Energy Flow and Enzymes
In the Real World
Environment and Energy Flow and Enzymes
Although the first law of thermodynamics says that energy cannot be created or destroyed, we have learned that not all types of energy can be easily re-created. We are constantly hearing that we only have a limited supply of fossil fuels left as an energy source and that we need to refocus our efforts on "alternative energy" methods like wind, solar, and nuclear energy. Although we may not hear about it as much, fossil fuels are actually used for a lot of things other than energy. For instance, fossil fuels are needed for the production of plastics.
It is estimated that in the last 10 years, more plastics have been created than were created in the whole last century combined.7 We know that rapidly burning through our fossil fuels is not great for the Earth in the long run, but the increased use of plastics will also leave a significant footprint on our environment for years after their production. Not only are these plastics difficult to dispose of, they also contain compounds that are believed to be a danger to human health. What is it about plastics that cause these environmental concerns? Nothing less than the plastics' thermodynamic properties. What else?
While we are accustomed to seeing and using plastics at every stage of our daily lives, we rarely take a moment and reflect on the thermodynamic and energy properties of plastics that make them super materials. That's right; plastics are super materials.
Plastics are polymers, or molecules that are made of repeating units, or monomers. There are loads of biological polymers. Like the polymers in your body, the polymers of plastics take on unique characteristics specific to a particular type of polymer. The plastics polymers are extremely resistant, which is a characteristic that also makes them hard to dispose of. Most plastics require heating to several hundred degrees Celsius in order to melt or decompose. Knowing all that you do about thermodynamics, can you think of a reason for why this is the case?
Plastics contain substances that make them more durable, pliable, and flame-resistant. Some examples of these substances are lead and tributyltin—found in polyvinyl chloride (PVC)—and phthalates and bisphenol A (BPA). Studies investigating the safety of these additives to laboratory animals have raised some concerns, especially for children and pregnant women. Future work is needed to better compare the doses of these substances given to animals with the amount of these substances humans receive from environmental exposure. Meanwhile, current research is focusing on developing plastic stabilizers that do not have adverse effects (that we know of) on human health.
Plastics have become a major problem in landfills despite the increased use of recycling. As you go about your day, pay attention to the number of times you use or eat food from a plastic-containing container, or the number of times that the container finds itself in the trash. Even simple containers like potato chip bags are made from petroleum (fossil fuel) byproducts. SunChips, on a quest to make both our stomachs and the environment happy, developed a bag made from a substance called polylactide (PLA). PLA is made from plants instead of from petroleum, and it dissolves in a little over 3 months in the compost. Very environmentally friendly. Unfortunately, the bags are also noisy, and after repeated complaints from consumers, SunChips pulled the bags from the shelves. You can't have your cake and eat it, too, SunChips bag-haters. However, most people agree that the PLA bags are a step in the right direction. In all of this, it does become clear that our current use of plastics and their method of disposal is not sustainable in the long-term. Who knew that potato chips could be such a heavy topic, in more ways than one? Remember the days when potato chips came in boxes? No? Ah, nevermind then. Maybe it's time for some Kettle Chips…
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