Biochar granulation enhances plant performance on a green roof substrate

• Published in: The Science of the total environment 2022-03, Vol.813, p.152638-152638, Article 152638
• Main Authors: Liao, Wenxi, Drake, Jennifer, Thomas, Sean C.
• Format: Article
• Language: English
• Subjects: Bulk density; Charcoal; Conservation of Natural Resources; Ecosystem; Green infrastructure; Particle size; Plants; Water retention
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.152638

Green roofs have been widely promoted as a means to enhance ecosystem services in cities, but roofs present a harsh growing environment for plants. Biochar is suggested to be a highly beneficial substrate additive for green roof systems due to its low weight, high nutrient and water retention capacity, and recalcitrance. However, biochar is susceptible to wind and water erosion, which may result in biochar loss and negative environmental impacts. Applications of biochar as large particles or in granulated form may mitigate biochar erosion potential, but relevant data on plant performance and substrate properties are lacking. We examined the effects of granulated and conventional biochars at a range of particle sizes on plant performance of the drought-tolerant forb Agastache foeniculum. We found that granulated biochar strongly enhanced plant growth, reproduction, and physiological status, acting to neutralize pH and enhance water retention capacity of the substrate. In contrast, although conventional biochar reduced substrate bulk density and enhanced substrate total porosity and water retention capacity, it suppressed plant growth. Our results also suggest that granulated biochar at intermediate particle sizes (2–2.8 mm) best enhanced plant performance. We conclude that use of granulated biochars on green roofs can strongly promote plant performance while increasing water infiltration and retention. [Display omitted] •Biochar benefits green roofs due to low bulk density and high water-holding capacity.•Granulation may address the problem of biochar erosion losses.•Plant growth responses to granulated biochars exceeded conventional biochars.