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Chemical Engineering in the study of Landfill gas

  • 1.  Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 01-31-2018 22:57

    I want to make a report about the study of the production of landfill gas from municipal waste (MSW). Any experience on field.



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    Bertha E. Ibarra Lopez Msc
    Assistant Profesor
    Technical University of Ambato
    Ambato
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  • 2.  RE: Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 02-01-2018 00:40
    ​I have had some design reviews for a local plant. So depends on what area you desire support.

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    Michael Akindeju (PhD, CEng, RPEQ, MIChemE)
    Principal Consulting Process Engineer & Director
    MKProro Engineering Pty Ltd
    VIC, Australia
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  • 3.  RE: Chemical Engineering in the study of Landfill gas

    FELLOW
    Posted 02-02-2018 06:16
    I am currently working with landfills developing technology to monitor gas production and have served as an expert witness for environmental issues of landfills.  I would love to collaborate.

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    Joseph Smith PhD
    Wayne and Gayle Laufer Endowed Energy Chair
    Missouri University of Science and Technology
    Rolla MO
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  • 4.  RE: Chemical Engineering in the study of Landfill gas

    Posted 02-02-2018 10:29
    There have been cases where there have been underground fires.  And in the case of very old landfills, mixed industrial and municipal waste.
    Notable instances are the landfill near St. Louis, Missouri, and near Philadelphia, Pennsylvannia.
    I would expect that newer landfills with controls over municipal waste only would be more consistent in the sour methane production.
    In the USA, there are consultants who assist in remediation of these cases, and are especially concerned about leachate migration out of the landfill site.

    Also, FYI, landfills on Native American reservations were exempt from local rules, and that is where the EPA has found what became Superfund sites.
    The most public case is a reservation  NW of the Salton Sea. Look in the  Utne Reader winter edition, where the EPA sued the tribe ( which has no money).
    There was some major dumping of POTW sludge from San Diego and waste brokers handling waste from military contractors.





  • 5.  RE: Chemical Engineering in the study of Landfill gas

    FELLOW
    Posted 02-03-2018 08:38
    Edited by Joseph Smith 02-03-2018 08:48
    Tim is correct - Landfills have a checkered past due to some very serious examples of bad operation which have resulted in serious environmental impact.  However, in most cases Landfills that are properly designed can be used to gather methane which is used to generate "green" electric power.  Landfills basically operate as large Bio-digestors when properly cared for and operated.  One I've worked with near Tulsa, OK generates up to 150 MW of electricity that provides value to the community.  Another I worked with near Midland, MI was effectively used to store residual ash from incinerating waste water treatment sludge.  Well designed and operated Landfills include cells lined with several layers of plastic and clay to collect leachate and prevent it from entering the ground water.  Landfills also have large gas collection networks to gather Landfill gas (50% CH4/50% CO2) fed to gas turbines that generate electricity.  These gas collection networks have wellheads where gas composition is monitored to check for fugitive emissions and air in-leakage (which can lead to underground fires).  EPA regulations require Landfills to monitor fugitive H2S and CH4 emissions and to use flares to burn waste gas with 98% Combustion Efficiency if not used to generate electricity.  Landfills also monitor leachate quality and treat excess leachage in waste water treatment plants.  A challenge landfills have is caused by silicon in makeup, packaging material, etc. which becomes part of the bio-gas and creates SIO2 deposits in SCR units used to reduce NOx emissions from gas turbines.  In summary, although Landfills have a checked history, well operated landfills are a key part of a well designed environmental program that make it possible for communities and companies to effectively care for waste generated during normal operation.

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    Joseph Smith PhD
    Wayne and Gayle Laufer Endowed Energy Chair
    Missouri University of Science and Technology
    Rolla MO
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  • 6.  RE: Chemical Engineering in the study of Landfill gas

    LIFE MEMBER
    Posted 02-03-2018 23:27
    It is not just very old landfills (before 1986?) that may contain industrial solvents, paints and automotive fluids.  It is still legal for homeowners and commercial businesses to dispose of small amounts of paint thinners, etc. after absorbing them on newspapers, so that there are no free liquids.  That does not mean that the vapors remain in the paper.  Theoretically, flammable solvents should not be disposed in this manner, but cities are poor educators and home owners and small business are slower learners, and so it continues, especially for spills.

