## 4 Discussion  
From the environmental control perspective, the four factors evaluated show substantial improvements and benefits with respect to the solid waste management. Regarding the generation of waste, a similar behavior is observed (Figure 3), taking into account that the two municipalities are included in different scenarios, as Arbelaez is considered a medium producer and Tibasosa a large producer. Regarding recyclers, although the Colombian regulation is aimed at legally formalizing recyclers in order to have greater control of the reuse activity and provide labor and economic guarantees, this has not led to the expected results, and the process is very slow. Therefore, in the modeling, a distinction is made between formalized recyclers and professional recyclers. The results show that it is evident that the recyclers will gradually increase over time to enhance the use of solid waste. All of this promotes a more solid economic activity that will allow the generation of employment in these municipalities. The model predicts a clear reduction in methane emissions. According to the projection made, this reduction is due to the decrease in cardboard and paper waste that would be disposed of in a sanitary landfill. With the implementation of recycling techniques, the reuse of these types of waste will be increased in both municipalities. The model also predicts a reduction in the carbon footprint for both municipalities. This reduction includes methane emissions, the generation of leachate and emissions produced by transportation. The reductions induced by the effects of the implementation of recycling techniques on transport are due to the fact that the inorganic solid waste will have a classification site, and the collection centers will be located at no more than a 5 km distance from the center of the urban area, so the distance traveled until its final disposal will decrease. On the other hand, with time, the vehicle fleet will be changed into one with better technology, helping reduce the emissions, as shown in Figure 6.  
Regarding financial control, the net present value in all cases is positive. However, an important difference is observed when comparing the results obtained for the municipalities of Arbelaez and Tibasosa. In Arbelaez, the implementation of the circular waste management model generates a higher NPV (NPV = EUR 180,494), that is, greater net benefits are generated than expected a priori. However, in Tibasosa, the opposite occurs, and the current system of collecting and disposing of waste in landfills without reusing it turns out to be the best alternative from the economic point of view ((NPV = EUR 325,415), which is 2.9 times higher than the NPV of the circular model in this municipality (EUR 109,398)). This result is justified because, in this scenario, no new investments are required, since the implementation of a waste processing and utilization plant is not necessary, which translates into a lower cost structure. In addition, the income from the waste collection fee and other incomes derived from the transfers from the National Participation Fund that Tibasosa receives from the Colombian national government are much higher than those registered in Arbelaez because the municipality of Tibasosa has a larger population, which means a higher proportion of subscribers to the waste collection service. Regarding economic viability, the results show that the IRR, both in the linear model and in the circular model, has a similar behavior in the municipality of Arbelaez, registering returns on investment of 34.2% and 33.4%, respectively, widely exceeding the expected minimum profitability (OR = 10%). These results infer the capacity of the circular model to generate higher profits, since by requiring a higher level of investment (EUR 123,605 more than in the linear model), the returns on investment are still very similar, showing a difference of less than 1% between them.