TY - JOUR
T1 - Possibilities to improve soil aggregate stability using biochars derived from various biomasses through slow pyrolysis, hydrothermal carbonization, or torrefaction
AU - Heikkinen, Jaakko
AU - Keskinen, Riikka
AU - Soinne, Helena
AU - Hyväluoma, Jari
AU - Nikama, Johanna
AU - Wikberg, Hanne
AU - Källi, Anssi
AU - Siipola, Virpi
AU - Melkior, Thierry
AU - Dupont, Capucine
AU - Campargue, Matthieu
AU - Larsson, Sylvia H.
AU - Hannula, Markus
AU - Rasa, Kimmo
N1 - Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/3/7
Y1 - 2019/3/7
N2 - Various thermochemical conversion technologies can be applied in producing biochar from a wide range of raw materials. We studied the chemical quality of 10 different biochars produced via torrefaction (TOR), slow pyrolysis (SP), or hydrothermal carbonization (HTC), in order to assess their potential in improving clay soil aggregate stability and thus contribute to mitigation of erosion from agricultural soils. X-ray tomography was used to visualize soil aggregates in some selected biochar treatments. Feedstock type had a major influence on the properties of the biochar, but in general biochars derived through SP were alkaline and exhibited higher electrical conductivity and ash content and lower surface activity than acidic HTC and TOR biochars. Alkyl peak areas determined from FTIR spectra were higher in biochars produced by TOR and HTC than in SP biochars, which indicates a higher degree of hydrophobicity in the former. Significantly higher aggregate stability and reduced colloid detachment were achieved with HTC biochars, most likely due to hydrophobicity reducing wetting rate and aggregate slaking. When mixed with initially aggregated soil, the biochar particles settled in inter-aggregate voids. According to image analysis, the internal porosity of soil aggregates was not affected by biochar addition, i.e., biochar did not enter the aggregates during the short incubation period. Addition of hydrophobic HTC biochar decreased the soil water content at field capacity, whereas more inert SP chars tended to increase it. The overall effect of biochar hydrophobicity on soil functions needs to be explored prior to wider use of biochar as a soil amendment.
AB - Various thermochemical conversion technologies can be applied in producing biochar from a wide range of raw materials. We studied the chemical quality of 10 different biochars produced via torrefaction (TOR), slow pyrolysis (SP), or hydrothermal carbonization (HTC), in order to assess their potential in improving clay soil aggregate stability and thus contribute to mitigation of erosion from agricultural soils. X-ray tomography was used to visualize soil aggregates in some selected biochar treatments. Feedstock type had a major influence on the properties of the biochar, but in general biochars derived through SP were alkaline and exhibited higher electrical conductivity and ash content and lower surface activity than acidic HTC and TOR biochars. Alkyl peak areas determined from FTIR spectra were higher in biochars produced by TOR and HTC than in SP biochars, which indicates a higher degree of hydrophobicity in the former. Significantly higher aggregate stability and reduced colloid detachment were achieved with HTC biochars, most likely due to hydrophobicity reducing wetting rate and aggregate slaking. When mixed with initially aggregated soil, the biochar particles settled in inter-aggregate voids. According to image analysis, the internal porosity of soil aggregates was not affected by biochar addition, i.e., biochar did not enter the aggregates during the short incubation period. Addition of hydrophobic HTC biochar decreased the soil water content at field capacity, whereas more inert SP chars tended to increase it. The overall effect of biochar hydrophobicity on soil functions needs to be explored prior to wider use of biochar as a soil amendment.
UR - http://www.scopus.com/inward/record.url?scp=85062386073&partnerID=8YFLogxK
U2 - 10.1016/j.geoderma.2019.02.028
DO - 10.1016/j.geoderma.2019.02.028
M3 - Article
AN - SCOPUS:85062386073
SN - 0016-7061
VL - 344
SP - 40
EP - 49
JO - Geoderma
JF - Geoderma
ER -