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Compostable Biobags Have Higher Carbon Footprint, Report Says

Non-biodegradable bioplastics have a smaller carbon footprint than those that are designed to decompose, according to a white paper by U.K. firm Biome Bioplastics.

Bioplastics: an important component of global sustainability uses figures from Brazilian plastic and bioplastic company Braskem, among other sources, to show that for every kilogram of non-biodegradable biopropolyene manufactured there is a net sequestration, or negative carbon footprint, of about 2.3kg of CO2.

This is compared to a net gain of over 5kg of CO2 for each kilogram of traditional plastic.

Degradable bioplastic also offers advantages over its petroleum-based cousins, the report said, but these advantages are less pronounced. Degradable plastics compost back into carbon dioxide and water, returning all the sequestered carbon to the atmosphere.

This situation is worsened if the bioplastic did not compost in air, “but rotted in an oxygen-poor landfill,” according to the report.

“In these circumstances, the plastic would degrade into methane (CH4) and other byproducts. Methane is a global warming gas of greater impact than CO2 and so the full carbon footprint needs to include any uncaptured CH4 produced in landfill,” the report says.

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9 thoughts on “Compostable Biobags Have Higher Carbon Footprint, Report Says

  1. It always seems that the whole picture isnt immediately considered. i have seen green “biodegradable” poop scooping bags all over the place and somehow folks think this is a license to toss them everywhere. as they break down it seems that all that happens is they get to be smaller and smaller pieces. i think the full understanding of how things biodegrade is important and it needs to be known what they do in and out of a landfill situation, in sun or no sun, and all the other considerations of how the bag will really exist and for how long once it has been disposed of.

  2. Hi Tim,
    The plastic doesn’t sequester 2.3Kg… the sugar cane grown in Brasil in order to make Braskem’s Green PE does it…

  3. Tim,

    two things.

    The first is that the claim is 2.3 kg of CO2 sequestered, not Carbon. 1kg of Carbon makes about 3 kg of CO2 when burned.

    The second point is that the article goes further than Braskem’s presentation claims (the Braskem presentation has no supporting evidence or citations to go with it). The Braskem presentation ( http://www.braskem-ir.com.br/braskem/web/arquivos/Conference_Mar2011_Citi_1x1_v2.pdf ) states that 2.3 – 2.5 kg of CO2 are “captured” in each kg of PolyEthylene or Polypropylene made by Braskem’s bioplastic process (reverse this and you get 2.3 – 2.5 kg of CO2 produced by burning 1 kg of PE PP). That’s entirely credible, if it just refers to the CO2 equivalent physically locked up in the non-biodegradable plastic.

    However, the EL article alters the Braskem claim by stating that there is a “NET” Carbon sequestration (or negative Carbon footprint) of 2.3 kg of CO2 for every kg of bio-plastic manufactured. These are two very different statements.

    The White Paper linked in the article above makes the difference very clear between the CO2 physically locked in non-biodegradable plastic compared to the overall Carbon footprint of producing the plastic. The White Paper suggests that the Carbon footprint is usually a positive value, albeit smaller than the C footprint from producing fossil fuel based plastics due to pulling Carbon from the air by the original plant and lower temperature processing.

    Your scepticism is warranted. Poor reporting by EL

    • Hi Nigel,

      This is taken straight from the Biome white paper, “Braskem, the large Brazilian producer manufacturing both bioplastic and oil-based equivalents, has calculated much higher figures for the capture of CO2 by a growing sugar cane plant. It estimates a net sequestration (that is, a negative footprint) of about 2.3 kilogramme of CO2 for every kilogramme of biopolypropylene manufactured.”

      So I don’t think we altered anything, unless I’m missing something…?

      Tamar Wilner
      Senior Editor

  4. I find this to be positively insane. This should have been known. Who’s doing the tests on these things? This should have been known before they were ever approved. The approval process needs to be re-examined.

  5. Tamar, That’s the danger of just “taking something straight from the Biome (or any) white paper” without exercising editorial judgement

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