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Methane reduction possibility study in Rasht city landfills considering green development mechanism.

Introduction

The main gas generation in landfills is methane. The greenhouse effect of methane is about 21 times of COZ (Kyoto Protocol, 1998), on the other hand, methane has a high potential in energy generating. Besides obtaining and using large amounts of energy by operating an appropriate technology would be possible. The appropriate management of generated methane gases in landfill helps public health and environment and it creates conditions of receiving the financial mechanism of green development. During a research process, Lenard Milich from Arizona University introduced and reviewed different sources of generating methane in 1998. Also introduced and described the effect of biochemistry cycle of methane on increasing the total temperature of the Planet Earth (Lenard, 1998). In 1999 a group of researchers of earth studies Academy and Society of Civil Engineering and Environment in the USA reviewed the reduction of methane in landfills. In this study in addition to direct measuring of generated methane in landfills, a method of energy recovering was suggested to decrease volume of produced methane in landfills (Byard et all, 1999). In 2005, 2 Dutch researchers examined 6 different models for estimation of generated methane volume in landfills in 3 various places and compared the results with the calculated values of direct estimation of Methane. These results indicated wide differences of the two cases (Scharff and Jacobs 2005). Also, some studies have been done in Energy Studies Centre of Technology Institute, Dehli by Talyan and his colleagues. The method of dynamic modeling has been used for estimation of the outcome methane volume. Using the different analysis, there have been forecasts for managing the municipal solid waste materials and the outcome results indicate decreasing the methane volume in case of operating appropriate management during future years (Talyan, et a1.2006).

The aim of this work is to estimate generated methane gases from Saravan landfill in Rasht city and then introducing two methods of methane burning and energy recovering with regard to decreasing its volume in the landfill and comparing these 2 methods considering the environmental and economical effects in Rasht and Saravan area. Regarding the obtained results, the most appropriate option to decrease methane volume will be introduced.

Methodology

The first step in gas pollution reduction in landfill is an estimation of gas generation. Various methods have been presented to estimate the gas volume in landfills and all these methods consist of developing models of these gases generation. Most models use first order equation to describe the rate of produced gas in landfills. In this study, the software of LandGEM has been used as a tool to estimate of gas generation from landfills, (Alexander, et a1.2005).

This software uses a first equation to estimate the rate of generated methane and it is indicated in equation 1:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1)

[QCH.sub.4] Annual Methane generation in the year of calculation ([m.sup.3/yr])

i : Year time increment (1 year)

n : (Year of the calculation)-(Initial year of waste acceptance)

j : Year time increment (0.1 year)

K : Methane generation rate (1/yr)

[L.sub.o] : Potential Methane generation capacity ([m.sup.3]/Mg)

[M.sub.i] : Mass of waste accepted in the ith year (the ith year)

[t.sub.y] : Age of the j section of waste mass Mi accepted in ith year (decimal years, e.g. 2,3 year)

For applying equation 1 some information such as the volume of existing solid waste in landfill, the operation years and the potential of methane generation and methane generation constant is necessary. Assume opening the landfill in Rasht is 2009 and considering a 40 years period for design which the landfill is in operation the amount of entering solid waste to the landfills is computed during the years 2010 to 2048 methane generation potential and its constant have been considered regarding

the weather conditions in Rasht as 173 [[[m.sup.3]] and (1/year) 0.1-0.35 (EPA, 1996).

For methane generation constant various values have been presented in different references. One of these values is 0.693 (1/year) (Hoeks, 1983) and it is proper when high percentage of solid waste consist of foods, vegetables, fruits (organic compounds) because about 80 percent of solid waste in Rasht consist of foods. It seems that the value for methane generation constant is reasonable. In this software, generation of 4 main pollutants including methane, carbon dioxide, total landfill gas and non methane organic compounds are computed and indicated by charts and tables. After the estimation of generated methane in landfill, two methods of methane burning in flare and converting to the electrical energy using the gas burner motor are compared. In methane burning method, the amount of methane generation from landfill calculated using equation (2).

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (2)

[PE.sub.flare,y] Project emissions from flaring of the residual gas stream in year Y

[TM.sub.RG,h] Mass flow rate of methane in the residual gas in the hour h

[[eta].sub.flare,h] Flare efficiency in hour h

[GWP.sub.CH4] Global warming potential of methane valid for the commitment period (=21)

For calculation of amount of emission reduction, the rate of controlled methane obtained from equation 2 is subtracted from the total generated methane in landfill.

In second method, a flare engine would be used to convert the Methane gas to the energy and the volume of produced Methane in the landfill is decreased highly. The rate of emission reduction would be calculated using "Emission Reduction and Environmental and Energy Benefits for Landfill Gas Energy, (EPA) Projects" software which is one the accepted software's of EPA This software calculates the emission reduction using the expressions 3 and 4. Using the expression 3, the amount of emission reduction would be calculated in the first step which is the Methane burning and using the equation 4, it would be calculated in the second step which is converting the gas into energy.

