BIOGAS

Page 1: Biogas

Page 2: Palm Oil Mill Effluent (POME)

Overview

• POME treatment involves several processes:

  • Cooling

  • Mixing

  • Anaerobic treatment (Tank/Pond)

  • Facultative treatment

  • Algae treatment

  • Final discharge into a river

Characteristics

• Composition: 95% water, 5% solid

• Treatment results in significant reduction of BOD from 25,000 ppm (inlet cooling) to < 100 ppm / 20 ppm (final discharge)

Spatial Requirements

• Area required for treatment is extensive, consuming over 70% of the mill area, approximately 12-15 hectares or 5 times the area of the mill premises.

Environmental Issues

• Methane gas emissions during the anaerobic treatment contribute to greenhouse gas (GHG) problems.

• Concerns related to landfill treatments.

Page 3: Kyoto Protocol (1997)

Objectives

• Achieve sustainable development through quantification of emission limitations and reductions of GHG.

Clean Development Mechanism (CDM)

• Facilitates cooperation between developing (Annex B) and developed countries (Annex A) for GHG reduction projects.

• Encourages financial and technological investments.

Page 4: Sustainable Development

Definition

• Development that meets current generation needs without compromising future generations' ability to meet their own needs.

Page 5: Fuel Availability

Biogas Generation

• Produced during the anaerobic treatment of POME.

  • Composition: 55-65% Methane (CH4)

• Under the Government Economic Transformation Program, by 2020, 500 mills are expected to capture biogas for electricity generation or other fuel uses.

Potential Production

• Malaysia aims to produce between 80-100 million tonnes of Fresh Fruit Bunches (FFB), generating up to 60 million tonnes of POME with potential biogas release of up to 1,680 million cubic meters.

• Potential to generate up to 2 kWh of electricity per cubic meter of biogas.

Page 6: Politics

Current Policies

• Electricity supply policies favor existing Independent Power Producers (IPP) using natural gas or coal due to heavy subsidies.

  • Government spends RM19 billion/year on natural gas subsidies.

  • Current tariff at RM0.21/kWh is not viable for biogas projects.

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Page 8: Kyoto Protocol (1997) [Repeat]

Objectives

• Achieve sustainable development via quantification of emission limitations and reduction of GHG.

Clean Development Mechanism (CDM)

• Facilitates cooperative projects between developing and developed countries, providing opportunities for financial and technological investments.

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Page 10: Biogas Pilot Plant at Serting Hilir Mill, N. Sembilan

Project Overview

• R&D project initiated in 2005 for constructing Biogas Pilot Plant in collaboration with Universiti Putra Malaysia (UPM) and Kyushu Institute of Technology (KIT), Japan.

• A pioneering R&D venture anticipated to extend to additional mills.

Focus Areas

• Continued R&D until end of 2010 focusing on bioplastics, bioethanol, and biocompost.

Page 11: Biogas Plant Layout

• Components Overview:

  • Flaring unit

  • Gas engine

Page 12: Location Map

• Pasoh Serting Hilir - geographical context of the project.

Page 13: Project Areas

• Besout, Maokil, Kemahang - additional locations related to biogas projects.

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Page 15: Biogas From Landfill

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Page 19: Potential Electricity Generation

Calculations

• Based on 1 m3 methane gas:

  • Potential electricity generation: 3 kWh

  • Potential biogas production: 28 m3 / mt POME

  • Methane composition in biogas: 50-60%

  • H2S content pre-scrubbing: 3000 ppm

  • Expected H2S content post-scrubbing: <300 ppm

Page 20: Applications of Biogas

Electric Power Generation

1. Utilizing gas engine/microgas turbine.

2. Potential for biomass-related projects: briquette/pellet plant.

3. Additional income from selling electricity to TNB (National Electricity Utility).

4. Replacing diesel generators with biogas in internal applications.

5. Continuous power supply for aeration in tertiary treatment plants, enhancing POME treatment efficiency and reducing land use requirement.

6. Methane combustion for steam/electricity generation with reduced shell usage and smoke emissions from combustion.

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Page 22: Characteristics of POME

Note: All parameters except temp and pH are expressed in mg/L.

Page 23: Anaerobic Fermentation

Overview

• Treatment focused on waste sludge and high-strength organic waste.

• Generates lower biomass yield but recovers energy in the form of methane.

• Processes include mesophilic (30-35°C) and thermophilic (50-60°C) digestion.

Types

• Anaerobic treatments differ from aerobic processes in effluent treatment.

