**5. Proclamations**

Due to the rapid growth of the world population, improvements in urban environments, structures and services are necessary to meet citizen's needs. New technologies open the door to innovative systems, to move conventional cities towards becoming smart cities. The generation and managemen<sup>t</sup> of MSW is an important issue in the development and managemen<sup>t</sup> of smart cities, where waste collection has a significant influence on the environmental sustainability. European Directives enhance selective collection systems and recycling of different MSW fractions, ensuring the capability of smart cities to move towards a circular economy. In addition, the current trend of decreasing the amount of waste disposed in landfills fosters the selective collection of the biodegradable fraction and its subsequent treatment by means of anaerobic digestion. The selective collection of MSW, in particular the organic waste, in historic areas of cities is an issue which has opened the door to a discussion in Spain about which is the best collection system for these zones, since the conventional street-side collection systems is not feasible due to tra ffic and access restrictions. In those areas where the lack of historical remains that can compromise the installation of the system is guaranteed, and from an energy point of view, this study encourages the use of pneumatic collection. However, in order to make a more comprehensive study, the energy assessment of the collection systems should be complemented including social and economic aspects, whose deployment can shift the balance towards one or another managemen<sup>t</sup> options. In addition, an environmental sustainability evaluation of the collection systems could confirm the benefits of pneumatic collection mainly due to the environmental benefit deriving from the anaerobic digestion of the organic fraction, as stated some authors such as Ranieri et al. [63] and Digiesi et al. [64].

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1996-1073/12/7/1407/s1, Section S1: Waste collection plant, Section S2: Central collection points, Section S3: Underground pipes.

**Author Contributions:** Conceptualization, R.A.; Formal analysis, A.B., P.F.-i.-P., A.I. and R.A.; Investigation, J.L. and I.G.-H.; Methodology, A.B., P.F.-i.-P., A.I. and R.A.; Supervision, M.M. and R.A.; Writing–original draft, J.L. and I.G.-H.; Writing–review & editing, J.L., I.G.-H. and A.B.

**Funding:** This work has been made under the financial support of the Project Ceres-Procom: Food production and consumption strategies for climate change mitigation (CTM2016-76176-C2-1-R) (AEI/FEDER, UE) financed by the Ministry of Economy and Competitiveness of the Government of Spain.

**Acknowledgments:** The authors want to acknowledge the earlier contributions within the LIFE+ project: FENIX-Giving Packaging a New Life (LIFE08ENV/E/000135) by Bala, A. and Fullana-i-Palmer, P.; and to the UNESCO Chair in Life Cycle and Climate Change. In this respect, the authors are responsible for the choice and presentation of the information contained in this paper as well as for the opinions expressed therein, which are not necessarily those of UNESCO and do not commit this Organization.

**Conflicts of Interest:** The authors declare no conflicts of interest.
