Chapter 29. Chapter 29: Biofuels

What are biofuels and what are potential biofuel sources?

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Guiding Question 29.1

What are biofuels, and what are potential biofuel sources?

Why You Should Care

Biofuels are "hot" these days because they are currently offering the most promise as a replacement for petroleum-based fuels. A biofuel is, not surprisingly, fuel produced from living organisms. Nearly all such fuel is either produced directly by autotrophs or by yeasts or bacteria fermenting the carbohydrates produced by autotrophs. These fuels can be hydrocarbons, oils, or alcohols, but all share the quality of being able to release a lot of energy when combusted. Many different sources of biofuels are being researched: Algae, grass, corn, and oil palms are just a few examples. One biofuel is already being used commercially: Biodiesel has been available for years as an alternative to petroleum-based diesel fuel. Biodiesel is produced by chemically altering vegetable oil (usually used frying oil reclaimed from restaurants and food manufacturing plants), and can be used interchangeably with diesel in vehicles, machinery, and household oil-furnaces. Although a renewable, carbon-neutral fuel source, biodiesel alone can’t meet the world’s fuel needs because there isn’t enough used vegetable oil. Since it is likely that other biofuels will soon join the market, it is important to be informed about their pros and cons.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
thbCndys2V+cNoINDvjX3SYAnTpgetyi2xDmUYmdlYBHSVz0IdX7yGy4j2sie5xVOwRrdmkI0AP6+RfHqu8VduRerW7hovwquo0CK4IFtC28xEaUtFJ3PQ== Solids, liquids, or gases that produce energy from biological material.
ezEGnkRlE91Ith6gZEeeypqMORuUu8inTm1f7bm5ea01fIGWHIbjOs6kHhf3vcKzllPLOmA1jObSnzGiG8LbmOi0YMI/9ErZchkGCRxUrVSQeawwKFyq9Q== Plants that live for more than a year, growing and producing seed year after year.
SHTICxiOLYuMSMB/96cykNWB7JfmRRoOi+XMTiY8l5Cslc0cIC++sXbC8bd3q8z7CXjfLhkeI+P44dUir26EO5WndZIdsxgF8F8CsgqE9/9CCJiHTdcFpA== Biomass sources used to make biofuels.
Eq4tYLpXwoSFXlJleOR2wZECaEBXPAT8N1wO9jcsLNvk154CJMxwa8EsiM87rNmzMuO5JattimY2UC/nQO3BriOx5us5zX+o+kXQwYUHgR2iGMYifiiDSg== An alcohol fuel made from crops like corn and sugarcane in a process of fermentation and distillation.
A8SPEudr57taJcxsbelUPH5C7mIwh0nGDJ7f5uO6nrtxSaJVkma0h8dU2MsTYtKR6tPkva+39evWjmLnUKc9AxYCIhK+Fsppxe+bwTwmslTLMhh/F7HNoA== Crops specifically grown to be used to produce biofuels.
O2hZPNCJHVx0ZuL5EOJZ/659CTKudPi1ZAriZUPZgHhsyDZzbQ0k/xBRw6RJtkoIGI3EZxpoa0MSXYHINVhPuW5D3q4nQHafWfmH233GKM5WYxREKzECbg== A liquid fuel made from vegetable oil, animal fats, or waste oil that can be used directly in diesel internal combustion machine.
AWEVs3wHG6H1oPNuuQFQ/iVj8XyDrx3BnwvIi27qf9TNK2fC22DAqDuY53oqg32vmXCjQYNcnQLzti9R5DhFS2jhzNCtAjD+3B0v2GrjUozA3WmNgN6DDg== Plants that live for a year, produce seed, and then die.
t6TuY8cds59i9F9ECUqU9Gl0qO/PNN35to3jePmjfi0cRwJXjASy6utcYOzdJiVurlq1YxAi3i98kDEJGRgt39YiNdS6A1F7jPlUovfR65Tex6Nxn7uzgg== Material from living or recently living organisms or their by-products.
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Question 29.1

5S99UObaQ+FYP5NM5kmn161Qf7bAL6T49NqXj+X4xxaDRDW01VY9GPwphVhC41z4+MeIllQMG1FsfJ6TTAhkpsBRk063tmhj4X/fFQE3VxlFBU8rqFR1Bs2dO11NxisugrhzK0T6mUL5ILtB0/RWYpiHfPJv8oLGep3fl5GhCBZJoDhoFoMyuvK7YqJ0B4YhHNr4vvyvXLiPJhl/
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Question 29.2

