Biochar from raw and spent common ivy: Impact of preprocessing and pyrolysis temperature on biochar properties

Abstract

Hedera helix L., the common ivy, is an excellent evergreen climbing plant to be applied in vertical green walls to improve urban ecosystems. These green walls need to be trimmed regularly, yielding a biomass stream, which could be promising as a renewable feedstock for biochar production and the extraction of valuable chemicals. The potential of raw and spent (extracted) common ivy as a biochar feedstock was evaluated using slow pyrolysis at different temperatures: 400, 550 and 700 degrees C. Biochars produced at 400 degrees C showed a high carbon, nitrogen and ash content, while still having residual surface functionalities. These biochars are therefore interesting to be applied as soil fertilizer. Additionally, it was found that the impact of different green extraction processes (ethanol extraction versus steam distillation) before pyrolysis on the biochar properties was generally positive. Ethanol extractions increased biochar yields and the fraction of inorganic nutrients. Furthermore, ethanol extractions increased the carbon sequestration potential compared to raw ivy. Steam distilled biochar exhibited a very high carbon content (83 %), biochar stability (97 %) and aromaticity (100 %). Steam distillation did not affect the carbon sequestration potential. In conclusion, this investigation affirms common ivy as a promising feedstock for pyrolysis based biorefinery processes.