A Solution to Beirut’s Dark Smog: The World’s First Wonder Forest

Abstract

The Lebanese population, and residents of Beirut in particular, has been facing a severe economic crisis exacerbated by pre-existing environmental challenges including access to clean water and poor air quality. A growing urban population and a high influx of refugees imposed unprecedented challenges that were deepened following the 2020 Beirut port explosion. Green roofs and rainwater harvesting (RWH), two simple techniques, have previously been proposed and studied in the literature with RWH being piloted in some areas of Lebanon. A comprehensive Social and Environmental Cost Benefit Analysis (SCBA) was designed for this thesis research to evaluate the financial, social and environmental feasibility of a green roof and RWH project for the city of Beirut, Lebanon. Costs of installation and maintenance, heat island effect alleviation, stormwater management, air pollution removal, reduction in water costs, carbon sequestration potential and aesthetic enhancement were included as main variables in evaluating costs and benefits. Applying the avoided-cost approach and a discount rate of 5% for a timeframe of 50 years, cost and benefit items were tallied. The Net Present Value (NPV) was then calculated. The analysis showed that an extensive green roof's NPV is positive throughout a 50-year timeframe following the installation, with the final cumulative NPV also being positive. Moreover, results suggested that a green roof and rainwater harvesting project would generally be cost effective when implemented in the target districts and offers a net cashflow of USD 459 million over a 50-year timeframe. Benefits are borne both privately (residents) and publicly (society). Analysis also demonstrated that the project would not be cost effective on a social cost basis (level two) when costs are borne by the government only. However, for multifamily buildings (level one), it remains a highly appealing investment. Assessed separately, both a rainwater harvesting project and a green roof project were found to be highly beneficial at level one. These results should encourage Lebanese authorities, through the relevant ministries, to consider projects of this type and scale.