PET (polyethylene terephthalate) manufactured results in 2.29 kg of 50 bioplastics MAGAZINE [06/13] Vol. 8

Politics Basics Biological Carbon Cycle sunlight energy CO 2 + H 2 O (CH 2 O) X + O 2 photosynthesis 1-10 years Biomass, Agr. & Forestry crops & residues NEW CARBON CO 2 removal from the environment. For the current Coca-Cola PET plant bottle with 20% biobased carbon content, 0.46 kg of CO 2 is removed from the environment per kg of plant bottle PET. For every kg of PLA (polylactic acid) manufactured there is 1.83 kg of CO 2 removed from the environment. For fossil based products there would be zero removal of CO 2 from the environment as discussed above and illustrated in Figure 1 of the biological carbon cycle. The above discussions and calculations represent a cradle to gate (in LCA terminology) assessment of the material carbon in the polymer. It does not reflect the end-of-life and ultimate release of the carbon bound in the polymer to the environment as CO 2 . As can be seen from Figure 1, this does not change the basic value proposition of reducing the carbon footprint. For example when the biobased carbon in biobased PE is released back to the environment as CO 2 (as it would be) then the 3.14 kg CO 2 e/kg of PE removal would become zero – zero material carbon footprint. By the same token the fossil based PE carbon would result in +3.14 kg of CO 2 e/kg of PE released to the environment – the net result being the same. Biodegradable-compostable plastics – these are plastics designed to be completely biodegradable in the targeted disposal environment (composting, soil, marine, anaerobic digester) in a short defined time period. They are assimilated by micro-organisms present in the disposal environment as food to drive their life processes. They are not necessarily biobased and can be petro / fossil based. Biobased plastics are not necessarily biodegradable-compostable, and as discussed earlier they derive their value proposition from contributing to a reduced carbon footprint during the beginningof-life stage. The fundamental intrinsic carbon footprint reduction value proposition described above does not address the carbon emissions and other environmental impacts for the process of converting the feedstock to products, use, and ultimate disposal – the process carbon and environmental footprint. LCA methodology and standards (ISO 14040 standards) are the accepted tools to compute the process carbon and environmental footprint, and is required for all products irrespective of whether it is biobased or fossil based. 1-10 years > 10 6 years USE – for materials, chemicals and fuels Rate and time scales of CO 2 utilization is in balance using biobased/plant feedstocks (1-10 years) as opposed to using fossil feedstocks Short (in balance) sustainable carbon cycle using bio based carbon feedstock Material carbon footprint ( Fig. 1: Understanding the Value Proposition based on the origins of the carbon in the product - biobased carbon vs petro/fossil carbon [1]) NET 6nCO 2 + 6nH 2 O nC 6 H 12 O 6 2nC 2 H 5 OH 2nC 2 H 4 4nCO 2 + 4nH 2 O (88 kg) photosynthesis fermentation dehydration polymerization nC 6 H 12 O 6 + 6nO 2 2nC 2 H 5 OH + 2nCO 2 2nC 2 H 4 + 2nH 2 O 2—CH 2 —CH 2 — n 2—CH 2 —CH 2 — + 6nO 2 n (28 kg) Stochiometric equation showing CO 2 ‘removal’ from the environment and incorporation the carbon into biobased polyethylene molecule 14 CO 2 - Solar radiation 12 CO 2 C-14 signature forms the basis to measure biobased carbon content (ASTM, EN, ISO standard) Cosmic radiation ation 14 14 14 N C CO 2 Fossil Resources (Oil, Coal, Natural gas) OLD CARBON 12 CO 2 Biomass ( 12 CH 2 O) x ( 14 CH 2 O) x NEW CARBON Defining biobased carbon and differentiating from fossil carbon using radiocarbon analysis [1] > 10 6 years Fossil Recources (petroleum, natural gas, coal) ( 12 CH 2 O) n ( 12 CHO) x OLD CARBON bioplastics MAGAZINE [06/13] Vol. 8 51

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