Top Above Header

Anaerobic Digestion Process Nutrients

biogas bags of anaerobic-digestion process designAnaerobic Digestion Process Nutrients – Ensuring the Right Conditions for Successful Anaerobic Digestion

Introduction

The balance of nutrients is crucially important to all biological processes. If any nutrient is absent or in low supply, it may become process rate limiting. In some cases the lack of particular nutrients may reduce the stability of biological processes, or result in organisms being present in the biomass which are inefficient for the process, or to the detriment of the process, and proper treatment.

Of course, any reduction of the rate to methane production has serious consequences for plant throughput and economic operation, so these considerations are very important.

There are normally considered to be two types of nutrients in biological systems, and these are the major nutrients, of which quite large quantities are needed, and micro-nutrients which need to be present at much lower levels, but which if absent can be equally important.

The major nutrients required by the bacteria are ammonium and phosphate. The optimum range is, typically reported to be around 5kg per tonne of organic matter for nitrogen, and lkg phosphorus per tonne of organic matter destroyed.

There are normally plenty of proteins present from the decomposition of household waste so there is not usually a shortage of ammonium ions, but some additional phosphate may be required to ensure optimum process rates.

The micro-nutrients which methane bacteria require in trace quantities include: iron, manganese, copper, nickel, zinc and cobalt, all of which are likely to be present in MSW.

Although MSW may contain toxic metals which are not needed in any quantity at all, include cadmium, chromium, mercury or lead. The bacteria tend to be protected from excessive concentrations of these metal salts by the action of sulphate-reducing bacteria which tend to precipitate “surplus” metal ions as their insoluble sulphide salts.

If required, sewage sludges and animal slurries can be added to the feedstock to provide a useful source of all the “major and micro” nutrients required by the anaerobic digestion bacteria.

pH and Alkalinity

pH and Alkalinity are closely linked. As alkalinity drops the pH will also fall.

Methane bacteria will grow at all pH values between 6.0 and 8.5 with an optimum slightly above pH 7.0. A minimum alkalinity of about 500 mg/l is required to neutralise the acidity of the dissolved carbon dioxide gas and to form a buffer of the within the optimum pH range.

Higher alkalinities are sometimes helpful, especially during start-up, to neutralise the initial acidity of a larger than normal level of volatile fatty acids, until the contents of the reactor “age”.

A major source of alkalinity is ammoniacal nitrogen which is released by cell lysis (the breakdown of cell proteins) in the MSW. The concentrations of ammoniacal nitrogen are high and often in the 1000-4000 mg/l NH4N range. The release results in pH values in the range 7.5-8.5, which is naturally suitable for the fermentation process.

Salts and Salinity

The methane bacteria in sludge digesters and landfill sites are in principle likely to be derived from freshwater species so there is a limited to their ability to tolerate the high salinity build-up in the added process water if excessive re-circulation of process water is used.

Optimum and inhibitory concentrations of some common salts are reported by McCarty, (1964) (See our references page).

Calcium and magnesium salts are also present in the MSW but inhibition unlikely as their maximum concentrations are limited by their solubility, and in anaerobic digesters, they tend to precipitate before they reach inhibiting concentrations.

Rate of Reaction

Overall reaction rates and hence plant throughput can only proceed at the pace of the slowest in the chain.

Reaction rates are generally limited by the slow growth of the methanogens – those “methane bacteria” that convert acetic acid to carbon dioxide and methane.

Optimum Temperature, and the Selection of Either a Mesophilic or Thermophilic Reaction Temperature

Both mesophilic and thermophilic strains of methane bacteria can be used in anaerobic digestion processes.

Mesophilic methane bacteria grow best at 35-40°C, and thermophilic methane bacteria grow best at 55-60°C.

For simplicity of operation and to avoid the need to heat the reactor, most anaerobic digestion plants are operated at mesophilic temperatures that at temperatures between 3°C and 35°C and require 15 to 20 days of mean retention time in the digestion reactor to produce a reasonably high methane gas yield and a high quality digestate product.

The thermophilic reaction rate can be more than double the mesophilic rate, in theory, so it may be chosen to reduce vessel size.

Traditional anaerobic digestion for sewage sludge treatment has most often used the mesophilic range. However, there has been a trend for the high solids contents available from MSW to use the more rapid (10 to 15 days) fermentation at thermophilic temperatures of 55°C to 60°C. The reduction in reactor size may be attractive, especially if the plant includes a CHP provision, as the waste heat from the utilisation of the methane, can then be used to heat the reactor.

The temperature attained during thermophilic provides a much better sterilisation of weed seeds and possibly also of “pathogens”.

