Lecture 4 Slides

Lecture 4 Slides - Correction/Clarification: Gasoline...

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Correction/Clarification: Ethanol vs. Octane Gasoline mix of hydrocarbons with 5-12 C/molecule Major constituents toluene, benzene, trimethylbenzene, MTBE (5-35%) Combustion generates 34.8MJ/l Ethanol 2 Carbons Specific energy of combustion: 1307.7kJ/mol Combustion generates 23.5mJ/l Octane 8 Carbons Specific energy of combustion: -5430kJ/mol Octane rating: resistance to knocking (pinging)
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Lecture 4 Cattle: grass-fed vs. corn-fed Feedlots Prion diseases Antibiotic resistance
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Cattle digestive system is specialized to process cellulose and other low-grade plant materials found in grass
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Feeding cattle: Ruminants have four “stomachs”: • Reticulum: – Honeycomb (waffle-like) structure – Sold as tripe in market – Important for regurgitation – 7% of food energy is lost as methane (CH 3 ) – Adult cattle produce 800L/day of gas (mostly CO 2 and CH 3 ) – Significant contributor to greenhouse gasses and thus global warming
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The Greenhouse Effect Hydrocarbons in atmosphere trap heat CO2 from fossil fuels is the major contributor to global warming, but not the only one Methane is responsible for 4-9% of this effect Enteric fermentation (i.e., livestock eruction) accounts for about 20% of U.S. methane generation
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Regurgitation (chewing cud) aids in the difficult job of digesting cellulose –Frothy bloat endangers health because gas and cud are trapped; roughage (hay) stimulates salivation and prevents bloat
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Ruminant digestion (continued-2) • Rumen : – 125L fermentation chamber – Normally at neutral pH in grazing cattle – Micro-organisms (bacteria and protozoa) • secrete enzymes to digest cellulose
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Lecture 4 Slides - Correction/Clarification: Gasoline...

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