“Biochar,” a bit of myth busting Lukas Van Zwieten Principal Research Scientist Adjunct Professor, Rural Climate Solutions University of New England and Tony Walker Richmond Landcare

What is biochar and how is it made?

Biochar and Terra Preta Downie, AE., Van Zwieten, L., Smernik RJ., Morris, S., Munroe, PR (2011) Terra Preta Australis: Reassessing the carbon storage capacity of temperate soils. Agriculture Ecosystems Environment 140, 137-147.

Pyrolysis is an engineering term “energy and biochar can be produced” High efficiencies are gained through the recyclying of heat and all emissions. Biomass goes into the drier before the pyrolysis kiln. Typically the kiln will operate at 550 degrees cencius, and the biomass residence time is up to an hour- it is a full continual process. Syn gas which is made up primarily of hydrogen, methane and carbon monoxide is collected and purified, before it is used to heat the kiln, with surplus gas going to the electrical generator.

Why pyrolyse biomass Biosecurity Odour Concentration of C and nutrients Transport costs Beneficial agricultural reuse Renewable energy

Biochar is carbon that is going to last for hundreds of years Diagram source: Lehmann et al., 2006, Mitigation and Adaptation Strategies for Global Change

Agronomic trials Over 350 plots being managed as part of the Richmond Landcare collaborative project Key soil constraints on ferrosols Declining C Immobilisation of P Low pH High Al saturation Low CEC

Biochar “can” significantly improve soil fertility and crop production 1900mm 1200mm Control corn (13t cob/ha) Poultry litter biochar, 50t/Ha (35t cob/ha)

Long-term field sites testing biochar

Trials in a macadamia orchard 45 trees used testing poultry litter char and greenwaste char (@10t/ha- 40kg per tree) 2 years on

Trials in coffee 2 years on 3.3kg per tree, 30 trees per block, 4 treatments, 4 replicates, testing poultry biochar and rice husk biochar

Sections of x-ray computed tomography scans of a vertosol soil, packed into tubes of ~ 30 mm, at a resolution of 70 µm 3D imaging and calculation of pore space and connectivity currently being undertaken. control 1% biochar 5% biochar P Quin (PhD student) and I Young

Summary of effects of some biochars in some soils Properties of biochar Soil and crop outcomes Nutrients Stable C content Liming effect Reactive surfaces and redox CEC and AEC Porosity/ water holding capacity and bulk density Porosity / microbial habitat Smoke chemicals? Increases in nutrient use efficiency allowing reduced fertiliser inputs Improved water use efficiency Reduced leaching and gaseous losses of fertiliser Reduced denitrification Lowered Al toxicity Reduced heavy metal bioavailability Increased P availability on P sorbing soils Improved mycorrhizae and biological N2 fixation Long-term accumulation of soil C

Myth Busting Not all biochars will be valuable Biochars may not be beneficial in all soil types Value of the crop will limit application of biochar- and bottom line Biochar certification is coming

More myth busting Understand biochar characteristics to ameliorate soil constraints Farming system impacts the way biochar works: Possible C accumulation under permanent pasture, but tillage and biomass removal under cropping can still result in a decline in C Biochar can particularly target chemical constraints in ferrosols including low pH, high Al availability and low P availability Biochars with high mineral ash component are more effective at improving crop production Biochars with high C content are more effective at accumulating additional C in soil