ViVxsmxzaSYC3xh1WdQNur0rAI6J+VEH4n0zH3WN4zlPEgnJa1Wr9IQtq6eMut0QgWcSTEA9MIegld6F5wYQayNRu2UJgIr0ykP2bI2RTqxIJeTgsLcfg9FctZ5zf35iH2Ct3MNhM91JK/15UDgEhk3jWKb2aSQB2ePTeMxf5/IN35C7XSdpAuRGmoaU4wyEO4QealZLqcaD7XgGb5urnzr4sypzDck81IX39AbUY5t1VRTClgGzc84gkhA2HdF7wyvfO0ClSlOUnyyIbHUQctiS8CvIDNCQBxxj6WS73EWkfVGg6u98I4g8kh8mlUU2t0DJXOdIYzEWt+payjSzW6M82IAa79/8vGcx2NruQWBJ5F4oFM4aDd6G99g=
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Question 29.3

BFywPgvFt6TWVRcGHVE7/1rIpH3XexuKgPoTDBdjSl509DU/5mLpCSs3LSZGIyyw0YerrCseE3TsuwbZfAueimT7akm6ZD9Eti/z7HnIoC3TNCd65JxbFI9qaFJ14ZXETHcSpWKZnS2T5joVsHXp3B13jbyARWnLLf/gt9Zz8YJmPggNc+qLmqnXwRckbYUdRwrOHosQhP9JKapVDmgd/gBAU4Q8yToa95l0b2ZEfLiZUzL2OZ1O0DM3zSe9AOge7YG2nRiXQ3G8UhwJl7WP3U1/fFJmvqwGSW81p97W5xDqIH6CNS5bE2YKgMzzAMb8vx/MBqcU+TivsJ38JR38YCrql6DAA3dBR7gftw==
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Question 29.4

Bim3KywkT0PLLafXVxX9iuR/bMpoKzQGwVboRjTNd1JmvZPSegZC6RlBJtaSSw0Dyv+0PxGPU3xTfkmWhz5Nx6DQKlCf1X0ediL12RQ3kGCW0SwwNX1kXh6iUEchWecGGt5JzDODy7bFE4iwRT1wRFVQ9RnLRdaQNQWUgH5eqr5xMdmrJ4le5lKh5jDhx+SktzqFPUhrP5xNQCU7zPHIFBqZd1rQT6RXtHU6dq8TuuXQzEbz
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Although surplus corn would otherwise be wasted, it is a new product, not one derived from material left over from another use.
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Question 29.5

m/W6iM1rlGeEouy177xGvTxMlXB78abPs4zkubNeAx1T8FxUiVtuaRiN9zishsWCQhsynt19BfBnO01h6/4VU8ZHP8/Nxi9ImWXyQGMnWwdhpLVlVhSVVWwaCioqIGnN5wAg9ejjg2qqsjyBJGPgahBthBjIKjKHkN6PTSStF7yD8+r3Crcxmg==
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Biomass is simply matter created from biological processes. Direct biomass energy comes from burning biomass. Biofuels are fuels derived from biomass, so the end product that is combusted is not the same as the biomass energy source.
Infographic 29.1 part 1
Infographic 29.1 part 2

Question 29.6

kYvL1eqIv8fE4ESrMoLbpb9nQ84K3v/ABSnkCso9V2BOi4gOQFPqFxQr/i2PQ2wQIS0VYFM9QJJabm8A4CMs6beqXuG/+G5F//S61/y32i2sS3Gr+0T+2Jwt5Q2xDawEr0RS1/PW05g0mAO+znod8DOONVI=
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Being pictured with the other direct biofuel sources is the first clue that these briquettes are also considered a direct source, but why? The briquettes are definitely manufactured, so they are different in form from the original biomass, which makes them seem to fit into the biofuel category. But, the waste biomass that makes up the briquettes hasn't actually been chemically changed into a different substance, and that makes them a direct source.

Match the descriptions below with all of the possible energy sources that fit them:

Question 29.7

Non-edible source that can be used for direct biomass energy and produced expressly for that purpose:

aFyLQOV9P9qF6KzY Wood

6Tla4sTC7UhhcmHA Corn stalks

6Tla4sTC7UhhcmHA Manure

6Tla4sTC7UhhcmHA Switchgrass

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Hint: Think about which source(s) is/are not waste products and used directly for biomass energy.

