With the increase in pollution levels due to burning of fossil fuels, the is a need for an alternative and cleaner fuel. Biogas production through anaerobic digestion can fulfill that requirement.

1. Biogas production
through Anaerobic
Digestion
By Sabin Shaji
(20PCE031) 1

2. Overview
• Need for Biogas
• Anaerobic Digestion
• Biogas production from Algae through Anaerobic Digestion
i. Advantages compared to other biofuel sources
ii. Limitations with regards to the methane production from algae
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3. Need for Biogas
• In 2016, about 62 million tonnes of MSW was generated in
India, which is projected to rise to 165 million tonnes by 2030.
As per a study, it was calculated that 51% of the waste was
organic or biodegradable, 32% is inert or inorganic and about
17% is recyclable.
• A major proportion of the waste is being dumped in the
landfill thus, increasing the load on the landfills. So, some of
the waste needs to be diverted.
• The waste in landfill gets degraded over time resulting in
harmful methane emission. This could be recycled into
valuable green energy, biofertiliser and biochemicals.
• Harnessing the energy from biogas can reduce global climate
change emission by 20%.
• It delivers home grown, distributed, storable and dispatchable
green energy.
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4. Continued…
• Production of biogas makes substantial contribution to 9 out
of the 17 UN Sustainable Development Goals.
i. Goal 2: End hunger, achieve food security and improved
nutrition and promote sustainable agriculture.
ii. Goal 3: Ensure healthy lives and promote well-being for all
at all ages.
iii. Goal 5: Achieve gender equality and empower all women
and girls.
iv. Goal 6: Ensure availability and sustainable management of
water and sanitation for all.
v. Goal 7: Ensure access to affordable, reliable, sustainable
and modern energy for all.
Source : worldbiogasassociation.org
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5. Continued…
vi. Goal 9: Build resilient infrastructure, promote inclusive and
sustainable industrialization and foster innovation
vii. Goal 11: Make cities and human settlements inclusive, safe,
resilient and sustainable
viii. Goal 13: Take urgent action to combat climate change and
its impacts
ix. Goal 15: Protect, restore and promote sustainable use of
terrestrial ecosystems, sustainably manage forests, combat
desertification, and halt and reserve land degradation and
halt biodiversity loss
Source : worldbiogasassociation.org
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6. Anaerobic Digestion
• It is a process carried out in the absence of oxygen where the
microorganisms break down the biodegradable material.
• It starts with the bacterial hydrolysis of input materials where
the large organic polymers like carbohydrates are broken
down to smaller constituents.
• The acidogenic bacteria further breaks down the smaller
constituent like simple sugars, amino acids and fatty acids to
produce some simple molecules, ammonia, carbon dioxide,
hydrogen sulfide and some more byproducts.
• Now, the actenogenic bacteria breaks down the simple
molecules producing acetic acid along with carbon dioxide and
hydrogen. 6

7. Continued…
• Finally, the methanogens convert the products of the previous
stages to methane, carbon dioxide and water which makes up
the majority of the biogas emitted.
• The entire process can be summed up by the following
chemical reaction where glucose is biochemically digested by
an aerobic microorganisms to produce carbon dioxide and
methane.
6 12 6 2 4C H O 3CO 3CH 
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8. Biogas production from Algae
through Anaerobic Digestion
Source: Biogas Production from Algae through Anaerobic Digestion: A Review,
Analysis, and Research Needs by Pavlo Bohutskyi and Edward Bouwer
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9. Advantages compared to other
biofuel sources
• Higher productivity
• Water quality is less critical
• Non competitive to food production
• Carbon dioxide sequestration
• Elimination of some energy consumption steps
• Deeper level of algal biomass utilization is possible
• Partial recycling of nutrients with anaerobic digestion effluent.
• Environmental friendly process.
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10. Limitations with regards to
methane production from
algae
• High capital cost
• Relatively low algae productivity
• Incomplete digestibility of algal cells
• Conversion rate is relatively slow
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11. Thank You
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