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BioChar - AgriChar -

BioChar (sometimes called AgriChar) is short for Bio-Charcoal and refers to processes that take the carbon that is captured by living plants and turns the biomass into the solid form of charcoal. Such processes appear to offer one of the most promising technologies for carbon capture and sequestration (storing it permanently away).

Although plants are nature's primary way of absorbing carbon dioxide from the atmosphere, they only store the carbon temporarily. When the plant dies and decomposes, the carbon is released back into the atmosphere. Or if the plant is burnt, the carbon is immediately released. BioChar processes take the waste material from food crops, forest debris, and other plant material, and turn it into a stable form that can be buried away permanently as charcoal. In other words, they turn it back into coal.

The processes involved also produce energy as a by-product, creating an alternative energy source, which reduces the need for further fossil fuel burning. Moreover, some of the processes under development use the carbon to create a fertiliser that is ploughed back into the land, promoting the growth of further crops.

Details of the BioChar Process

A typical process starts with the plant material undergoing pyrolysis. It is heated in a closed chamber, in the absence of oxygen, breaking down the complex organic molecules into simpler compounds that are released as gases. This is what charcoal makers have done for centuries; but they allowed the gases to escape. With BioChar, the gases are drawn off and put to use. A small proportion of the gases released are used to drive the pyrolysis process.

(The same process occurs with a wood fire. The wood itself does not burn, but as it heats up, inflammable gases are driven off and it is these that burn, further heating the wood, and driving off more gas. This understanding lies behind the building of a good fire. See: The Art of Fire.)

Under the right conditions, the pyrolysis produces hydrogen, which can be used in fuel cells, or used to create ethanol and biodiesel, two valuable alternative fuels. To get an idea of the energy potential of such processes, if (and it is a big "if") the waste from all world's agricultural processes were used in BioChar processes, the alternative fuels produced would be equivalent to the world's total consumption of diesel oil.

Some of the hydrogen is also fed into the Haber-Bosch Process which combines hydrogen with nitrogen from the atmosphere to produce ammonia. The ammonia is then combined with carbon dioxide (from flue gases or from the atmosphere) to produce ammonium bicarbonate, a widely used low-tech fertilizer, which is absorbed into the charcoal. (Note this capture of carbon dioxide is in addition to that already achieved by the plants). The activated charcoal is a good host for beneficial microbes such as mycorrhizal fungi adding to the nutritional value.

Three big advantages of BioChar processes are:

1. They mimic the natural carbon cycle.
2. They are local. They work best on farms or forest areas where the waste plant material is gathered locally, the energy produced is used locally, and carbon fertilizer created can be returned to promote the growth of local crops.
2. The technologies involved are all old-tech, and would be familiar to any chemist or engineer in the early 1900s. They are tried and tested, small-scale, and cheap to manufacture.

If (again that big "if") the process were used on all the world's agricultural waste, the total carbon absorbed and buried away safely as charcoal would equal our current global carbon emissions.

More information:
Eprida - a company developing this technology. Good flash presentation on basic process.
Best Energies - another company active in this field.
The BioChar Page

Research projects: Cornell University, the University of Georgia, and Iowa State University.

Recent articles on BioChar appeared in Nature, Scientific American, and Science Daily

See Also: Carbon Sequestration | Runaway Climate Change


Deep, rich, black soil is a farmers dream come true. Healthy soil is full of life, with entire communities living just below our feet. Healthy soil can retain and purify water, provide an abundance of food, and even act as way to sequester carbon dioxide. One key to getting there is amending soil with biochar. Biochar is what you get when biomass is heated in the absence of oxygen through a process called pyrolysis. When incorporated into soil, biochar provides the structural habitat needed for a rich community of micro-organisms to take hold. Incorporating biochar into soil can also act as a way to sequester carbon.

Carbon dioxide sequestration was not likely the original goal of biochar, or terra preta, developed thousands of years ago by the Native Americans in the Amazon region. But today, as we recognize the cost of emitting green house gases, we also recognize the wisdom of using biochar as micro-habitat to improve our soils. Biochar is a classic win-win scenario, a solution that can provide us with a valuable tool for fighting climate change, world hunger, poverty, and energy shortages all at the same time.