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    Caroline Reynolds BA,MA,MS,PE
    President
    CR Solutions
    Austin TX
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  • 7.  RE: Chemical Engineering in the study of Landfill gas

    LIFE MEMBER
    Posted 02-03-2018 23:33
    Additional thoughts.....

    You might wish to seek information regarding the remediation of San Antonio's West Avenue Landfill in the 1980s and 90s.  While not large, it had apparently received significant amounts of home and automotive liquids disposed by soldiers prior to moving to the subsequent base, because the moving companies will not pack and move them.  You might expect to find this problem in any city with a large military base or several smaller bases.  When samples of the landfill gas were analyzed, benzene and chlorinated solvents were found to have migrated through soils and faults into a surrounding neighborhood.

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    Caroline Reynolds BA,MA,MS,PE
    President
    CR Solutions
    Austin TX
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  • 8.  RE: Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 02-06-2018 08:33
    ​If you are studying how landfilled materials can be used to generate fuel gases, it might be interesting to consider alternatives like energy-from-waste facilities.   I heard a presentation by Michael Van Brunt from Covanta last year that was quite interesting.  Michael's presentation included a comparison of the environmental impacts of their facilities with the impacts from landfills.   One of Michael's presentations is at this link:  http://swanaoregon.org/images/VanBrunt2015-04_NW_SWANA.pdf
    Swanaoregon remove preview
    View this on Swanaoregon >


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    Mark Petrich PE
    Director, Single Use Systems Eng
    Merck & Company, Inc.
    West Point PA
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  • 9.  RE: Chemical Engineering in the study of Landfill gas

    FELLOW
    Posted 02-07-2018 06:19
    Thank you Mark for posting the link to Covanta's very interesting presentation on Waste-to-Energy.  However, the comparison to landfills is misleading because it characterizes landfills separately from Waste-to-Energy generation.  Many landfills collect biogas (methane) and generate "green" electricity in efficient gas fired engines.  The presentation limits EfW (Energy from Waste) to electricity generated by burning MSW (municiple solid waste) in very expensive and complex MSW fired plants.  A key challenge for MSW based electricity generation is related to their feedstock quality.  A second challenge is the cost of collecting (harvesting) and preparing the fuel feedstock for MSW fired systems. I believe Europe is more efficient in using MSW is due to their widespread implementation of waste recycling to concentrates and improve feedstock quality fed to their MSW fired EfW systems.  Landfill gas based EfW electricity generation is typically more efficient and economical than MSW based EfW generation.

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    Joseph Smith PhD
    Wayne and Gayle Laufer Endowed Energy Chair
    Missouri University of Science and Technology
    Rolla MO
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  • 10.  RE: Chemical Engineering in the study of Landfill gas

    DIVISION TREASURER
    Posted 02-08-2018 23:34
    Edited by Neil Yeoman 02-09-2018 07:54
    Re: Feb 7 posting by Joseph Smith:
        Comparing landfill disposal of MSW, including where the landfill gas is recovered, to Waste-to-Energy (WtE) is very situation specific and pretty complex.  Landfill gas is a mixture of CH4 and CO2, the ratio depending on a number of factors with which I am not currently totally familiar.  The CO2 part represents the oxidation of carbon in the MSW that produces nothing useful. In a WtE plant all the carbon not already oxidized produces heat that produces electric energy.  For the CH4 to CO2 ratio to be high enough to make landfill gas recovery practical the landfill must be pretty deep to ensure that enough carbon is digested anaerobically.  
        Another key factor is geography, specifically the availability of landfill sites.  For example,  I live in the Town of Hempstead, NY (population about 762,000) which is about 300 miles away from the nearest landfill site that can take the town's MSW.  The logistics of moving a million tons per year of MSW 300 miles would be a major problem, economically and environmentally.  The town has a centrally located WtE plant run by Covanta that delivers about 80 megawatts to the local power grid.  The plant is just like the one shown in the reference offered and is a very good neighbor to the surrounding business and residences.  As a "civilian" member of the town's Solid Waste Advisory Committee since 1988 I have been monitoring the operation of that plant for nearly 30 years.   
        Studies have shown that landfill works better in low population density areas where there is nearby space for landfills but those landfills tend to be small (and numerous) and not usually suitable for landfill gas recovery.
          Sometime in 2018 I am hoping that the Virtual Local Section of AIChE will host a speaker on the subject of Waste-to-Energy.
          Neil Yeoman, PE, FAIChE
     





