The document discusses various processes for converting biomass into solid, liquid, and gaseous biofuels. It describes drying, sizing, and densification processes to produce solid biofuels like wood pellets from raw biomass. Slow and fast pyrolysis are discussed for producing solid charcoal and liquid bio-oil. Liquefaction and gasification are presented as methods for creating liquid and gaseous biofuels, along with anaerobic digestion to produce biogas. The document provides an overview of the key conversion techniques to transform biomass into different forms of bioenergy and biofuels.

1. Biomass to Biofuels
S K Singh
Centre for Energy Studies
IIT Delhi

2. Contents
1. Definition of biomass and biofuels
2. Conversion of biomass to solid biofuels
- Drying
- Sizing
- Densification
- Slow Pyrolysis
1. Conversion of biomass to liquid biofuels
- Fast Pyrolysis
- Liquefaction
1. Conversion of biomass to gaseous biofuels
- Gasification
- Anaerobic Digestion
1. References

3. Biomass
Biomass
● So all the organic matter is called biomass.
● Examples -
“Bio” - Life “Mass” - Matter
Any living matter or matter
derived from living
organisms
Vegetation
Animals
Agricultural waste

4. Biofuel
● Biofuel - Biomass used for energy production.
● Energy produced is called Bio Energy.
● May or may not require any conversion.
Examples -
Firewood Charcoal
Biodiesel

5. Classification of Biofuel on the basis of state
Biofuel
Solid Biofuel Liquid Biofuel Gaseous Biofuel

6. Biomass to Solid Biofuels

7. Unprocessed Solid Biofuels
● Do not require any processing.
● Can be directly burnt for heat production.
● Examples -
Firewood Dry Agricultural Residue Cow Dung Cakes

8. Processed Solid Biomass

10. Drying
● A part of combustion heat goes into evaporating the water content of the
biomass.
● Lesser the moisture in biofuel, more energy will be available for our use.
- It leads to increased flame temperature which leads to
- More complete combustion
- Lesser carbon monoxide and fly ash production
● Becomes an important step before any further processing.

11. Drying
● Requirements for drying
- Heating Source
- Method for Removing evaporated water
- Introduction of new material
● Dryers can be divided into two broad categories -
- Direct Dryers
- Indirect Dryers

12. Dryers
1. Direct Dryers
● Material get heat from direct contact with the fluid.
● The fluid is either hot air or hot steam.

13. Dryers
1. Indirect Dryers
● Material is separated from the heat source by a heat exchange surface.

14. Sizing
● The combustion process depends on the surface area of the fuel. More the
surface faster is the combustion.
● Breaking up solid biofuel increases overall surface area
● Sizing also makes drying easier.
● Size is reduced by shredding, chopping, crushing, milling, grinding etc.
Wood chunks Wood chips

15. Sizing

17. Densification
● The low density of biomass poses a challenge for handling, storage and
transportation.
● The densification process advantages -
- Reduced transportation cost due to increased energy density.
- Simplified mechanical handling and feeding.
- Simplified storage and handling infrastructure.
- Reduced possibility of spontaneous combustion in storage.

18. Densification
● Process
- Done using hydraulic or mechanical piston drive.

19. Densification
Pellets Cubes

20. Carbonisation
● Conversion of organic material into carbon or carbon containing residue
through pyrolysis.

21. Pyrolysis
● Thermal decomposition of biomass in the absence of oxygen.
● Pyrolysis can be categorized as -
- Slow Pyrolysis
- Fast Pyrolysis
Slow Pyrolysis
● Slow heating of organic matter in the absence of oxygen.
● The volatiles from organic material evaporate and charcoal as solid product
remains.
● Charcoal contains large part, normally 80% of the carbon.
● Slow pyrolysis is also called carbonisation, and it emphasizes charcoal as
main product.
● Fast Pyrolysis in contrast emphasizes the liquid product.

22. Slow Pyrolysis
● The thermal decomposition starts between 260-300oC
● The cellulose, hemicellulose and lignin components of the wood break down
and volatiles are released.
● The volatiles consist of CO, CO2, CH4, H2 and tars.