Most policy and much research concerning the application of biomass to reduce global warming gas emissions has concentrated either on increasing the Earth's reservoir of biomass or on substituting biomass for fossil fuels, with or without CO2 sequestration.

Suggested approaches entail varied risks of impermanence, delay, high costs, and unknowable side-effects. An under-researched alternative approach is to extract from biomass black (elemental) carbon, which can be permanently sequestered as mineral geomass and may be relatively advantageous in terms of those risks. This paper reviews salient features of black carbon sequestration and uses a high-level quantitative model to compare the approach with the alternative use of biomass to displace fossil fuels.

Black carbon has been demonstrated to produce significant benefits when sequestered in agricultural soil, apparently without bad side-effects. Black carbon sequestration appears to be more efficient in general than energy generation, in terms of atmospheric carbon saved per unit of biomass; an exception is where biomass can efficiently displace coal-fired generation. Black carbon sequestration can reasonably be expected to be relatively quick and cheap to apply due to its short value chain and known technology. However, the model is sensitive to several input variables, whose values depend heavily on local conditions. Because characteristics of black carbon sequestration are only known from limited geographical contexts, its worldwide potential will not be known without multiple streams of research, replicated in other contexts.

biomass "cooked" by pyrolysis.

BioChar Explained

It produces gas for energy generation, and charcoal - a stable form of carbon.

The charcoal is then buried in the ground, making the process "carbon negative".

Researchers say biochar can also improve farm productivity and cut demand for carbon-intensive fertilisers.

Burying the biochar can also improve soil fertility, say experts.

Field trials are about to begin at Rothamsted, south-east England, to assess the benefits to soil structure and water retention.

Experiments in Australia, US and Germany are already showing some remarkable results - especially on otherwise poor soils where the honeycomb granules of biochar act as a reservoir for moisture and fertilisers.

The buried carbon will be kept from entering the atmosphere for a projected 1,000 years or more.

The porous biochar attracts worms. It also captures nutrients that would otherwise run off the land, which reduces the need for carbon-intensive fertilisers.

^New Zealand start-up Carbonscape is using industrial-scale microwaves to turn biomass into biochar.






Welcome to the International Biochar Initiative.  IBI is a registered non-profit organization supporting researchers, commercial entities, policy makers, development agents, farmers and gardeners, and others committed to supporting sustainable biochar production and utilization systems that remove carbon from the atmosphere and enhance the earth’s soils. It advocates biochar as a strategy to:

  • improve the Earth’s soils;
  • help mitigate the anthropogenic greenhouse effect by reducing greenhouse gas emissions and sequestering atmospheric carbon in a stable soil carbon pool; and
  • improve water quality by retaining agrochemicals. 
The IBI also promotes:
  • sustainable co-production of clean energy and other bio-based products as part of the biochar process;
  • efficient biomass utilization in developing country agriculture; and
  • cost-effective utilization of urban, agricultural and forest co products. 

Organic matter, such as agricultural waste, heated in the absence of oxygen splits into two types of material: a charcoal (biochar), and hydrocarbon gases and liquids. When added to soils, the charcoal can provide a powerful fertiliser. The hydrocarbons can be burnt, either to generate electricity or to power an internal combustion engine.

Biochar is exciting growing attention around the world. Charcoal’s ability to improve soils can sometimes be spectacular. But more importantly from a climate change perspective, charcoal is almost pure carbon and is strangely stable in soils. It seems to persist for centuries. Charcoal can therefore offer substantial opportunities for long-term sequestration of carbon. The valuable fuels from the biogases and liquids are also carbon-neutral since they contain CO2 previously captured during photosynthesis. As a third major benefit, soils fertilised with charcoal seem to need less artificial fertiliser, thus saving fossil fuels. Fewer applications of fertiliser would reduce the level of emissions of nitrous oxide, a particularly dangerous greenhouse gas.

Several biochar stoves have been developed for use in developing countries. Belize and a number of African governments are attempting to get biochar accepted as a climate change mitigation and adaptation technology for the post-2012 treaty.


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Last modified: 06/20/08