Evaluation of Estimated Density of Municipal Solid Waste in

There have been several researches studying density of solid waste in Surabaya. However with the growth of population and other factors like economic growth and consumption growth, it is necessary to check whether the result is still relevant or not to today`s condition of municipal solid waste in Surabaya.

Finish Start

Alternative 1

Statistical Analysis Using Zoning Method

Data Collection

Evaluating density from previous study Classifying area served by each LPS

Formulating database of district demography and spatial surround 37

observed LPS

Comparing existing and estimation cost of solid waste transportation activity

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Density refers to weight of solid waste per unit volume. It is used to represent characteristics of solid waste in particular condition and the value can be vary depend on the facilities used and the composition of the solid waste. In this research, the range of density to be found is the value that represents density of solid waste in LPS (temporary solid waste disposal site) which using dump container to facilitate the transferring process of solid waste.

The technique to evaluate the relevance of municipal solid waste density known from previous studies to be used as the conversion factor to estimate volume of solid waste transferred to LPS is using forecast or estimated error. The error measures how closely the model fits the actual data at each point. The estimated error is computed by comparing the trend line of estimated value with actual past data. The actual past data used in this computation is the volume and weight of solid waste being transported from LPS to TPA within range of one year period. Three commonly measures of fit are Mean Squared Error (MSE), Mean Absolute Deviation (MAD) and Mean Absolute Percentage Error (MAPE).

These error measures are particularly helpful to compare four estimated density factors. The values that give smallest MSE, MAD or MAPE is generally considered to provide the best fit. Table 4.1 is the example of table used to compute the estimated error of each density factor in LPS Benteng.

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Table 4. 1 Comparison of Actual Weight and Estimated Weight of Solid Waste in LPS Benteng from July 2014 – June 2015

305 MAPE MSE MAD 355.8 MAPE MSE MAD 288 MAPE MSE MAD

Januari

Month Date Volume (m3)

Actual Weight (kg)

Estimated Weight (JICA) - d = 305 kg/m3 Estimated Weight (Tchobanoglous) - d = 355.8 kg/m3 Estimated Weight (DKP 2014) - d = 288 kg/m3

1 102 28660 31,110.00 0.09 6,002,500.00 2,450.00 36,291.60 0.27 58,241,318.56 7,631.60 29,376.00 0.02 512,656.00 716.00

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From the example shown in the comparison of actual weight and estimated weight of solid waste in LPS Benteng, density factor from Studi DKP 2014 has the smallest percentage error of 37.68% as shown in column MAPE.

Followed by other measurement error, MSE and MAD, they also show the smallest value compare to other density factors. It indicates that the result of Studi DKP 2014 in determining solid waste density in Surabaya provide the best fit in estimating the solid waste generation in LPS Benteng. However it cannot be judged directly that the density of solid waste in LPS Benteng is 288 kg/m³, as according to the result of Studi DKP 2014. Even though it has the smallest percentage error, but the value of its percentage error is still considered high.

Thus, further research to determine the most fit density factor for LPS Benteng is necessary in order to reduce the percentage error value in the estimation model.

The same computation is done for other 36 observed LPS as well to find which one from the four density factors provide the best fit of estimation. Table 4.2 shows the recapitulation of each measurement error for all 37 observed LPS.

Table 4. 2 MAPE Value from Comparison of Actual Weight and Estimated Weight of Solid Waste in 37 LPS in Surabaya

No LPS

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Table 4. 3 MAPE Value from Comparison of Actual Weight and Estimated Weight of Solid Waste in 37 LPS in Surabaya (Cont`d)

No LPS

Density factor that has the smallest percentage error in estimating volume of solid waste in LPS is highlighted in yellow color. The result shows among four density factors known from previous study, density of solid waste taken from Studi DKP 2014 having the best fit to most of LPS. Total there are 27 LPS that is best estimated using density factor 288 kg/m³ taken from Study DKP 2014.

Another 7 LPS is best estimated using density factor 355.8 kg/m3 which is taken from Tchobanoglus research. There are also 2 LPS that is best estimated using density factor 302 kg/m³ which is taken from Studi ITB. While density factor taken from JICA study, 305 kg/m³, showing the least best fit as estimation factor.

There is only one LPS that is best estimated using this density.

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Even though the result of error measurement shows that 288 kg/m³ having the smallest percentage error for most LPS in Surabaya, it still cannot be judged directly that density of municipal solid waste in Surabaya is 288 kg/m³. The percentage error itself ranged widely from 15.44% to 69.83%. The higher the error value is, the less accurate it is to be used as the estimation factor. The list of LPS that have percentage error more than 30% when it is estimated using density factor 288 kg/m³ are LPS Semolowaru, LPS Benteng, LPS Krembangan, LPS Simolawang and LPS Waru Gunung I/II. It is likely that there is another value of density factor that represents the amount of solid waste weight per unit volume for LPS that have high percentage error.

Thus it is required to conduct direct observation in several LPS to get a comprehensive understanding about the actual system of solid waste management in the field. The purpose of this observation is also to figure out the factors that affect the variety of density factor among LPS. The observation may also lead to the necessity to conduct experiment in figuring out another density value that is more accurate to estimate the generation of solid waste in Surabaya.

4.3.2 Comparison between Actual Transportation Cost and Estimated