Biochar may look like simple pieces of charcoal, but each particle contains a network of pores. The size of the finished particles also creates spaces when biochar is mixed into soil or another material. These two levels of structure work together, influencing how biochar holds water and nutrients, supports airflow, provides microbial habitat, and blends into different applications.
Particle Size and Pore Size Are Different
Particle size describes the outside dimensions of a piece of biochar. A fine particle may be smaller than a grain of sand, while a granule may be several millimeters wide. Pore size describes the tiny openings inside and across that particle.
Scientists often group pores as micropores, mesopores, and macropores. Micropores are smaller than 2 nanometers, and mesopores range from 2 to 50 nanometers. Larger pores extend into scales visible through advanced imaging. Together, these openings give wood-based biochar a large internal surface where water, dissolved nutrients, microorganisms, and other compounds can interact.
How Particles Change Soil Structure
When biochar enters soil, water can occupy pores inside each particle. It can also collect in the new spaces formed between biochar and soil grains. Research describes these as intrapores and interpores. Intrapores are part of the biochar itself. Interpores form as particles change the way the surrounding soil packs together.
Fine particles spread widely and make close contact with soil. They can fill small gaps and help increase water storage, especially in coarse or sandy soil. Larger, irregular particles create wider pathways that support drainage and airflow. A range of particle sizes can therefore build a connected structure instead of performing only one job.
This is one reason biochar supports soil in several ways at once. Its internal pores retain resources, while its finished particles change the physical root zone. Learn more about the science of biochar and its porous carbon structure.
Why Porosity Varies Among Biochars
The original biomass influences the pore network. Wood already contains channels that once moved water through the tree, and many of those structures remain after pyrolysis. Production temperature and time also shape the finished carbon, including its internal surface and the chemistry of its pore walls.
Grinding changes particle size after production, but it does not create an entirely new internal pore system. Breaking a larger piece can expose pores that were previously inside it. Very aggressive milling can also create excess dust and make the material harder to handle. Product sizing is therefore about balancing surface contact, movement, and practical use.
Particle Size Matches the Application
Gardens, farms, turf, potting media, filters, and manufactured materials do not all need the same form of biochar. Finer material blends evenly into growing media and makes broad contact with soil. Granular material is easier to spread with less dust and helps maintain larger open spaces. Filtration systems need particles that allow water or air to pass while providing enough surface contact to capture compounds.
The broader benefits remain the same across these uses: biochar provides durable porosity, a large reactive surface, stable carbon, and a structure that manages water, nutrients, airflow, and biological activity. Particle size helps place those qualities where they can work most effectively.
A laboratory study of biochar particle size, shape, and porosity shows how internal and between-particle pores influence water storage. Explore additional Wakefield BioChar products or contact Wakefield for information about product forms and applications.
