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===Biomas gasification===
===Biomas gasification===
    
    
While there are many methods for processing biomass currently in use, the most important three are [[gasification]], [[syngas]] cleaning/processing, and [[Fischer-Tropsch synthesis]].<ref name=Damartzis>{{cite journal| author=T. Damartzis and A. Zabaniotou|title=Thermochemical conversion of biomass to second generation biofuels through integrated process design-A review|journal=Renewable & Sustainable Energy Reviews|volume=15|issue=1|pages=366-378|date=Jan. 2011|id=|url=}}</ref>
== Biomass gasification ==
Gasification is a process of burning the biomass source at a relatively high temperature to release carbon monoxide and [[hydrogen]].  This process can occur through the use of [[oxygen]], [[air]], [[steam]], or mixtures similar to these.<ref>{{cite journal| author=S. Albertazzi et al|title=The technical feasibility of biomass gasification for hydrogen production|journal=Catalysis Today|volume=106|issue=1-4|pages=297-300|date=Oct. 15, 2005|id=|url=}}</ref> When air is used to carry out the gasification process the required amount of [[heat]] is a relatively low to medium heating value.  This process requires less thermal energy to complete but creates higher levels of unwanted by-products such as [[methanol]] and less of the useable hydrogen product.  The use of steam requires a higher amount of thermal energy to carry out the process but will yield higher amounts of actual hydrogen and lower amounts of by-products.  Gasification involves four main steps, drying, [[pyrolysis]], [[reduction]] and [[combustion]].  The drying process consists of taking the biomass source and removing all the moisture.  After the moisture is removed the resulting substance enters the pyrolysis zone.  This is where [[Volatility (chemistry)|volatiles]] are removed in the form of carbon monoxide and carbon dioxide and also where tar is produced.  After this process occurs the resulting substance goes over to the reduction zone where the raw materials are completely gasified in order to create a syngas product.  Finally in the combustion zone the left-over char material is burned which produces more gaseous product and also produces the necessary heat for the reactions in the previously mentioned reduction zone. The end product is known as syngas.  Syngas can be used as a fuel or it can be further processed to create [[synthetic natural gas]] (SNG) or synthetic [[Petroleum crude oil|petroleum]]. 
== Syngas purification ==
When syngas is used for further processing it undergoes a cleaning and purification stage.  The gas cleaning stage is the first stage of syngas purification.  This process involves the use of mechanical filters which remove [[particulate matter]], and [[Adsorption|adsorbents]] that remove the [[alkali]] and [[sulfur]] compounds in the gas.  The remaining tar in the gas is then broken down through the use of [[catalysis]] and steam.<ref name=Damartzis/> Syngas cleaning is a crucial step in preventing the fouling of machinery or contamination of catalysts when further processing the gas. 


== Fischer-Tropsch synthesis ==
== Fischer-Tropsch synthesis ==
The last commonly used stage of processing biomass is known as Fischer-Tropsch synthesis.  Purified syngas will be processede through a series of catalytic steps which will eventually transform the gas into a liquid fuel.<Ref name=Damartzis/> This fuel can be used in standard piston engines and can substitute for the use of fossil fuels.  This process requires substantial thermal energy to carry out and is a relatively costly process.  Efforts have been made to reduce the costs of this process to make it a reasonable competitor to the processing of oil for the creation of petroleum based fuels. 




==References==
==References==
{{reflist}}
{{reflist}}

Revision as of 17:09, 1 April 2011

Biomass, a source of renewable energy, is biological material such as wood, wood waste, municipal solid waste, straw, sugar cane, algae, and many other byproducts derived from agricultural and forestry production as well as other sources. Since biomass derives from plants generated by solar energy in the photosynthesis process, it can also be defined as the biological material on Earth that has stored solar energy in the chemical bonds of the organic material.

The fossil fuels (coal, petroleum crude oil and natural gas) are currently thought to have been formed from prehistoric, ancient biomass buried deeply underground over millions of years of geological time. Therefore, they are not considered to be renewable sources of energy

Uses of biomass

Biomass fuel for electric power production

The direct combustion of biomass for producing heat and electric power provides a ready disposal mechanism for municipal, agricultural, and industrial organic wastes. In 2009, about 11,350 megawatts (MW) of electric power, amounting to 1.1% of the summertime electrical supply in the United States was generated by burning biomass that included: wood, wood waste, municipal solid waste (MSW), landfill gas, and agricultural byproducts and waste.[1]

The New Hope Power Partnership in Florida is the largest biomass power plant in North America. It generates 140 MW of power using uses sugar cane fiber (bagasse) and recycled wood as fuel.[2] It has been in operation for more than 10 years.

Production of ethanol and biodiesel as liquid transport fuels

There are several processes available for converting the chemical energy contained in biomass into liquid automotive transport fuels such as biodiesel and ethanol.

Ethanol fuel:

Ethanol fuel is ethyl alcohol (C2H5OH) and it is most often used as an automotive motor fuel, mainly as an additive for gasoline. Ethanol can be produced by fermentation of sugar cane, bagasse, sugar beets, barley, potatoes, corn and many other grains as well as many agricultural byproducts and wastes.

The worldwide production of ethanol for automotive fuel in 2007 was 52,000,000,000 litres. From 2007 to 2008, the share of ethanol in global gasoline use increased from 3.7% to 5.4%.[3] In 2009, worldwide ethanol fuel production reached 73,900,000,000 litres (19,500,000,000 gallons) and was expected to reach 85,900,000,000 litres in 2010.[4]

Ethanol fuel is widely used in Brazil and in the United States, and together both countries were responsible for about 86 percent of the world's ethanol fuel production in 2009.[5]

Biodiesel fuel:

Biodiesel refers to a diesel fuel produced by chemically reacting lipids such as vegetable oils or animal fats with an alcohol such as methyl alcohol. The resulting biodiesel consists of esters of long-chain fatty acids. The process is known as "transesterification" and it may be carried out by several methods: the common batch process, supercritical processes and ultrasonic methods.

In 2009, the worldwide production of biodiesel was 17,900,000,000 litres. The three countries with the largest annual biodiesel production were Germany (16%), France (12%) and the United States (11%).

Biomas gasification

Fischer-Tropsch synthesis

References

  1. ↑ U.S. Electric Net Summer Capacity U.S. Energy Information Administration (EIA), part of the U.S. Department of Energy
  2. ↑ Agriculture & Renewable Energy: The Partnership for a New Frontier Florida Power Service Commission (FPSC) Workshop, July 26, 2007.
  3. ↑ Assessing Biofuels (2009) From the website of the United Nations Environment Programme (UNEP)
  4. ↑ Global ethanol production to reach 85.9 billion litres (22.7 billion gallons) in 2010 March 22, 2010. From the website of the Renewable Fuels Association (RFA).
  5. ↑ VSEP Filtration in Ethanol Production Based on data from the U.S. Department of Energy.
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