Sustainable biochar is a powerfully simple tool to fight global warming. This 2,000 year-old practice converts agricultural waste into a soil enhancer that can hold carbon, boost food security, and discourage deforestation. Sustainable biochar is one of the few technologies that are relatively inexpensive, widely applicable, and quickly scalable.
Farmers in Brazil have long known about the “black earth,” or terra preta, found over vast areas of the Amazon. In the last decade or two archaeologists have begun to realise that the terra preta was not a naturally occurring phenomenon, but had been cultivated over centuries, if not millennia. They turned some of the wood into charcoal and then worked it back into the soil, creating an unusually rich and fertile ground.
Traditionally, people have used biochar and ash in their fields. This practice exists all over the world. There is a need to recognize the value and create awareness on biochar. Farmers know that wherever biomass is burnt in the field’s crop grows stronger, healthier and better.
In East Africa, sugarcane and maize waste is normally burned in the field, as it has no other value. In-field burning returns approximately 2-5% of the original carbon to the soil and a negligible amount of NPK. It does little to improve soil, and is considered a major source of particulate and soot emissions in the region.
Burning without oxygen can also mean burning without smoke, which leads to the idea of replacing home heating and cooking stoves with pyrolizing kilns that provide the same functions but are clean-burning, inexpensive and easy to use, and instead of generating smoke and ash.
Biochar is essentially charcoal, but burnt at a lower temperature and with a more restricted flow of oxygen; it has the potential to end the slash-and-burn cycle in Sub-Saharan Africa.
According to researcher Bruno Glaser at the University of Bayreuth, Germany, a hectare of meter-deep terra preta can hold 250 tons of carbon, as opposed to 100 tons of carbon in unimproved soils.
THAT MEANS THAT THERE IS A POTENTIAL OF 150 TONS OF CARBON CAPTURE/ HA POSSIBLE. (THIS DOES NOT INCLUDE THE FORESTATION ON THE SAME HECTARE)
In addition, the bio-char itself increases soil fertility, which allows farmers to grow more plants, which allows more bio-char to be added to the soil. Johannes Lehman, author of Amazonian Dark Earths, claims that combining bio-char and bio-fuels could draw down 9.5 billion tons per year, or 35 Gt CO2 per year equal to all our current fossil fuel emissions.
This is the simplest and convenient method for farmers to convert the crop residue / biomass in the farm lands into biochar trenches. All the biochar, burnt soil remains within the field could be conveniently spread by the farmer within the whole field.
It is more convenient to make such trenches after ploughing the field. Trenches perpendicular to the slopes also benefit the steep sloppy areas as water harvesting means. The entire crop residue otherwise burnt openly can be collected and dumped into these trenches lengthwise. More biomass can be added during the process. Once the trench is filled with biomass and compact, it should be covered by grass, weeds, broad leaves, etc. After covering it up, soil should be spread on the trench, a lengthy mound is created. Some water could be used to make the soil compact and for sealing the mound of biomass. A small hole is left open for lighting the biomass at one end and at the other end a very small opening is left open. Once it is lit, white smoke starts emitting at the other end. The result is a smoking mound over the trenches.
When it smokes too much or when it cracks, too much oxygen is getting in. You must plastered more mud and earth over that part until the leak was stopped. You must keep an eye on the smoke, in order to stop the burn when it changed color. You can stop it by covering it with more earth to entirely cut off the oxygen.
The trenches are 2 to 3 feet depth and 1.5 to 2 feet width. Small holes are to be made in a biochar along the length of the trench at every 10 to 15 feet in a biochar trench. After 24 hours the biomass is converted into biochar. Any little smoke or embers should be quenched with water or covered with soil while removing the biochar from the trench.
The alternative is to burn the biomass openly, which causes pollution and very little carbon is formed.
Over the three year study period, t was observed that the chances of seeds germination are 20% to 30% higher in the soils with biochar compared to control soils. All soil properties except pH showed significant changes. In both biochar amended and control soils, salt, manganese, and potash content showed consistent increases while phosphate content decreased. Additional phosphate fertilizer may be needed. Organic phosphorus fertilizers come primarily from mineral sources, like rock dust or from bone sources such as steamed bone meal or fish bone meal.
Cacao plants planted into soil rich in biochar started producing fruits half the normal time. Plants seem to be supported for longer and there is less yellowing of leaves.
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