ENV100 Lecture Notes Mar 9, 2012
Black: The New Green?
Guest Lecture: By: Carolyn Winsborough
1) What is Biochar
2) How is Biochar produced?
3) Environmental Benefits
• Soil Improvements
• Climate Change and Energy Production
• Food Security
4) My Research
WHAT IS BIOCHAR?
Terra preta do Indio-- ‘If you read the text books, it shouldn’t be here!”
• An anomaly in the Tropics
• Typically soil is:
o Red and yellow soil
o Highly weathered
o Low in organic matter
o Low in essential nutrients
What did they find:
• Thousands of burial urns and ceramic pieces (date back 2000 yrs – 7000yrs)
• Terra preta found on low hills overlooking rivers
• 70% more charcoal than adjacent soils
Why more charcoal???
• “Slash- and-Burn”: an agricultural practice where farmers clear their fields and burn the
biomass to flush enough nutrient into the soil
• “Slash and Char”: farmers burned biomass incompletely creating charcoal, and stirred
this into the soil then added nutrients (animal bones and excrement)
To test if charcoal was the culprit:
• A trial was performed on the “infertile” soils of the Amazon by adding various
treatments of charcoal and nutrients
• In two years, treatments of charcoal and fertilizer grew as much as 880% more than
plots with just fertilizer alone!
Basis For Strong Recent Interest:
• High amounts of charcoal substances explained the high carbon content and sustained
fertility of soil in the Amazon.
• Over last 5 years, research has demonstrated that charcoal is more stable than, and
retains more nutrients than any other organic matter in soil
What is Biochar?
• A fine-grained, porous charcoal high in organic carbon and resistant to decomposition
• Obtained when biomass is heated in a closed container with little or no oxygen at
relatively low temperatures (500 – 700oC)
• Similar to charcoal production, but differs in its intended use.
• Improvement of Soils
• Mitigation of Climate Change
• Energy Production
• Reduction of Environmental Pollution
• Food Security
Increased Nutrient Retention in Soils
• Cation Exchange Capacity (CEC):
o > surface area
o > surface
• Can strongly adsorb phosphate (PO43-) (not sure why)
o Keep this in mind!!!
• Nitrates and Phosphates, when leached to waterways can cause EUTROPHICATION
• Scrubbing Air Pollutants
• Reduces the need for Fertilizers
OTHER GREENHOUSE GASES:
• NITROUS OXIDE (N2O)
o 300 times more potent than CO2
o 50-80% reduction in emissions in greenhouse experiments
• METHANE (CH4)
o 21 times more potent than CO2
o Emissions completely suppressed in a grassland with biochar additions
Biomass Energy: derived from living or recently deceased organisms
Direct Combustion for Heating
-Wood cut from trees (fuel wood)
-Charcoal from charred wood
-Manure form farm animals
Biofuels for Powering Vehicles
-Corn grown for ethanol
-Bagasse (sugar cane residue) for ethanol
-Soybenas/rapeseed etc. For biodiesel
Biopower for generating electricity
-Crop residues (corn stalks) burned at power plants
Biomass energy brings PROS and CONS:
Carbon-neutral, releasing no net carbon into the atmosphere.
o But…Harvesting fuelwood can lead to deforestation and soil erosion if over
o Supports rural communities
o Reduces dependence on fossil fuel imports
But…We would need to expand acreage by 60% to achieve what we
achieve today (and Biofuel vsFood Production)
$$$$Million Dollar Question$$$$
Can biochar sequestration coupled with bioenergy production make a difference to the
national and global carbon budgets???
Johannes Lehmann of Cornell Univeristy calculates:
3 scenarios that could sequester 10% of US fossil fuel emissions:
Pyrolysis of forest residues (~3.5 tonnes per hectare/yr) from 200 million hectares of US
forest used for timber production)
Pyrolysis of fast-growing vegetation (20 tonnes of biomass per hectare per year grown
on 30 million hectares of idle US cropland)
Pyrolysis of crop residue (5.5 tonnes biomass per hectare per year from 120 million
hectares of harvested US cropland)
o If captured gases are used for biofuel, even more carbon can be sequestered!
FORESTS IN CANADA
• Canada contains 10% of the world’s forest area and is the largest exporter of forest