Terra Preta:Ancient soil for a sustainable

future

Jacob KelseyMaster’s candidate

Gund Institute for Ecological EconomicsRubenstein School for Environment & Natural

Resources, University of Vermont

• Terra Preta (“dark earth” in Portuguese) refers

to the very dark, fertile soils found throughout

the Amazon River basin.

• Also known as Amazonian Dark Earth

• Made by humans as far back as 7,000 years

ago

• Characterized by the amendment of charcoal,

or “biochar” to natural soil

• Extremely high in nutrients…3x N and P

content of surrounding soils

• Plot sizes range from 1 acre to 900 acre, for a

total size estimated equel area to France!!

• Biochar is charcoal produced from biomass through the process of pyrolysis

• Pyrolysis uses relatively low temps (~400 degrees C) in Oxygen deprived environment

• Maintains high levels of C from biomass (50% released to atmosphere instead of 97% when burned)

• Ranging levels of techological production methods

3 (4?) main benefits of biochar:

• Carbon sequestration

• Increased yields

• Re-newable energy production

• Water Filtration

Carbon Sink

• I ha, 1m deep biochar enriched soil sequesters 250 tons C/year

• Normal soils, on average, sequester 100 tons

C/ha/year• This difference of 150 tons C/ha/year is more

than carbon stored in mature tropcial hardwood forest.

• Meaning that biochar engineered soils, alone, can store more carbon than growing forest on the same land

• Combining the two is VERY promising

Increased Yields

• 200% increases in yield, compared to soil w/o biochar

• Yields as high as 800% have been recorded• Better retention of nutrients means less need for

chemical or organic fertilization

Peak P!!• Peak P• World’s phosphorus

production estimated to peak around 2035

• Finite resource• Price of P has risen 700% in

last 2 years

• 1,000 year old biochar found with 3x phosphorus content of surrounding soils

Slash and char vs. Slash and burn

• Slash and burn releases 84% C to atmosphere--remaining 14% released from soil within 5-10 years

• Slash and char releases 50% C to atmosphere, other half remains in soil for….1000s of years!

• Slash and char soil maintains fertility and productivity for MUCH longer

• Native Americans of central Amazon are still farming Tera pretta sites created by the slash and char method!

One more possibility…

• Steel slag for phosphorus removal• Can biochar replace slag as a way to

uptake phosphorus which could easily be recycled to the soil??

Thank You!