| dc.description.abstract | Global warming has increased the precipitation in Northern Europe. For cities, this has led to increased stormwater runoff and flooding, due to undersized sewage systems and lack of natural water sinks. Green roofs have shown to reduce storm water runoff and thus reduce overall flood intensity in cities. To increase this potential, adding soil amendments of high water-holding capacity relative to own weight has proven to be beneficial. Biochar produced by pyrolysis have shown promising results for this purpose, but there is a lack of data comparing different char types to conventional products.
We tested two types of biochar: active char from Standard Bio and biochar from Carbon Cycle GmbH, in addition to crushed Leca as reference. These products were tested as pure products and as soil amendment (30%), for their relative saturated bulk density, relative field capacity, porosity, drainage delay and permanent wilting point. Empty samples (Control1) and non-treated growth media samples (Control2) were used as control groups.
Both types of biochar yielded significantly higher water-holding capacity than the Leca as pure products. Additionally, they both also increased water-holding capacity of the growth media, but only the active char from Standard Bio was significantly different to that of the crushed Leca. The active char was also the only product which yielded significant effect on porosity in growth media relative to Control2 and crushed Leca. Treated growth media did not increase delay of drainage or days before wilting relative to non-treated growth media.
Results in this study showed that biochar significantly increased water-holding capacity of growth media compared to non-treated growth media. Although further testing is required, our findings indicates that both types of biochar (active char and biochar) could be useful in green roofs to improve water uptake and thus decrease stormwater runoff. | |