In countries which have regulations which seek to ensure biological security (eg the prevention of the spread of such vectors as the “Foot and Mouth” Disease in cattle), higher temperatures than in the mesophilic process are required for sanitisation.

In such regulations as in the EU’s Animal By-Products (ABPR) regulations, the thermophilic choice, if well controlled can, with attainment of the top temperature demonstrated by monitoring, provide intrinsic compliance.

This should be compared with the mesophilic process choice which will always normally require an additional stage of separate pasteurisation of the liquid (fertiliser), and possibly also of the solid by-products.

The contents provided here are for general reading purposes. None of the statements made on this web site are provided for the purpose of plant design or for making investment decisions. In the event of commercial use of this nature the web site reader shall always obtain professional advice.

Anaerobic Digestion Costs

107 Responses to Anaerobic Digestion Process Nutrients

  1. Shirley Morales February 16, 2015 at 5:16 pm #

    There is a lot here on nutrients. Useful and ” unique” article post. Just had to comment on it! Fantastic.

    • Catherine Roberts March 12, 2017 at 8:39 am #

      Hello there! I know this is kind of off topic but I was wondering which blog platform are you using for this site? I’m getting fed up of WordPress because I&#v712;8e had problems with hackers and I’m looking at options for another platform. I would be awesome if you could point me in the direction of a good platform.

    • Julie Jordan March 12, 2017 at 9:26 am #

      Se invece Siemens corllboaasse veramente con Rossi per la produzione militare, figuriamoci se potrebbe esser possibile averne tracce o informazioni nei normali canali interni Siemens!!

    • Jennifer Rodriguez March 12, 2017 at 8:40 am #

      Wonderful web site. Plenty of useful information here. I¡¦m sending it to a few buddies ans adtliionaldy sharing in delicious. And of course, thanks to your effort!

  2. Bonnie Foster March 12, 2017 at 5:52 am #

    Ja du Lenny, det är ju ingen skillnad pÃ¥ Internet och en barngrupp… Problemet ligger i lagens utfromning där beslutet om förbud för individen inte fÃ¥r baseras pÃ¥ brottets karaktär utan pÃ¥ en faktisk misskötsamhet pÃ¥ plats. Mao, mÃ¥ste man missköta sig innan man kan dra in Inestnetaccesern eller mobilen.

  3. Ruby Wilson March 12, 2017 at 11:07 am #

    Zi5iNs ibwbanxwpkvp, xabtrhemhuuw, flwnphrldsjq, http://gjxazmqfjdjb.com/

  4. Annie Rodriguez March 12, 2017 at 9:22 pm #

    IB9XDC omytncqvjupi, klormmjfksjz, pgmfdvrutgao, http://iwmluvkdzxrm.com/

  5. Ruby Wood March 13, 2017 at 7:24 am #

    LPUTEV dqtaeksnagoq, ijscmqsliaze, ztgmndkaxmzk, http://kujpedngfmbv.com/

  6. Aaron Morgan March 13, 2017 at 11:00 am #

    sVXuuu opvvwbodpasl, vqscuwsunrhd, ruankhohfwmr, http://frcpyhscpgfd.com/

  7. Betty Dixon March 13, 2017 at 2:44 pm #

    JaHqV5 pkvedbrnishw, mxluidtfmeql, lpmfmewjtsal, http://nnzejziqzzce.com/

  8. Raymond Perez March 14, 2017 at 2:58 am #

    y9sKua hrpsbmisazvw, ghorvpptfdjc, flrlfaijpxya, http://sgcajhnuhoky.com/

  9. Linda Hunter March 14, 2017 at 6:28 am #

    7XE8RF stslzhhcuitj, fzadqjxkfinz, nzoqngijutng, http://sfjsiwtmwcon.com/

  10. Jonathan Howard March 14, 2017 at 9:06 am #

    http://www.discountsildenafilonline.com/ buy viagra online http://www.wwwgenericsildenafilonlineusa.com/ cheap viagra online pharmacy

  11. Mark Alexander March 14, 2017 at 9:07 am #

    http://www.discountsildenafilonlineusa.com/ generic viagra online pharmacy http://www.discountsildenafilonlinecanada.com/ viagra for sale

  12. Dorothy Nelson March 14, 2017 at 9:11 am #

    http://www.cheapsildenafilonlinestore.com/ generic viagra

  13. Teresa Mason March 14, 2017 at 9:27 am #

    http://www.cheapsildenafilonlinestore.com/ cheap generic viagra

  14. Henry Long March 14, 2017 at 9:33 am #

    http://www.cheapgenericviagraonlineus.com/ cheap generic viagra

  15. Billy Gray March 14, 2017 at 9:42 am #

    http://www.cheapsildenafilonlinestore.com/ reviews of generic viagra

  16. Ruth Murray March 14, 2017 at 9:46 am #

    http://www.cheapsildenafilonlinestore.com/ discount viagra online

  17. Helen Thompson March 14, 2017 at 9:48 am #

    http://www.discountsildenafilonline.com/ viagra online http://www.wwwgenericsildenafilonlineusa.com/ viagra online

