Should the Use of Coal to Generate Electricity be Replaced by Biomass Energy?
Should the Use of Coal to Generate Electricity
be Replaced by Biomass Energy?
Coal is used as a fossil fuel to generate electricity due to its high production of energy when combust. In Australia, the quantity of coals is commercially available and inexpensive for the government to purchase to produce electricity for the country. However the use of coal produces dirty emissions, which is a great concern to the environmentalist.
Coal is a carbonaceous black sedimentary rock that is solid but brittle. It is a fossil fuel, made up of mainly carbon, but consists of hydrogen, oxygen, nitrogen, lesser amount of sulfur, and other trace of elements (RockTalk, 2005). Due to its high content in hydrocarbon, coal is easily combustible and is used as a production of electricity.
To generate electricity, coal is reacted with oxygen in the combustion process and produces carbon dioxide gas and water, as well as energy;
Coal + Oxygen -> Carbon Dioxide + Water + energy
C(s) + O2(g) -> CO2(g) + H2O(l)
The heat energy produced is used to boil water to create water vapor. The vapor then gets forced through a high-pressure steam line, which then pushes the turbine/generator; thus the movement created from the push generates electricity (Energy, 2008).
Significantly, 77% of electricity in Australia (IEA, 2008) is produce from the combustion of coal. ‘The Sydney Morning Herald’ reported that an average Australian person uses 5 tons of coal each year for electricity (Manning, 2012).
Coal is relatively inexpensive in Australia as there are high content of coal viable, and this is one of the main reason for the continuous use of coal to generate electricity (Australian Coal Association , 2011). ‘Mongbay’, an environmental science website, showed that it costs up to a maximum of 180 dollars to purchase a metric ton of coals in Australia (Butler, 2012). Thus the combustion of a metric ton of coal produces approximately 2000kWh of electricity (Department of Energy , 2000). This is equivalent to the use of electricity for up to 2000 hours (Rouse, 2006), which can supply 111 homes with power each day.
Furthermore not only is coal commercially viable throughout Australia but also viable for marketing. Due to the high quality and quantity of coal, Australia markets the coal to neighboring countries such as China. The selling price of exporting coal to China is approximately $114 per tone (Hays, 2008). The transportation of coal is also inexpensive, as coal does not require high-pressure container or airtight vessel. Thus the profit made from marketing coals goes toward services in Australia such as roads and schools.
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Since there are sharp incline of coal usage and requirement in Australia, as well as other countries demanding to purchase coal, the process of collecting coal must quickly meet this situation. Due to this, many civilians are given an opportunity to be employed to mine coal. This creates wealth to some people as an average coal miner can earn up to $65000 to $250000 per year (Fairfax, 2012).
However, the usage of coal to produce electricity by complete combustion creates by-product such as carbon dioxide.
Australia releases approximately 399,219 metric tons of carbon dioxide each year from the combustion of coal (IAEG, 2008). This makes up 1.32% emission of carbon dioxide in the atmosphere. Carbon dioxide gas is a greenhouse gas, and is a major concern to earth as it accounts for 60% of the greenhouse effect (West). The continuous emission of carbon dioxide gas creates an elevation of increase heat within earth. This causes ice to melt and ocean level to rise, which results to coastline to recede (Juerg, 2007).
Nevertheless not all by-products are of carbon dioxide, as in reality; there are incomplete combustions involved with the creation of electricity. In cases, where there is insufficient supply of oxygen during the combustion process, coal, does not get completely converted to carbon dioxide but rather other by-product such as carbon monoxide and soot.
Incomplete combustion, emission of carbon monoxide
C(s) + O2(g) -> CO(g) + H2O(l)
Incomplete combustion, emission of soot
C(s) + O2(g) -> C(s) + H2O(l)
Carbon monoxide and soot are hazardous emissions. The emission of carbon monoxide gas to the troposphere causes major concern to the environment. It is chiefly a product of volcanic activity as well as causing bushfires to occur naturally.
In addition to having mixture of elements other than carbon, such as nitrogen, nitrogen oxide and other primary pollutants are also emitted to the atmosphere when coal comes to combust. Nitrogen dioxide is formed during the combustion process where it reacts with oxygen.;
N2(g) + O2(g) -> 2NO(g)
Hence once when it is in the atmosphere, it further reacts with oxygen forming nitrogen dioxide;
2NO(g) + O2(g) -> 2NO2(g)
High quantity of nitrogen dioxide in the atmosphere reacts with solar radiation during daytime and undergoes photochemical dissociation, forming photochemical smog; an air pollutant.
NO2(g) + hv -> NO(g) + O(g)
The photochemical smog leads to the formation of ozone
O2(g) + O(g) -> O3(g)
Ozone affects the environment by breaking and cracking rubbers and leaves yellowing to the plant, hence lowering the rate of photosynthesis on plants (EPA, 2011). It also affects the marine ecosystem, as ozone increases the solar ultraviolet radiation. Early developments of marine life are affected by this change causing marine animals to have decrease in reproductive capacity and impaired larval (Gelache, 2012).
Nevertheless using biomass energy can reduce the by-products from the combustion of coals and secondary pollutants formed from those by-products.
Biomass energy is a renewable source of energy of organic matter originally derived from plants, through the process of photosynthesis (Crown , 2011). The carbon based biological material contains molecules of hydrogen but mainly based on carbon. Biomass is not fossilized such as coal, thus it is a clean source of energy.
Considering that biomass resource consist of wood from plantation forests, residues from agricultural and forest production, and organic waste stream from industry, livestock, food production, and general human activities. (Crown , 2011) When these resources combust, it produces heat energy used to boil water and create water vapors to push the generator and/or turbines to generate electricity, similar to the process in creating electricity from the use of coal (Canadian Centre for Energy, 2012 ).
Although it still produces carbon dioxide gas, it does not produce it significantly unlike coal. This is because the carbon dioxide is reabsorbed in equivalent stores of biomass through photosynthesis from the plant (BEST). Consequently, capturing the combustion emission is more economical than sequester them underground, in using fossil fuel such as carbon does. This results in a carbon-negative energy source that removes carbon dioxide gas from the atmosphere rather than continuously emitting it to the atmosphere (BEST).
Photosynthesis removes carbon dioxide and react it with water to produce glucose and oxygen.
6H2O(l) + 6CO2(g) + Sunlight -> C6H12O6 + 6O2(g)
In which the produce of photosynthesis can be combust to produce energy;
C6H12O6 + 6O2(g) -> 6H2O(l) + 6CO2(g) + Energy
With biomass resources the size of the Sydney Opera House, or a large barn, it can be used as a cleaner source to generate electricity to power 500,000 Australian homes (NEED, 2011). Though this would cost millions of dollars, but emission such as carbon dioxide and other by-products such as nitrogen oxide are reduced.
Nonetheless, the idea of replacing coal with biomass energy to generate electricity is inconvenient at current state. Although biomass energy reduces the emission of fouled by-product such as carbon dioxide, it still continues to produce it. Also the coal is commercially viable and the cost of purchasing coal is rather cheaper than the cost of collecting biomass resource. A metric ton of coal at a cost of $180 can generate electricity for up to 111 homes, while a Sydney Opera House size of biomass resources would only generate electricity for only 500,000 homes and that would cost Australia millions of dollars to collect the resources.
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