1. DAVID CLAY BY A NON EXPERT
BIOCHAR PRIMER
DAVID CLAY
BY A NON EXPERT

2. Ethanol vs Biochar Biochar vs ethanol
Biochar produces a variety of products
Oil, gas, tar, heat, CO2
Stable carbon
Ethanol
CO2, high quality feed, ethanol

3. Biochar There may be a place for biochar
Switching from slash and burn to slash and char techniques in Brazil can decrease both deforestation of the Amazon and carbon dioxide emission, as well as increase the crop yield.
Under the current method of slash and burn, only 3% of the carbon from the organic material is left in the soil.
With biochar we may increase this to 20 to 50%.

4. Biochar If the products we need are not high quality feed and ethanol
This technology can be very low tech.

5. Biochar
The lower the temperature, the more char is created per unit biomass.[60] High temperature pyrolysis is also known as gasification, and produces primarily syngas from the biomass.[61]
The two main methods of pyrolysis are
“fast” pyrolysis , which yields 60% bio-oil, 20% biochar, and 20% syngas, and can be done in seconds
“slow” pyrolysis can be optimized to produce substantially more char (~50%), but takes on the order of hours to complete

6. Precision farming
Biochar is relatively stable that can be used to increase the soil organic contents of eroded areas.
The half live of biochar ranges fro 100 to 200 years, while the half life of fresh organic plant material.
Adding these materials may make a longer term impact on the soil productivity.

8. Outline What is Biochar? How is it Made? What are its Properties?
Pyrolysis and Hydrothermal Carbonization Processes
Feedstocks
Yields
What are its Properties?
Physical
Chemical
How can it be Used?
Energy
Soil Fertility
Carbon Sequestration
Where does it fit in the Environmental Technology Landscape?
Summary

9. What is Biochar?
“Biochar is a fine-grained charcoal high in organic carbon and largely resistant to decomposition. It is produced from pyrolysis of plant and waste feedstocks. As a soil amendment, biochar creates a recalcitrant soil carbon pool that is carbon-negative, serving as a net withdrawal of atmospheric carbon dioxide stored in highly recalcitrant soil carbon stocks. The enhanced nutrient retention capacity of biochar-amended soil not only reduces the total fertilizer requirements, but also the climate and environmental impact of croplands.”
(International Biochar Initiative Scientific Advisory Committee)

10. What is Biochar? Product Technology
Solid product resulting from advanced thermal degradation of biomass
Technology
Biofuel—process heat, bio-oil, and gases (steam, volatile HCs)
Soil Amendment—sorbent for cations and organics, liming agent, inoculation carrier
Climate Change Mitigation—highly recalcitrant pool for C, avoidance of N2O and CH4 emissions, carbon negative energy, increased net primary productivity (NPP)

11. How is Biochar Made? Major Techniques: Slow Pyrolysis Flash Pyrolysis
traditional (dirty, low char yields) and modern (clean, high char yields)
Flash Pyrolysis
modern, high pressure, higher char yields
Fast Pyrolysis
modern, maximizes bio-oil production, low char yields
Hydrothermal Carbonization
under development, wet feedstock, high pressure, highest “char” yield but quite different

12. Fast Pyrolysis Fluidized Bed Reactor

13. Pacific Pyrolysis Slow Pyrolysis Simplified
Process Flow Diagram

14. Pyrolysis Competition between three processes as biomass is heated:
Biochar and gas formation
Liquid and tar formation
Gasification and carbonization
Relative rates for these processes depend on:
Highest treatment temperature (HTT)
Heating rate
Volatile removal rate
Feedstock residence time

15. Competition Among Pyrolysis Processes
Factors favoring biochar formation:
Lower temperature
Slower heating rates
Slower volatilization rates
Longer feedstock residence times
In general, process is more important than feedstock in determining products of pyrolysis

17. Feedstocks
Essentially all forms of biomass can be converted to biochar
Preferable forms include: forest thinnings, crop residues (e.g., corn
stover, alfalfa stems, grain husks), yard waste, paper sludge,
manures, bone meal
Trace element (Si, K, Ca, P) and lignin contents vary
Lignin content can affect char yields

