Waste to energy

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  • The U.S. EPA defines energy recovery from waste as the conversion of non-recyclable waste materials into useable heat, electricity, or fuel through a variety of processes that include, and are not limited to – combustion, gasification, pyrolysis, anaerobic digestion, and landfill gas (LFG) recovery, just to name a few.How then do we actually go about converting waste to energy?
  • Syngas can be fed into a combined cycle gas turbine (CCGT) power plant achieving up to 60% efficiency via a Brayton cycle from the gas turbine and recovered heat (steam generator) in a Rankine cycle
  • Biogas can be produced via anaerobic digestion either from biogas plants or by capturing biogas in landfills. The first method is a more conventional one, and the second is more problematic because methane is combustible in contact with O2. It is also difficult to capture it completely.
  • Biogas is produced from the anaerobic digestion of organic waste such as manure, sewage, municipal solid waste (MSW), plant material and crops. It consists mainly of methane and carbon dioxide, and is a renewable substitute for natural gas. It can be used as fuel for heating purposes, as well as in gas engines to convert the energy found in the gas to electrical and heat energy.
  • *Provided new technologies are in place to ensure no leakage of gas to the atmosphere. Global warming potential of CH4 c.f. CO2 is 23x over 100 yr as stated by IPCC.**Nitrification and denitrification both produce N2O. N2O production during denitrification can be reduced if carried out in an oxygen-deprived environment and nitrification is significantly reduced at temperature >40oC. N2O contributes to 300x radiative forcing c.f. CO2 over a 100 year time frame.
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, DrXiujin Li.pdf
  • Biogas can be cleaned to remove impurities and upgraded to pure biomethane.
  • Biogas Upgrading Technologies (ref:http://www.bcfarmbiogas.ca/files/pdf/Biomethane%20Feasibility%20Study.pdf page 12+)Water WashBased on the Chemical Removes CO2; but adds H2O; H2S not removedChemisorption / PhysisorptionSpecial solvents to remove CO2, H2O, H2SCan be heated to remove water, H2S to be regeneratedHowever, overall toxicPressure Swing Adsorption High pressure + Adsorbent material leaves 97% MethaneRemainder gas can be burnedHigh throughput; 2nd most effective in SwedenMembrane separationMembrane retains methane, vents all other gases; “reverse osmosis process”Horses for Courses: must match the upgrading technology to the demand+ Power Generation – powers sewage plants+ Pipeline injection:>>> High-Pressure injection: strong dilution factor so less stringent contaminants; but needs compression>>> Med-Pressure Network-injection: less pressure but less dilution+ Vehicle use – needs to be compressed, etc.
  • Currently, only 8% of waste plastic is recycled in the US, 15% in Western Europe and much less in developing countries. Annually, the world produces 227 billion kg of plastic of which a-third are single-use and are thrown away. In addition, plastic accounts for 4/5 of the garbage in the oceans. Seeing that so little plastic is recycled, the mindset must be changed to reframe plastic waste as an underused resource rather than being something that is landfill destined.
  • Let’s use this case study of Cynar, a company in the UK, to learn about how plastic can be converted to fuel. And instead of me talking, I’ll let the video speak for itself.
  • The conversion of plastic to fuel is rather simple. Waste plastic is first shredded, then heated in an oxygen-free chamber (known as pyrolysis) to about 400 oC. As the plastic boils, the gases are separated and reused to fuel the machine itself. The remaining fuel is distilled and filtered to obtain different fractions that can be sold and used.
