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Biochar, Terra Preta and Biomass Energy


What is biochar?
Biochar is charcoal produced from wood or other biomass such as coconut shells, rice husk, corn cobs etc. When biomass is burned in partial or complete absence of oxygen, it is converted into charcoal. This thermal decomposition of biomass is called pyrolysis; it can also produce wood gas and bio-oil, which can be used as fuels.

However, not all biochar is equal. The properties of biochar vary, depending on temperature at which it was produced, and on the extent to which the volatile organic compounds (VOCs) are driven out of it. Biochar produced at low temperatures with high amounts of VOCs can immobilize nitrogen in soil and reduce the crop yields temporarily. Different feedstocks (biomass types) also produce different qualities of biochar.

Why add it to the soil?
Charcoal when mixed properly with compost, makes a good quality fertilizer for the soil. When added in the right way and in right amounts, crop yields can increase significantly while also improving the soil quality. Research in the last few decades showed that the indigenous people in Brazilian Amazon supported large populations on highly weathered and nutrient-poor soils for nearly 2500 years. They created fertile soils called “terra preta do indio” or Amazonian dark earths. Even now, hundreds of years later, these soils retain their productivity, sometimes up to 400% higher than the surrounding soils. The most commonly accepted theory is that indigenous people created these soils by adding the charred material from their cooking fires to the soil along with bones and other biodegradable materials. Researchers and farmers today have rediscovered the beneficial effects of biochar amendment and are working to create these highly fertile soils once again in other parts of the world.

Here are a few benefits of biochar as soil amendment:

  1. Biochar provides habitats for soil microbes, thus improving the overall health of the soil ecosystem.
  2. It provides many nutrients like potassium, which are otherwise very costly to add through complete chemical fertilizers (e.g. 15-15-15).
  3. Charcoal helps the soil to store more nutrients and reduces the losses of nutrients with water. This is particularly true for sandy soils, since they have very low fertility of their own.
  4. The carbon added to the soil by compost usually gets lost very quickly. However, the carbon in charcoal can remain in soil for thousands of years and it also helps the soil to keep the carbon added by compost, plant roots and other biomass.
  5. Charcoal increases the moisture-holding capacity of the soil. This reduces the cracking of soil and improves its structure. With regular use, it can reduce the cost of irrigating the fields.
What does biochar have to do with global warming?
Soil is a storehouse for carbon. The natural soil carbon pool is more than two times higher than the atmospheric carbon pool and the terrestrial biomass carbon pool (approximately 1500-2000 petagram, one Pg being 1015 g). Carbon added to the soil not only helps in countering the effects of global warming, but also improves soil productivity and other ecosystem functions of soil. However, in cultivated soils, especially in tropical climates, carbon added through compost and crop remains gets decomposed very quickly. Charcoal, on the other hand, can remain in soil for thousands of years and actually helps to reduce the loss of other carbon from soil.

Recent research has also shown that, when biochar is added to the soil, it reduces the loss of other greenhouse gases such methane and nitrous oxides, while biochar added to compost during composting reduces the loss of carbon from the compost.

What is EcoPro doing about it?
We are promoting three different methods of sustainable charcoal production and incorporation of charcoal in soil. Different methods of making biochar differ in their impact on the environment. For example, charcoal production by means of open burning followed by dousing has low efficiency and emits lot of harmful gases and volatile compounds to the atmosphere, while improved charcoal kilns reroute the emitted wood gases to get burnt more completely. We are promoting technologies that have significantly lower environmental impact. Currently our activities are limited to Auroville and a few surrounding villages, but we hope to take this technology further as time and funding permits.

1. TLUD gasifier cookstove
EcoPro recently became an authorized dealer of the TLUD stove, developed by Dr. Paul Anderson, an internationally recognized expert of improved stoves. TLUD is an energy-efficient and clean-burning gasifier stove which produces excellent quality charcoal as a byproduct. It is designed for household cooking, though it has also been used in kindergartens for cooking meals for 30 children.

2. Improved Biochar kilns
Since July 2012, we have installed three different designs of biochar kilns, Iwasaki kiln, ARTI kiln and Adam retort, in Auroville farms and forests. The first two are simple, light-weight and small-scale kilns, while Adam retort is a medium-scale kiln. The Iwasaki biochar kiln can process up to 40 kg wood at a time (less for light-weight biomass like coconut husks) with 33% efficiency. ARTI kiln can process up to 20 kg wood at a time with 27% efficiency, while the Adam retort can process up to 750 kg wood with >30% efficiency.

3. Terra preta farm trials
The biochar is charged with nutrients from cattle urine, compost or human urine and then applied to the soil to improve soil productivity. Discipline Farm in Auroville, a demonstration site for EM practices, was the first demonstration farm in July 2012. Now the farm is routinely producing biochar from coconut husks and other waste biomass that is resistent to decomposition and using the nutrient-enriched biochar in the fields. Two other farms, Windarra and Auro-Orchard, have also started using biochar while another farm, Annapurna, is in the process of doing so.

4. Biomass gasifiers for electricity and thermal use
While the gasifier stove uses the energy released during pyrolysis for cooking, the heat and the wood gas produced in a charcoal kiln is wasted. On the other hand, biomass gasifiers can produce charcoal as well as wood gas, which can be used for producing electricity or cooking or heating. There is a well-developed gasifier industry in India, but most of the gasifiers are beyond the reach of households or small-scale businesses. We are currently exploring the possibility of installing biomass gasifiers in Auroville as a demonstration project.

5. Education and consultancy
Our philosophy is to share the knowledge and technical know-how with as many people as we can reach. We are currently working with five volunteers, training them in various aspects of biochar production and use. So feel free to contact us for lectures, volunteer opportunities, demonstration or trainings/workshops.

Where can I find more information on this topic?
Here are a few links for further information:

http://www.sciencedaily.com/releases/2006/03/060301090431.htm
http://news.nationalgeographic.com/news/2008/11/081119-lost-cities-amazon.html
http://drtlud.com
http://www.mendeley.com/research/impact-biochar-enriched-dairy-manure-effluent/#
http://servalsgroup.blogspot.in/2009/05/tlud-gasifier-stoves-wood-stove-with.html
http://iwasaki-sumiyaki.com/eindex.htm
http://www.biocoal.org/3.html

If you have any further questions, please write to ecopro@auroville.org.in

   

 

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