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Liquid biofuels: ethanol and biodiesel

Biofuels may be considered to be carbon-neutral because the plants that are used to make them (such as corn and sugarcane for ethanol, and soy beans and palm oil trees for biodiesel) absorb CO 2 as they grow and may offset the CO 2 produced when biofuels are made and burned. Calculating the net energy or CO 2 generated or reduced in the process of producing the biofuel is crucial to determining its environmental impact.

Even if the environmental impact is net positive, the economic and social effects of growing plants for fuels need to be considered, since the land, fertilizers, and energy used to grow biofuel crops could be used to grow food crops instead. The competition of land for fuel vs. food can increase the price of food, which has a negative effect on society. It could also decrease the food supply increasing malnutrition and starvation globally. Biofuels may be derived from parts of plants not used for food (cellulosic biomass) thus reducing that impact. Cellulosic ethanol feedstock includes native prairie grasses, fast growing trees, sawdust, and even waste paper. Also, in some parts of the world, large areas of natural vegetation and forests have been cut down to grow sugar cane for ethanol and soybeans and palm-oil trees to make biodiesel. This is not sustainable land use.

Biofuels typically replace petroleum and are used to power vehicles. Although ethanol has higher octane and ethanol-gasoline mixtures burn cleaner than pure gasoline, they also are more volatile and thus have higher "evaporative emissions" from fuel tanks and dispensing equipment. These emissions contribute to the formation of harmful, ground level ozone and smog. Gasoline requires extra processing to reduce evaporative emissions before it is blended with ethanol.

Biodiesel can be made from used vegetable oil and has been produced on a very local basis. Compared to petroleum diesel, biodiesel combustion produces less sulfur oxides, particulate matter, carbon monoxide, and unburned and other hydrocarbons, but more nitrogen oxide.

Endless sources of energy: earth, wind, and sun

Geothermal energy

Five percent of the United States’ renewable energy portfolio is from geothermal energy (see Figure U.S. Energy Consumption by Energy Source, 2009 ). The subsurface temperature of the earth provides an endless energy resource. The environmental impact of geothermal energy depends on how it is being used. Direct use and heating applications have almost no negative impact on the environment.

Installing a Geothermal Pipe System
Installing a Geothermal Pipe System Drilling to install geothermal ground source pipe system . Source: Office of Sustainability, UIC

Geothermal power plants do not burn fuel to generate electricity so their emission levels are very low. They release less than one percent of the carbon dioxide emissions of a fossil fuel plant. Geothermal plants use scrubber systems to clean the air of hydrogen sulfide that is naturally found in the steam and hot water. They emit 97 percent less acid rain-causing sulfur compounds than are emitted by fossil fuel plants. After the steam and water from a geothermal reservoir have been used, they are injected back into the earth.

Questions & Answers

what is mutation
Janga Reply
what is a cell
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Sifune
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mahase Reply
classification of plants, gymnosperm features.
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What is Atoms
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Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
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Konadu
how is urine formed in human
Rahma
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Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
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a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
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how are lungs work
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in the mouth
EZEKIEL
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stimulates the follicle to release the mature ovum into the oviduct
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endocrine secrete hormone and regulate body process
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while pituitary gland is an example of endocrine system and it's found in the Brain
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Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
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Source:  OpenStax, Sustainability: a comprehensive foundation. OpenStax CNX. Nov 11, 2013 Download for free at http://legacy.cnx.org/content/col11325/1.43
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