For over two centuries, the United States and other developed countries have profited from inexpensive and abundant fossil fuels. Oil, coal and natural gas have afforded us richness and great affluence, while the cost of energy has remained moderately low. Nevertheless, the previous few years have brought out a consciousness that our unrestricted using up of fossil fuels has added to global warming (Themelis 43). That consciousness has also revealed another fact; the "golden era" of inexpensive energy is coming to a halt. Because of global shortage and unavoidable emissions laws, fossil fuels will keep on being more and more costly. Saving funds on energy costs and saving the earth will necessitate us to alter our "business as usual" approach and cut our reliance on fossil fuels. We can start by advancing energy effectiveness and integrating renewable energy supply into our residence, business and cities.
The massive augmentation in the quantum and variety of waste material produced by human actions and their potentially destructive effects on the broad environment and the general health of the public, have led to a growing consciousness about a burning need to accept scientific ways for safe dumping of wastes. While there is an apparent requirement to diminish the production of wastes and to reprocess and reuse them, the technologies for generation of energy from the garbage can play a critical function in extenuating the issues (Stevenson 63). In addition to the recovery of sizeable energy, these technologies can ensure there is a considerable drop in the general waste quantities necessitating final discarding.
These wastes can better be managed for secure dumping in a restricted method while meeting the general pollution control norms. The social-economic setting, level of industrialization and climatic conditions, influences waste production rates. In general, the more a society is economically prosperous and the higher the population of urban areas, the larger the quantity of solid waste generated. The lessening of the volume and mass of solid waste is a critical problem especially when considered vis-à-vis the availability (or lack of it) of ultimate disposal sites in parts of the world. Although numerous waste and byproduct recovery processes have been brought in, the bio-chemical conversion method, including Methane generation and Cogeneration in a lesser scale Technology, are preferred for wastes in the United States.
Landfill gas collection
The most uncomplicated and the oldest, time-honored garbage disposal system, landfill gas collection, is still extensively used in the US. This is due to its perceived low cost of working, availability in a lot of locations, and appropriateness for most solid wastes. The choice of managing wastes while generating energy is dependent on several factors. Chief among these factors is the size and depth of the landfill and climatic conditions. The landfill must hold in excess of a tone of waste in place and must be 30 feet deep or more. The landfill also ought to be in a place that has a rainfall capacity of more than 25 inches yearly. Landfill gas, i.e. methane is trapped using a landfill gas collection well.
Methane gas, CH4, is a greenhouse gas that can remain in the atmosphere for a period ranging from ten to fifteen years. While this time is short when compared to that of CO2, methane is twenty percent more efficient at locking in heat than carbon dioxide. Consequently, the rising level of methane release into the atmosphere is a growing concern to global warming. Methane, or CH4, is emitted both by the natural environment and through various human activities. Landfills are the top synthetic emitters of methane accounting for roughly 23% of US synthetic emitters of methane.
Landfill gases are generated from the anaerobic breakdown of waste. Gases that are generated from landfill plants are roughly 50% Carbon Dioxide and 50% Methane. Generally, landfill gases account for roughly 2% of greenhouse gases emitted as waste. Methane, a natural gas, contains roughly 500 Btu per average cubic foot and therefore, landfill emissions could be trapped and made into constructive energy. Many large landfills in the US started trapping methane and converting it to energy. This has been popularized by the regulations requiring that landfills collect the gas. After such trapping, it either can be converted to energy or flared- which in essence is burning the gas.
Chemical Reaction of burning Methane
CH4 CO2 + H20+Heat
However, before this process occurs, Methane burns into formaldehyde HCHO. This formaldehyde undergoes oxidative pyrolysis to form Carbon Monoxide, Hydrogen and Water.
After this reaction, Hydrogen gas burns to release water and heat
Carbon Monoxide further burns to form Carbon Dioxide and heat and this is the slowest process among all the other aforementioned reactions.
