Biomass
Figure 17.11: Three-stone stove used for cooking in many countries. Fig. 17-11, p. 571
Introduction Biomass energy = energy from living matter field crops trees algae agriculture wastes (e.g. manure) municipal solid wastes solid (wood), liquid (ethanol), and gas (methane) potential to provide 4-25% of U.S. energy storage and collection costs are low efficient for poorer nations 20% of U.S. is cropland/30% is forest Biomass might support 1/3 of our transportation energy needs
Burning biomass does not increase net atmospheric carbon dioxide levels (i.e. carbon neutral) because the carbon in the food chain cycles in and out of the atmosphere constantly.
Fossil fuels, although organic and derived from living matter, are NOT considered biomass because they are not renewable nor are they carbon neutral. The carbon in fossil fuels is (for all practical purposes) finite and when burned increases the net carbon dioxide in the biosphere (and potentially contributes to anthropogenic climate change).
Biomass conversion reactions Photosynthesis- puts energy in Fermentation Anaerobic digestion Combustion Pyrolysis Esterification of vegetable oil
Bioconversion Biogas Fig. 17-1, p. 546 Figure 17.1: Conversion of biomass into useful fuels. Fig. 17-1, p. 546
Food, Fuel, and Famine Energy efficiency in food production 13% of U.S. energy is used to make food Corn provides 3x the energy needed to make it 90% of U.S. corn crop is used to feed animals for the meat, pork, poultry industry A cow uses 100x more energy than it provides We should eat the corn not the cow! Compare growing broccoli to buying broccoli.
Figure 17.5: Energy used in the production of a loaf of bread. Fig. 17-5, p. 557
Energy justice? The U.S. could feed millions of people in third world nations if we didn’t feed so many cows Is using corn to make ethanol making food more expensive?
Figure 17.2: Flow diagram for production of ethanol from corn. Fig. 17-2, p. 549
Table 17-2, p. 556
Municipal Solid Waste Every year, each American tosses into landfills: 80 million tons of paper 50 million tons of food/yard wastes 20 million tons of metal 10 million tons of glass 25 million tons of plastics
Figure 17.6: National waste profile. Fig. 17-6, p. 558
+24,000 tons of garbage each day the Fresh Kills landfill near NYC is the tallest “mountain” on the east coast +24,000 tons of garbage each day 2 million gallons of leachate contaminates groundwater each day Municipal dump in Chile. p. 559
What can we do with our garbage? Reduce 10% of food cost goes into packaging 50% of waste volume is packaging 30% of household waste is packaging Recycle 30% of U.S. waste is recycled 45% of all paper is recycled to insulation, bldg. mat. recycling the Sunday edition of the NYTimes would save 75,000 trees! recycling 1 aluminum can saves enough energy to run a television for 3 hours Incinerate to make energy financially breaking even at best concerns over dioxin and metal pollution in ash
Figure 17. 7: Waste-to-energy facility Figure 17.7: Waste-to-energy facility. The steam produced can be used to drive a turbine-generator or to provide process heat to a nearby customer. Fig. 17-7, p. 562
Construct “secure” landfills using liners and clay to contain leachate monitor groundwater for contamination decomposition can be sped up by bioremediation biogas can be generated- “garbage in ,gas out”
Figure 17. 8: Cross section of a secure landfill Figure 17.8: Cross section of a secure landfill. Note the multibarrier liner of plastic and clay to protect the groundwater from leachate. Fig. 17-8, p. 564
Figure 17. 4: Fixed-container methane digester Figure 17.4: Fixed-container methane digester. Family-sized digesters using manure are relatively common in countries such as India and China. In China, an estimated 4.5 million biogas digesters are currently in use. Fig. 17-4, p. 554
Wood combustion In 1860, 75% of U.S. energy needs were supplied by wood. In 190025% In 19732% Environmental impacts include deforestation and pollution Handling wood and ash can be burdensome Fires can be hazardous
Figure 17. 9: Heat transfer from a conventional fireplace Figure 17.9: Heat transfer from a conventional fireplace. Heat output to house is offset by heat loss as a result of room airflow up the chimney. Fig. 17-9, p. 566
Figure 17.10: Airtight stove, with secondary combustion in the upper chamber. Fig. 17-10, p. 567
Table 17-4a, p. 569
If natural gas costs $1 per therm, what should be the price of a cord of mixed hardwoods to deliver the same Btu?
Table 17-6, p. 575
Figure 17.3: Energy density of various fuels. Fig. 17-3, p. 553