Page 24: Waste Transformation: Biogas

Characteristics

• Formed by microbiological degradation processes.

• Anaerobic bacteria convert organic matter to methane (CH4) and carbon dioxide (CO2).

• Primary sources of biogas are waste treatment systems using anaerobic digesters or from solid waste landfills.

Comparison

• Landfills rely on batch digesters for methane production, which occurs over an extended period, while continuous treatments enable more effective control.

Page 25: Anaerobic Digestion Technology

Significance

• Effective waste treatment for high-strength organic and agroindustrial wastes like POME.

• Offers resource recovery opportunities beyond mere waste treatment.

• Produces methane-rich biogas suitable for energy generation (heat/power).

• Enables nutrient recovery as fertilizer from digested liquor.

• Features low energy requirements for processes and high stability with proper control.

Page 26: Stages of Anaerobic Digestion

Definition

• A series of microbial processes decomposing organic matter into methane and carbon dioxide, conducted in the absence of oxygen.

• Also known as Anaerobic Fermentation, Methane Fermentation, Biomethanation, Biogasification.

Process Stages

1. Hydrolysis: Conversion of complex organics (proteins, cellulose, lignin, lipids) to soluble monomers (amino acids, sugars, fatty acids, glycerol).

2. Acidogenesis: Fermentation of hydrolysis products into organic compounds, mainly volatile fatty acids.

3. Acetogenesis: Conversion of fatty acids (propionic, butyric) and alcohols to acetate, hydrogen, and carbon dioxide.

4. Methanogenesis: Final conversion of acetic acid from the preceding processes into methane and carbon dioxide.

Page 27: Bacterial Types in Anaerobic Digestion

Groups

1. Mesophilic Bacteria: Active in 20°-40°C, optimal at 35°C.

2. Thermophilic Bacteria: Active in 45°-60°C, optimal at 55°C.

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Page 29: Temperature Factors Affecting Anaerobic Digestion

• Key factors:

  • Retention time

  • pH levels

  • Chemical composition of wastewater

  • Toxicants

Page 30: Factors Affecting Digester Gas Production

Page 31: Factors Affecting Landfill Gas Production

Page 32: Microbial Degradation - Anaerobic

Page 33: Microbial Degradation - Anaerobic

Types of Bacteria

A) Fermentative Bacteria:

• Both anaerobic and facultative microorganisms that can decompose complex organic materials (carbohydrates, proteins, lipids) to simpler compounds (fatty acids, alcohols, carbon dioxide, hydrogen, ammonia, and sulfides).

B) Acetogenic Bacteria:

• Utilizing primary organic products to yield hydrogen, carbon dioxide, and acetic acid.

C) Methanogenic Bacteria:

• Two groups identified:

  1. Reduces carbon dioxide to methane.

  2. Decarboxylates acetate to methane and carbon dioxide.

Objective: Optimize biochemical conditions for formations leading to methane production.

Page 34: Methanogenic Bacteria Characteristics

• Methanosarcina: Spherically shaped bacteria.

• Methanothrix: Long, tubular form.

• Short, curved-rods metabolizing furfural and sulfates.

Page 35: Loading Capability vs Temperature in Anaerobic Digestion

• Graph illustrating maximum loading rate of POME digestion against varying temperatures.

Page 36: Optimal Gas Yield from Anaerobic Digestion

• Chart representing optimal gas production at various reaction temperatures.

Page 37: Energy Rate of Biogas from 30 t FFB/hr Plant

Estimates

• Methane Production: 6,160 Nm3/day (11,120 m3/day biogas at 308K).

• Energy Value of 1 Nm3 Methane: 35,800 kJ; 8,550 kCal; 33,930 Btu; 9.94 kWh.

• Energy Rate: 2.2 x 10^8 kJ/day; 5.3 x 10^7 kCal/day; 2.1 x 10^8 Btu/day; 6.13 x 10^4 kWh/day.

Power Generation Potential

• Projected power generation at 40% efficiency is 1.02 MW.

Page 38: Anaerobic Digestion Process

• Enzyme-Mediated Transformation: Hydrolysis of higher molecular mass compounds into energy-utilizable lower molecular compounds.

• Acidogenesis: Bacterial conversion of compounds into identifiable lower molecular mass intermediate compounds.

• Methanogenesis: Bacterial conversion of intermediates into primary products, chiefly methane and carbon dioxide.

Page 39: Typical Reactor Configurations for Anaerobic Wastewater Treatment

• Overview of various configurations used in anaerobic digestion.

