## 4 Discussion  
The proposed methodology allows for the eco-design of products based on the LCA methodology but in a more simplified and direct manner. Compared to other eco-design methodologies that apply a complete LCA [25; 27; 28], the proposed methodology focuses on providing a simplified life cycle inventory, which, however, includes all phases of product life--the extraction of raw materials, transport, manufacturing processes, and waste treatment at the end of its useful life. In this way, once the materials, processes, transport, and waste treatment that can be used in the design have been established, the designer is free to propose alternatives in a simple and smooth way, without having to rely on an LCA specialist.  
To achieve an effective transition to a circular economy, at least part of the barriers slowing down the implementation of circular economy concepts in companies must be removed from the equation [2; 3]. One of these barriers is the specialised knowledge needed in the LCA area to be able to design new products that comply with the ideas of circular economy, which analyses products from cradle to grave in an attempt to reduce their environmental impact in all phases of their life cycle. If with the proposed methodology, the need for LCA experts is limited, companies might see it as an easier way to get started with the principles of a circular economy.  
Figure 5: Environmental impact contribution for wood desk + reduced materials + recycling scenario.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Material** & **Weight** & **Active** & **Fab/Use Imp.** & **Distance** & **Transport** & **Transport Imp.** & **Waste Treatment** & **Waste Imp.** & **Total Imp.** \\ \hline Steel & \(5.36\times 10^{9}\) & YES & \(5.14\times 10^{9}\) & 10 & Lorry 16–32 t & \(8.82\times 10^{-4}\) & Landfill & \(6.18\times 10^{-3}\) & \(5.14\times 10^{9}\) \\ Aluminium & \(4.48\times 10^{9}\) & YES & \(6.76\times 10^{9}\) & 10 & Lorry 16–32 t & \(7.38\times 10^{-4}\) & Landfill & \(9.80\times 10^{-3}\) & \(6.77\times 10^{9}\) \\ PVC & \(3.00\times 10^{-13}\) & YES & \(6.96\times 10^{-2}\) & 10 & Lorry 16–32 t & \(4.94\times 10^{-5}\) & Landfill & \(1.94\times 10^{-2}\) & \(8.91\times 10^{-2}\) \\ Chipboard Wood & \(2.21\times 10^{11}\) & NO & \(0.00\times 10^{9}\) & 10 & Lorry 16–32 t & \(0.00\times 10^{9}\) & Landfill & \(0.00\times 10^{9}\) & \(0.00\times 10^{9}\) \\ Wood & \(2.52\times 10^{1}\) & YES & \(2.93\times 10^{9}\) & 10 & Lorry 16–32 t & \(4.15\times 10^{-3}\) & Recycling & \(-2.14\times 10^{9}\) & \(7.94\times 10^{-1}\) \\ Paperboard & \(3.00\times 10^{9}\) & YES & \(3.74\times 10^{-1}\) & 10 & Lorry 16–32 t & \(4.94\times 10^{-4}\) & Incineration & \(9.36\times 10^{-2}\) & \(4.68\times 10^{-1}\) \\ WOOD DESK + REUCED MATERIALS + RECYCLING & & & & & & & & \(1.33\times 10^{1}\) \\ PRICE: & \(\copyright\)132.30 & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 12: Results of chipboard wood desk + reduced materials + recycling scenario.  
In addition, a successful transition to a circular economy also requires that the end-customer can easily assess the environmental improvement of one product over another [22]. The use of an endpoint LCIA leads to environmental impact results in a single, dimensionless value without the need for the end-customer to get confused with different impact categories that are complex to explain in a simple manner. For instance, Figure 6 shows a simple graphical comparison of the different environmental impacts and prices of each of the alternatives studied for the traditional desktop case study. In this way, the end-customer would have a clear, visual, and easy-to-interpret presentation of each of the alternatives, and thus would be able to assess the advantages/disadvantages in each case.