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It’s summertime and people are out camping, barbecuing, and using FIRE! But what’s a better fuel to use for your summer activities? Wood or charcoal? There are pros and cons to both fuels, so check out this episode of SciShow to decide for yourself!

Hosted by: Hank Green
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Sources:
http://science.howstuffworks.com/environmental/earth/geophysics/fire1.htm
http://www.planete-energies.com/en/medias/close/wood-source-thermal-energy
http://www.ipst.gatech.edu/faculty/ragauskas_art/technical_reviews/chemical%20overview%20of%20wood.pdf
https://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/32_2_DENVER_04-87_0036.pdf
http://virtual.vtt.fi/virtual/innofirewood/stateoftheart/database/burning/burning.html
http://www.heartheat.com/flameworksOLD/index_WoodComb.htm
http://www.sciencedirect.com/science/article/pii/S001623610600490X
http://www.fao.org/docrep/s4550e/s4550e09.htm
http://www.greenpeace.org/international/Global/international/publications/forests/2012/Amazon/423-Driving-Destruction-in-the-Amazon.pdf
http://www.fao.org/3/a-i5134e.pdf
http://www.carbonbrief.org/is-burning-wood-for-energy-worse-for-the-climate-than-coal

Images:
Charcoal: https://www.flickr.com/photos/toasty/2643569674
Firewood: https://commons.wikimedia.org/wiki/File:Stack_of_firewood.jpg
Glucose: https://commons.wikimedia.org/wiki/File:D-glucose-chain-3D-balls.png
Cellulose: https://commons.wikimedia.org/wiki/File:Cellulose-Ibeta-from-xtal-2002-3D-balls.png
Deforestation: https://commons.wikimedia.org/wiki/File:Deforestation_2074483b.jpg
[SciShow intro plays]

Hank: Summer is upon us, which means it’s time to grill up some barbecue and make s’mores around a campfire! But, which is better fuel: wood or charcoal? Fires are a combustion chemical reaction: you take some fuel, add some heat, and react those molecules with oxygen, then, whoosh you got that fire there. And it’s an exothermic reaction, meaning it releases energy in the form of light and heat, the flames you see and feel, and some other byproducts.

Wood and charcoal are a little different chemically, so charcoal releases more heat energy and less smoke when it burns. Wood is made up of long chains of glucose molecules, called cellulose, plus some other structural organic compounds. When those compounds are heated to about 250 degrees Celsius, they’ll start to break apart in a process called pyrolysis. These organic molecules break down into simpler molecular components and release volatile gases, which evaporate easily and are combustible.

Water, carbon dioxide, and volatile gases combine to create smoke. And all the gases reacting with oxygen create lots of heat, which causes even more pyrolysis and combustion reactions, and creates more flames. If you try to start a fire with damp wood, or fresh wood that contains a lot of water, heat will boil the liquid water into vapor, which isn’t a combustible gas. This basically releases energy into the air, instead of generating more heat.

The remaining material from burning wood is called char or charcoal, which is 70 to 80% pure carbon. And there are some other leftover minerals which become ashes. Industrial companies can mass produce charcoal by heating up wood or wood products without much oxygen. This initiates the pyrolysis step, but doesn’t really cause combustion, since there’s not much oxygen for the volatile gases to react with. So, from a chemical standpoint, charcoal seems like the better fuel source, because it’s mostly carbon, and burning it releases more heat energy for a longer period of time, with fewer smoky byproducts.

But from an industrial standpoint, there are also big economic issues that come into play. Industrial factories need massive amounts of fuel. And since charcoal is a product of wood pyrolysis, it’s become a big factor toward deforestation in parts of Africa and South America.

So policies and research efforts need to be initiated to conserve these resources, or use them more efficiently. Ultimately, whether you use charcoal for a smoke-free grilling experience, or wood for a big toasty bonfire, use whatever fuel suits your needs to have a fun and safe summer!

Thanks to Patreon patrons Lauren, Rob Margolis, and Jake M for asking questions about fire that inspired parts of this script, and thanks to all of our patrons who keep these answers coming. If you’d like to submit questions, or get some videos early, go to patreon.com/scishow, and don’t forget to go to youtube.com/scishow and subscribe!