Carbon Footprint Basics: understanding the value proposition for bio carbon vs. petro/fossil carbon

March 24, 2011

Hello and happy almost Friday day!

Today we are going to talk about the process of deriving carbon from annually-renewable resources for synthesis into bio-based polymers. As per yesterday’s discussion, substituting bio-based carbon for petro-based carbon provides a value proposition in the context of material carbon footprint for plastic packaging.

Slide 7: Carbon Footprint Basics—Value Proposition

Consider the following chemical process for manufacturing traditional, fossil-based plastics:

Fossil feedstock (oil, coal, natural gas)–>Naptha–>ethylene/propylene–>polyethylene (PE), polypropylene (PP)

Now, consider the process of manufacturing bio-based plastics from a renewable feedstock:

Bio/renewable feedstock (crops and residues i.e. corn, sugarcane, tree plantations i.e. lignocellulosics, algal biomass i.e. algae)–>BIO monomers, sugars, oils (continue)

These BIO monomers, sugars and oils can then be synthesized into EtoH, which is then used to make ethylene/propylene, the building blocks of PE and PP;

OR, these BIO monomers, sugars and oils can be synthesized to make PLA and PHA.

The difference between something like PLA and the PlantBottle, therefore, is that the PlantBottle derives its carbon from biomass, as explained in the process above, yet has the same chemical composition as tradition, petro-based PET. Therefore, it is not designed to “biodegrade” in an industrial composting facility or others, whereas PLA, which is of a different chemical composition though it derives its carbon from, like the PlantBottle, an annually renewable source, is designed to “biodegrade” in the intended disposal environment as stipulated by the manufacturers of PLA. Check out the molecular structures of PLA vs. PP on the 7th slide of Narayan’s presentation; as you will see, the carbon, highlighted in red, can come from petro-based or bio-based feedstocks. Cool, huh!?!

Slide 8: Understanding the value proposition for bio carbon vs. petro/fossil carbon

Narayan then went on explaining the difference between old carbon (fossil fuel) and new carbon (crop residue/biomass). Consult the 8th slide of the PPT for an explanation of how old carbon is synthesized from new carbon.

Consider the following processes of synthesizing new vs. old carbon:

CO2 (present in atmosphere) + H20–>photosynthesis (1-10 years)–> (CH20)x +O2–>NEW CARBON (biomass, forestry, crops)

Vs.

C02+H20–>photosynthesis (1-10 years) –>(CH20)x–>–>–>(10,000,000 years)–>OLD CARBON (fossil resources i.e. oil, coal, natural gas)

He then argued that all the criticism about manufacturing plastics out of non-renewable sources is misplaced because it doesn’t really matter where you get the carbon from—be it old or new carbon. The issue, however, is the rate and scale at which we have been taking old carbon (oil) out of the earth: it is inherently unsustainable to continue to derive carbon from fossil fuel for synthesis into disposable plastic packaging because it takes millions of years to create old carbon from the process described above, whereas it takes just 1-10 years to derive new carbon from crop residue/biomass.

Does that make sense?

He concludes: “Rate and time scales of CO2 utilization is in balance using bio/renewable feedstocks (1-10 years) as opposed to using fossil feedstocks.”

Goodness!

And, for your viewing picture, here is a picture of my pops (and Dordan CEO) and I for our feature in the May edition of Plastics Technology magazine!

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