# Circular Economy Strategy Selection Through a Digital Twin Approach
## 5 Discussion
### Main Findings  
The results of the simulation demonstrated that when only 50% of returned flooring is suitable for remanufacturing, the two RL strategies showed different economic and environmental outcomes. Centralizing inspection at the manufacturer's facility tended to be more cost-effective--especially for short distances--due to the lower operational complexity, time requirement, and costs. However, this approach is generally less sustainable because it involves more transportation, increasing carbon emissions. On the other hand, conducting inspections at the customer's location reduced transport-related emissions and costs, especially for long distances. Although this approach introduces additional expenses for operator travel and on-site work, it was often both economically and environmentally beneficial when the transportation distances were significant. As the share of high-quality returned flooring increased and low-quality returns decreased, more products were eligible for recycling rather than being discarded. This resulted in more items needing to be transported back to the manufacturer, particularly for recycling. For short distances, the best strategy became less obvious and depended heavily on the flooring thickness, which affected the transport and processing efficiency. When the distances  
Figure 9: Impact of remanufacturing process on performance and strategy.  
grew, the environmental impacts from logistics rose sharply, even if the economic gains remained steady due to the continued need to transport items for recycling. Thus, the trade-off between sustainability and cost-effectiveness is influenced by a combination of factors, including the distance involved, the quality of the flooring, and the operational requirements of each strategy.  
When 60% of the flooring was of top quality, more products went through remanufacturing. In this case, if this was performed at the customer's location, only a new surface sheet needed to be shipped, reducing the overall logistics efforts. This makes on-site remanufacturing more sustainable--even for short distances--compared to centralized processing. If the percentage of medium-quality returns (recycling candidates) increased, neither strategy was clearly more sustainable. Again, factors like product thickness and distance played a crucial role. Economically, on-site inspections tended to offer better savings by avoiding unnecessary transportation, even though they involved more labor.  
With 70% high-quality returns, on-site inspections offered the best environmental results in almost all cases, as they avoided multiple long-distance trips. This benefit, however, was offset if low-quality returns increased, as these must still be transported and discarded or recycled. From a cost perspective, identifying low-quality products on-site helps to avoid unnecessary shipping and disposal costs. In contrast, centralized strategies require transporting all returns, even for products that are later discarded, thus increasing the costs.  
Finally, when 80% of returns were high-quality, the environmental advantage of on-site inspections became even more evident, regardless of distance. The only exception was short-distance scenarios with very few low-quality returns. Economically, on-site inspection was more cost-effective in these conditions, as it eliminates the need to ship the entire product back to the factory.  
In summary, when a high percentage of products can be remanufactured, on-site inspections are both economically and environmentally preferable. They reduce transportation costs and emissions, even when considering the extra labor and travel involved. The best strategy ultimately depends on distance, return quality, and product characteristics like thickness.