Tag-Archive for ◊ biochar ◊

• Wednesday, April 18th, 2012


What is BioChar?

Biochar is essentially a product of heating carbon-rich biomass in the absence, or minimal presence of, oxygen. Wood, cornstalks, coconut and nut shells, bamboo, grass, even dung can be baked in this way to produce a charcoal product called Biochar. This process is known as pyrolysis.

There are by-products of Biochar production that are useful too. If tremendous heat is used to bake the biomass it will drive off oil and gas, which can be collected and used as fuel. Char heated to great temperatures is bone dry, stripped of all bio-oil condensate. This results in what we call ‘active charcoal’ – a product that is thirsty to absorb moisture and nutrients [and toxins in our gut when used medically – as discussed previously]. However, if baked at lower temperatures these oils will line the tunnels and crevices and help to feed the micro-organisms. It is not essential to drive them off. It is believed that low temperature pyrolysis produces the best Biochar, with higher temperatures producing a more traditional charcoal. In this way the temperature is high enough to achieve maximum surface area, but also low enough to achieve some bio-oil condensate retention.

Enriching the Charcoal

Charcoal cannot be called BioChar in an active state because if placed in the soil in this state it will pull all nutrients toward it and leave the environment nutrient poor for any plants in the area until saturation occurs. This Charcoal needs to be charged with nutrients to ensure it become the desired soil amendment. This is not difficult to do.

Research shows that Biochar is an ideal microbial media, preferred by microbial cultures. Charged with water and minerals, Biochar is ready to be inoculated with microbes.

Innoculating the Biochar

Urine can be used to charge the Charcoal with nutrients. It is best to soak the Biochar in some sort of nitrogen rich solution. Some use compost or fish emulsion. Manure is an obvious choice too.

Compost is rich in microbes and will quickly. The decaying biomass feeds the growing microbe population. Compost tea can be made by adding compost to water, adding some molasses, and then stirring and bubbling air through the mixture to ensure oxygenation. This is then sprayed over the Biochar.

Depending on particle size and microbial vigour, inoculation can take anywhere from two weeks to six months.

Efficient Microbes

Inoculating the Charcoal with EM [Efficient Microbes] will get the colony started. These microbes thrive in the tunnels and crevices of this carbonised biomass. One teaspoon of powdered charcoal has the surface area of a football field, so the Biochar acts as a kind of reef in harbouring these beneficial organisms. You must remember that these organisms are what the earthworms feed on, not the compost waste as so often believed. EM also exchange nutrients for sugar with the plant roots. The more EM in the soil, the more fertility.

The very first thing the EM will do is to feed off all pyrolysis residues and potentially toxic poly-aromatic hydrocarbons [PAH]. The shiny black colour of fresh Charcoal is from hydrocarbon residues. Once inoculated and aged the Biochar looks dull and grey, without any shine.


The addition of biochar materials to soil often results in significant responses by both plants and mycorrhizal fungi.  Mycorrhizae also prefer Biochar as a habitat. They live in its micropores, sending out white fungal hyphae into the soil to suck up water and nutrients, and store them in the Biochar. This creates a rich source of water and nutrients for plant hairs.

Nitrogen Fixing Bacteria

The nitrogen fixing bacteria fostered within Biochar are different to the Rhizobia found on legume root nodules. Tropical nitrogen-fixing bacteria are also different to those found in temperate zones.

These Nitrogen-fixing bacteria love Biochar for the low oxygen conditions where such anaerobic bacteria thrive. In this environment Legumes will then create more nitrogen-fixing nodules due to the added bio-char, which in turn results in a multiplication of free-living nitrogen-fixing bacteria. A wonderful cycle that enhances effort free – on your part – nitrogen addition to the soil. This can be easily seen in Terra Preta soils [soils that are enriched by Biochar]. There is an increased natural event of nitrogen-fixing nodules in the plants in forests on such soil when compared to adjacent soils without the benefit of Biochar.

Biochar and soil pH

Of immense importance with the use of Biochar, is the resulting raising of soil pH. This has a powerful effect on soil quality. Soil pH determines the availability of nutrients to the roots of the plants. The ideal garden soil pH is 6.0 -7.0.

At low pH aluminium toxicity can prove a severe to plants. Aluminium toxic soils are everywhere and at a low pH aluminium becomes available to plants and is particularly harmful to plant growth. The corrective soil amendment is Biochar.

The availability of phosphorus to plants is also highly dependent on soil pH too. Biochar within the soil structure will make phosphorus more available in soils below the ideal pH range for phosphorus uptake of 6.5 – 7.0.

Particle Size of Greatest Benefit

When used as a culture media for microbes then powdered Biochar is the best, but as a soil amendment it is best to use from sand-grain-size to pea-size. You don’t want to use powdered Biochar in clay soils because of it’s water holding capacity, but larger pieces will benefit soil structure.

Crush in a large pot with a heavy branch [much as the African women crush the maize seed to make mielie meal]. Crushing the Biochar particles greatly improves efficiency. More surface area is available to water, ions, and microbes. The Biochar is also more easily saturated.

Are there Different Types of Biochar?

Yes. The chemical properties would naturally differ with source of material used in making the Biochar and also the temperatures used in the pyrolysis process.

My main interests is as a soil amendment and so the Biochar’s ability to lower acidity in the soil [sweeten the soil] is of particular interest to me. This is measurable as calcium carbonate equivalent (CCE) in a laboratory. Acid loving plants would need a Biochar with negligible CCE [such as that derived from Mulga (Acacia species native to the Australia bush country) wood, bamboo, and pine needles]. If, however, you are wishing to raise soil pH and combat aluminum toxicity, then a Biochar with substantial CCE is needed. Oak and Maple hardwoods seem to have high CCE.

