Experiments for Carbon Sequestration Performance of Green Roofs Using Waste-building-materials Soil as Roof Substrate

Green roofs can make full use of its carbon sequestration when the nutrition by substrates was provided for the green roof life. It is important to find available and economical ways if construction waste can be used as a green roof substrates to boost the carbon sequestration of green roof and emission reduction in China. This work aims to investigate the mitigate of climate change and the improvement of the resource utilization rate of waste materials in determining the green roof as a carbon sink or source in a long-term experiment. Six green segments constitute to two green roofs (green roof-1 and green roof-2) with two substrates whose depth was 20cm, 25cm and 30cm respectively, waste-building-materials soil (WBMS) and local-natural soil (LNS). Three native plants (L. vicaryi, N. auriculata, and L. spicata) were planted in both two green roofs. Experiments were conducted and tested from July 2012 to July 2017 in order to obtain long term results. It shows that the average carbon storage of N.auriculata in green roof-1(9.9kg C m^-2) was 1.3 times more than that in green roof-2 (7.5kg C m^-2). The average carbon storage of L.spicata (4.8 kg C m^-2) and L.vicaryi (15.6 kg C m^-2) in green roof-2 was 1.2 times and 1.1 times more than that in green roof-1. The average carbon sequestration of L.spicata, N.auriculata and L.vicaryi was 1.8, 3.6 and 5.3 kg C m^-2yr^-1 respectively. In addition, the two substrates (WBMS and LNS) on the six green roofs were potential candidates as green roof substrates with a strong ability of carbon sequestration. Annual mean carbon sequestration of the WBMS was 1.8 times higher than LNS. The overall average carbon sequestration in green roof-2 (12.8 kg C m^-2 yr^-1) was 1.1 times than corresponding in green roof-1 (11.4 kg C m^-2 yr^-1). Consequentially, WBMS substrate and L.vicaryi could be consider as the most adaptable green roof configuration, which can be a recommendation to promote the carbon sequestration and the function of green roof in Chengdu plain.