ChE 6405, Water Pollution & Control Maskur Nakib Asif, Abdullah Al Moinee Course Teacher: Dr. Md. Shahinoor Islam ChE, BUET

1. Biochar
Preparation & Application
ChE 6405
11.03.2019
Department of Chemical Engineering
Bangladesh University of Engineering & Technology

2. Biochar
Biochar (Biomass Charcoal) is the
carbon-rich solid formed by
heating biomass in an
environment limited to oxygen
This pyrogenic carbonized material is typically known as biochar when it is intended as a soil amendment or to provide
related environmental benefits.

3. Biomass + Charcoal = Biochar
▪ Biomass
The total quantity or weight of organisms in a given area or volume i.e. organic
matter which is used as a fuel.
▪ Charcoal
Porous black solid, consisting of an amorphous form of carbon, obtained as a residue
when wood, bone, or other organic matter is heated in the absence of air.
[smoke (produced and directed to the process) + Air = Heat ]
▪ Biochar [First Appearance: National Meeting (1998), American Chemical Society]
Charcoal produced from plant matter and stored in the soil as a means of removing
carbon dioxide from the atmosphere.
[smoke (produced and do not directed to the cool charcoal rather used in producing heat for a
separate process]

4. What is Biochar?
▪ The placement of charcoal into soils.
▪ The presence of nearly pure carbon in soils, in the form of amorphous
graphite.
▪ NOT carbon that is in living organisms.
▪ NOT fossil carbon, as in coal, oil, or natural gas.

5. Biochar
According to International Biochar Initiative Scientific Advisory
Committee, Biochar is
▪ a fine-grained charcoal high in organic carbon & largely resistant to
decomposition.
▪ produced from pyrolysis (Elevated T, Limited O2) 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
▪ sustaining enhanced nutrients, microbial activity, and moisture retention
capacity
▪ reducing the requirements of fertilizers and so environmental impacts

6. Feedstocks
 Sawdust
 Nut shells
 Grain crops
 Organic waste
 Kitchen waste
 Sewage waste
 Agricultural waste

7. Biochar is
Carbon Negative
When put in soil,
biochar sequesters carbon
for 1000’s of years.
It’s carbon-negative because it
holds carbon from that would
otherwise remain in the active
carbon cycle.

8. Biochar is
Carbon Negative

9. Biochar
in
Carbon System
CO2
Biomass
(living and dead)
Natural short-term
cycle of growth and
decay (including
biomass burning) is
Carbon Neutral: C=
Fossil Fuels Biocarbon
Biochar in Soils
Hundreds or thousands of years
as long-term carbon sequestration: C-
100 million
years ( C- )
100 minutes ( C- )
Optional human activity,
creating Terra Preta
Burn it. Burn it.
200+ years of fossil
fuel consumption is
Carbon Positive:
C+
Storing carbon is
Carbon Negative: C-

10. Microbial Activity
Pre-Columbian Amazonians are believed to have used
biochar to enhance soil productivity.
They seem to have produced it by smoldering agricultural
waste (i.e. covering burning biomass with soil) in pits or
trenches.
European settlers called it terra preta de Indio. [Terra
Preta (Dark Earth)]
Following observations and experiments, a research team
working in French Guiana hypothesized that the
Amazonian earthworm Pontoscolex corethrurus was the
main agent of fine powdering and incorporation of
charcoal debris to the mineral soil.

11. Charcoal
Biochar
Activated Carbon
Charcoal Biochar Activated Carbon
Feedstock Sawdust,
Hardwood
Organic wastes
from forestry or
agricultural lands
Peat coal,
petroleum pitch,
coconut
Relative Qualities Burnability
Low smoke
Adsorption
(Porosity)
Carbon
sequestration
Adsorption
Production Slow pyrolysis
Kiln
Slow pyrolysis
Kiln
Gasification
Pyrolyzed,
activated ,
chemically
impregnated and
cooked
Carbon Footprint Carbon Neutral
(Lead to
deforestation)
Carbon Negative Carbon Positive
Common Uses Fuel Soil Amendment
Remediation
Filtration
Binding Agent
Filtration
Remediation
Odor control
Binding Agent

