I’ve always been interested in historic methods used in farming, cooking, and healing. While I was reading through a few old magazines, I came across an article on biochar. Being interested in ancient methods, I did some more research and found that it was indeed something I wanted to try. So I continued my research and this is what I found…
What is biochar?
Biochar dates back thousands of years, perhaps even further. The earliest known reference to it comes from people who resided in the Amazon Rainforest from 500 BC up to the mid 1500’s when the European settlers arrived. It tells of pits dug into the earth, filled with wood, leaves, or anything that could be burned. After the fire began burning hot, a layer of soil was placed on top which smothered the flames. The wood continued to “cook,” charring it. When it was completely charred it would be doused with water to keep it from burning up completely. When cooled the charred wood was chipped up and plowed into the earth. The result was healthier, more productive plants such as cassava, maize and fruits.
Amazingly enough, these pits – or the results of them – can still be seen today. They are called “terra preta” or “Dark Earth.” The soils of the Amazon region are naturally rich in nutrients where the silt has been washed in from the annual flooding of the Amazon River. In other areas, this silt has been washed away, leaving less than desirable conditions. The people of the Amazon area in Brazil found a way to combat this. They made biochar from the dead wood and used it to revitalize the soil.
Benefits of biochar
Once added to the soil, by itself, biochar does nothing. However, when used along with organic fertilizers and compost, it has the ability to hold on to nutrients better than anything else. Charcoal has been used for hundreds of years as a filtering medium. This is due to the many holes or pores that the char has. Biochar -essentially the same as compost, but in a rough form – also has these pores. When wood ash breaks down, as smaller pieces of biochar and ash will do, it contains nitrogen, phosphorus, potassium, calcium and magnesium – all very essential to plant life.
Making your own biochar
So how do you make biochar? It’s very easy. Pick a spot in your garden away from anything that could burn. Be sure to choose a day that’s not windy or too low in humidity. Obtain a burning permit if necessary. Dig a trench large enough to accommodate the items you want to burn. Loosening the soil on the bottom of the pit will save time and effort later.
Don’t be too picky about the wood you choose, but remember green wood will take longer to char. Deposit the wood and scraps you want to burn into the pit. Start it on fire and keep a close eye on it.
At first the smoke will be white. This is the water vapor burning off. After a while, it will turn yellowish. The sugars in the wood are being burned off at this point. What you are watching for is when the smoke turns a bluish-gray. When you get to this stage, cover the wood with about an inch of soil. This will put out the flames while still allowing smoldering. Keep in mind wood needs an anaerobic (low oxygen) environment to char. Otherwise, it will just burn – and when burning is complete, char amounts lost are upwards of 80%. However, when making biochar, up to 50% of the char is retained.
(If you don’t want to dig a large pit burning can be done in a metal barrel. Just be sure there are no holes in it or oxygen will seep in and feed the fire. You can still throw soil over it if using a barrel. When it’s cool, simply tip it over and roll the char out.)
Once the biochar is done and the wood is all charred, douse it with water. This will stop the burning action. When it is cool, break it into pieces and turn it into the soil with some compost or organic fertilizer. How about some mushroom compost? Or beneficial bacteria? All of these can be contained by the biochar. Once you create your own biochar you’ll have:
- more available nutrients for the plants,
- reduced nutrient leaching into the soil,
- reduced watering demands,
- reduced soil acidity (but be careful, you may need to make your soil more acidic again for certain plants such as blueberries and rhododendrons),
- reduced fertilizer requirements
- and therefore, increased crop production.
And another bonus, when heavy metals are present in the soil, biochar, used at a 10% rate, has been shown to reduce heavy metals in the soil by up to 80%!
As another huge plus, CO2 gasses are retained when producing biochar so they don’t escape into the atmosphere and become part of the greenhouse effect. Imagine – if farmers across the globe were to start using biochar, a huge percentage of the carbon dioxide gas that escapes every day could be contained in the soil, where it would not harm the ozone layer and plants could make use of it as a nutrient. It’s hard to believe that such a simple thing could potentially mean so much.
I’m planning to burn a biochar pit this week. Now that I know all the benefits, with very little output, I’m going for it. After all, something that’s been around for over 3,000 years can’t be wrong!