Question 29.8

Source that is used both for direct biomass energy as well as for producing biofuels:

aFyLQOV9P9qF6KzY Wood

aFyLQOV9P9qF6KzY Corn stalks

aFyLQOV9P9qF6KzY Manure

6Tla4sTC7UhhcmHA Switchgrass

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Hint: Eliminate as an answer any source(s) that is/are not listed both as a direct and indirect biomass energy source.

Question 29.9

Source of biodiesel:

aFyLQOV9P9qF6KzY Soy

6Tla4sTC7UhhcmHA Poplar trees

6Tla4sTC7UhhcmHA Sugarcane

aFyLQOV9P9qF6KzY Sunflowers

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Hint: Biodiesel is made from crops harvested for their oil.

Question 29.10

A waste product that is a potential source of cellulose for bioethanol production:

6Tla4sTC7UhhcmHA Poplar trees

aFyLQOV9P9qF6KzY Sawdust from lumber mills

aFyLQOV9P9qF6KzY Corn stalks

aFyLQOV9P9qF6KzY Dead soy bean plants

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Hint: Make sure you don't select any choice that's grown primarily for ethanol production, and make sure you consider what would qualify as crop or forestry waste.
Infographic 29.2

Question 29.11

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Question 29.12

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Question 29.13

3C3nOVr+9h28kkAJkDMwbLVqUCw+ym6Kt0+jXP1Wa4m4vxlGOxysjSbEZcKvfy6buZopXjtshos3KdQTelIuYhKvZo9QEYrUqk+nNszDNUeTaw3911MPWs5SLjsqCBk9CpzD8OU+9APD94rTu2DpbYxTDGSNT9m9fXXJxeT2XY8QX+KblKnsHFB0hP6ysydQmTbLrdT66UaLtuLec9fEX3b1qrynmgzhv2P/RDKoGSQD90KRk5lchtImVWQ7xr6JdVq52E0ksw/dtXLW7YDqDbsRtw0y6MTwiiHbB5Po4dJKIqMK0f4Ui6KxeQIilp1VDuG6QA==
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Question 29.14

ZOwc8bBVi0q2pk9ImvlgPW3YxRk2b9qcMW65COz15nUX6Vjy9hKbPHiN99GjSU1BEOR1MkaKLS4pWHIdYP6alWIcoYMvt4SjXXKHWlyw+l+9vmAYGXtkdzuIyTmSJK3y6/jcFAgW0hhpwv3tXBDT2NpozJYj7ca9S37OMiw4VI4AhOhojbHWKu5LMxv/DlDdhMzU2xSoD+ElLh9AqvVs4DFloZgTdZevPw3p6w==
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Infographic 29.2

Question 29.15

Select the number in the figure that best corresponds with the items below:

Glycerin: oaws7xH5uFIpbfe9qTg85YaQfghiy4cnLkLT2ilA2zGnVF9Qd0oYzg==

Lye and methanol: jv4lH0JyzQaJmBIG22NDOtFx2xIA+1CF3OszpxWjoKVacGfcEiuk6Q==

Methanol: BZGLAcSm+0S0nqdCYIkWTD6UenQ7x/+6TLZWJ2+XS++aHrSnr78+rw==

Feedstock: 4yyF1jF3qZMp9DFu5MPjYoRatBX6Fhc1yQ+btXeH+jcRIpFssy+QcA==

Water: 9ZJT67LicZvX2ZCVoROxJCRvTFvQMVMgp/VRPN4GyQtLu/1jyM4F+Q==

Pre-processing: w80Alz7KYO9XabN5Ib89dDLPzo1uKJ/sfPOGzRNPBGydvRQvcE0UNg==

Step that includes filtering solids: w80Alz7KYO9XabN5Ib89dDLPzo1uKJ/sfPOGzRNPBGydvRQvcE0UNg==

Washing to remove impurities from biodiesel: VhHy3n51qZ2RWyPEwxWYkPR8qQY96nl3N4iu6BVfaRPko8ZO7U+ISw==

Chemical reaction: ToizPIsgXSslhLX7kxSrbLyY/tgwVAMajOb4wYFJ7q/SbeXXgX2eyg==

By-product that can be sold for other uses: oaws7xH5uFIpbfe9qTg85YaQfghiy4cnLkLT2ilA2zGnVF9Qd0oYzg==

