Biomass Energy and Photosynthesis

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What percentage of the energy used in the world is accounted for by biomass?

10%

20%

15% (correct)

What is the wavelength range of visible light used by plants for photosynthesis?

0.7-1.0 ?m

0.4-0.7 ?m (correct)

0.1-0.4 ?m

1.0-1.4 ?m

What is the percentage of energy lost during photosynthesis due to the absorption of green light?

50%

30%

40%

20% (correct)

What is the efficiency of converting incident solar energy into chemical energy in plants?

28% Signup and view all the answers

What is the percentage of carbohydrates energy used in respiration?

40% Signup and view all the answers

What is the optimal temperature range for photosynthesis to occur at its maximum rate?

20°C to 30°C Signup and view all the answers

Which of the following factors increases photosynthesis?

Concentration of carbon dioxide Signup and view all the answers

What is the energy density of charcoal in MJ/kg?

30 MJ/kg Signup and view all the answers

What is the primary component of biogas?

Methane gas (CH4) 65-75% Signup and view all the answers

What is the purpose of anaerobic digestion in biogas production?

To decompose organic matter in the absence of oxygen Signup and view all the answers

What is the primary function of seeding digestion slurry with methane-forming bacteria?

To achieve maximum biogas generation rate Signup and view all the answers

What is the ideal pressure range for the proper functioning of a digester?

6-10 cm of water column Signup and view all the answers

What is the primary benefit of anaerobic digestion in waste management?

Production of fertilizer in the form of sludge Signup and view all the answers

What is the optimal temperature range for the growth and functioning of anaerobic bacteria?

20-65°C Signup and view all the answers

What is the primary role of hydrolysis in the biochemical process of anaerobic digestion?

Breaking down large molecules into simpler compounds Signup and view all the answers

What is the primary compositions of biogas in terms of percentage?

50-60% methane gas, 55-40% carbon dioxide Signup and view all the answers

What is the primary advantage of biomass energy in rural areas?

It helps in improving sanitation in rural areas Signup and view all the answers

What is the ideal temperature range for anaerobic digestion to occur?

Lower than 65°C Signup and view all the answers

What is the primary role of anaerobe microorganisms in biogas production?

To consume oxygen for survival and growth Signup and view all the answers

What is the primary factor that favors anaerobic digestion in biogas production?

Wetness, warmness, and darkness Signup and view all the answers

What is the primary consideration for locating a biogas plant near the area where biomass is generated?

To reduce the cost of transporting biomass Signup and view all the answers

What is the purpose of using a solar energy system in a biogas plant in hilly areas?

To increase the temperature of biomass slurry in the digester Signup and view all the answers

What is the primary benefit of community biogas plants?

Generating electricity for various applications Signup and view all the answers

What is the purpose of using hot exhaust from a power generating system in a biogas plant?

To operate biogas plants at higher temperatures Signup and view all the answers

What is the primary consideration for deciding the size of a biogas plant?

The amount of waste generated with the number of animals and people Signup and view all the answers

What is the primary purpose of thermochemical conversion of biomass?

To produce a gaseous mixture of gases Signup and view all the answers

What is the purpose of gasification in biomass conversion?

To produce charcoal and producer gas Signup and view all the answers

What is the ideal moisture content for biogas production in landfills?

60% Signup and view all the answers

What is the purpose of the leachate collection system in landfilling?

To collect and recycle leachate for biogas production Signup and view all the answers

What is the primary benefit of using biomass gasification for power generation?

It can replace up to 75% of diesel in a diesel engine Signup and view all the answers

What is the ideal pH range for the methane forming stage of anaerobic digestion?

6.5-7.5 Signup and view all the answers

What is the purpose of seeding in anaerobic digestion?

To add a small amount of digested slurry containing methane forming bacteria Signup and view all the answers

What is the primary function of the partition wall in the digester chamber of a floating drum type biogas plant?

To provide optimum conditions for growth of acid forming and methane forming bacteria Signup and view all the answers

What is the main advantage of continuous type biogas plants over batch type plants?

They operate continuously and require less maintenance Signup and view all the answers

Why is the pressure inside the digester of a floating drum type biogas plant constant?

