What is biochar?
- Biochar is charcoal made by heating biomass.
- It is distinguished by definition from charcoal for which the source material may be, for example, petroleum products.
- Biochar is around 55%-85% carbon by weight, and usually also contains the inorganic materials such as phosphates, calcium, and trace elements (collectively known as ash) that were in the original biomass.
- It is highly resistant to chemical degradation, hence it persists in soils and sediments for hundreds to tens of thousands of years.
- u Biochar IS sequestered carbon, effectively unavailable to the atmosphere.
Why is it so?
- Biochar has been made by nature for millions of years, as long as there have been fires in forests and grasslands.
- Its formation is one of nature’s ways of regulating global carbon cycles.
- The natural biomass burning cycle is an important shaper of our terrestrial environment and significantly influences global carbon balances.
Where does it come from?
- Carbon pathways in the biomass burning cycle – study the diagram
- When biomass (such as leaf litter) is heated (perhaps by a lightning strike) chemical reactions set in, which decompose it partly to charcoal and partly to hot volatile organic compounds.
- At each fire event, SOME of the carbon in the biomass – from a few % to 50% – is sequestered as biochar and SOME is put back into the atmosphere as CO2.
- Photosynthesis captures atmospheric CO2 into the biomass. . . and the cycle begins again.
Where does it go?
Residence times of carbon in burning cycle reservoirs:
| biomass | ~1-100 years |
| volatile products of thermal decomposition | 0 years |
| atmosphere | ~3-200 years |
| biochar | thousands of years |
These facts alone tell us that biochar is a significant natural carbon storehouse, or sink.
The story so far
- So – nature makes biochar during vegetation fires.
- We can also manufacture biochar by adapting and optimising this natural process.
- Typically, charcoal is made by heating wood or other biomass in pits or kilns and excluding the air so that the char does not burn and the amount of charcoal product is maximised at the expense of volatile products.
- For hundreds of years charcoal has been produced this way, and until the mining and use of fossil coal became widespread in the nineteenth century it was the only fuel available for reducing metals from their ores
What is the CharXive Challenge?
First – the gurus:
So are we doomed?
There is one way we could save ourselves and that is through. . . farmers turning all their agricultural waste. . . into charcoal. Then you can start shifting really hefty quantities of carbon out of the system and pull the CO2 down quite fast.
Would it make enough of a difference?
Yes. The biosphere pumps out 550 Gt of carbon yearly; we put in only 30 Gt. Of the carbon fixed by plants 99% is released back into the atmosphere within a year by consumers like bacteria and nematodes. We can cheat those consumers by getting farmers to turn their crop waste into charcoal. . . This is THE one thing that will make a difference. . .
New Scientist interview with Prof. James Lovelock, originator of the Baia theory.
Another guru:
Biochar may represent the single most important initiative for humanity’s environmental future. . . [yet] our debates about climate change continue in ignorance of it, while industries that could benefit immensely have barely considered it. . . Diverse and clean energy supplies, more food per unit of input, and climate security. In simple terms, this is what the biochar revolution offers us.
Prof. Tim Flannery, scientist, explorer, 2007 Australian of the Year, and author of The Weather Makers.
The CharXive challenge
- The term “charCive” was coined as a succinct description of the concepts and process of sequestering atmospheric carbon in the global reservoir of black carbon.
- You pronounce it as “tcharckive”. The character C is the Greek letter “Chi” not an “X”.
(The visual effect will have potentially broad appeal and strong impact in future logo and web and print graphics.)
- As a mnemonic term “charCive” is expressive of long timescales – carbon is archived, i.e., safely stored for the long term – A whimsical word-play (cha cha, jive) also suggests the importance of periodic action on shorter timescales. Indeed charCiving is a pretty lively process, as it involves the reactive thermochemical oscillations that produce biochar and volatiles.
- Can we safely and sustainably produce and distribute enough biochar – over and above that produced by nature, and without burning fossil fuels or otherwise adding to environmental problems – to significantly lower atmospheric CO2 levels in a time frame compatible with human responses to climate change?
- In broad terms, charCiving involves increasing the global biochar pool at the expense of the atmospheric carbon pool, given that the only way into the biochar pool is through thermoconversion of biomass.
- Speculation: Products and processes in future may be charCive-rated or certified – e.g. a computer or a car might be rated on the fraction of its components that are charCive-able, and an office might earn a three-C rating if it has systems for charCiving its paper waste (and its coffee grounds!).
What should we do with all the biochar that is produced?
- For centuries it has been known to folk wisdom that the most fertile soils are those containing a high proportion of charcoal or black carbon.
- Now scientists are studying the fertility of such soils seriously and in detail.
- The results are consistently impressive – plantings in soils that have added biochar significantly outperform those in control plots.
- Furthermore, a single amendment with biochar may increase yields for decades.
- Biochar amended soils emit less nitrous oxide and methane – both very potent greenhouse gases- than control soils.
What is the catch? Why aren’t everyone and their dog jumping on the biochar bandwagon?
They are – now. In 2009 we are seeing see an explosion in biochar R&D as people recognise that biochar is one of our most valuable commodities in terms of –
- responding to the inevitability of climate change by adapting our land use and management practices,
- sequestering surplus CO2 that is already, and will continue to be, dispersed in the atmosphere, and
- reducing our dependence on fossil fuels.
Summary
- Biochar is a significant natural carbon storehouse.
- The CharCive Challenge involves increasing the global biochar pool at the expense of the atmospheric carbon pool, in a safe, sustainable manner.
- Scientists have shown that plantings in soils that have added biochar significantly outperform those in control plots.
- In 2009 we are at the dawn of a biochar revolution.