23. Slow Pyrolysis
● The main product of slow pyrolysis is charcoal.

24. Charcoal Briquettes
● The components of charcoal briquettes are -
❖ Charcoal
- Main component of charcoal briquette

25. Charcoal Briquettes
❖ Accelerant
- To accelerate the combustion process.

26. Charcoal Briquettes
❖ White Ash
- By observing the degree of turning white we can judge the degree up to which
the briquette has burnt.

27. Charcoal Briquettes
❖ Briquette binder
- To bind the mixture together
- Popular briquette binder is arabic gum or acacia gum.

29. Biomass to Liquid Biofuels
● Fast Pyrolysis
● Liquefaction

30. Fast Pyrolysis
● Pyrolysis of biomass at high temperature decomposes it into charcoal and
volatile matter.
● The temperature ranges from 650-1000oC.
● The volatile matter comprises of
- Condensable vapours at room temperature called pyrolysis oil(also called bio-
oil or biocrude)
- And non condensable gases CO, CO2, H2, CH4. This mixture is also called
biogas.
● This process is primarily used to produce bio-oil and biogas.
● It yields 60% bio-oil, 20% biochar, 20% biogas.

31. Fast Pyrolysis

32. Bio-Oil

33. Liquefaction
● Thermochemical conversion of organic matter into bio-oil and co-products
● At moderate temperature(300-400oC) and Pressure(10-20 MPa) with CO or
H2 as reducing agents.
● The biomass used is wet(high water content) - Food processing waste,
animal manure.
● Process -
- The long carbon chain are thermally broken down
- Oxygen is removed as H2O (dehydration) and CO2 (decarboxylation)
- Recombination of reactive fragments
- Results in high H/C ratio bio-oil.

34. Liquefaction

35. Biomass to gaseous biofuels
● Gasification
● Anaerobic digestion

36. Gasification
● Converts organic matter at high temperatures(>700oC), without combustion,
with controlled amount of oxygen and steam into CO, CO2 and H2.
● The CO reacts with H2O to give more CO2 and H2.
● Adsorbers or special membranes can be used to separate the H2 from the
gaseous mixture.
● A simple example of reaction
C6H12O6 + O2 + H2O CO + CO2 + H2 + Other products
CO + H2O CO2 + H2 + Heat

37. Anaerobic Digestion
● Biomass is broken down by microorganisms in the absence of air.
● The microorganisms digest the biomass and release methane gas which can
be used for power generation.
● The four key stages of anaerobic digestion involve hydrolysis, acidogenesis,
acetogenesis and methanogenesis.
● The overall process can be described by the chemical reaction, where organic
material such as glucose is biochemically digested into carbon dioxide and
methane by anaerobic bacteria.

38. Anaerobic Digestion

39. ● We have looked at various processes used to produce solid, liquid, gaseous
biofuels from biomass.

40. References
● https://energypedia.info/images/1/1b/Solid_biomass_fuels_for_cooking_-
_beyond_firewood_and_charcoal._GIZ_2017.pdf
● https://www.nrel.gov/docs/fy99osti/25885.pdf
● http://northwestchptap.org/nwchpdocs/biomassdryinganddewateringforcleanheatandpower.pd
f
● http://ecoursesonline.iasri.res.in/mod/page/view.php?id=1255
● http://www.omafra.gov.on.ca/english/engineer/facts/11-
035.htm#:~:text=The%20low%20density%20of%20biomass,properties%20than%20the%20ra
w%20biomass.
● https://www.intechopen.com/books/pyrolysis/pyrolysis-a-sustainable-way-to-generate-energy-
from-waste
● https://www.uaex.edu/publications/PDF/FSA-1052.pdf
● http://www.esru.strath.ac.uk/EandE/Web_sites/03-04/biomass/background%20info8.html
● http://pyrowiki.pyroknown.eu/index.php/Slow_pyrolysis#:~:text=Slow%20pyrolysis%20is%20t
he%20slow,normally%2080%25)%20of%20carbon.

41. References
● https://www.ftmmachinery.com/blog/composition-and-processing-of-charcoal-
briquette.html#:~:text=Charcoal%20briquette%20is%20a%20kind,smoke%20and%20odor%2
0during%20combustion.
● https://en.wikipedia.org/wiki/Hydrothermal_liquefaction