Page 40: Typical Reactor Configurations for Anaerobic Wastewater Treatment [Repeat]

Page 41: UASB Reactor and Anaerobic Contact Process

Page 42: Anaerobic Digester Overview

• Properties and operational needs for various types of anaerobic digesters.

• Operating Conditions: Feeding methods, temperature ranges, nature of wastes, and the importance of optimum loading rates for effective biogas production.

Gas Composition

• Mixture generally contains 60-70% CH4, 30-40% CO2, <1% hydrogen sulfide (H2S), trace nitrogen, and hydrogen.

Page 43: Anaerobic Digester Details

Gas Production Estimation

• Gas production relates to:

  • Volatile solids (VS) loading of the digester.

  • Percentage of VS reduction during the process.

• Organic Loading Rate (OLR): Critical for optimizing gas production, as overfeeding can inhibit methane generation.

Page 44: Landfill Comparisons

Characteristics

• Lower methane content (40-55%) compared to digesters, primarily composed of carbon dioxide and trace amounts of hydrogen sulfide and various gases.

• Conditions for optimal methane production in landfills are often inconsistent but can be managed.

Page 45: Biogas Process Technology

Page 46: Process Evaluation

Evaluation Criteria

• Methane yield, production rate, organics reduction, culture stability (pH, volatile acid concentration), thermal efficiency, and economic evaluation of the process.

Page 47: Mesophilic Digestion

Conditions

• Range: 25°C - 40°C with optimal biogas production at temperatures no lower than 32°C.

• Challenges: If the temperature drops below optimal, fermentation products accumulate leading to process inhibition and failure.

Page 48: Thermophilic Digestion

Characteristics

• Range: 40°C - 50°C with optimum temperature for biogas plants between 50°C and 55°C.

• Higher microbial activity compared to mesophilic conditions, leading to enhanced digestion efficiency.

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Page 50: Substrate Composition

Considerations

• Different organic material types carry varying energy contents impacting biogas and methane yield.

• Efficiency relies on balancing energy use by microorganisms during growth against available energy produced as methane.

Page 51: Example Calculation for Biogas Yield

Biogas Potential from Food Waste

• Weight parameters based on food waste composition for theoretical biogas yield estimations.

Page 52: Answer Calculations for Biogas Yield

Calculated Biogas Outputs

• Total biogas and methane production from defined food waste parameters:

  • Total biogas = 156 m3

  • Total methane = ~92 m3

Page 53: Loading and Retention Time

Relationship

• Consistent decomposition and the importance of the organic loading rate (OLR) and optimal retention time for maximized methane production.

Page 54: Example Calculations on Retention Time and Loading Rate

Parameters

• Volume of digester: 2500 m3

• Daily substrate feeding: 75 m3

• Calculated retention time: 33 days

• Organic loading rate: 2.7 kg volatile solids/m3 digester/day.

Page 55: Anaerobic Digestion of Sewage Sludge

Influencing Parameters

• pH, alkalinity, temperature, and ammonia concentration significantly affect digestion efficiency and biogas generation.

Page 56: Upgrading of Biogas

Key Processes

• Biogas uses: vehicle fuel, natural gas grid injection.

• Key steps: removal of CO2 and water.

Page 57: Water Vapour Challenges

Important Notes

• Biogas is typically saturated with water resulting in the need for drying in many upgrading processes.

Page 58: Methods to Reduce Water Vapour in Biogas

Techniques

A) Refrigeration: - Heat exchangers cool biogas to condense water vapour, recovering condensate for recycling.B) Absorption: - Single pass and regenerative absorption processes utilize hygroscopic materials to extract water.C) Adsorption: - Dry agents are used to lower moisture levels effectively.

Page 59: Water Scrubbing Process

Details

• Utilizes counter flow of water to remove CO2 and H2S, maximizing methane concentration.

Page 60: Carbon Dioxide Removal Techniques

Importance

• Removal of CO2 enhances the energy value of biogas vehicle fuel and ensures reliability across different applications.

Page 61: Hydrogen Sulphide Removal

Process Overview

• Various techniques address H2S, including iron chloride dosing, sodium hydroxide scrubbing, and biological desulfurization, improving overall gas quality.

Page 62: Conclusion

• Advances in biogas technology contribute to effective waste management, reduce environmental impact, and foster sustainable energy practices.

Page 63: Final Thoughts

Thank You

• Acknowledgment for engagement and attention in understanding biogas processes.