Waste to Energy (WtE) plant has been acknowledged as one of the important approaches to solve solid waste management issues. The knowledge of the current and future trends of solid waste disposal rate are important to assess the feedstock sustainability of WtE plant. Future trend study requires the understanding of the factors influencing the disposal rate. Gross Domestic Product (GDP) has been acknowledged to be positively correlated with the waste disposal rate and could be used as dependent variable in waste disposal forecasting model. The implementation of compulsory recycling program might decouple the waste disposal rate and the economic indicator. This study aims to investigate the effect of recycling program on the correlation between waste disposal rate and GDP by analysing the correlation coefficient between both variables before and after separation at source program. Results of the study showed that the annual average daily disposal rate was reduced by 105 t/d or 5.5 % after the implementation of the SAS program. Decoupling effect between the waste disposal rate and gross domestic product was observed with a change in the Pearson correlation coefficient from 0.92 to -0.46 after the program implementation. The estimated maximum diversion rate from the program was 11 %. Taking the program's impact into account, waste disposal rates in Kuala Lumpur were projected to increase from 1,649 t/d or 0.93 kg/capita/d in 2021 to 2,706 t/d or 1.3 kg/capita/d in 2050, which indicated the sustainability of the waste supply even after the program implementation. The study also found a significant reduction in solid waste disposal rate during the period of movement control order. This was not considered in the forecasting model due to its' temporary effect.