discovering terra preta australis: rethinking temperate soils

Adriana Downie, Asia Pacific Biochar Conference 2009

Discovering Terra Preta Australis:

Rethinking temperate soils

capacity to sequester carbon

Adriana Downie, Lukas Van Zwieten, Ronald Smernik, Timothy Flannery,

Derek Barnstable, and Paul Munroe


If civilisation is to avoid

catastrophic climate change,

the sequestration of atmospheric greenhouse gases

into low risk sinks

via inexpensive and sustainable means should be a priority.


The Proposition

Addresses challenges of sequestration?

• Impermanence

• Urgency

• Costs

• Side-effects

BioChar: a Low Risk Sink which can

add value


Amazonian Dark Earth: Terra-Preta• Case for investigating

side effects

• Demonstrates carbon

holding capacity

• 500-2500 years old

• Amazon - Extreme environment for fast

organics turnover

• Evidence of long-term productivity benefits


Australian Context

Geographical Differences:

• Climate

• Land Management Practices

• Soil Types

What is the capacity of Australian soils to sequester carbon?

The potential for soils to sequester carbon is often assumed to be to the capacity of native,

pre-cultivation soils. (Lal et al. 2007; Paustian et al. 1997)


In search of Terra preta Australis…..


How?

When?


Operation of an Australian Aboriginal

Cooking Oven

Source: Coutts PJF, Henderson P & Fullagar RLK (1979) A Preliminary Investigation of Aboriginal Mounds in North-Western Victoria. Records of the Victorian Archaeological Survey 9: 1-116


Radiocarbon Dating

Terra Preta Australis, 14C

measurement by accelerated

mass spectrometry (AMS) :

• 650 ± 30 years BP

high clay, agricultural grazing field

site

• 1609 ± 34 years BP

sandy site on the border of a

heavily timbered area in close

proximity to the river

Australian oven mound sites

surveyed in the 1970s, further north-

west along the Murray river were

radiocarbon dated to between

600 to 3500 years BP

Coutts PJF & Witter DC (1977) New radiocarbon dates

for Victorian Archaeological sites. Records of the

Victorian Archaeological Survey 4: 59-73

Contemporary with Terra Preta de Indio soils of the Amazon basin.


Solid-state 13C CP NMR spectra

Contributed by Dr. Ron Smernik, University of Adelaide


Biochar from Terra Preta Australis


A B


In comparison to their adjacent sites, the Terra Preta

Australis sites had higher :

•pH,

• cation exchange capacity,

• organic and total carbon,

• total nitrogen,

• calcium,

• potassium and

• phosphorous.


Organic carbon in the top 30cm compared with adjacent soil, a range of results across the sites analysed:

TPA1 - 3.2% increase

TPA2 - 0.46% increase

Increases in organic carbon of more than 4% were measured in soil profiles of several sites.

The upper limit of beneficial biochar incorporation is therefore considered to be in excess of this value for the temperate climate soils examined.


Potential

Applied to Australia’s 42 million hectares of cropped soils (DEWHA, 2007), 4% in the top 30cm represents 7.5 Gt of solid C or 27 Gt of CO2-e sequestered.

Cropped Land already has the vast infrastructure for soil amendment management. Product transport etc.


Meeting Emissions Targets

Australia’s net greenhouse gas emissions across all sectors totaled 576 Mt CO2-e in 2006 (DCC, 2008).

27 Gt represents 48 years of Australian emissions at this level.

(co-production of bioenergy would extend this)


Therefore:

• Not limited by Australia's, old, temperate climate soils capacity to beneficially hold biochar

• Limited by sustainable biomass supply

• Limited by ability to roll out technology.


Acknowledgements

Australian Research Council

BEST Energies Australia Pty Ltd

NSW Department of Primary Industry

The Yorta Yorta people as the Aboriginal

Traditional Owners of the areas studied.

discovering terra preta australis: rethinking temperate soils

Documents