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Establishing an experimental green roof in association with a greywater recycling system

: Combined Greywater Recycling System & Pilot Green Roof Application. The objectives of this project were to recycle grey water for the irrigation of the green roof during the dry months, and to test the potential use of Maltese indigenous plants in a pilot green roof application.
: Malta
: Paola
: 250 ha
: 8442
: 2015
: 1 Year
: Complete
: Yes
: MCAST and the Global Water Partnership – Mediterranean (GWP-Med)
: 35.8772
: 14.5059
Reduced drought risk, cooling effect, urban heat island mitigation
Yes, a green roof acts as insulators for buildings (United States Environmental Protection Agency, 2019) and plants absorb and reflect sunlight (Sempergreen, 2019); so this helps to create a cooler and more pleasant climate. For the indoor climate this means that the air conditioning doesn't have to work so hard, which in turn means energy savings. And this too has an extra positive effect on the climate in the immediate vicinity of the building and on the temperature in the city (Sempergreen, 2019). Reduced air pollution and greenhouse gas emissions: By lowering air-conditioning demand, green roofs can decrease the associated air pollution and greenhouse gas (GHG) emissions from conventional power sources (United States Environmental Protection Agency, 2019).
Biodiversity conservation or increased biodiversity
Yes, green roofs provide habitats for plant and animal species in urban areas (ERA, 2018d).
Increased quality and quantity of green and blue infrastructures
Yes, green roofs provide an opportunity to better control stormwater in the built environment and dense urban areas (ERA, 2018e), which are characterised by a limited availability of green infrastructure (Balzan et al., 2018).
Sustainable urbanisation
A green roof improves human comfort, by reducing heat transfer through the building roof, can improve indoor comfort, and lower the incidence of heat stress associated with heat waves. (United States Environmental Protection Agency, 2019).
Education, knowledge exchange and learning
Yes, the green roof is used as an educational resource by academic staff and students.
Low air quality
National data indicates exceedances of the EU limit values have been observed for both ozone and particulate matter (PM10). PM10 exceedences are attributed to the combined effect of human caused (traffic congestion and to a minor extent power generation) and environmental factors (e.g. dust from the Sahara). Ozone is a transboundary pollutant arriving in Malta from Europe. The concentration of Nitrogen Dioxide (NO2) higher in traffic congested areas and may pose a significant problem in dense urban areas (ERA, 2018b).
Drought and heat risk
The Mediterranean Region is considered as a "hot-spot" of climate change, having been identified in global climate scenarios as one of the most responsive regions to climate change (Lionello and Scarascia, 2018). There is a consensus in scientific literature that average temperatures will rise across most of the Mediterranean Region, and that precipitation will decrease (Ulbrich et al. 2013; Lionello and Scarascia, 2018). Observed annual mean temperatures in the Mediterranean Region are now 1.4 °C higher than the average late-nineteenth-century levels particularly during the summer months (Cramer et al., 2018).
Low availability of green infrastructure
Yes, densely populated urban areas were characterised by a lower availability of green infrastructure (Balzan et al. 2018).
Limited knowledge about biodiversity
The Malta National Biodiversity Strategy and Action Plan (NBSAP) reports that the results of the Eurobarometer Surveys on Attitudes of Europeans towards Biodiversity in 2007 and 2010 indicate that 14.4% and 18% respectively of Maltese respondents had heard of the term “biodiversity” and knew what it meant. A survey commissioned by MEPA in 2011 indicates that out of the 500 persons interviewed, 24.6% of Maltese respondents heard of the term “biodiversity” and knew what it meant. In general there is a need to continue enhancing biodiversity awareness and gain more knowledge on the meaning of ‘biodiversity’. (ERA, 2018d).
Industry, innovation and infrastructure (SDG9)
Yes, this experimental trial tested the pairing of a greywater treatment system with a green roof using plants from the Mediterranean region.
Sustainable cities and communities (SDG11)
Yes, this experimental trial tested the pairing of a greywater treatment system with a green roof using plants from the Mediterranean region.
: Balzan, M. V., Caruana, J., Zammit, A. 2018. Assessing the capacity and flow of ecosystem services in multifunctional landscapes : Evidence of a rural-urban gradient in a Mediterranean small island state. Land Use Policy, 75, 711–725. Retrieved from: doi:10.1016/j.landusepol.2017.08.025.

Cramer, W., Guiot, J., Fader, M., Garrabou, J., Gattuso, J.-P., Iglesias, A., Lange, M.A., Lionello , P., Llasat , M.C., Paz, S., Peñuelas, J., Snoussi, M., Toreti , A., Tsimplis, M.N., Xoplaki, E. 2018. Climate change and interconnected risks to sustainable development in the Mediterranean. Nature Climate Change. doi:10.1038/s41558-018-0299-2.

ERA. 2018b. State of the Environment Report 2018: Chapter 2: Ambient Air. Reporting status from 2009 to 2015. Information obtained: 2019-11-08. Available at:

ERA. 2018d. State of the Environment Report 2018: Chapter 8: Biodiversity. Reporting status from 2009 to 2015. Information obtained: 2019-11-08. Available at:

ERA. 2018e. Investing in the Multi-functionality of Green Infrastructure (GI) – An Information Document to support GI Thinking in Malta. Information obtained: 2019-11-08. Available at:

Lionello, P., Scarascia, L. 2018. The relation between climate change in the Mediterranean region and global warming. In Regional Environmental Change, 2018, Volume 18, Issue 5, pp 1481–1493. Sempergreen. 2019. Benefits of a green roof. Information obtained: 2019-11-03. Available at:

Ulbrich U, Xoplaki E, Dobricic S, García-Herrera R, Lionello P, Adani M, Baldi M, Barriopedro D, Coccimiglio P, Dalu G, Efthymiadis D, Gaetani M, Galati MB, Gimeno L, Goodess CM, Jones PD, Kuglitsch FG, Leckebusch GC, Luterbacher J, Marcos-Moreno M, Mariotti A, Nieto R, Nissen KM, Pettenuzzo D, Pinardi N, Pino C, Shaw AGP, Sousa P, Toreti A, Trigo RM, Tsimplis M. 2013. Past and current climate changes in the Mediterranean region. In: Navarra A, Tubiana L (eds) Regional Assessment of Climate Change in the Mediterranean. Springer, Dordrecht, pp 9–52. doi:10.1007/978-94-007-5781-3_2.

United States Environmental Protection Agency. 2019. Using Green Roofs to Reduce Heat Islands. Information obtained: 2019-11-10. Available at: