4D structural changes and pore network model of biomass during pyrolysis

Area of Science:

• Materials Science
• Environmental Science
• Agricultural Science

Background:

• Understanding biochar microstructure is crucial for its applications.
• Biomass feedstock and pyrolysis conditions significantly influence biochar properties.
• Previous analyses of biochar's physical structure changes during pyrolysis were limited.

Purpose of the Study:

• To visualize and quantify the changes in biochar's internal structure during pyrolysis.
• To investigate the impact of feedstock type and pyrolysis temperature on biochar porosity.
• To establish a relationship between pyrolysis temperature and biochar pore development.

Main Methods:

• Utilized synchrotron X-ray micro-tomography for 3D imaging of biochar.
• Analyzed biochar derived from diverse feedstocks: miscanthus straw, wheat straw, oilseed rape straw, and rice husk.
• Collected sequential scans at 50°C intervals during pyrolysis from 50°C to 800°C.

Main Results:

• Biochar porosity ranged from 7.41% to 60.56%, highly dependent on feedstock and temperature.
• Porosity, surface area, pore volume, and largest pore diameter increased with pyrolysis temperature up to ~550°C.
• Significant pore structure development occurred between 350°C and 450°C.

Conclusions:

• Pyrolysis temperature and feedstock type are key determinants of biochar's pore structure.
• Optimizing pyrolysis conditions can tailor biochar properties for specific applications.
• This research provides critical insights for advancing biochar utilization in agriculture and environmental management.