In Amazonia, a great agricultural civilization fertilized poor forest soils with terra preta, the first biochar, to feed tens of thousands of people.
Today, we are rediscovering the value of biochar as the world staggers under climate change, environmental degradation and human poverty.
Biochar is a super charcoal made by heating any biomass – for example, corncob, husk or stalk, potato or soy hay, rice or wheat straw – without oxygen. All of the cellulose, lignin and other, non-carbon materials gasify and are burned away. What remains is pure carbon – 40% of the carbon originally contained in the biomass.
Climate change is threatening food security around the world. When farmers use Biochar as a soil amendment they will benefit from:
• Bigger yields • Healthier soil • Lower acidity • Better water retention
• Stronger plants • Richer soil life • Less contamination • Higher fertility
• Promotes seed germination
Biochar seems to have no end of uses that derive from a handful of key characteristics.
Tiny holes, huge surface area – retaining water for a dry day
If you look at biochar under an electron microscope, you see an extraordinary moonscape of holes upon holes. What’s this mean? Biochar is an amazing sponge that will hold (absorb) huge amounts of water. All those little holes also provide very convenient condos for soil microbes; we’ll revisit this below.
pH of 8 – unlocking even poor soil’s nutrients
Plants like soil that has a nice, neutral pH of say 6.5 to 7, but most soils in the developing world are acid to very acid – 4 to 5.5. In soils this acidic, most plants cannot take up nutrients, even if they are present in the soil. Stick some biochar in this soil, however, and you can push the pH as much as a whole point higher. As the pH rises, more and more nutrients become available to crops.
Electrically charged surface – very attractive to chemicals
Biochar is attractive to chemicals of all types. Stick a bit of pure carbon biochar in the soil and six months later it is covered with scales of calcium, iron, magnesium, phosphorous, potassium, and sulphur. It’s become a little mineral ball. Sprinkle fertilizer on the soil and instead of seeing 50% of it leach away with the rain, that fertilizer, too, will glom onto the biochar, providing long-lasting, slow-release nutrition. Stick biochar in a heavy metal contaminated field and soon the cadmium, lead or mercury are chemically bound to it (adsorbed) where plants can no longer take them up and water can no longer wash them away.
Bug friendly – encouraging soil life
Plants can’t eat their elements raw. No matter how much they need nitrogen, they can’t just suck it up; they need microbes to digest it first and pee it out as nitrates or nitrites. If you look at the root systems of plants, you find all sorts of similar, collaborative relationships. To put it differently, if you don’t see such relationships, chances are, you can’t grow anything.
Biochar production is a simple process that anyone can do. Warm Heart has designed cheap and easy methods for converting biomass waste into biochar. The simplest and cheapest method is to
dig a hole in the ground. You can also build a cheap
biochar oven using an old oil drum, or
build a trough.
Whichever method is used, the process is the same, biomass is burned with a lack of oxygen, turning the biomass in biochar, smoke free.
Benefits of making Biochar
If you live in the developed world, field fires are a thing of the past. If you live in the developing world, smoke from agricultural field fires can obscure the sun for days.
Field fires are often smoky, slow smolders burning the residue of crops containing fertilizers fortified with nitrogen and sulphur. These generate large quantities of greenhouse gases (GHGs) such as methane and the NOxs (nitrous oxides) that are many times more warming than CO2. (Methane has a global warming potential (GWP) of 25, NOx 298!)
They also produce large quantities of smog precursors such as ammonia and the SOx (sulphur oxides) that react with sunlight to form smog. Finally, that smoke that blocks the sun is PM2.5 – particulate matter so small that it passes through the walls of the lungs into the bloodstream to wreak havoc throughout the body.