  • PE: PolyethylenePP: PolypropylenePVC: Polyvinyl chloridePETE: Polyethylene terephthalate
  • Waste to energy

    1. 1. CM4282 Energy Resources Tutorial Presentation Waste-to-Energy Group J FOONG CHUERN YUE DARREN NATASHA E GOUW MING ZHI RAYSTON LEONG YU MIAO YU YUEBO
    2. 2. Presentation Outline •What is Waste-to-Energy? •Incineration •Gasification •Waste to Fuel •Plastic to Fuel
    3. 3. •Turning non-recyclable waste to a useable form of energy •E.g. Electricity, heat or fuels •Through combustion, gasification, anaerobic digestion, landfill gas recovery, and pyrolysis http://www.epa.gov/osw/nonhaz/municipal/wte/ Image: http://wastetoenergyinternational.com/wp-content/uploads/2013/03/Promoting-a-clean-future.jpg
    4. 4. Incineration • Works primarily on the combustion of municipal waste to generate heat for use in electricity generation. • Key features: Waste storage and handling Waste feeding Combustion Steam and electricity generation Air pollution control Ash residue handling • Combustion Stages: Ignition Drying Moisture is evaporated Combustion Devolatilization Combustible volatiles are released http://www.rpi.edu/dept/chem-eng/Biotech-Environ/incinerator.html Volatiles are ignited in the presence of oxygen Volatile matter is completely combusted and fixed (Carbon is oxidized to CO2)
    5. 5. Incineration Advanced Stoker System http://www.khi.co.jp/english/kplant/business /environment/g_waste/heat.html
    6. 6. Incineration A Rankine Cycle http://upload.wikimedia.org/wikipedia/commons/0/00/Rankine_cycle_layout.png
    7. 7. Incineration Pros and Cons Advantages  Waste volume reduction (95%-96%)  Destruction of combustible toxins  Destruction of pathogenically contaminated material  Energy recovery http://www.rpi.edu/dept/chem-eng/Biotech-Environ/incinerator.html Disadvantages  Air pollution  Ash must be landfilled and may be hazardous  High capital and operation cost  Wastewater problems
    8. 8. Gasification https://www.gasification.org/page_1.asp?a=87
    9. 9. Gasification Schematics for a CCGT plant fed by syngas http://www.killingholme-energy.com/
    10. 10. Waste to Fuel: Biogas Biogas Production • Anaerobic digestion of organic matter in airtight digesters • Anaerobic digestion in landfills Image: http://www.mnn.com/green-tech/research-innovations/blogs/landfill-methane-could-power-3-million-homes# Image: http://www.daviddarling.info/encyclopedia/A/AE_anaerobic_digestion.html
    11. 11. Waste to Fuel: Biogas Image: http://www.cowpattypatty.com/
    12. 12. Waste to Fuel: Biogas Advantages • • • • Efficient way of energy conversion Household and bio-wastes can now be disposed of in a useful manner Provides a non-polluting and renewable source of energy* Significantly lowers the greenhouse effect on the earth’s atmosphere • E.g. removing N2O from manure** • Excellent solution for agricultural & livestock waste Disadvantages • Less efficient than natural gas as direct fuel (low % purity) • Process is not suitable for commercial use – largely domestic/rural cooking, etc.
