Appropedia is looking for service learning partners. Instructors, supervisors, and students interested in internships, please contact us.

From Appropedia

[edit] Background

Note: This page was transwikified from Open Source Ecology - please help adapt it to Appropedia.

According to the International Biochar Initiative:

Biochar is a fine-grained charcoal high in organic carbon and largely resistant to decomposition. It is produced from pyrolysis of plant and waste feedstocks. As a soil amendment, biochar creates a recalcitrant soil carbon pool that is carbon-negative, serving as a net withdrawal of atmospheric carbon dioxide stored in highly recalcitrant soil carbon stocks. The enhanced nutrient retention capacity of biochar-amended soil not only reduces the total fertilizer requirements but also the climate and environmental impact of croplands. Char-amended soils have shown 50 - 80 percent reductions in nitrous oxide emissions and reduced runoff of phosphorus into surface waters and leaching of nitrogen into groundwater. As a soil amendment, biochar significantly increases the efficiency of and reduces the need for traditional chemical fertilizers, while greatly enhancing crop yields. Renewable oils and gases co-produced in the pyrolysis process can be used as fuel or fuel feedstocks. Biochar thus offers promise for its soil productivity and climate benefits.

Some of the world's most productive soils (e.g. Canadian prairies, Russian Chernozem / or "black earth") are very rich in organic carbon. This is now thought to be pyrogenic in origin, likely originating from prairie or forest fires. The black carbon is often thousands of years old, demonstrating its stability in soil. For more extensive background on Biochar, please look up the Wikipedia entry

[edit] The Biochar Economy

(image from Flickr user visionshare by CC license)

[edit] Biochar in the Appropriate Technology context

• Inexpensive soil amelioration for degraded land (i.e. biochar as a liming agent)
• Need less land = lower startup costs for a Sustainable Village
• Increased biomass productivity
• Efficient use of biomass waste for energy generation
• Reduced need for fertilizer input (e.g. manure)
• Combine biochar with vermicompost to make superb fertilizer.
• Pyrolysis gas can be used for energy and as a heat source
• Bio-oil and tars are also by-products of pyrolysis, can be turned into biodiesel
• Add charcoal to compost heap to speed up composting (probably works via enhanced microbial activity)
• Biochar for sale as a source of income for an emerging community
• Combine with solar thermal heat source to make a solar pyrolysis unit for charcoal production
• Charcoal is useful for other purposes, e.g. metal smelting
• Charcoal as filter: it has very high absorptive capacities and therfore can be used for water purification and filtration, later become biochar; can also be used to filter pyrolysis gas itself, although it may not be suitable as biochar later (depending on feedstock and potentially hazardous polycyclic aromatic hydrocarbons produced during combustion)
• Lastly, charcoal powder can also neutralize smell when put into a composting toilet. Then it becomes biochar, ultimately.

[edit] Suitable Feedstocks

A variety of feedstocks can be used. Since these often constitute agricultural residues in rural communities, a form of waste is turned into an asset. Possible feedstocks include:

• agricultural leftovers: straw, rice hulls, corn stalks, chicken/cattle poop
• fast-growing biomass: bamboo, switchgrass, miscanthus,
• other: leaf litter, grasses, macroalgae, bones (high P content),

[edit] Specifics

The pyrolysis temperature appears to be a critical factor determining char yield vs. energy yield (tradeoff). Flexi-pyrolysis units are being developed that can be set for either char yield or gasification yield. Dry biomass can be pyrolyzed at regular atmospheric pressure. For wet biomass, pyrolysis at higher pressure ("supercritical") may be necessary, requiring a more sophisticated technical set-up.

When large chunks of wood are used as feedstock, the charcoal may need to be crushed before use (beware: coal dust explosion !). Many agrigultural feedstocks and leaf litter will not need to be pulverized but will readily break into smaller pieces by themselves. For information on small-scale gardening, please consult the Gardening with Biochar FAQ, an excellent resource.

[edit] Criticism

Critics are worried that large-scale biochar production may increase deforestation. However, a variety of biomass feedstocks other than wood can be used (see above). Old-growth forest is likely not a good feedstock because of extensive pre-processing that would be required.

[edit] Links

Wikipedia page on Biochar [1]

Gardening with Biochar FAQ [2]

BioEnergy Lists: Terra Preta (Biochar) [3]

International Biochar Initiative (IBI) [4]

Biochar Fund [5]

Folke Günther's "the simplest of the simple" two-barrel charcoal retort

Please add this page to one or more categories. See Appropedia:Categorization for more information on categories.