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Transcript of Anaerobic Digestion
17th Century CE
21st Century CE
Biogas was used to heat bath water in Assyria.
Flammable gases can be made from decaying organic material.
Bombay, India (1859)
World War II
Amount of decaying organic matter = amount of flammable gas produced.
Count Alessandro Volta
World War II (1939- 1945)
England used biogas to power buses during WWII.
Discovered: methane gas is produced during the anaerobic digestion of manure from cattle.
Sir Humphry Davy (1808 CE)
Anaerobic sewage treatment facility powered streetlamps
The first anaerobic digester was built.
Oil Embargo of 1973
Price of oil increased during oil embargo -> Made anaerobic digestion a promising industry.
Price lowered after the 1980s -> Anaerobic digestion faded.
Assyria (10th Century BCE)
(17th Century CE)
Increased concern about the environment
Big push for alternative energy operations, including anaerobic digestion
Green Revolution (21st Century)
Reduces greenhouse gas emissions
Energy can be used to displace burning fossil fuels
Improves water quality
Creates nutrient rich fertilizer
Increases sustainability in the long run
Produces heat and electricity
How it Works:
Different Types of Digesters
The Farm Security and Rural Investment Act of 2002
Gave federal grants to farmers
Food and Conservation Act of 2008
Loans for biogas technology exploration
Agricultural Act of 2014
Storage & Delivery
Greenhouse gas emission reduction
Current research and development
What is Anaerobic Digestion?
Define "anaerobic" + "digestion"
(1350 cows) × (40 tonnes manure/year per cow) = 54,000 tonnes manure/year
On average, a milking cow produces 40 tonnes manure per year.
Example farm: 1350 dairy cows, 200kW generator
(54,000 tonnes manure/year) × (48 kWh electricity/year) = 2,592,000 kWh electricity/year
1 tonne of manure=48 kWh electricity/year.
When biogas is combusted, about 35% of its energy is converted to electricity while 50% is converted to heat.
(2,332,800 kWh electricity) × (1.4 kWh heat/ kWh electricity) = 3,265,920 kWh heat/year
50 kWh heat/35 kWh electricity
= 1.4 kWh heat/1 kWh electricity
2,332,800 kWh electricity/year × $0.134 = $312,595.20/year
1 kWh of electricity in the United States costs 13.4 cents
I I I I I I I
(2,592,000kWh electricity/year) × 0.90 = 2,332,800 kWh electricity/year
Digestion plants only operate 90% of the time.
Enzymes break down proteins, carbohydrates, and fats in organic matter.
Byproducts of acidogenesis are carbon dioxide, ammonia and hydrogen sulphide
Converts into hydrogen gas, carbon dioxide, and acetic acid
Converts acetic acid and hydrogen into carbon dioxide and methane
Methanosarcina and Methanosaeta
Found on dairy farms
Suitable for all types of manure
Cheapest kind of digester
The cost of operation: $ 84,613/year
Yearly profit: $312,595.20 − $84,613 = $227,982
The farm will break even in a bit under 5 years and 4 months