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. 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)
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
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. Waste to Fuel: Biogas
Image: http://www.cowpattypatty.com/
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. 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. 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.
16. 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
17.
18.
19. 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
20.
21.
22. 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
23. 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
24. 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
25. Waste to Fuel: Summary
Image:
http://www.biogasmax.co.uk/biogas-strategybiofuel-opportunities/from-biogas-tobiomethane-and-biofuel.html
26. 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
27. Plastic to Fuel
Case Study: Cynar in the UK
http://www.youtube.com/watch?v=0SDS58y0hDY#t=149
29. 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
30. •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
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.