MMTCO2E l yr = Megawatts of Generating Capacity x 0.93 x 11700 x 21 (3)

MMTCO2E / yr = Megawatts of Generating Capacity x 0.85 x 1.58 (4)

The parameters in expressions 3 and 4 are described as follows: 0.93: The capacity agent for electricity generating units

11700: The thermal value of the flare engine Btu (kilowatt--hour

21: Methane worldwide thermal potential

0.85: The pure capacity agent for electricity generating units

1.58: The pollutant factor [PoundsCarbonDioxide/Kilowatt-hour]

The necessary investment to installation and operation is calculated after computation of pollution reduction using both methods. According to statistics in worldwide market the average cost of using a kilo watt of energy obtaining from the gas in landfill using the flare would be 350 Euros and 850 Euro, using the engine these expenses consist of installation costs of system and also repair and maintenance during the usage period. On the other hand, according to financial mechanism of green development, Iran would receive a sum of about 15.2 dollars in return for reduction the volume of generated Methane in landfills, this amount would be in return for 1 ton of pollutant decreasing of carbon dioxide (Capoor & Ambrosi, 2007). At last comparing all expenses and economic advantages obtained from selling Carbon using the mentioned methods, the appropriate method will be selected, considering economical and ecological conditions.

Case Study

The landfill locates in Saravan area, 21 kilometers far from South of Rasht and surrounded by Saravan forest. Figure 1 shows location of Saravan landfill. Solid waste is transported to the place daily. According to Iran's Statistic Centre, Table 1 indicates the changes in Rasht population during a 40 year period (1956-96).

[FIGURE 1 OMITTED]

Considering Table 1, the prediction for the next 40 year period may be calculated using expression 5:

[P.sub.n] = [P.sub.o] [(1+[gamma]).sup.n] [right arrow] [gamma]= n square root of ([P.sub.n]/[P.sub.0] -1

[P.sub.n] : Population in time t

[P.sub.0] : Population in origin time

[gamma] : Rate of population growth

[DELTA]t : Time changing according to year

Rasht population prediction reveals that rate of population growth is nearly constant, except for some particular days of the year (late of March to late of April and late of August), totally 40 days, number of populates would increase up to 300000-400000. An increase of 350,000 people is considered.

According to existing information of Recycling and Solid Waste Management organization of Gilan, solid waste generation per capita in 2006 was 900-1000 [gr/c.d] and it is predicted to be the same for the future. Therefore, during the years of this period the average of solid waste generation per capita is contemplated 0.95 (kg/c.d).

Considering the existing information, the rate of solid waste receiving could be calculated during the years that the landfills are open. The rate of solid waste receiving to this place during the year of opening and closing is shown in Table 3.

Results

Considering the existing data and using the LandGem software, gas generation process in the landfill during 140 years gas production has been indicated in Figures 2.

Comparing the graphs in Figure 2 shows that there are a high percent of organic compounds in case 3. High percentage of organic compounds in the landfill caused an increasing in gas generation rate in this place. In case 3, considering that approximately all solid waste receiving to the landfill during the early few years, are organic compounds (rapidly biodegradable), in this period gas generation is very fast and high slop in the graph prove it. Comparing the rate of gas generation in 3 graphs in Figure 1, the high rapidity of gas generation during the primary years of land fillings would be revealed in case 3. Gradually, receiving the new solid waste and also considering the reduction rate of gas generation from the old solid waste in the landfill, the slope in the figure decreases. In this case the existence of old solid waste in the landfill causes the rapidity adjustment of gas generation in the landfill. Regarding the rate of generated Methane in the landfill and using the previous equation, the rate of pollution reduction in both cases applying the flare and engine are calculated. The results of these calculations are presented in Table 4.

[FIGURE 2 OMITTED]

Considering that Iran receiving 15.2 dollars from the World Bank in return for every ton pollutant decreasing equivalent of Carbon and because of green development mechanism, this pollution decreasing will have financial advantages in addition to the safety of environment and human beings. This income would be calculated regarding the rates of pollution decreasing and the results have been represented in Table 5.

Applying the above two mentioned methods requires necessary appropriate equipments. In addition to investments, each method, flare and engine, involve expenses for repair and maintenance during the years of usage. The total necessary investment expenses has been estimated and indicated in Table 6.

Conclusion

The results state that the rate of Methane decreasing in both methods is nearly the same. Therefore, considering the effects in environment, there is no much difference between the two methods. But regarding that the investment expense for energy recovery is 4 times of expenses for Methane burning, the second method (Methane burning) would be preferred. As it was mentioned, Iran can obtain a sum in return of pollution decreasing, a part of expenses would be compensated. But the results shows that the advantages are equal for the two methods and this advantage compensate the main expenses of investment in case of using the flare. Therefore, applying the Methane burning method could be acceptable from economical point of view and is equal to the other method energy recovery on Methane decreasing. Thus, Methane burning could be acceptable for Rasht landfill.