CO CO2+ Heat
Under standard conditions, this reaction can be summed up as
CH4 (g) +2O2 (g) H2O(l)+CO2(g) + 891 kj/mol
g stands for gas
l stands for a liquid
kj/mol stands for kilojoules/mole
891 means the amount of kilojoules of heat produced per mole of Methane.
Just like natural gas, methane produces a lot of energy when burnt and does so without releasing soot like coal, or oil. As such, most methane-producing plants burn their methane and use it to heat their operations, and buildings. Once their heating requirements are met, the residual gas is "flared" into the atmosphere. In the past ten years, though, businesses and metropolises have commenced using methane more resourcefully. They are now exploiting the energy generated by the combustion of the gas to produce electrical energy, in a similar manner to coal-fired or natural-gas fired power plants. This procedure is known as "Combined Heat and Power" or "Cogeneration," and is now being put into use by landfills, wastewater treatment facilities, dairies, and other plants that produce methane by-products all over the United States.
Despite the fact that methane is generated easily, is plenty and renewable, methane is a potent greenhouse gas, and a volatile organic compound. These characteristics increase its prospects of leaking from the landfill into the air, and could be injurious to both human welfare, and the environment. In addition, leaked methane during incineration has 23 times higher global warming latent than CO2. CH4 is an extremely flammable gas and as such creates a potentially explosive situation if it is not well managed. This technique of waste management and energy production is also limited by the amount of waste/technical risks. Though the method is widely popular for its low operation costs, it is a very expensive when one considers the cost per unit level produced. Cogeneration of methane from landfills as a method of waste management and energy production also has a disadvantage in that there is a shortage of landfill sites. The method also is limited by the fact that there is a high bulk volume of untreated wastes in existence already, which means more sites for landfills. There is also growing local hostilities towards landfills due to the noise and stench they produce, appearance, etc. Another drawback for the reliance of this method is the financial duties and/or legislative restrictions that are placed on landfills (Wells B, et al. 25). The fact that this method of waste management is limited to biodegradable waste is also a disadvantage. Finally, landfills have are disadvantageous in that they release leachate into groundwater (lots of landfill facilities sites are not set with leachate collection)
Waste-to-energy "innovations": Series of case studies in Europe - Sweden, Denmark, Germany. A great challenge concerning waste management is the augmentation of waste production. This puts great pressure on waste management facilities and makes it harder for nations to increase the recycling rate and diminish landfills. In response, novel energy answers are being found out, developed and brought into the open. Interestingly, this has not attracted many headlines in the United States waste or energy discourses. Since the cogeneration of methane from landfills in the US is clearly not viable, (for the above economical, social and technical reasons) burning of waste in order to recover energy is a plausible step depending to the waste hierarchy (Fuller and Pora, 35). The new burning technology is a huge energy plant that smolders thousands of tons of domestic waste and industrial refuse continuously.
Burning of waste materials has been utilized for several years as a method of cutting down on the volumes of waste materials and neutralizing the possibly harmful materials within the waste. Combustion can only be employed to generate an energy supply when heat recovery is integrated. Heat generation from the combustion of waste materials can then be utilized either to power turbines for electrical energy generation or to supply direct room and water heating. Some waste streams are also appropriate for powering a combined heat and power system, though quality and consistency of delivery are vital factors to put into consideration. Thermo-treatment, characterized by high temperature and high-conversion rates, is best suited for lesser moisture waste materials and is more often than not nondiscriminatory for waste materials. The burning technology is the incineration of waste in a controlled setting to recover of heat, which in turn produces steam, which in turn generates power that turns steam turbines, which generates electricity.
