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Dr Lukas van Zwieten, a senior research scientist for the NSW Department of Primary Industries, brings a new twist to some old agricultural practices, one that provides benefits from carbon sequestration.
    
Pre-Columbian inhabitants, particularly those around the Amazon River, were very wise in their management of their agricultural systems. They knew thousands of years ago that if they put charcoaled material from their pottery kilns, ovens and kitchens into the soil, then the soil quality would improve. Even today those soils are highly sought after in the region. Scientists are now testing ways to reproduce this agricultural benefit and a new form of waste, called biochar, seems to be a great new technological triumph.

 
In NSW, Best Energies Australia is using a process of slow pyrolysis, an engineered version of what the pre-Columbians did. In the modern version, biomass from wood waste, forestry by-products, putrescible wastes, animal manure and other biosolids are placed into a large kiln and heated in the absence of oxygen to produce biochar, a heterogeneous mixture of carbon and minerals.

 
Since the carbon returned to the soil in this way is extremely stable, this is an environmentally positive way of sequestering carbon since it will endure for hundreds (and possibly thousands) of years. Another environmental benefit of the slow pyrolysis process is that it releases energy from the biomass in the form of gases not unlike town gas being com[posed of hydrogen, methane and carbon monoxide. These gases can be used, for instance, to run a gas fired turbine to produce electricity and or burnt to heat the kilns used in the pyrolysis process.

 

 
The potential of such systems is huge, with both agricultural and environmental outcomes at the top of the list. Different biochars have been produced and tested. Some have strong lime value, with minerals such as calcium, magnesium and calcium oxide. Others, like those based on green waste, increase the water-holding capacity of soils. Biochars made from poultry manure and sawdust have strong fertiliser values. Others have high phosphorus, potassium or nitrogen contents. Different biochars are being evaluated in field trials across NSW.  In the Tweed Valley trials involve a variety of crops and soil types as well as different biochars. Other sites include a commercial sugarcane property as well as other commercial crops such as macadamia nuts and avocados. Dr van Zwieten is looking to expand the trial to other areas, more particularly to canola in Wagga Wagga. The trials are supported by Richmond Land Care and the Northern Rivers Catchment Management Committee, with funds for the project coming through National Landcare.

 

 
 Biochars are international, with excellent work being done in the USA (particularly Hawaii) and South America. Indeed, biochars are seen as a potential solution to energy and poverty in developing countries. Not only do they improve the soil but they also reduce the need for land fill and supply energy that can be fed back into energy grids. In a boost to its reputation, the International Biochar Initiative is currently looking at having biochars accepted for carbon trading. Dr van Zwieten sees a network of small biochar facilities dotted around particular regions but that vision will depend on the economics of the process, something that potential investors need. For now though, this great breakthrough is massive in its potential.
If successful, we will truly reap what we sow.

Text: V.B. October 08

 

All photos from  Lukas van Zwieten
Top: A biocharb field site established at Wollongbar Agricultural Institute in 2006. 
Middle:
Sweet corn crop demonstrating benefits of biochar to biomass production and yield.
Bottom: Measuring the benefits of biochar in a pasture field trial on greenhouse gas emissions from soil.

    

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