TechNorCal Notes


Video on Making BioChar from Forest Thinnings

Last spring I attended a workshop on BioChar and Conservation Burning sponsored by Sonoma BioChar Initiative. Peter Hirst demonstrated his technique for burning brush piles that resulted in very little smoke and a good amount of biochar produced at the end. I went home and tried it out and set up a camera in time-lapse mode to record it. It’s pretty choppy and rough but it shows the process. I’m the guy in the nomex.

Peter’s technique is based on how whiskey distillers make charcoal. They cut slats of hardwood and crisscoss them in layers then light the fire from the top and let it burrn downward. This allows the fire to burn very hot without much smoke. When the wood burns down to coals but before it turns to ash, the fire is quenched with water and the coals allowed to cool.

This is a primitive but effective way to make biochar. Stoves, kilns, retorts, and other mechanisms get a higher yield of char and may burn cleaner but this works and costs nothing.

I’m coming to biochar from a forest improvement/fuels reduction angle. I am working on my homestead to thin out the forest and make it safer if and when a fire comes through. The land is a mix of oak woodland, douglas fir and pine forest, grassland, and manzanita patches. Fifty years of fire suppression have left it crowded and overgrown. Many young fir trees are growing up under the black oaks and choking them out. Large patches of manzanita are too thick to walk through and are ready to become blast furnaces in August. In wildfires, a thick understory spreads a fire quickly and allows it to get up into the tops of trees and become a crown fire which burns incedibly hot and fast. Cleaning out the undergrowth and thinning the trees keeps a fire cool and on the ground and is actually good for the forest’s health and people, animals, and buildings.

Once you cut a lot of brush and young trees, you are faced with the dilemna of what to do with all that wood. Larger trees and limbs can bcome firewood and poles for building. The rest can either be chipped or burned or left to rot. Left to rot is very slow and you’re just creating piles of tinder waiting for a spark. Chipping is effective but the machines are expensive and dangerous and take fossil fuels to run. You also have to haul material to a road where the chipper can get to it. Burning during the winter is probably the best choice and is a local pastime but it takes a lot of time and releases all the carbon into the air and creates a lot of smoke.

Making biochar is a great alternative. You’re burning the material in a more controlled way and about 50% of the carbon is saved from release into the atmosphere. You can use some of the heat to create power or heat water and you end up with a great soil conditioner you can spread in the forest or use in your garden. I am using this biochar in my garden, mixed with compost, earthworm castings, rice hulls, and azomite as a top dressing and mulch. Makes big tomatoes.

Details of this BioChar Burn:

Material: young douglas fir and ponderosa pine saplings 2-5” in diameter
Moisture content: estimated 20-50%. Sat on ground for one year.
Date burned: May 4, 2014
Size of pile: about 5 feet square cube, estimated 2000 lb
Biochar yield: about 60 gallons(8 cu ft)

Resources

Sonoma BioChar Initiative

New England Biochar

Book: The Biochar Revolution

Bellsprings.net – Our local volunteer fire department

About This Blog

This is the online notebook of Will Emerson, country geek and web developer residing in Mendocino County, California. Read more...

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