Bio-char: a Carbon Negative Way to Improve our Food Supply

  • Published on February 22nd, 2009

charcoal burningBio-char is a finely-grained charcoal-like substance made from plant waste. It is highly resistant to decomposition and produced via the carbon neutral process of pyrolysis  or carbonisation, which is the ancient technique used to produce charcoal – the modern version heats organic waste airtight metal vessel to reduce pollution and condense volatile by-products like gases which would otherwise escape into the atmosphere, and the bio-energy produced can be converted to electricity, as well as producing and conserving ethanol and methanol.

Overall, the bio-char process is carbon negative because it produces both bio-energy (in the form of usable gases) and a form of fertiliser that stores the carbon produced by agricultural waste – which means there is a reduction of carbon dioxide (CO2) in the atmosphere.

Because bio-char is both stable and inert, it can store the carbon it sequesters for centuries – and as the char improves soil fertility by adding valuable trace elements, improving drainage and amending and improving exhausted soils.  Terra Prata soils, which are found on highly fertile islands in the Amazon Basin, were created naturally, through a unique combination of climatic and environmental conditions, but bio-char aims to use the same process on a speeded up and industrial scale to create highly fertile and long-lasting soil additives that can improve crop yield and end the reliance on high-input and imported fertilisers and soil amenders.

At present, there is an American research programme that makes grants to bio-char initiatives and both Australia and New Zealand have bio-char initiatives listed in their climate change action plans, but there are no large-scale bio-char projects being run on an international basis. Since the bio-fuels initiative had its rocky start, with high hopes being somewhat dashed by evidence that the diversion of grains and oils from traditional uses to creating bio-fuel has worsened poverty and damaged environments in some areas, bio-char pioneers are revisiting their projections to ensure that the development of bio-char programmes won’t cause inadvertent harm to other environmental projects.

One problem with all these projects is that they tend to be ‘silo’ programmes, with dedicated experts who have spent many years working on a specific environmental programme but with little or no interdisciplinary relationship with other programmes that are often considering use of the same resource material for differing aims. This can mean that projects that become viable at similar times discover that they are competing not only for the same funding, but also for the same source material – leading to the kinds of environmental conflicts that have been seen around bio-fuels in the last twelve months.

Image: sarahemcc at Flickr under a creative commons licence

About the Author


  • Soil Carbon Commandments:

    1) Thou shalt not have any other Molecule before Me

    2) Thou shall not make wrongful use of the name of Biochar, It will not acquit anyone who mis-charactorizes it's name

    3) Observe the Fallow days and keep them, as Sustainability commands thou

    4) Honor your Micro Flora & Fauna , as the Soil Carbon commands you, so that your days may be long and that it may go well with you in the land that High Soil Carbon has given you.

    5) Thou shall not murder the Soil Food Web

    6) Neither shall thou adulterate the Soils with Toxicity

    7) Neither shall thou steal Biomass from the Soil Food Web

    8) Neither shall thou bear false witness against your neighbors Biochar, or about Thy own

    9) Neither shall thou covet your neighbor's Fertility

    10) Neither shall thou desire your neighbor's house, or field, or Pyrolysis Reactor, or farm implements, or anything that belongs to your neighbor, as thou may Create thy Own

    Soil Carbon Dream

    I have a dream that one day we live in a nation where progress will not be judged by the production yields of our fields, but by the color of their soils and by the Carbon content of their character.

    I have a dream today.

    I have a dream that one day, a suite of earth sensing satellites will level the playing field, giving every farmer a full account of carbon he sequesters. That Soil Carbon is given as the final arbiter, the common currency, accountant and Judge of Stewardship on our lands.

    I have a dream today.

    I have a dream that one day every valley shall be exalted, every hill and mountain shall be made forest, the rough soils will be made fertile, and the crooked Carbon Marketeers will be made straight, and the glory of Soil Sequestration shall be revealed, and all flesh shall see a Mutually assured Sustainability.

    This is our hope.

    My apologies to Dr. King, but I think he would understand my passion


  • HI, I live in Darwin Australia which is in the southern hemispheres sub-tropical zone. The soils here are very impoverished due to heavy wet season rain fall. In urban areas we produce huge amounts of green waste, mainly due to a 1980s trend to plant exiotic and local palm trees on every block. This waste is currenlty put into land fill or turned into partially composted mulch and sold back to house holders for 20-30 aussie dollars per cubic metre. It is very popular and would probably be suitable to create Bio-char.Problem is there is very little will in Australia to really do anything and we have a three tiered government system which is fairly disfunctionnal … heres praying that our children maybe more enlighted then us and some countries may have the will to take real action on climate change..

  • The problem with biochar is that plant biomass contains little carbon. Most plants are 50% or more water and only 25% carbon. Think of a forest as holding about 100 tonnes of carbon per hectare (2.5 acres). A hay feld contains about 1 tonne of carbon per hectare. So if one wants to store CO2e as biochar one has to burn one hectare of hay to obtain one ton of carbon or 3.6 tonnes CO2e. Of course the efficiency of burning plants to biochar is not 100% efficient but perhaps under ideal circumstances 50% efficient. So when making biochar one emits as much CO2 in making it as one stores. Big burning piles of plant biomass like that pictured in the story offer no help for the climate but perhaps help the soil.

  • The problem with land-fill cellulose is the separation costs, which make it prohibitive if mixed rubbish collection is used (called comingling) but there is no essential additional waste cost to crop usage in most parts of the world.

    Essentially the system would be self-sufficient, as organic farms are supposed to be, with each farm or agricultural collective using its own pyrolisis unit to produce bio-char. The capital cost is about equivalent to producing silage in the UK. Silage is a high-moisture fodder that can be fed to ruminants and is similar to the balage systems used in the USA.

    We don’t have any reliable figures on sequestration yet, because the first research projects haven’t finished measuring the bio-char breakdown in various circumstances.

  • I loved this article. Of course it didn't have the important details like cost and global impact if all crop waste and land fill cellulose could be used to provide energy and carbon for farming.

    How much carbon would be stored?

    But the combination of pyrolisis and carbon storage is fantastic!

  • The Terra Preta Prayer

    Our Carbon who art in heaven,

    Hallowed be thy name

    By kingdom come, thy will be done, IN the Earth to make it Heaven.

    It will give us each day our daily bread and forgive us our atmospheric trespasses

    As we forgive those who trespass against soil carbon in the Kyoto protocols

    And lead us not into fossil fuel temptation, but diliver us from it's evil

    low as we walk through the valley of the shadow of Global Warming,

    I will feel no evil, your Bio-fuels and fertile microbes will comfort me,

    For thine is the fungal kingdom,

    and the microbe power,

    and the Sequestration Glory,

    For ever and ever (well at least 2000 years)


Comments are closed.