Why hardwood feedstock matters for biochar

What the feedstock does to the final biochar

When wood pyrolyses, it loses volatile compounds and retains a skeleton of the original plant structure. That skeleton is what ends up in your soil. Different feedstocks have different pore networks, different densities, different ash contents, and those differences carry through.

Hardwood

The default for Charged Earth. Maple, oak, beech, birch — closed-structure woods with smaller, denser cellular architecture. The resulting biochar is:

• Denser per volume than softwood chars
• Lower ash fraction (typically 6–12 %)
• More consistent batch-to-batch because hardwood feedstocks are less variable in their composition than crop residues
• Longer-lived pore structure that holds up through freeze-thaw cycles

For home gardeners, the consistency is the real value. You blend 10 % into a potting mix and you get the same effect whether the bag was packed in April or October.

Softwood

Pine, spruce, hemlock. Less dense, more open pore structure. Softwood chars are perfectly usable — in fact, commercial biochars often use pine because it is abundant and cheap in parts of Canada. The trade-off is lower density (more volume per kg, so bag-to-bag the per-application feel is different) and higher variability from the sap and resin fraction.

Crop residue

Rice husk, corn stalk, wheat straw. These chars have high ash content (sometimes 20–40 %), high silica content (rice husk particularly), and act closer to a potassium-rich fertiliser than a structural amendment. Valuable in certain soils, but not what you want if the goal is soil structure.

Manure

Poultry-manure chars are extremely nutrient-dense. They are a fertiliser first and a structural amendment second. Also highly regulated — manure-derived chars have their own CFIA and feedstock-declaration requirements. Not a feedstock we use.

What this means for your garden

• If you are amending soil structure — drainage, water retention, cation-holding — hardwood is the feedstock you want.
• If you are building nutrient density and the ash content is acceptable for your bed, crop-residue chars are an option.
• If you want consistency across applications and seasons, hardwood delivers that more reliably than any other feedstock.

All Charged Earth biochar is hardwood-sourced, declared in writing by our supplier and tested against that declaration.