BIOGAS: GENERATION,UTILIZATION AND PIPING SYSTEM
EDWIN B. BARAL rmp/ce Chair, University Technical Working Group Physical Plant and Site Development Services Nueva Vizcaya State University Bayombong, Nueva Vizcaya
Biogas is a major by product of anaerobic processes. All decaying organic matters produced biogas when it undergoes decomposition. The process of decomposition even without the presence of oxygen is anaerobic decomposition. “Anaerobic digestion is a process of allowing bacteria to allow bacteria to grow through metabolic process of fermentation where organic materials is broken down.
Biogas is produced when bacteria digest biomass in condition when air is lacking. Garbage buried deep in the land fill produces biogas and any biodegradable materials place in air tight tanks or Anaerobic digesters
Biogas – A mixture of gases, about two thirds methane & other one third is made up of carbon dioxide, water vapor and small proportion of other gases.
Biomass – Method to change plants and animal materials into high quality fuel.
- It can be use directly as fuel - It can be carbonized first and then used as fuel.
- To produced ethanol yeast is added for a biomass placed inside a container to change sugar into ethyl alcohol.
Methane, the simplest Hydrocarbon A carbon atom has four valence electrons and forms for covalent bonds. Therefore, the simplest hydrocarbon consists of one carbon atom to which four hydrogen atoms are bonded. The C-H bonds in this simplest hydrocarbon, called methane, are formed from tetrahedrally directed sp3 hybrid orbitals on the carbon atom. You can represent the structure of methane by its molecular formula, CH4, which gives the number and kind of atoms in the molecule, or by its structural formula, which shows how the atoms are bonded to one another: (Ebbing and Gamon, General Chemistry,
6th edition, Houghton Mifflin Company, 1999)
Adapted from Robert D. Whitaker et al., Concepts of General, Organic and Biological, p.231 as cited by Ebbing and Gammon, General Chemistry, Sixth Edition p.1038, published by: Houghfton Mifflin Company, 1999
Why is it necessary to tap biogas as an alternative source of energy?
• It is a renewable energy • It is better to burn the methane than let it escape in the atmosphere because its heat trapping effect is 21 times than that of CO2 (Methane is 21 times harmful than CO2) • It is a contributory factor in global warming as two thirds of biogas is methane
Anthropogenic Greenhouse Gases in the Atmosphere
Source: Nebel & Wright, Environmental Science, 6th Edition, Prentice Hall, 1998, p.412
Anthropogenic - referring to the pollutants and other forms of impact on natural environments that can be trace to human activities
Greenhouse gasses- Gases in the atmosphere that absorb infrared energy and contribute to the air temperature. These gases are like a heat blanket and are important in insulating Earth’s surface. They include CO2, water vapor, CH4, N2O, and CFCs and other halocarbons.
Why we have to tap biogas from land fill and sewage treatment facilities
• To control methane gas emission into the atmosphere • As a source of alternative energy • Ratification of Kyoto Protocol • Proper waste management & sewage effluent treatment
Energy Flow Diagram (Biogas from Landfill)
Energy Flow Diagram (Biogas from Anaerobic Digester)
Biogas treatment/ cleaning – process of removal of water vapor in H2S (hydrogen sulfide) Removal of water vapor – can be done by installing refrigerated driers and coalescent filter. Removal of H2S – can be done by installing filters
How much biogas can recover from garbage on landfill
• Landfill biogas recovery = landfill biogas generation x collection efficiency
Methane generation potential of garbage: depends on the quantity of volatile solid present , type of waste, acidity/alkalinity
Energy Flow Diagram (Household Application)
Estimated Biogas per kilogram of waste/manure
1. Swine (pig) manure - 3.75 kg/head per day estimated quantity biogas in cubic meters: 0.0403 m3/kg - 0.0504 m3/kg 2. Cow/Bufallo manure – 8 -12 kg/head per day estimated quantity biogas in cubic meters: 0.023 m3/kg - 0.04 m3/kg
3. Chicken (poultry) manure – 0.09 kg/head per day estimated quantity biogas in cubic meters: 0.065 m3/kg - 0.116 m3/kg 2. Human estimated quantity biogas in cubic meters: 0.020 m3/kg - 0.028 m3/kg
Required Diameter of Gas Pipe from Processed Biogas
By Darcy-Weisbach Equation • D = f L V2 / 2 hL g
where: f = frictional factor hL= head loss L = length of processed biogas pipe V = flow velocity of processed biogas g = acceleration due to gravity
Gas Requirements for Some Appliances
Source: Philippine Agricultural Engineering Standard, 2002
Appliances (Type) – Gas Requirements(m3/hr 1. Gas Burner (non-continuous) 5 cm, 10 cm, 14 cm - 0.2267; 0.2800; 0.4200 2. Mantle Lamp (non-continuous) ordinary lamp - 0.0710 25-watt equivalent - 0.1000 60-watt equivalent - 0.1950
3. Gas Refrigerator (continuous) 0.01 m3 0.17 m3 0.225 m3 4. Engine (per KW output) gasoline (non-continuous) diesel (non-continuous)
- 0.0530 - 0.0670 - 0.0780
- 0.5690 - 0.7000
List of Companies
• SCS ENGINEERS (Environmental Consultants and Contractor, http//www.scsengineers.com/) • FIRST BALFOUR (A Lopez group of company, www.firstbalfour.com) • BIOGAS TECHNOLOGY (INDIA) PVT.LTD (http://www.biogasindia.com/services.html) • CHENGDU ENERGY- ENVIRONMENT INTERNATIONAL CORPORATION (CEEIC) –China • APPLIED FILTER TECHNOLOGY INC.- company that design construct and built LFG processing system that removed CO2 and contaminants from gas stream.