User:Milton Beychok/Sandbox

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.

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. It has been in operation for more than 10 years.

Production of ethanol and biodiesel fuels

There are several processes available for converting the chemical energy contained in biomass into liquid 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%. In 2009, worldwide ethanol fuel production reached 19.5 billion gallons (73.9 billion liters).

Ethanol fuel is widely used in Brazil and in the United States, and together both countries were responsible for 86 percent of the world's ethanol fuel production in 2009. Most cars on the road today in the U.S. can run on blends of up to 10% ethanol, and the use of 10% ethanol gasoline is mandated in some U.S. states and cities. Since 1976 the Brazilian government has made it mandatory to blend ethanol with gasoline, and since 2007 the legal blend is around 25% ethanol and 75% gasoline (E25). In addition, by December 2010 Brazil had a fleet of 12 million flex-fuel automobiles and light trucks and over 500 thousand flex-fuel motorcycles regularly using neat ethanol fuel (known as E100).

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.

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.

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. 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 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.

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 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. Syngas cleaning is a crucial step in preventing the fouling of machinery or contamination of catalysts when further processing the gas.

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. 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.

Risks of biomass processing

The risk level of biomass processing depends largely on the inspection and maintenance standards of the processing facility. From 2006 to 2010 there have been approximately 100 incidents in the United States regarding the processing of biomass to produce biofuels. From 2006 to 2009 there have been 8 fires and 6 explosions on the basis of about 200 biodiesel facilities. Some of these explosions were responsible for the complete destruction of their respective plants. However, 50% of the incidental cases in the last 5 years have not involved the process under normal conditions and 22 % of the incidents have been related to tank storage (overfilling, leaks, etc.). Given that maintenance is properly carried out, incidents such as these will rarely occur. The unstable nature of the materials in addition to the poor plant regulation is the reason why incidents are so frequent. As a result, improvement efforts on regulation, inspection, and maintenance of the processing plants have been carried out with the goal of drastically reducing the number of incidents.

Setbacks and the future of biomass

The cost of collecting and processing biomass is the current main concern for the energy and transportation industries. Efforts are being made to expand the production and distribution of these fuels in order to lower costs to the consumer. However, costs of biofuels are still far higher than the costs of petroleum based fuels. The environmental availability of biomass is not an issue because sources such as food waste and other forms of waste are constantly being renewed. As prices for petroleum based fuels continue to rise and more efficient technologies for processing biomass are developed, demand for these alternative fuels will begin to increase considerably. As a result, biomass may very well be the alternative fuel source of choice for the immediate future.