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  • Your car,

  • the heating system in your house,

  • your gas stove.

  • Most of the energy you use

  • comes from fossil fuels,

  • which present a couple of problems.

  • First, there are limited supplies of fossil fuels,

  • so the more we use, the less we've got.

  • And second, the use of fossil fuels

  • is the main cause of climate change

  • because it releases large amounts

  • of carbon dioxide into the atmosphere.

  • Biofuels come from natural, renewable sources like plants,

  • so they have the potential to reduce our reliance

  • on those limited supply fossil fuels

  • and reduce the risk of climate change.

  • Most biofuels today are made from corn grain

  • that is fermented into ethanol.

  • But we have a limited supply of this corn,

  • so it's not a solution to the limited supply

  • part of the quandary.

  • It also takes a lot of resources to grow corn grain.

  • Strike 2!

  • A potential solution:

  • Using cellulose instead of corn grain to make ethanol.

  • Cellulose is far more abundant than corn grain

  • and takes less energy to produce.

  • In fact, it's the most abundant organic molecule on the planet!

  • Cellulose is the main ingredient

  • found in a plant's cell wall.

  • Plants generate cellulose from water and carbon dioxide

  • during photosynthesis.

  • So, where as using fossil fuels produce carbon dioxide,

  • using cellulose-based ethanol might help remove

  • carbon dioxide from the atmosphere.

  • The main obstacle is that the cellulose molecule,

  • a long, connected chain of glucose sugar

  • protected by a tough, molecular sheath,

  • is difficult to break apart.

  • Creating cellulose-based ethanol

  • means first unwrapping that protective sheath

  • and then chopping up the cellulose

  • into its individual glucose molecule.

  • Only once we have unpacked each glucose molecule,

  • can we begin fermentation.

  • But some microorganisms,

  • like bacteria or fungi,

  • break down cellulose for energy all the time.

  • For example, dairy cows eat foods

  • like hay or alfalfa, which are full of cellulose.

  • Microbes that live in their stomachs

  • produce an enzyme called cellulase,

  • which breaks apart the cellulose molecules

  • so that the cow can use what's left for energy.

  • Researchers are now studying

  • these kinds of microorganisms

  • in the hopes of finding better ways

  • to break down cellulose

  • so we can use it for our own energy needs.

  • The solution, they think,

  • lies in finding microbes in nature that can produce

  • the kinds of cellulase enzymes that we need.

  • This process of searching for species in nature

  • that can produce valuable products

  • is called bioprospecting.

  • To test whether or not a sample of microbes

  • can break down cellulose effectively,

  • researchers first grow the microbe in a test tube.

  • Then, they add a source of cellulose

  • as the sole form of energy.

  • If the microbe can't produce cellulase

  • and break down cellulose,

  • the test tube will remain unchanged.

  • But if the microbe produces the enzymes

  • we are looking for,

  • it will be able to break down cellulose,

  • use it for energy,

  • and thrive in its test tube environment.

  • If our microbial sample can break down

  • the cellulose in the test tube,

  • there is a chance we could use it to create

  • a renewable and sustainable source of fuel

  • for our cars from cellulose.

Your car,

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B2 US TED-Ed cellulose test tube fossil ethanol corn

【TED-Ed】Biofuels and bioprospecting for beginners - Craig A. Kohn

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    Halu Hsieh posted on 2014/07/05
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