Even as some people still confuse current waste-to-energy combustion plants with incinerators of yore, the performance of these plants in regards to the environment is beyond reprimand. Research has revealed that nations that utilize waste-to-energy technology have elevated recycling rates than those that do not exploit waste-to-energy (Lauber, Morris, Ulloa, and Hasselriis 98). The recovering of both ferrous and non-ferrous metals from waste-to-energy plants for reuse is good and rising through the years. Research has also determined that waste-to-energy plants in fact, trim down the quantity of greenhouse gases that is released into the atmosphere (Deriziotis 51). In the present times, waste-to-energy plants that are founded on combustion technology are vastly efficient energy plants that make use of municipal solid waste as their fuel in place of coal, oil or natural gas. Instead of using energy to search for, recover, process and ship the fuel from some far-off place, waste-to-energy plants consider valuable what the rest regard as garbage. Waste-to-energy plants fundamentally recover the heat energy "trapped" in the garbage in highly efficient boilers that produce steam. This steam is either sold to manufacturing industry customers directly or used on-site to propel turbines for electricity generation.
However, though America is lagging behind, some states have began actively contemplating the technology as the current landfills top out and demands to shrink the heat-trapping gases grow. Several plants already in existence are also being expanded. Europe is ahead of the pack with the modern cogeneration, waste-to-energy (WTE) or combined heat and power (CHP) technology. By 2002, eight European nations were incinerating less than 15 % of municipal refuse, five incinerating between 15 and 30 %, while another 5 countries were incinerating more than 30 % of the waste. Far cleaner than traditional incinerators, these fresh kinds of plants used in Europe converts local trash into heat and electrical energy. Dozens of filters ranging from mercury to dioxin catch pollutants, which would have been revealed into the atmosphere through the smokestack only ten years.
Europe is the obvious dominant force, in the field of Waste-to-Energy. In an attempt to diminish the exploit of landfills, the European Union is progressively substituting the landfills by establishing waste-to-energy. Traditionally, the sector of waste-to-energy was a public sector forte; nevertheless, the market setting is shifting with the private sector also putting huge funds into the waste-to-energy sector. This change of aims set by the Landfill Directive, increasing oil prices and the ever-rising requirement for power are the chief factors that drive the development of the European waste-to-energy market. Environmental laws in Europe have hurried the growth of waste-to-energy plants. The European Union strictly controls the conception of more landfill sites, and its members by now have made binding pledge to trim down their carbon dioxide emissions by 2012. This pledge refers to the global agreement otherwise called the Kyoto Protocol, which was not ratified by the United States.
In European states, waste in smaller and sparsely populated cities cannot simply be wished out of sight and out of mind as it often the case in the United States. Most of the 87 waste-to-energy plants in the United States are in highly populated areas such as Long Island and Cape Cod. Though these waste-to-energy plants are usually two decades old, numerous plants have been increasingly fitted with pollution filters. Even then, a few of though few generate both heat and energy like the most modern Danish versions. In Horsholm, just 4 percent of waste products goes to landfills, and a mere 1 percent (chemicals, paints and a few electronic apparatus) is dispatched to "particular disposal" in areas like safe storage vaults in deserted mines, in Germany. Sixty one percent of municipalities' garbage is recycled, and 34% is taken to waste-to-energy plants to incinerate. In Europe, there are appropriate 400 plants, with Denmark, Germany, and the Netherlands leading the group in upgrading and constructing new ones.
Cogeneration energy, with a market divide of 6% is the fourth spot in Germany, after natural gas at 47%, oil at 25% and electrical energy at 11.5%. For space heating, cogeneration energy is ranked third in the market. Previously, overrated numbers have been released for cogeneration energy, i.e. approximately 80 TWh5. This miscalculation was caused by the addition of electricity generated by condensing heat to cogeneration energy. This is applicable predominantly to the cogeneration plants in industry. Nowadays, rule FW 308 is mandatory for the computation of cogeneration energy. Based on this rule, the yearly generation totals to 55 TWh.
This is approximately 10% of the joint electricity generation in Germany for 2004 (roughly 554 TWh). Germany's cogeneration plants function more often in the joint regime and less regularly in condensation regime in comparison to other European States. With a market share of 10%, Germany lags behind Denmark with 40%, Holland with 39% and Finland, which has 34% for cogeneration electrical energy, but is in front of Italy with 9%, Sweden with 8%, UK with 5% and France with 5% as at 2002 (Themelis 46). When computation is made, using the rule of FW 308, the rank of Germany improves drastically. This is so because leading Nations such as Denmark produce a higher portion of electricity from condensing heat in cogeneration facilities. While Denmark is the most cited example, it is worthy noting that laws have discouraged the growth of space heating using natural gas for over a long period, while fuel oil prices have been kept synthetically high by taxes.
