Microbial Biotechnology_ Biological Fuel Generation.pdf

Biological fuel generation

1. Microbial Biotechnology:
Biological Fuel Generation
Dr G.O Oyetibo
Dept of Microbiology,
University of Lagos, Nigeria

2. Global warming
•Climate change is linked to the increased level
of greenhouse gases in the atmosphere.
–Human activity especially through the combustion
of fossil fuels is a major contributing factor
•CO
2, the main greenhouse gas, account for
65% of global warming

3. Significance of fossil fuels
•Fossil fuels are the stored energy or ‘ancient
sunlight’ of aeons and millenia ago that mankind
has been burning extensively over a few centuries
and more prolifically in recent decades.
•CO
2 that been locked away for all those years is
released when fossil fuel is burned
•In contrast, when present- day plant material is
burned, the carbon locked into the biomass for a
relatively short period of time is released back into
the atmosphere.

4. Option for the conversion of biomass to energy

5. Biofuels from biomass
Sugar
crops
Sugar cane, sugar beet: sugar extracted and fermented to
bioethanol
Starch
crops
Maize (corn), barley, wheat, oats, cassava: starch
enzymatically hydrolysed to sugars and fermented to
bioethanol
Cellulose
crops/
wastes
Straw, bagasse, woody wastes, cropped trees: the
hemicelluloses can be enzymatically hydrolysed to sugars
and fermented to bioethanol.
Oil crops Rapeseed, linseed, sunflower, castor oil, groundnut: oils
extracted and transesterified to biodiesel.
Organic
wastes
Complex microbial fermentations to methane/methanol.
•Bioenergy (biofuel) is basically the production of
combustible/usable energy from biological sources.
•What are the main biological energy sources or crops?

6. Bioethanol from biomass
•The production of alcohol by
fermentation of sugars and
starch
•C
6H
12O
6 → 2CH
3CH
2OH + 2CO
2
•The raw materials require
some degrees of treatment
–Sugar cane require milling
–Corn or cassava, containing
starch, require the action of a
suitable saccharifying agent –
either acid or enzyme hydrolysis.
–
Cellulosic raw materials (timber
or straw) require more extensive
pre-treatment and is reflected in
the increased energy inputs.

7. Potential raw materials for ethanol
biofuel production

8. Wastes from bioethanol production
•This is called stillage. The huge wastes could
generate to useful end-products via
–Evaporation to feed or fertilizers
–Mineralization to ash
–Anaerobic fermentation for methanol generation
–Conversion by microorganisms into single cell
protein (SCP)

9. Importance of ethanol as fuel
•It is energy efficient
•It does not produce toxic CO during combustion.
Ethanol powered engines produce 57% less CO, 64%
fewer hydrocarbons, 13% less N
2O than fossil fuel
powered engines.
•It is much less polluting than conventional fuel.
•It is cheaper to produce ethanol from oil chemically
(hydration of ethene) than by fermentation process but
for global earth warming the later is preferred.
•Addition of anhydrous bioethanol to gasoline
eliminates the need for octane improvers to raise the
octane ratings.
•Green petrol production will help take some of the
pressures off petro production, consequently avert
competitive tensions and wars

10. Biotechnological improvement of
traditional alcohol fermentation process
•Production of more efficient microorganisms by genetic
engineering, which exhibit:
–Improve alcohol fermentation
–Resistance to high temp. & high alcohol levels
–Speed of fermentations & higher yields
•Improved immobilised enzyme bioreactor technology
and process design improvement
•
Novel introductions such as fermentations under partial vacuum and recycling of the fermentative yeast cells have increase ethanol productivity to 10 or 12 times that of convectional batch fermentation process,
thus reducing capital costs and energy requirements for
bioreactor operations

11. Biodiesel
•Diesel produced from vegetable oil instead of the
conventional crude oil distillation.
•It is produced by transesterification of plant oils
with methanol (or ethanol) in the presence of a
catalyst, NaOH, at 50
o
C, resulting in the formation
of fatty acid methyl esters and glycerol.
•The glycerol is allowed to settle and the biodiesel
purified and used directly, or as mixture, with diesel
as a fuel.

12. Merits of biodiesel
•Reduces the dependence on fossil fuel use/imports.
•Has a lower flashpoint and does not ignite.
•Free of toxic aromatic and sulphur compounds.
•Biodegradable – reducing environmental damage due
to spillage.
•Biodiesel is renewable.
•There is no net increase in CO
2 released into the
atmosphere with combustion, i.e it is carbon neutral.
•
France, Italy and Germany have been the leading
proponents of biodiesel: France for agricultural
reasons, Italy for environmental reasons, and Germany
for both.

13. Methane

14. Methane production methods
•Rumen is the most efficient and complex
methane-producing system in nature,
involving a complex interaction of large
numbers of bacteria, protozoa, and fungi.
•Other possible ways by which methane can be
produced include:
–Anaerobic digestion of sewage
–Methanogenesis of agricultural and urban wastes
–Biogas: by fermentation of animal dungs

15. Inherent problems of methane production
biotechnology
•The cost of collection of organic matter solely for
methanogenesis is too expensive
•Rate of methane production is inconsistent and low
in most processes
•Much research needs to be carried out on the
balance of nutrients for process optimization
•
Most agricultural and urban wastes contain lignin that are not easily degradable by anaerobic process, thus requiring physical and chemical pretreatment,
which places a considerable energy and cost burden
on the overall process.

16. Biogas
•Production of methane by fermentation of animal dung in an installation
called biogas plant or bioreactor
•It is a flammable mixture of 50-80% CH
4, 15-45% CO
2, 5% H
2O and other
trace gases
•It is produced via biomethanation and it’s self- regulating symbiotic
microbial process operating under anaerobic conditions, and functions best
at temp. around 30
o
C.
•Organisms involved are all naturally found in ruminant manures. As such,
animal dung is mixed with water and allowed to ferment in near- anaerobic
conditions
•It is widely used in India, China and Pakistan. China as the largest user with
over 7 million biogas units providing the equivalent energy of 22 million
tons of coals (with current subsidy, biogas plant unit in China is cheaper
than a bicycle). In the USA (California in particular) a biogas plant provides
electricity to 20,000 homes by way of cow-manure biomethanation. USA is
currently proposing use of high-yielding crops (water hyacinth of energy
content 3.8 MJ per Kg dry material) for methane production
•Under ideal condition 10 kg dry organic matter can produce 3 m
3
of biogas
that will produce 3 h cooking, 3 h lightning, or 24 h refrigeration with
suitable equipment

17. The future of biofuel
•The ability of biofuel to realistically enter energy market will
depend on:
–The availability of existing energy chain to biofuels
–The resistance to adoption of biofuels by the current energy
management
–The ability to reduce the cost of biofuels
–The retrofitting of the existing energy supply-chain to
accommodate biofuels
• biotechnology future of biofuel will involve
–Developing new biofuel components and improving the efficiency
and flexibility of those currently blended with transport fuels
–Devising new technology to enhance and accelerate the
conversion of organic matter to biofuel molecules, with aim of
increasing the proportion of crop that can be used to produce
feedstock
–Using modern plant science to develop species that produce a
higher yield of energy molecules that can be grown on land not
suitable for food production

18. Future advances in plant and agricultural
biotechnology towards biofuel production
•The potential use of genetically modified
plants
•Enhanced bioprocess biotechnologies
•Improved carbon- fixation of photosynthesis
•Improved enzymology and nitrogen- fixation
pathways in bioenergy crops