18. What are the Properties of Biochar?
Pine Wood Char
Corn Stover Char
Corn Cob Char

19. Physical Properties Change with HTT

20. Physical Structure and Chemical Properties Depend on Carbon Bonding Network
13C CP-MAS NMR
Amonette et al., 2008

21. Chemical Properties
Slow Pyrolysis chars produced in presence of steam tend to be acidic (carboxylic acid groups activated)
Fast Pyrolysis chars produced in absence of steam tend to be very basic and make good liming agents

22. How can Biochar Technology be Used?
Generate Carbon-Negative Energy
Soil Amendment
Carbon Sequestration

23. Comparison of Biochar Production Methods

24. The Biofuel N2O Problem
Recent work (Crutzen et al., 2007, Atmos.Chem. Phys. Disc. 7:11191; Del Grosso, 2008, Eos 89:529) suggests that globally, N2O production averages at 4% (+/- 1%) of N that is fixed
IPCC reports have accounted only for field measurements of N2O emitted, which show values close to 1%, but ignore other indicators discussed by Crutzen et al.
If 4% is correct, then combustion of biofuels except for high cellulose (low-N) fuels will actually increase global warming relative to petroleum due to large global warming potential of N2O
Biochar avoids this issue
Ties up reactive N in a stable pool
Eliminates potential N2O emissions from manures and other biomass sources converted to biochar
Decreases N2O emissions in field by improving N-fertilizer use efficiency and increasing air-filled porosity

25. Carbon Sequestration Why? How? Decrease atmospheric GHG levels
Stop acidification of oceans by CO2 absorption
We only have one Earth
How?
Create stable C pool using biochar
Use energy to offset fossil-C emissions
Avoid emissions of N2O and CH4
Increase net primary productivity (NPP)

26. Creating a Stable Carbon Pool with Biochar

27. Carbon Sequestration using Biochar
Slow pyrolysis biochars are highly recalcitrant in soils with half-lives of years
Sensitivity analysis suggests that half lives of 80 years or more are sufficient to provide a credible C sink
Recent evidence using 14C-labeled biochar shows no evidence for enhanced rates of soil humic carbon degradation in agricultural soils (Kuzyakov et al., 2009)
No evidence for polyaromatic hydrocarbon (PAH) contamination has been seen
Down-side risks seem very small

28. Soil Amendment
Biochar typically increases cation exchange capacity, and hence retention of NH4+, K+, Ca2+, Mg2+
N from original biomass, however, may not be readily available
P, on the other hand, is generally retained and available
Liming agent
Enhanced sorption of organics (herbicides, pesticides, enzymes)
(Good? Bad?)
Some evidence for increased mycorrhizal populations, rhizobial infection rates
Used as carrier for microbially-based environmental remediation
Lowers bulk density

29. Low temperature (550 C)
High temperature
(650 C)
Increasing time

30. Low temperature (550 C)
High temperature
(650 C)
Increasing time

31. Switchgrass biochar pH
Processing temperature

32. *
Atrazine sorption by soil

34. Atrazine
Atrazine sorption is known to increase at when soil pH is either low (<5) or high (>8)
The increased sorption (Kd) when biochar is present implies
Increased herbicide rates to get consistent weed control
Longer residence time at high pH (due to unavailability to soil microbes)
Shorter residence time at low pH (due to chemical hydroxylation)
Changed leaching potential

35. *
Kd 2,4-D to soil = 1.0

36. 2,4-D
2,4-D is not a soil applied herbicide, however, small sorption coefficients to soil due to it’s negative charge give a model compound as comparison
2,4-D sorption also increased when specific biochar types were added
Less leaching by the negative compounds
Longer residence time

37. Where does Biochar Fit?
Offers a flexible blend of biofuel energy, soil fertility enhancement, and climate change mitigation
Limited by biomass availability and, eventually, land disposal area
How much biomass can be made available for biochar production vs.
other uses?
Crop-derived biofuels cannot supply all the world’s energy needs
Maximum estimates suggest 50% of current, 33% of future
Biodiversity (HANPP)?
N2O?
Perhaps best use of harvested biomass is to make biochar to draw down atmospheric C levels and enhance soil productivity, with energy production as a bonus (but not the driving force).
This will require government incentives (C credits?) and a change in the way we value cropped biofuels