Testing for Toxicity

If unsure of the source of Biochar it is easy enough to test for toxicity to plant and soil life. Use 4 pots: 2 with soil-only and 2 with soil + Biochar to be tested. In 1 soil-only pot put seeds to be germinated, and in the other soil-only pot put earthworms. Repeat with the soil+Biochar pots – one with seeds and one with earthworms. Check the results. If no germination occurs in the Biochar pot then an obvious problem. Check which pots the earthworms prefer too.

Benefits of Using Biochar in the Soil

  • Increased plant growth and crop yields
  • Prevents leaching of nutrients in the soil, especially in the tropics
  • No chemical fertilizers needed
  • Can correct soil acidity [Biochar is acid or alkaline, depending on temperature, time and oxygen used in pyrolysis]
  • Stores carbon long term, sometimes for centuries
  • Increased EM population
  • Increased earthworm population
  • Inexpensive soil amendment
  • Sustainable farming possible for the poor
  • Neutralizes bad odors, so perfect to add to a compost toilet
  • Improved water retention in the soil
  • Improved aeration and tilth
  • Reversal of desertification
  • Reforestation possible
  • Reduced runoff of phosphorus into surface waters
  • Reduced leaching of nitrogen into groundwater
  • Reduced soil compaction
  • Improved soil drainage
  • Increased nutrient cycling
  • Improved germination
  • Improved plant resistance to fungal disease, root feeding nematodes and insect infestations
  • Suppressed methane emission
  • Reduced nitrous oxide emission
  • Reduces aluminium toxicity
  • Increased soil aggregation [gathering together of the soil] due to increased fungal hypha
  • Increased soil levels of available Ca, Mg, P, and K
  • Stimulated symbiotic nitrogen fixation in legumes
  • Increased arbuscular mycorrhyzal fungi [the kind that attach to plant roots and exchange nutrients for sugars]
  • Increased cation [a positively charged ion] exchange capacity

Some Interesting Quotes

“Energy market forecasts in the 1970s did not foresee the rapid development of gas-powered generation through integrated gasification combined cycle (IGCC) plants and it is very possible that similar new energy options will arrive in future. An example of one such promising technology, Biochar….a charcoal-like material produced by heating biomass with minimal oxygen (pyrolysis)…Biochar systems need to be developed on a meaningful scale to determine better their true sequestration potential.” Tony Blair, Former UK President

“[Biochar] has not only consequences for mitigating climate change, but also for agricultural sustainability, and could provide a strong incentive to reduce deforestation, especially in the tropics.” Dr. Christoph Steiner, University of Geogria Biorefinery and Carbon Cycling Program

“Foster pyrolysis based technologies in Australia. These technologies convert crop waste into fuel and charcoal (which can be used to enhance soil fertility and store carbon long term). Using this technology and natural gas, we should be independent of foreign oil imports by 2025. This will involve the development of much infrastructure in rural Australia.” Dr. Tim Flannery, Macquarie University, Australian of the Year 2007, Author of “The Weathermakers”

“Research consistently reveals that poor soils enriched with biochar grow bigger, stronger plants that yield higher crop quantity and quality.  Even better, soils retain nutrients and sustain their productivity better than soils without biochar.” David Yarrow, Sea-Agri Inc.

“If you could continually turn a lot of organic material into biochar, you could, over time, reverse the history of the last two hundred years.”  Prof. Bill McKibben, Middlebury College, Founder of 350.org

“Much as the green revolution dramatically improved the developing world’s crops, terra preta could unleash what the scientific journal Nature has called a ‘black revolution’ across the broad arc of impoverished soil from Southeast Asia to Africa. Key to terra preta is charcoal, made by burning plants and refuse at low temperatures. In March a research team led by Christoph Steiner, then of the University of Bayreuth, reported that simply adding crumbled charcoal and condensed smoke to typically bad tropical soils caused an ‘exponential increase’ in the microbial population—kick-starting the underground ecosystem that is critical to fertility.” National Geographic Magazine

“Researchers trying to replicate the fertility of terra preta have concluded that its secret is in the charcoal. Work by soil scientists like Laird, Johannes Lehmann of Cornell, and Mingxin Guo of Delaware State University suggests that the benefits of supplementing soil with charcoal – which they call ‘biochar’ to distinguish it from the fuel of backyard barbecues – could be dramatic, widespread, and durable.” The Boston Globe

“The knowledge that we can gain from studying the Amazonian dark earths, found throughout the Amazon River region, not only teaches us how to restore degraded soils, triple crop yields and support a wide array of crops in regions with agriculturally poor soils, but also can lead to technologies to sequester carbon in soil and prevent critical changes in world climate.” Dr. Johannes Lehmann, Cornell University, Chairman of The International Biochar Initiative Board of Directors

“Biochar can be used to address some of the most urgent environmental problems of our time—soil degradation, food insecurity, water pollution from agrichemicals, and climate change.” Dr. Johannes Lehmann, Cornell University, Chairman of The International Biochar Initiative Board of Directors

“With a one-off addition [of biochar], the soil quality appears to be permanently improved.” Dr. Mingxin Guo, Delware State University

“Not only has biochar the potential to raise high yield rates of corn another 20%, but we believe there is a real possibility the char trial could also result in evidence that could point the way to dramatic improvements in water quality, which could have far-reaching beneficial consequences.”  Dr. Lon Crosby, Farmer and Agricultural Consultant with Heartland BioEnergy

Until next time,



Urban Evolution
BioChar Farms
International Biochar Initiative
Slash and Char as Alternative to Slash and Burn


Related Articles:
Making Biochar
Terra Preta
How To Build A Banana Circle

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