An Experimentally Validated Selection Protocol for Biochar as a Sustainable Component in Green Roofs

Abstract

Green roofs contribute to more sustainable cities, but current commercial substrates suffer from important limitations. If carefully selected, biochar could serve as a viable option for a more sustainable green roof substrate. We propose a protocol to select an optimal biochar for green roof substrate amendment. Coffee husks, medium-density fiberboard, palm date fronds, and a mixture of waste wood, tree bark, and olive stone kernels are selected as residues for biochar production to develop a selection protocol. The residues are pyrolyzed at 350, 450, 500, and 550 °C in a lab-scale reactor. A pyrolysis temperature of 450 °C is selected for upscaling and is based on biochar yield, pH, salinity, and elemental composition. From evaluating the biochar characteristics after upscaling, it can be concluded that the biochar’s carbonization degree is mainly controlled by pyrolysis temperature, while yield, pH, and salinity are more dependent on the biomass properties. Ultimately, our procedure evaluates the presence of important contaminants, the biochar’s water holding capacity, salinity, pH, and carbonization degree. To validate the developed protocol, plant coverage experiments on green roofs are performed, which are quantified using a novel digital image processing method, demonstrating its efficient use to facilitate future biochar selection in substrates.

Improving Nitrogen Retention in Algal Biochar Pyrolysis by Co‐Pyrolysis with Glucose

“…Moreover, bench‐scale pyrolysis experiments will be carried out, using a pyrolysis set‐up that has proven to be scalable to pilot‐scale (2 kg h −1 biomass input). [ 23 ] Micro‐scale pyrolysis experiments coupled with sophisticated hyphenated analysis techniques (Py–GC–MS and TG‐IR) will complement the bench‐scale experiments to gain insights into the origin of the evolved gases during the pyrolysis experiments. Ultimately, the pyrolysis should yield nitrogen‐rich biochar, which will be characterized (CHNS, XPS, and Raman spectroscopy) to improve our understanding of the effect of co‐pyrolysis on the final biochar's properties.…”