  • 11.  RE: Chemical Engineering in the study of Landfill gas

    FELLOW
    Posted 02-11-2018 09:20
    Neil,
    Thank you for sharing a positive experience regarding waste to energy.  It's very appropriate to process waste and recover as much value from it as economically possible.  My first experience with burning MSW was as a  young boy in Death Valley taking the trash out to the burn barrel.  During my career I've been involved in burning things so I appreciate the challenges of burning MSW efficiently.
    When we lived in Midland, Michigan, we enjoyed a very active recycling program that kept most of the plastic, metal and paper out of the garbage which made it easier to provide a high quality MSW fuel to the WTE plant.  The first Waste-to-Energy plant I visited was in Nashville, TN where they produced process steam for a neighboring chemical plant by burning refuse derived fuel (RDF) composed of MSW blended with coal.  When I asked if they separated the plastic before preparing the fuel they said no so I asked if they had corrosion problems in their down stream equipment and they said they had just replaced their stack.  Other WTE plants I've visited in Illinois and Oklahoma have struggled economically due to challenges with collecting and burning MSW fuel.  I'm glad to hear the WTE plant near your community is doing well and is a good neighbor.

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    Joseph Smith PhD
    Wayne and Gayle Laufer Endowed Energy Chair
    Missouri University of Science and Technology
    Rolla MO
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  • 12.  RE: Chemical Engineering in the study of Landfill gas

    DIVISION TREASURER
    Posted 02-13-2018 01:56
    Re Feb 11 posting by Joseph Smith:
    Thanks, Joseph.
        In the Town of Hempstead we have an aggressive recycling program to remove paper, plastic, and metals, but with the technology used that is not really needed to ensure feed quality.  I do not see why collection is a problem specific to WtE since it has to be collected for landfill disposal also.  The economics are based on the WtE facility getting paid for disposing of the waste in addition to getting paid for the power delivered to the local grid.  As I wrote before, WtE vs landfill is very situation specific. 
        To learn more go to the Covanta web site and take the virtual tour.  It's accurate and complete, and almost exactly what we have in Hempstead.
        Neil Yeoman, PE, FAIChE  






  • 13.  RE: Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 02-15-2018 23:05
    I think I can provide a bit of clarification to the chemistry of landfill gas.

    The dominant part of landfill is paper, which is a polysaccharide, that is, (CHOH)n.  If for simplicity let us consider it glucose, (CHOH)6, then the anaerobic reaction is (approximately):

    (CHOH)6 => 3 CH4 + 3 CO2.

    The combustion value of glucose is about 673 kcal/gmol.  The combustion value of methane is 191 kcal/gmol.  Therefore, the thermal efficiency of the reaction is 3 x 191 / 673 = about 85%.   That is, the three moles of carbon dioxide do not mean that half of the heat content is lost.   And the amount of useful heat, which can be recovered in a landfill/gas turbine system is not much less than what can be recovered in a waste-to-energy plant.

