Biochar, Terra Preta, Slash-and-burn

Animal manure, from cattle feedlot wastes for example, can be converted into biochar. Photo: courtesy of Chris Stuart.

Reforestation.me – Terra Preta, biochar, charcoal, climate change, agroforestry, environment, carbon fixation / carbon sequestration, slash-and-burn agriculture, slash-and-char, slash-and-smoulder, soils, reforestation, mycorrhizal fungi, manure, human manure.

Biochar

Adding charcoal or charred material, (and ash), to soils can increase plant growth and food yield, and act as a bank of long-lasting organic matter, and generally speaking, the more the better. It is therefore likely that plants that produce a large volume of material (bulk rather than weight – biomass is usually measured in tons/ha/yr), that is light and porous (see photo below), will be best for producing quality biochar in the quantities desired. More research will probably determine whether large pores are more important, or small pores, or a distribution of pore sizes, for promoting beneficial micro-organisms, or retaining nutrients, etc.

Also, plant materials that have a higher nutrient content may be better, perhaps for example, Tithonia and Erythrina spp.

Finally, opportunities exist to use invasive weed species, creating a win-win situation.

SEM image of pores in biochar made from rubber trees. Photo: www.geos.ed.uk

SEM image of pores in biochar made from rubber trees. Photo: http://www.geos.ed.uk

Some plants that produce large volumes of material quickly that may be suitable:

Some of the plants listed would need to be dried first, chopped up, and lightly charred, before adding to soils (e.g. water plants and succulents).

Papyrus, Cyperus alternifolius, Typha spp., water hyacinth, bamboos, Napier grass, Arundo donax, sorghum, sugar cane, Tithonia, kenaf, hemp, sunflowers, etc.

Some dry climate plants that may be suitable:

Opuntia spp., Portulacaria afra, Sansevieria spp.

Some trees that may be suitable:

Inferior quality materials could be used such as crooked or knotty trunks, prunings, thinnings, smaller branches, bark, etc.

Colder climate trees

Poplars, willows, Pinus spp., Paulownia, etc.

Mediterranean climate trees

Pinus radiata, P. halepensis, P.canariensis, Acacia spp., etc.

Tropical and Equatorial trees

Pinus caribaea, Moringa spp., Bombax/Ceiba spp. and related trees, Balsa, annual and perennial Sesbania spp., Trema spp., Acacia spp., Falcataria, Erythrina spp., etc.

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Here are some papers kindly supplied by Getachew Agegnehu (a doctoral candidate at James Cook University in Cairns Australia) on biochar, compost, plant growth and soil improvement:

Biochar-compost on soil quality%2c yield &GHG flux (STOTEN)

Phosphorus response of wheat

Biochar-compost on soil quality and crop yield (AEE)

Biochar-compost on soil quality and crop growth (SR)

Getachew is from Ethiopia, and is a scholar and a gentleman. One can only hope that his work will be of great benefit to people across Africa, and elsewhere.

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Nutrients in ash

In an experiment in Peru, the ash from a partially burnt 17 year old forest had the following composition:

nitrogen 1.72% ( 67kg/ha), phosphorus .14% (6kg/ha), potassium .97% (38kg/ha), calcium 1.92% (75kg/ha), magnesium .41% (16kg/ha), iron .19% (7.6kg/ha), manganese .19% (7.3kg/ha), zinc 132 ppm (.3kg/ha), copper 79 ppm (.3kg/ha).

It should be noted that the nutrient content of ash is dependent on varations in soil properties and percentage of foresst biomass actually burned. Sanchez and Salinas, 1981, in Tivey 1990.

Terra Preta

For a possible way of making Terra preta, see the article “Making Terra preta“:  making terra preta 090212 . See also the page “Roof garden, Zai holes, circle gardens”. The article contains some speculation (which may turn out to be wrong), and is a work in progress. Below is a research paper on cattle feedlot manure biochar:

Sinclair-Slavich-van-Zweiten-Downie-2009 .

Understandably, most research into Terra preta has been in South America, but the following reference details a less well-known example of improving soils by charring organic matter and soil in Ethiopia: Charring cattle manure ands soil in Ethiopia . (Reference: Troeh, Frederick R. (1980). Soil and water conservation for productivity and environmental protection. Prentice Hall. ISBN 0-13-822-155-3).

In this example, the charred manure and soil might be better spread out to form rectangular beds, horizontally on the contour, with paths in between to catch water. During the fallow period, sowing an annual Sesbania species (e.g. Sesbania sericea) especially where the water collects, could increase fertility, shorten the fallow period, add more biomass, and provide fuel wood for fuel-efficient stoves (with the charcoal added to fields, possibly by feeding to livstock to disperse it in their manure), or be burnt with the manure and soil to provide a more woody biochar component to the soil.

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Maize field without biochar. Photo: biochar.info.

Maize field without biochar. Photo: biochar.info.

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Maize field with biochar. Photo: biochar.info.

Maize field with biochar. Photo: biochar.info.

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References and some sources for more information on biochar:

Tivey, J. (1990). Agricultural Ecology. Longman Scientific & Technical. ISBN 0-582-30163-7. Pge. 82.

http://www.biocharindia.com/biochar-trench-mound

http://www.biochar-international.org/

http://www.biochar-international.org/regionalgroups/southeastasia

http://www.biochar-international.org/node/1797

Http://www.biochar-international.org/Closing_the_loop_in_Germany

See also the biochar links on the “Links” page (click on the button at the top of the page).

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Bamboo can be very productive and can be used to make a good quality biochar. A company called Clenergen in India has tissue cultured Bambusa balcooa for energy production, see http://www.clenergen.com/biomass/bamboo/ , and http://www.ecoplanetbamboo.co.za/ , but this could also be a breakthrough for biochar production. Even more biomass production, for either fuel wood, energy production, or to produce biochar, may be possible if the bamboo is combined with a fast-growing, nitrogen-fixing tree, possibly Falcataria moluccana or Sesbania spp. Trials are needed.

Tomato grown in biochar on left, in peat on right. Photo: Biochar.org.

Tomato grown in biochar on left, in peat on right. Photo: Biochar.org.

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Reforestation.me

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