    13. 13. Waste to Fuel: Biogas Development History in China • First digester (8 m3) was built by Mr Luo Guo Rui ( ) in the 1920’s. Biogas was used for family cooking and lighting. • In 1950’s, the Chinese government started promoting biogas in rural areas to provide energy for farmers. • From 2003-2013, rapid development in rural areas. 41.68 million household small digesters (8-12 m3) were built. • Increase use of AD in municipal and industrial sectors. Advertisement for Luo’s biogas in Shen Newspapers, Shanghai 1932. http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, Dr Xiujin Li.pdf
    14. 14. Waste to Fuel: Biogas Current Status (Agricultural and Rural Sector) • Household small digesters 41.68 million units, providing clean energy to 160 million people in rural areas. • Small-scale biogas plants 24,000 units mainly for small animal farms • Medium and large-scale biogas plants 3,691 units • Biogas plants in animal farms 80,500 units (15 billion m3 p.a. (2012)) http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, Dr Xiujin Li.pdf
    15. 15. Waste to Fuel: Biogas Current Status (Municipal Sector) • For sludge 51 units • For refuse 10 units • For food waste 40 units Current Status (Industrial Sector) • 60-80 plants to treat waste waster • Largest in Nanyang City, processing waste water from ethanol plant producing 500,000 m3 biogas daily capable of providing energy for http://www.epa.gov/agstar/documents/conf13/Biogas Production in all residents China - Current Status and Future Development, Dr Xiujin Li.pdf
    16. 16. Waste to Fuel: Biogas Future Development • Biogas potential MSW: 15 billion m3 Industrial: 48 billion m3 Agriculture: 289 billion m3 • In total: 352 billion m3, if 100% utilized 176 billion m3, if 50% utilized (equivalent to current NG consumption) http://www.epa.gov/agstar/documents/conf13/Biogas Production in China - Current Status and Future Development, Dr Xiujin Li.pdf
    17. 17. Waste to Fuel: Biomethane Biogas Upgrading • Biogas is 65% methane, compared to 98.5-99% fuel grade • Also contains other contaminants • Inert diluents reduce energy content: CO2, N2 • Contaminants: Biologicals, Microbes, Trace Metals • Corrosives: Sulfur & H2S, Siloxanes, Ammonia Image: http://www.bio-methaneregions.at/?q=node/41
    18. 18. Waste to Fuel: Biomethane Biogas Upgrading Technologies • • • • Water Wash Chemisorption/Physisorption Pressure Swing Adsorption Membrane separation Biomethane Applications • Direct power generation • Direct gas injection • Vehicle use http://www.bcfarmbiogas.ca/files/pdf/Biomethane%20Feasibility%20Study.pdf http://www.apvgn.pt/documentacao/advantages_of_biomethane_as_a_fuel.pdf
    19. 19. Waste to Fuel: Biomethane Advantages • High CH4 content, effectively Natural Gas • “Carbon neutral” • Reduces waste, which would cost energy otherwise Current Developments • Biomethane is highly successful in Sweden & Germany – zero fuel taxes, financial support for biomethane production, 40% reduced personal income tax for CNG company car
    20. 20. Waste to Fuel: Summary Image: http://www.biogasmax.co.uk/biogas-strategybiofuel-opportunities/from-biogas-tobiomethane-and-biofuel.html
    21. 21. Plastic to Fuel Problem Image via: coastalcare.org • Only 8% of waste plastic is recycled in US, 15% in W. Europe and much less in developing countries • 227 billion kg of plastic is manufactured annually and 33% is single-use/thrown away • Plastic accounts for 4/5 of garbage in the oceans http://www.inspirationgreen.com/plastic-waste-as-fuel.html Change in Mindset • Plastic should be viewed as an underused resource rather than being landfill destined
    22. 22. Plastic to Fuel Case Study: Cynar in the UK http://www.youtube.com/watch?v=0SDS58y0hDY#t=149
    23. 23. Plastic to Fuel http://www.cynarplc.com/images/ProcessFlowDiagram.jpg
    24. 24. Plastic to Fuel Pros Cons • Process (pyrolysis) takes place in vacuum and plastic is melted, not burnt. Hence minimal to no resultant toxins released into the air • PVC produces chlorine that will corrode reactor and pollute the environment • PETE produces oxygen into the oxygen-deprived chamber • The synthetic fuel is low in thereby slowing down the sulfur process (PETE recycles efficiently traditionally, so just • Conversion rate of 95% (wt. send PETE to recycling to vol.) centres) • PE and PP produces fuel that burns cleanly http://www.inspirationgreen.com/plastic-waste-as-fuel.html
    25. 25. •Turning non-recyclable waste to a useable form of energy •E.g. Electricity, heat or fuels •Through combustion, gasification, anaerobic digestion, landfill gas recovery, and pyrolysis http://www.epa.gov/osw/nonhaz/municipal/wte/ Image: http://wastetoenergyinternational.com/wp-content/uploads/2013/03/Promoting-a-clean-future.jpg
    26. 26. Questions?

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