Because the gas holder is floating Signup and view all the answers

What is the effect of faster feeding rate on the digestion process?

It leads to the accumulation of acids and stops the digestion process Signup and view all the answers

What is the purpose of mixing and stirring in the digester?

To mix the floating masses of biomass for bacterial action Signup and view all the answers

What is the primary advantage of using a fixed dome type biogas plant over a floating drum type biogas plant?

Lower cost Signup and view all the answers

What is the stoichiometric air-fuel ratio of biogas?

5.27 by volume Signup and view all the answers

What is the maximum percentage of biogas that can be blended with gasoline to run an IC engine?

5-10% Signup and view all the answers

Study Notes

Biomass Energy Resources

Biomass is organic material that can be converted into energy through combustion or metabolic processes
Main sources of biomass energy: wood, agricultural waste, urban waste, and forest waste

Photosynthesis

Process by which plants convert solar energy into chemical energy (carbohydrates)
Requires chlorophyll, carbon dioxide, and water
Plants absorb red and blue light, but not green light, which is why they appear green
Biomass production efficiency: 28% of used energy is converted into carbohydrates

Conditions for Photosynthesis

Temperature: 20-30°C for maximum rate
Carbon dioxide concentration: increases photosynthesis
Oxygen concentration: reduces photosynthesis
Water: increases photosynthesis
Intensity and wavelength of solar radiation: increases photosynthesis with PAR (photo synthetically active radiation)

Biomass

Can be used in its original form or transformed into solid, liquid, or gaseous fuels
Examples of biomass fuels: fuel wood, charcoal, fuel pellets, bioethanol, biogas, producer gas, and biodiesel

Biofuels

Fuel wood: most common source of biomass energy, energy density of 16-20 MJ/kg
Charcoal: obtained from wood, energy density of 30 MJ/kg
Fuel pellets: formed from crop residues, energy density of 16-20 MJ/kg
Bioethanol: derived from sugarcane, starch, or cellulose, energy density of 26.9 MJ/kg
Biogas: gaseous fuel produced from biomass, energy density of 23 MJ/m3

Biomass Resources

Forests: source of fuel wood, charcoal, and producer gas
Agricultural residues: straw, rice husk, groundnut shell, coconut shell, and sugarcane bagasse
Energy crops: sugar plants, starch plants, and oil-producing plants
Urban waste: garbage, sewage, and liquid waste
Aquatic plants: water hyacinth, seaweed, algae, and kelp

Advantages and Disadvantages of Biomass Energy

Advantages: renewable, storable, waste management, indigenous, economic development, sanitation, and fertilizers
Disadvantages: low energy density, labor-intensive, and large land area required

Biogas

Gaseous fuel produced from biomass through anaerobic digestion
Composition: 50-60% methane, 25-35% carbon dioxide, and 5% hydrogen and other gases
Energy density: 23 MJ/m3
Uses: cooking, heating, lighting, and running small IC engines

Anaerobic and Aerobic Processes

Anaerobic: process occurring in absence of oxygen, used in biogas production
Aerobic: process occurring in presence of oxygen

Anaerobic Digestion

Process of biogas production from biomass slurry
Factors favoring digestion: wetness, warmness, and darkness
Three stages: hydrolysis, acid formation, and methane formation
Digester: airtight equipment used for anaerobic digestion

Advantages of Anaerobic Digestion

Energy production from waste materials
Fertilizer production
Waste management
Improved sanitation and hygiene
Containment of odors

Raw Materials for Biogas

Waste: industrial, agricultural, urban, and forest waste
Cultivated materials: rice, wheat, and cereals
Harvested materials: agricultural crops and residues

Factors Affecting Biogas Production

Temperature: 20-65°C
Pressure: 6-10 cm of water column
Water: 9-10% solid content
pH value: 6-7.5
Feeding rate: uniform feeding rate
Presence of nutrients: carbon, nitrogen, and other nutrients
Seeding: adding digested slurry to fresh feed
Mixing and stirring: mixing of biomass slurry
Retention time: 50-60 days
Toxic substances: presence of pesticides, detergents, and ammonia
Type of biomass: cow dung, poultry manure, etc.### Advantages and Disadvantages of Fixed Drum Type Biogas Plant
Lower cost
No corrosion problem
Better heat insulation
No maintenance required

