Fig. 6. Simulated results of dynamic behaviors of selected variables in six scenarios over time (for all 14 districts). (a) Total separated recyclable
waste of all districts. (b) Total separated organic waste of all districts. (c) Total waste to be landfilled of all districts. (d) MSW collection and transportation efficiency of all districts.Figure optionsDownload full-size imageDownload as PowerPoint slide
‘Scenario 1’;, presents a current situation that 8% of residents separate recyclable waste without organic waste separation. The 8% of recyclable waste separation results in a marginal change in segregated recyclable amount over a SB-715992
of simulation, as it only increases by 7% or about 962 tonnes of recyclable waste. The amount of waste being sent to landfill increases from 93,458 tonnes in the first month to 99,316 tonnes or a 6% increase in the last month of simulation period. In the same way, total cost for collection and transportation service increase by 15%, which means the BMA has to additionally allocate about 0.2 million USD/month for waste collection and transportation.
In Fig. 6d, there is a slight decrease of collection and transportation efficiency in the 65th month and slightly bounds back in the 66th month. This decline effects by cost inefficiency of Rajathewi district in the 65th month till the end of simulation period. The inefficiency happens because required amount of service provision cost is higher than allocated budget; therefore, it pulls down the MSW collection and transportation efficiency of the whole system. In this case, 8% recyclable waste separation cannot make the MSWM system effective.
The simulated results for proposed scenarios are explained from ‘Scenario 2’; to ‘Scenario 6’;, respectively. ‘Scenario 2’; represents a MSWM situation when there are 40% of residents willing to separate recyclable waste at source. With this rate of separation, a 36% increase in the amount of sorted recyclable waste is collected. As a consequence, a marginal increase, 2%, in amount of MSW to be landfilled is expected to occur. Comparing to ‘Scenario 1’;, if sorted recyclables are sold to junk shops or used as valuable materials, the 40% separation recyclable waste helps prevent 3847 tonnes to be landfilled. Monthly collection expense is about 0.8 million USD and if the separation rate is unchanged over time, additional 0.1 million USD is needed monthly. However, comparing to ‘Scenario 1’;, total cost for this scenario is 41% less which the BMA can save approximately 0.6 million USD a month. For service provision efficiency, it increases to be 36% and 50% from the first to the last months of simulation period. Thus, this scenario is not very effective in terms of the amount of MSW to be landfilled. However, it is promising in terms of total monthly cost for the BMA to put on waste collection and transportation. Therefore, it is essential that there be plan or policy to bring up willingness of people to do source separation.
‘Scenario 3’; shows a situation that there is a regulation enforcing Bangkok residents to do recyclable waste separation before disposing of. In this case, an 80% waste separation rate is applied to the simulation. The simulation results show that, there is a continuous increase of recyclable waste amount over time which is simulated to be 22,828 tonnes/month at the final simulation. This results a 3% reduction
of MSW amount to be landfilled comparing between the first and the last months of simulation, or decreases from 93,458 tonnes/month to 90,660 tonnes. In terms of total collection cost, the monthly expense declines to about 0.3-0.4 million USD/month. In other words, the BMA would save over 0.9 million USD a month. This is a consequence of less required resources necessitating in the collection and transportation process. The efficiency of this scenario starts at 56% and incrementally increases to be 71% over time. Therefore, the 80% separation at source rate provides a great amount of recyclables and exceptional amount of plausible saved budget. It also slightly extends landfill life.