    Another reaction, which may be considered, is:

    (CHOH)6 => 6 C + 6 H2O

    The heat of combustion of carbon is 94 kcal/gmol.  So, the thermal efficiency of the reaction is 6 x 94 / 673 = about 84%.  The carbon obviously cannot be sent as gaseous fuel to a gas turbine.  So this reaction will indeed lower the amount of energy recoverable in a landfill/gas turbine system.


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    Georg Christensen
    The Woodlands TX
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  • 14.  RE: Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 02-12-2018 06:36
    Thank you, Mark, for the valuable link, been presented by Micheal, regarding benefits of waste - to- energy.  We could I notice here in Middle East countries, in general, dispose of thousands tonnage of solid waste in the desert to be fired there in the atmosphere which is intern enhance increasing GHS.
    I think this is a great opportunity, we have to encourage the local authority along with environmental affair to convert this mass waste to useful energy in near future. It will work in reducing environmental impact but require coalition globally to move a step further.

    Thanks also for everyone who shares information & expertise in this important matter.

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    Ismail Abudoros
    Plant Manager
    Olympic Ice Production and Sweet Water S.P.C.
    Hidd
    Bahrain.
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  • 15.  RE: Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 02-13-2018 09:33
    ​I shared this discussion with Mike Van Brunt.  He says that he is not an AIChE member, so I did some recruiting!  Maybe this activity will motivate him to join.   Mike offered some comments for me to share, and he asked that anyone who wants to discuss in more detail please contact him.  I'm pasting his comments verbatim:

    Mark,

     

    Good to hear from you, and thanks for forwarding the thread. Unfortunately, I am not an AIChE member, so I cannot access the discussion directly. However, I do think it would be useful to respond to Dr. Smith's comments. In particular, since he references the efficiency of WTE via combustion versus landfill gas to energy, you may want to direct him to a paper co-authored by NC State University and U.S. EPA scientists, titled Is It Better to Burn or Bury? and published in ES&T, available here: https://pubs.acs.org/doi/abs/10.1021/es802395e

     

    The following excerpt from the paper is relevant:

     

    One notable difference between LFGTE and WTE is that the latter is capable of producing an order of magnitude more electricity from the same mass of waste. In addition, as demonstrated in this paper, there are significant differences in emissions on a mass per unit energy basis from LFGTE and WTE. On the basis of the assumptions in this paper, WTE appears to be a better option than LFGTE. If the goal is greenhouse gas reduction, then WTE should be considered as an option under U.S. renewable energy policies. In addition, all LFTGE scenarios tested had on the average higher NOx, SOx, and PM emissions than WTE. However, HCl emissions from WTE are significantly higher than the LFGTE scenarios.

     

    With regard to efficiency, Dr. Smith may be thinking of the efficiency of the energy recovery process itself. It is true that the combustion of landfill gas for electricity generation is more efficient than combusting solid fuel; however, this leaves out several crucial inefficiencies inherent to landfills: efficiency of gas collection (typically 50-60% on a lifetime basis), partition of carbon into CO2 and methane, incomplete conversion of biogenic feedstock to gas, and the stability of fossil-based components in the landfill.

     

    To Dr. Smith's second point, feedstock preparation is less critical than one might think. While it is true that Europe does have higher recycling rates, it has a relatively minor impact on boiler efficiency. Boiler efficiency is driven more by basic boiler design, and, more widely done in Europe, the incorporation of combined heat and power systems.

     

    I would be happy to speak with Dr. Smith and anyone else on the thread in more depth, if they are interested.

