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, specificallyhas 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 Amazon basin with the Terra Preta.
Terra preta owes its characteristic black colour to its weathered charcoal content and was made by adding a mixture of charcoal, bones, broken pottery, compost and manure to the low fertility Amazonian soil.
They lived with very high density of population in those areas, and the charcoal was a byproduct of cooking on open fires. Like in the English cottage garden tradition any natural household wastes were integrated into the garden beds including charcoal and ash.
Nowadays biochar is produced industrially losing 2/3 of the carbon and energy in the process of the precious wood which is condensed sunlight from decades to centuries of growth.
In my opinion the best solution for producing charcoal and adding it into your garden would be an integrated approach of investing in a biochar woodstove to make your own biochar, while using the waste heat produced in this reduction process (exclusion of Oxygen) for heating your house in winter.
Cost of Biochar?
The market cost for biochar is about £ 400 per 750 litres (55 pence/litre) or in smaller quantities of 60 litre bags for £ 50 (85 pence/litre).
How much Biochar do I Apply to my Garden?
The most effective way to apply biochar (charcoal) is by mixing 1 part biochar with 9 parts of well-rotted, half rotted compost and apply to soils at a rate of 10 litre of mix/m2 on a heavy soil and up to 15 litres/m2 on pure, sandy soils when starting a garden. For maintenance apply half that amount every year.
Why use Biochar (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.
Benefits of Biochar
- Increase of pH makes available nutrients from 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 up carbon in the soil for centuries
- Offsets your carbon footprint (1kg of biochar sequesters 3kg of carbon dioxide)
Disadvantages of Biochar
- -It breaks down nutrients in the soil
- -It absorbs nutrients from soil and locks them up
- -It denitrifies Nitrite (NO2 -water soluble form of Nitrogen) into N2 which is the gaseous form of nitrogen, meaning it can deplete the soil of nitrogen. Without adding nutrient rich compost and the lack of presence of rich micro- and macro flora and other forms of carbon like stable humus, adding charcoal could lower soil fertility and crop yields.
Is Biochar Compatible with the Biodynamic Approach?
Working with the biodynamic preparations, green manures, crop rotation and a high diversity cropping (Companion Planting) 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 make it in our own woodstoves or we look for alternatives like bracken or gorse and other invasive species, who destroy biodiversity in the heather habitats and pastures of farmland and make biochar from those.
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. We help mediate and connect the cosmic influences and that of the 3 kingdoms present in our garden environments to create a self- sustaining flow of life of abundance and fertility, without avoiding to import organic materials from outside our living garden and farm organisms.
Try making charcoal and do it with your children in small quantities – it is fun.
Happy days with regenerating soils however you deem best.
Hans-Günther