Can be reused for creating fuel: BZGLAcSm+0S0nqdCYIkWTD6UenQ7x/+6TLZWJ2+XS++aHrSnr78+rw==

Can be reused to remove impurities: D6rx4xLq5GrXjimlv/DHt5CalbTGgr0pI2z0HmKmUtw9SYa9u3XHIg==

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Question 29.16

iTiVhDdQX64UY43nfVoU5XfspxU1hiwiZ08RacwI4QWiD1G4XZd7dWmV9GCmekb7mTeRjiaR9hs2kC+JRDqnxtNe3i2KL0+E6SphwrZK7hNiAh4OT7F3te2B26E=
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You could say yes or no here depending on how you justify your answer. Both numbers 6 and 10 are biodiesel, but 6 is still un-purified because it hasn't had a water wash yet. So you could also say no because 6 is impure biodiesel and 10 is purified biodiesel.

Question 29.17

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During number 2, pre-processing, water is removed from the feedstock (oil, grease, etc.) as an impurity that will prevent the biodiesel chemical reaction from proceeding properly. The oil is also filtered to remove solid impurities. During number 9, washing, water is used to remove chemical impurities from the finished biodiesel and then removed from it. So both steps involve purification, but the first one involves purifying the oil and the second the fuel. Both involve water, but in the oil, it is an impurity, and in the fuel, it is a cleaning agent.

Question 29.18

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Question 29.19

EeNapVGZB68684Rv/2dlL/YfaAypoDgcYDMyF3CP5YqaOKpGnu2iwsNUZkKbKzYxcKoC8z0rDVsjAt9w2Kf5nyVePMZwYeHJOu1rMq/mLXpx4LaDbBf0tCN5TzgJEudIiT1Rbebt2nLJQ+a6W3vuSHvwxMmH+pFenKylvhyjTpAUc6RNhAPltGmv034iIh9jurjcWVA53oWCmC+cKfMOdg8TZUMZimNCN65cPqLSnrlUO2fN9FQyP7HEWs7RWRHvWJyMTSr5/n1wboRgSWTG4ixDmt89JxK7G0HZFPzTL3xsY4tzc0JZirVdRqq206+nyHEHb/WKp1viiIMv9+BQg21DHH/DdY7yMqmV5UPAL3Bsmb4Qo+i65NSQ2p/OHqy2KFV0ZtiWvn6mKJRqswv5nbaeWIQaZbHsn2Czjw==
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Question 29.20

41e2Xz0un/wnp7mriuW5Xcvw2tr30XbVzrlmGU/owrFi0eT2Oi1pS9Is2ehqwDUzx3vMBMjJACkBP+p3r6x8HsYFioCNIH1F9eaFIsakQPnYb66Hicx6gia0MZyfd0cHPShRN4P+Uhh9GAOWaUyDAMJjWCXJpM2KKvk4UlTNEj5RUXxQ6GxHake4eUanL9qFe5qEVueBaSc3e+PEqMiHJf8P4gLG4hpCpJQKa0qUfYJw3Jv3F2xS2unAuoXrRA1LjANOwXfH5qUdbRpm4gDc58VbpVN3QDor6u+dsVc8PS8YZsT9Qhpf8PNSekKWiSdfnSjwtteEwBi7PTRFSZl2Wg/i03g/Y2RX7z3U5EJzZeNIHYBzB/gkvJJylaDoCrA2Pmp9SOTXCic9U7eW2+NRSjkiD4lL4f9FrTs/yhIE4zCl8eQX2U51htRMnmCLejEi
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Question 29.21

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Question 29.22

IMGEZXP/zPCPDgIvbQMxEp5FYZd5XZgCJlRz9rUw4rUWjdSiQt14j3xX6VoMRU3jxVkW16FPNqQ1hRahef1owDkfbxcUfelpW5hgoWFH3uNUkWT0qS88rg+5y8zajM3KhYx3dwjmORp0x2iP
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On the benefits side: The algae used for biofuel production can produce about 16–30 times more oil per acre than terrestrial oil crops. Algae can also be used for bioethanol production and can be used as food for livestock, so they not only don't compete with human food, but they may help grow it. Most of the algae in development are marine, so they can be grown in seawater, which doesn't tax freshwater resources. Disadvantages are that current production methods are expensive because more research is needed to develop techniques that are already established with other fuel crops.