     

    Best regards,

     

    Mike



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    Mark Petrich PE
    Director, Single Use Systems Eng
    Merck & Company, Inc.
    West Point PA
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  • 16.  RE: Chemical Engineering in the study of Landfill gas

    FELLOW
    Posted 02-14-2018 08:51
    Thank you for continuing this discussion.  Certainly WtE plants contribute to our renewable energy portfolio as the examples you've described illustrate.  I am in favor of finding ways to extract more energy value from waste resources.  As shown in the US energy balance flow chart (see https://flowcharts.llnl.gov/), in 2016, the US consumed 97.3 Quads of energy with 78.6 Quads provided by coal+gas+petroleum and 4.75 Quads provided by biomass.  In 2014, 258 million tons of MSW was generated in the US of which 53% was landfilled and 13% was burned for energy (see www.eia.gov/energyexplained/?page=biomass_waste_to_energy).  As Mark correctly pointed out, WtE plant efficiency is mainly governed by the steam cycle since they burn MSW to produce steam to generate electricity.  As EIA points out, in 2015, 75 MSW powered generators burned 29 million tons (out of 258 total tons produced) in the US to produce 14 billion Kwthr of electricity (0.0478 Quads).  However, as Mark also correctly points out burning this MSW reduced the volume of waste by about 87% which means less use of the limited landfill volume for this waste.  I believe well designed and operated WtE plants should be used to capture value from our waste and I appreciate all that has been said regarding this form of renewable energy.  My earlier posts regarding the economics and efficiency of WtE plants were based on experiences I've had working with plants not designed nor operated like Covanta's plants.

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    Joseph Smith PhD
    Wayne and Gayle Laufer Endowed Energy Chair
    Missouri University of Science and Technology
    Rolla MO
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  • 17.  RE: Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 02-19-2018 09:49
    ​You might check with the American Biogas Council for information on landfill gas.

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    Thomas Stephens
    Transportation Systems Analyst
    Argonne National Laboratory
    Lemont, IL
    Homer Glen
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  • 18.  RE: Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 02-22-2018 17:57
    Thanks so much for your inputs, really appreciate, Michael, Joseph, Timothy, Caroline, Mark, Neil, Ismail, Georg and Thomas there are remarkable.
    -Is good to study the risk of flammable solvent deposited on landfills.
    -In South America Landfill Gas is produced in some cities in a technical operation where the garbage is weight and cover with soil.
    - There are environmental impacts in the operation of a landfills as the discussion group mentions. I was focusing on the methane emission. And considering the waste to energy options.
    In South America there is not an entity that regulates the emissions the operations of landfill. Most of the landfills are controlled by the municipalities.

    - EPA is a good options to consider as a base line of methane emissions on landfills. I will search for the cases of landfills that the group suggests. I will consider the amount of garbage that each landfill receives.
    - I’ll consider the reaction of methane production.
    - The location of Neil a landfill for operation is hard. I want to study in a landfill located in the highlands.

    I appreciate your inputs, and are really good considerations. I will evaluate the conditions of garbage, pH, humidity of the soil and garbage as a methane production.

    Also, considering the reaction of methane should be better to work with organic garbage, and a biodigestor should be considerate.

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    Bertha Ibarra Lopez Msc
    Assistant Profesor
    Technical University of Ambato
    Ambato
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  • 19.  RE: Chemical Engineering in the study of Landfill gas

    SENIOR MEMBER
    Posted 02-23-2018 01:16
    Many years ago I did some extensive modeling of methane generation in landfills.  A very good 2-stage model could be constructed with the simplification (already described above) of cellulose to glucose to CH4 and CO2.  It turns out that the limiting factor (and key modeling criteria) was the anaerobic conversion of cellulose to glucose.  You needed an aerobic cleansing to remove all oxygen, followed by the establishment of the appropriate anaerobic populations.  Those populations would grow nicely so long as the lanfill was fairly homogneous and stable.  Key components in the speed and maximum rate of gas generation were the water content in the waste (below 20% and nothing happens, like a landfill in a very arid area. Above ~ 36% and too much water became a problem), the density of the waste, and landfill temperature.  Liquid (leachate) recovery and recycling helped stabilize gas generation.

    Solvents in low concentration were not a major problem, but anything that adversely impacted the anaerobic species growth could shut down gas generation indefinitely.  Obviously, if you attempted aeration you shut down methane generation by converting the decomposition to the aerobic products of CO2 and H2O.

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    Henry Waldron
    Principal
    Self Employed
    Voorhees NJ
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