biomass/fuels apes. producing energy from biomass plant materials and animal wastes can be burned...
TRANSCRIPT
PRODUCING PRODUCING ENERGY FROM ENERGY FROM
BIOMASSBIOMASS
Plant materials and Plant materials and animal wastes can animal wastes can be burned to be burned to provide heat or provide heat or electricity or electricity or converted into converted into gaseous or liquid gaseous or liquid biofuels.biofuels.
PRODUCING ENERGY FROM PRODUCING ENERGY FROM BIOMASSBIOMASS
The scarcity of The scarcity of fuelwood causes fuelwood causes people to make people to make fuel briquettes fuel briquettes from cow dung from cow dung in India. This in India. This deprives soil of deprives soil of plant nutrients.plant nutrients.
Fig. 17-25, p. 405
Trade-Offs
Solid Biomass
Advantages Disadvantages
Large potential supply in some areas
Nonrenewable if harvested unsustainably
Moderate costsModerate to high environmental impact
No net CO2 increase if harvested and burned sustainably
CO2 emissions if harvested and burned unsustainably
Low photosynthetic efficiencyPlantation can be located on semiarid land not needed for crops
Soil erosion, water pollution, and loss of wildlife habitat
Plantation can help restore degraded lands
Plantations could compete with cropland
Often burned in inefficient and polluting open fires and stoves
Can make use of agricultural, timber, and urban wastes
Converting Plants and Plant Converting Plants and Plant Wastes to Liquid Biofuels: An Wastes to Liquid Biofuels: An
OverviewOverview Motor vehicles can run on ethanol, Motor vehicles can run on ethanol,
biodiesel, and methanol produced from biodiesel, and methanol produced from plants and plant wastes.plants and plant wastes.
The major advantages of biofuels are:The major advantages of biofuels are: Crops used for production can be grown Crops used for production can be grown
almost anywhere.almost anywhere. There is no net increase in COThere is no net increase in CO22 emissions. emissions. Widely available and easy to store and Widely available and easy to store and
transport.transport.
Case Study: Producing Case Study: Producing EthanolEthanol
Crops such as Crops such as sugarcane, corn, sugarcane, corn, and switchgrass and switchgrass and agricultural, and agricultural, forestry and forestry and municipal wastes municipal wastes can be converted can be converted to ethanolto ethanol.. Switchgrass can Switchgrass can
remove COremove CO22 from from the troposphere and the troposphere and store it in the soil.store it in the soil.
Case Study: Producing Case Study: Producing EthanolEthanol
10-23% pure ethanol makes gasohol 10-23% pure ethanol makes gasohol which can be run in conventional motors.which can be run in conventional motors.
85% ethanol (E85) must be burned in 85% ethanol (E85) must be burned in flex-fuel cars.flex-fuel cars.
Processing all corn grown in the U.S. into Processing all corn grown in the U.S. into ethanol would cover only about 55 days ethanol would cover only about 55 days of current driving.of current driving.
Biodiesel is made by combining alcohol Biodiesel is made by combining alcohol with vegetable oil made from a variety of with vegetable oil made from a variety of different plants..different plants..
Fig. 17-27, p. 407
Trade-Offs
Ethanol Fuel
Advantages Disadvantages
High octane Large fuel tank needed
Some reduction in CO2 emissions
Lower driving range
Low net energy (corn)
High net energy (bagasse and switchgrass)
Much higher cost
Corn supply limited
Reduced CO emissions
May compete with growing food on cropland
Can be sold as gasohol
Higher NO emissions
Corrosive
Potentially renewable Hard to start in cold weather
Case Study: Producing Case Study: Producing EthanolEthanol
Biodiesel has the potential to supply Biodiesel has the potential to supply about 10% of the country’s diesel fuel about 10% of the country’s diesel fuel needsneeds..
Fig. 17-29, p. 408
Trade-Offs
Biodiesel
Advantages Disadvantages
Reduced CO emissions Slightly increased emissions of nitrogen oxides
Reduced CO2 emissions (78%)Higher cost than regular diesel
Reduced hydrocarbon emissions
Low yield for soybean crops
Better gas mileage (40%)May compete with growing food on cropland
Loss and degradation of biodiversity from crop plantations
High yield for oil palm crops
Moderate yield for rapeseed crops
Hard to start in cold weatherPotentially renewable
Case Study: Biodiesel & Case Study: Biodiesel & MethanolMethanol
Growing crops for biodiesel could Growing crops for biodiesel could potentially promote deforestation.potentially promote deforestation.
Methanol is made mostly from natural Methanol is made mostly from natural gas but can also be produced at a gas but can also be produced at a higher cost from COhigher cost from CO22 from the from the atmosphere which could help slow atmosphere which could help slow global warming.global warming. Can also be converted to other Can also be converted to other
hydrocarbons to produce chemicals that hydrocarbons to produce chemicals that are now made from petroleum and natural are now made from petroleum and natural gas.gas.
Fig. 17-30, p. 408
Trade-Offs
Methanol Fuel
Advantages Disadvantages
High octane Large fuel tank needed
Some reduction in CO2 emissions Half the driving
rangeLower total air pollution (30–40%) Corrodes metal,
rubber, plasticCan be made from natural gas, agricultural wastes, sewage sludge, garbage, and CO2
High CO2 emissions if made from coal
Expensive to produce
Can be used to produce H2 for fuel cells
Hard to start in cold weather