12. Application and Benefits

13. Applications of Biochar

14. Waste Upcycling

15. Building Materials
Asphalt
3D Printing

16. Renewable Energy
Anaerobic Digestion
Microbial Fuel Cell

17. Water Treatment
• Gravel
Removes Turbidity (particles)
• Sand
 Removes problematic
microorganisms and chemical

• Biochar
Sorption
 Absorption
 Adsorption
Char
 Porosity
 Surface Area

18. Methods of Biochar Preparation
1. Hydrothermal Carbonization
[wet pyrolysis]
2. Pyrolysis

19. Hydrothermal Carbonization
▪ This process can be compared with the
process of coal formation from biomass
millions of years ago.
▪ Process conditions are temperature 200–
2500°C and pressure between 20 and 25
bar, The reaction time can vary from 1 to
72h based on the feedstock

20. Pyrolysis
C-rich residue of
heating biomass
without oxygen

21. Processes of Pyrolysis

22. Pyrolysis
▪ Pyrolysis is the thermal decomposition of materials at elevated
temperatures in an inert atmosphere
▪ There is different pyrolysis processes to produce biochar
▪ Fast pyrolysis: moderate temperature (600∘C), short hot vapor
residence time
▪ Intermediate pyrolysis: low to moderate temperature, moderate hot
vapor residence time
▪ Slow pyrolysis: low moderate temperature, long residence time
▪ Gasification: high temperature (>700∘C), long vapor residence
time
▪ Flash carbonization: (350–650∘C), residence time below 30
minutes, at elevated pressure (1–3MPa)

23. Pyrolysis
▪ Fast pyrolysis depends on very quick heat transfer, typically to fine biomass
particles at less than 650∘C with rapid heating rate ( 100–1000∘C/s)
▪ Slow pyrolysis (heating for seconds or minutes) may be described as a
continuous process, where purged (oxygen free) feedstock biomass is
transferred into an external heated kiln or furnace.
▪ For gasification in pyrolysis, the biomass feedstock to some extent is
oxidized in the gasification chamber at a temperature of about 800∘C at
atmospheric or elevated pressure. As already pointed out by its name, the
main product of this process is gas; only few or no BCs, liquids, or the likes
are formed.

24. Pyrolysis
▪ The hydrothermal carbonization of biomass is obtained by applying high
pyrolytic temperature (200–250∘C) to a biomass in a suspension with liquid
under high atmospheric pressure for several hours.
▪ In flash carbonization of biomass, a flash fire is lights up at an elevated
pressure (at about 1– 3MPa) at the underneath of a packed bed biomass The
residence time of the process is below 30 min, and the pyrolytic temperature
in the reactor is in the range of 330–650∘C.

25. Mechanism of Pyrolysis
▪ Pyrolysis is the breaking down (lysis) of a material by heat
(pyro). As the material is broken down, it releases gas. This
is the first step in the combustion or gasification of biomass.
▪ All the processes involved in pyrolysis, gasification, and
combustion can be seen in the flaming match.
▪ The flame provides heat for pyrolysis, and the resulting
gases and vapors burn in the luminous zone in a process
called flaming combustion, leaving behind char.
▪ After the flame passes a given point, the char may or may
not continue to burn.
▪ When the match is put out, the remaining wood continues to
bake, or pyrolyze, releasing a smoke composed of
condensed tar droplets as it cools.

26. Pyrolysis & Structural Composition of Biochar
 Thermal degradation of cellulose between 250º and
350ºC results in a rigid amorphous C matrix.
 Around 330ºC, polyaromatic graphene sheets begin to
grow laterally, at the expense of the amorphous C phase,
and eventually coalesce.
 Above 600ºC, carbonization becomes the dominant
process.
 Carbonization is marked by the removal of most
remaining non-C atoms and consequent relative increase
of the C content, which can be up to 90% (by weight) in
biochar from woody feedstocks.
 The presence of heteroatoms (O, N, P, S) is thought to be
a great contribution to the highly heterogenous surface
chemistry and reactivity of biochar.

27. Yield of Pyrolysis Process

28. Pyrolysis
Biomass
Bio-liquids
Gases
Solid –
biochar
1/3
1/3
1/3

29. Overall Pyrolysis Process in Biochar Production

30. Significance of Biochar

31. Recommendations

32. Thank You