References

[1] Byard W. Mosher, P. C. Czepiel, J. Shorter, E. Allwine, R. C. Harriss, C. Kolb and Lamb,B (1999) Mitigation of methane emissions at landfill sites in New England USA.

[2] Heijo Scharff' and Joeri Jacobs,(2005): Applying guidance for methane emission estimation for landfills.

[3] Capoor, K Sustainable Development Operations, World Bank and Philippe Ambrosi (2007), Development Economics Research Group, World Bank , State and Trends of the Carbon Market / Washington, D.C.

[4] Lamb (1999): Mitigation of methane emissions at landfill sites in New England, USA

[5] Milich, L (1998): The role of methane in global warming: where might mitigation strategies be focused?

[6] http://www.epa.gov/cppd/pdf/brochure.pdf (PDF, 16 pp., 152 KB)

[7] Scharff, H and Jacobs, S (2005) ; Applying guifance for methane emission , emission for landfills

[8] Talyan. V, Dahiya, R.P. Anand S and. Sreekrishnan T.R, (2006): Quantification of methane emission from municipal solid waste disposal in Delhi

(1) Gholamreza Asadollahfardi, (2) Fatemeh Joghatayi and (3) Edvin Safari (1,2,3) Civil Engineering Department faculty of engineering, Tarbiyat Moalem University, Mofatch Avenue Tehran, Iran

(1) Email: fardi@tmu.ac.ir, (2) Email: tara_f59@yahoo.com, (3) Email: ensafari@ut.ac.it
Table 1: Variation of Rasht population during 1956-1996.

Year         1956    1966    1977     1386     1991     1996
population   109491  143557  1188957  1290897  1340637  1417748

Calculation of population growth in Rasht may be
calculating from equation 5 and
the result is indicated in Table 2.

Year          1956-66   1966-76   1976-86   1986-90   1990-95   1995-05

Rate of
population
growth          2.75     2.79      4.41       3.21      4.17      2.8

Table 3: Rate of solid waste receiving to the landfill
in the year of opening and closing.

Year                             2009          2039

Rate of solid waste            220922   622845
receiving to Landfill (ton)

Table 4: Rate of Methane reduction in ton per
year (equivalent [Co.sub.2]).

Methane generation          0.1              0.35            0.693
Constant Technology

Methane burning         1.892 * 10^5     1.961 * 10^5     2.006 * 10^5
(flare)

Recycle Energy          2.379 * 10^5     1.991 * 10^5     2.033 * 10^5

Table 5: The benefit of Selling Carbon by milliard Dollar.

Methane                     0.1              0.35            0.693
Generation constant

Technology

Methane burning           3035129          3146370          3217799
(flare)

Energy recovery           3816159          3194379          3261124

Table 6: The necessary costs for investment in Milliard Dollar.

Methane Generation          0.1              0.35            0.693
Constant

Technology

Methane Burning           2005855          1604215          1604215
(Flare)

Energy recovery           6016393          4812646          4812646

The total results of calculations show in Table 7.

                                         Flare

                   K=0.1(year/1         K=0.35             0.693
                                        Year/1            Year/1

The Average         3.86 * 10^7       3.23 * 10^7       3.30 * 10^7
of Gas
production
(m3/year)

The Average        1.892 * 10^5      1.961 * 10^5      2.006 * 10^5
of pollution
decreasing
(ton/yr)Co2e

The Annual              --                --                --
average of
energy (kwh)

The                   2005855           1604215           1604215
investigation
expense
(Dollars)

Carbon                3035129           3146370           3217799
selling
Income
(Dollars)

                                 Converting to Energy

                       K=0.1            K=0.35            K=0.693
                      Year/1            Year/1            Year/1

The Average         3.86 * 10^7       3.23 * 10^7       3.30 * 10^7
of Gas
production
(m3/year)

The Average        2.379 * 10^5      1.991 * 10^5      2.033 * 10^5
of pollution
decreasing
(ton/yr)Co2e

The Annual          3.89 * 10^7       3.29 * 10^7       3.36 * 10^7
average of
energy (kwh)

The                   6016393           4812646           4812646
investigation
expense
(Dollars)

Carbon                3816159           3194379           3261124
selling
Income
(Dollars)
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Article Details
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Author:Asadollahfardi, Gholamreza; Joghatayi, Fatemeh; Safari, Edvin
Publication:International Journal of Applied Environmental Sciences
Article Type:Report
Geographic Code:7IRAN
Date:Sep 1, 2009
Words:2554
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