Waste-to-energy such plants has turned out to be not only the stronghold of garbage management and a critical fuel resource in Denmark, from affluent suburbs like Horsholm to Copenhagen's downtown region. The use of waste-to-energy has not only trimmed Denmark's energy costs but also its dependence on oil and gas. The waste-to-energy has also benefited the environment in Denmark as well as lessening the exploit of landfills and reducing carbon dioxide emissions (O'Brien and Swana 72). The Denmark's Waste-to-energy plants are so clean that more dioxin is now emitted released from domestic fireplaces and garden barbecues than from some incinerator. With all these advances, Denmark nowadays considers garbage as a clean substitute fuel, as opposed to a stinking, ugly quandary. Moreover, the incinerators, recognized as waste-to-energy plants, have attained significant respect as communities like Horsholm compete to have them put up. Denmark now has 29 waste-to-energy plants, managing garbage for 98 municipalities in a Nation of 5.5 million people, and 10 more plants are intended to be construction.
Sweden would appear to be an obvious center for cogeneration technologies. Swedish weather is characterized by lengthy, chilly winters, creating an enormous demand for heating, and the climax times of electricity, and that of heat demand, have a tendency to happen together. Nevertheless, cogeneration at present accounts for a comparatively small percentage of the Swedish energy blend. Numerous local heating plants have been put up in Sweden and, from as early as the 1940s when the first combined heat and power plants were set up to serve the Swede people. There is also a number of energy demanding industries, such as the tissue and the paper industry, where cogeneration has been used for many years. Conversely, cogeneration has a far better function in bordering Finland, where the conditions are alike.
The main rationale for the lack of combined heat and power large-scale utilization in Sweden is the largely the low cost of electricity energy (Wintner B, et al. 83). Hydroelectric and nuclear technology account for more than 90% of electricity generated in Sweden and which each have approximately account for 45% of the entire production. The difference, which at present is at less than 10%, is generated by other power facilities that are not nuclear or thermal plants. The abundant supply of comparatively low-priced electrical energy has priced out majority of combined heat and power plants and rendered numerous probable combined heat and power projects economically unfeasible. This is, owing to the low-market value of the energy that would be generated. Due to this, public utilities have often set up pure heat plants, instead of the combined heat and power plants, to supply their district heating networks.
Advantages and disadvantages of this technology
Unlike in majority of nations within the European Union, the new waste-to-energy plants technology is not being very accepted by the public or the key players in the United States of America. This has resulted into there being no new plants being designed or constructed in the United States. However, 24 states within the federal government presently categorize waste that is incinerated this way for energy as a renewable fuel, and in most of the cases entitled to subsidies. In a country with a population of over three hundred million people, there are just 87 trash-burning power plants and these plants are all at least in 15 years old. As an alternative, remote landfills continue to be the end for most of the nation's garbage. New York City by itself sends approximately 10,500 tons of residential waste daily to landfills in far-flung places like Ohio and South Carolina.
The US could profit from several advantages if it embraced this cogeneration technology.
This progress in incinerator technology offers an extra aspect that provides for strong benefits to the environment. These benefits include recovering of heat and energy characteristically in the form of hot vapor, hot water, or electrical energy. Known as cogeneration, waste-to-energy (WTE) or combined heat and power (CHP), this technology integrates the benefits of present incineration technology with the extra credit of recovering energy. The energy value got from heating a kilogram of plastic is about 40,000 kJ and marginally higher than coal. This makes plastic wastes from a one-use bioprocess system very appropriate for cogeneration and only produces a small quantity of ash. The fiscal benefits of cogeneration increase as the output increase. This results in big plants that are less in number. This will of course limits the availability cogeneration plants in local areas.