Effects of pyrolysis temperature on the hydrologically relevant porosity of willow biochar
| Autor: | Sampo Kulju, Kimmo Rasa, Kai Arstila, Markus Hannula, Hailong Wang, Jari Hyväluoma |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
porosity
Materials science FOS: Physical sciences Applied Physics (physics.app-ph) 010501 environmental sciences Raw material kuivatislaus 01 natural sciences Analytical Chemistry huokoisuus Adsorption image analysis Biochar medicine biochar ta216 Charcoal Porosity ta218 0105 earth and related environmental sciences Condensed Matter - Materials Science x-ray tomography biohiili ta114 Materials Science (cond-mat.mtrl-sci) Physics - Applied Physics 04 agricultural and veterinary sciences Atmospheric temperature range slow pyrolysis Water retention Fuel Technology kuvantaminen Chemical engineering visual_art kuva-analyysi 040103 agronomy & agriculture visual_art.visual_art_medium 0401 agriculture forestry and fisheries medicine.symptom Pyrolysis |
| Zdroj: | Journal of Analytical and Applied Pyrolysis |
| Popis: | Biochar pore space consists of porosity of multiple length scales. In direct water holding applications like water storage for plant water uptake, the main interest is in micrometre-range porosity since these pores are able to store water that is easily available for plants. Gas adsorption measurements which are commonly used to characterize the physical pore structure of biochars are not able to quantify this pore-size range. While pyrogenetic porosity (i.e. pores formed during pyrolysis process) tends to increase with elevated process temperature, it is uncertain whether this change affects the pore space capable to store plant available water. In this study, we characterized biochar porosity with x-ray tomography which provides quantitative information on the micrometer-range porosity. We imaged willow dried at 60 $^\circ$C and biochar samples pyrolysed in three different temperatures (peak temperatures 308, 384, 489 $^\circ$C, heating rate 2 $^\circ$C min$^{-1}$). Samples were carefully prepared and traced through the experiments, which allowed investigation of porosity development in micrometre size range. Pore space was quantified with image analysis of x-ray tomography images and, in addition, nanoscale porosity was examined with helium ion microscopy. The image analysis results show that initial pore structure of the raw material determines the properties of micrometre-range porosity in the studied temperature range. Thus, considering the pore-size regime relevant to the storage of plant available water, pyrolysis temperature in the studied range does not provide means to optimize the biochar structure. However, these findings do not rule out that process temperature may affect the water retention properties of biochars by modifying the chemical properties of the pore surfaces. Comment: 10 pages, 5 figures |
| Databáze: | OpenAIRE |
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