Plastic waste in Indonesia has become global issues, where Indonesia itself has been stated as the second plastic waste polluter in the world. Semarang City, as one of the major cities in Indonesia, is also facing plastic waste problems. Reverse logistics network study for plastic waste recycling could be used as an alternative method to reduce emissions. In this study, the reverse logistics network of plastic waste is evaluated based on the estimation of greenhouse gases (CO2, CH4 and N2O) generated from recycling activities. The results showed that the most significant GHG emissions came from the plastic waste grinder (intermediates) for about 513 kgCO2eq/day. According to the calculations, the optimal number of informal recycling businesses is 224 units of scrap dealers, 358 units of small-scale enterprises, 23 units of large-scale enterprises, and 18 units of grinders. Total greenhouse gases produced from the 623 recycle business units were 932 kgCO2eq/day. Optimizing existing reverse logistics scenarios was needed to evaluate greenhouse gas emissions and mitigation scenario for reducing greenhouse gas emissions.