Disadvantages of Fixed Drum Type Biogas Plant

Gas production per cubic meter of the digester is less
Variable pressure of biogas
More risk of leakage due to higher pressure of gas
More risk of explosion
Complex installation

Properties of Biogas

Composition: 60% methane, 40% carbon dioxide, and traces of hydrogen, hydrogen sulphide, and other gases
Calorific value: 5,600 kcal/m3 or 4,250 kcal/kg
Stoichiometric air-fuel ratio: 5.27 by volume
Calorific value of mixture: 767 kcal/m3, equivalent to 85% of gasoline

Application of Biogas in IC Engine

Biogas cannot be used in IC engine without modification
Blending biogas with petrol and diesel can run IC engine with small modification
A mixture of biogas and gasoline containing 5-10% biogas can be used as IC engine fuel, reducing gasoline consumption by 5-10% and fuel cost

Models of Biogas Plants

Common circular digester with floating gas holder without water seal (KVIC design, India)
Common circular fixed dome digester (China)
Flexible gas type combined digester and gas holder
Taper digester with floating gas holder (Nepal)
Two-chamber rectangular digester with floating gas holder and water seal (Philippines)
Jet digester with separate gas holder (Thailand)
KVIC model
PRAD model
ASTRA model
Ganesh model

Biogas Plant in Hilly Area

Average temperature remains below 15°C in hilly regions
Anaerobic bacteria grow and digest biomass in the temperature range of 25-75°C
Methods to overcome temperature limitations:
- Hot water circulation
- Use of chemicals (e.g., urea and urine)
- Solar energy system

By-Product of Digestion

By-products of digestion are shown in Figure

Location of Biogas Plant

Considerations for locating a biogas plant:
- Distance from well or spring used for drinking water purposes
- Proximity to biomass generation area
- Availability of water source
- Open and exposed site for better performance
- Proximity to point of gas consumption

Size of Biogas Plant

Considerations for deciding the size of the plant:
- Waste generation and animal/people population
- Gas requirements
- Volume of digester tank needed
- Size and shape of digestion tank
- Size of floating drum of the digester

Community Biogas Plants

Advantages of community biogas plants:
- Efficient cooking fuel
- Electricity generation for various purposes
Suggestions for improving productivity and efficiency:
- Using biogas in dual fuel engine to generate power
- Using hot exhaust to operate biogas plants at higher temperature
- Using additional materials (e.g., water plants with animal waste) to generate biogas
- New methods of biogas generation using bacterial support structures and recycling of spent slurry

Biomass Conversion Technologies

Basic technologies to convert biomass into:
- Direct energy
- More valuable or convenient products
Technologies:
- Incineration
- Thermochemical (pyrolysis)
- Biochemical

Incineration

Burning or combustion of biomass to obtain useful heat
Heat can be used for:
- Space heating and cooking
- Generating steam in boiler to run turbine with electric generator

Thermochemical (Pyrolysis)

Conversion of biomass into more valuable and convenient fuels
Process:
- Heating biomass in absence of air or partial combustion
Products:
- Gaseous mixture (H2, CO, CO2, CH4, N2)
- Liquid (acetic acid, acetone, methanol, oil, and tar)
- Pure carbon char

Biomass Gasification

Conversion of solid biomass into combustible gas mixture (carbon monoxide and hydrogen)
Process:
- Partial combustion of biomass in absence of sufficient air
Types of gasifiers:
- Fixed bed updraft gasifier
- Fixed bed down draft gasifier
- Cross draft gasifier
- Fluidized bed gasifier

Energy Recovery from Urban Waste by Landfill Reactors

Municipal solid waste (MSW) disposal by controlled sanitary landfilling
Biodegradable urban wastes are segregated and compacted to generate biogas
Preparing the landfill site:
- Lining with plastic liner and clay to prevent groundwater contamination
- Leachate collection system to collect and recycle leachate
Optimum moisture content of garbage: 60%
Biogas production using anaerobic bacteria
Temperature rises to 60°C during digestion

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Learn about biomass energy resources, main sources, and the process of photosynthesis, including the role of chlorophyll and plant energy production.