What is biochar and how is it made?
Biochar is a high-carbon, fine-grained residue that is produced via pyrolysis; it is the direct thermal decomposition of biomass in the absence of oxygen (preventing combustion), which produces a mixture of solids (the biochar proper), liquid (bio-oil), and gas (syngas) products.
Biochar, specifically has been produced and utilized for several thousand years and is best known as charcoal (when produced from woody biomass).
Historic use of Charcoal or Biochar
So to build long lasting soils the Incans in Peru used it in their terraces, which were analysed and where they found in Machu Pichu black soils generated possibly over centuries deep fertile soils as well as in other places like in the Amazonas.
As they lived with very high density of population in those areas, where the charcoal was found in the soils, I assume they didn’t make specifically charcoal and wasted like now with biochar 2/3 of the carbon and energy, the wood has accumulated from the sun over decades, but each time they emptied their fire pits they had charcoal and ash mixed and dumped it all on the beds, which then over time the ash disappeared, the charcoal being stable like humus in the soil, it accumulated and left behind black and very rich soils.
Cost of biochar?
The market cost for biochar is about £ 600 per ton that is roughly 50% of the price of activated carbon (£ 1150 per ton)
Why use bio char (charcoal) in your garden?
If you start a new garden on very sandy or silty soils, with no structure, poor in humus, nutrients and water, charcoal can absorb many more times the water and nutrients compared to humus.
If you are in a heavy water-logged, clay soil, biochar will help to create drainage and aeration and alleviate the acidity in soils, generally speaking.
If charcoal is applied it raises the pH and even more so with ash.
If it is not applied with ash or other organic composts as can be seen in the commercialisation of biochar in ‘Carbon Gold’ £ 50/ 20 kg (application rate, it will actually rob the soil of Nitrogen and other nutrients.
Therefore biochar is usually sold as a mix with fast return compost with a high nutrient content and charcoal.
Benefits of Biochar
Increase of pH makes available nutrients form rest of soil
Fixes heavy metals and other poisons in the soil, like agrochemicals
Increases water holding capacity
Improved water holding capacity
Increased vegetable and plant growth
Breaks up compacted soil
Refugia for natural soil biology
Reduces water run off in compacted soils
Improves nutrient retention in soil
Locks carbon in the soil for centuries
Offsets your carbon footprint (1kg of biochar sequesters 3kg of carbon dioxide)
Disadvantages of Biochar
-It helps to break down nutrients in the soil
-It absorbs nutrients from soil
-It denitrifies Nitrogen (NO2) into N2 which gaseous form of nitrogen, meaning it can deplete soil of nitrogen, without presence with rich micro flora and other forms of carbon like stable humus
General Application Rate Suggestions:
0.5-1% OM equivalent is recommended for realizing maximum ecological benefit
0.25-05% OM equivalent is often more economically feasible in the short term
2% OM equivalent is suggested as upper limit for initial applications.
If you would apply 5 kg of biochar and incorporate it 15 cm (6inches) deep in the top soil layer the OM equivalent would be 0.3% OM equivalent.
Makes sense?
Working with the biodynamic preparations, green manures, crop rotation and a high diversity crops of deep rooting and fibrous root systems, we could accumulate biomass (organic matter) with less cost and waste of wood being sacrificed to make biochar.
Unless we look for alternatives like bracken or gorse and other invasive species, who destroy biodiversity in the heather habitats and pastures of farmland.
So, take it with a pinch of salt if you work biodynamically as we are looking to create from the soil upward, via the plants and animals and we help mediate and connect the cosmic influences and that of the 3 kingdoms present in our garden environments to create self- sustaining abundance without importing organic material form outside our living garden and farm organisms. We only import substances from the outside of the garden or farm if we need to remediate the soil.
Try making charcoal and do it with your children. It is fun, but wasteful if applied on large surfaces.
You could of course invest in a biochar woodstove and make your own biochar, while using the waste heat produced in this reduction process (exclusion of Oxygen) from this process, for heating your house in winter.
Happy days with regenerating soils however you deem best,
Hans-Günther