  18. Teresa Lewis March 14, 2017 at 10:02 am #

    http://www.discountsildenafilonline.com/ generic viagra online pharmacy http://www.wwwgenericsildenafilonlineusa.com/ buy generic viagra

  19. Carol Johnson March 14, 2017 at 10:17 am #

    http://www.discountsildenafilonline.com/ viagra online http://www.wwwgenericsildenafilonlineusa.com/ sildenafil

  20. Teresa Reed March 14, 2017 at 10:22 am #

    http://www.cheapsildenafilonlinestore.com/ cheap viagra

  21. Joe Perry March 14, 2017 at 10:38 am #

    http://www.cheapsildenafilonlinestore.com/ sildenafil

  22. Laura Brooks March 14, 2017 at 10:43 am #

    http://www.discountsildenafilonline.com/ viagra online http://www.wwwgenericsildenafilonlineusa.com/ viagra

  23. Evelyn Hernandez March 14, 2017 at 10:47 am #

    http://www.cheapsildenafilonlinestore.com/ generic viagra

  24. Joshua Moore March 14, 2017 at 10:50 am #

    http://www.cheapgenericviagraonlineus.com/ cialis vs viagra

  25. Elizabeth Taylor March 14, 2017 at 11:00 am #

    http://www.cheapgenericviagraonlineus.com/ cheapest viagra online

  26. Irene Powell March 14, 2017 at 11:03 am #

    http://www.cheapsildenafilonlinestore.com/ generic viagra

  27. Rachel Thompson March 14, 2017 at 11:07 am #

    http://www.discountsildenafilonlineusa.com/ generic viagra http://www.discountsildenafilonlinecanada.com/ viagra online

  28. Donna Harrison March 14, 2017 at 11:07 am #

    http://www.discountsildenafilonline.com/ viagra online http://www.wwwgenericsildenafilonlineusa.com/ order generic viagra cheapest price

  29. Mark Rice March 14, 2017 at 11:19 am #

    http://www.cheapsildenafilonlinestore.com/ cheap viagra online

  30. Daniel Washington March 14, 2017 at 11:19 am #

    http://www.cheapgenericviagraonlineus.com/ cheapest viagra online

  31. Timothy Wells March 14, 2017 at 11:25 am #

    http://www.discountsildenafilonline.com/ buy generic viagra http://www.wwwgenericsildenafilonlineusa.com/ sildenafil

  32. Shirley Webb March 14, 2017 at 11:32 am #

    http://www.cheapsildenafilonlinestore.com/ sildenafil

  33. Lawrence Torres March 14, 2017 at 11:37 am #

    http://www.cheapsildenafilonlinestore.com/ generic viagra online

  34. Deborah Ford March 14, 2017 at 11:40 am #

    http://www.cheapgenericviagraonlineus.com/ viagra online

  35. Pamela Ford March 14, 2017 at 11:41 am #

    http://www.cheapsildenafilonlinestore.com/ cheap viagra

  36. Timothy Marshall March 14, 2017 at 11:46 am #

    http://www.cheapsildenafilonlinestore.com/ generic viagra

  37. Patrick Sanders March 14, 2017 at 11:46 am #

    http://www.discountsildenafilonlineusa.com/ generic viagra online http://www.discountsildenafilonlinecanada.com/ cheap viagra

  38. Kimberly Richardson March 14, 2017 at 11:51 am #

    xQCXSZ xffnvrurfeda, zygauttxbggr, xqflcrgaogpa, http://ihsxqglzzrtb.com/

  39. Teresa Simpson March 14, 2017 at 11:52 am #

    http://www.cheapsildenafilonlinestore.com/ viagra

  40. Carol Sanchez March 14, 2017 at 11:55 am #

    http://www.cheapgenericviagraonlineus.com/ cheap generic viagra

  41. Wayne Anderson March 14, 2017 at 11:56 am #

    http://www.discountsildenafilonline.com/ cheap generic viagra http://www.wwwgenericsildenafilonlineusa.com/ generic sildenafil citrate

  42. Helen King March 14, 2017 at 12:05 pm #

    http://www.cheapsildenafilonlinestore.com/ buy generic viagra

  43. Benjamin Dixon March 14, 2017 at 12:11 pm #

    http://www.cheapsildenafilonlinestore.com/ viagra generic online

  44. Diana Perry March 14, 2017 at 12:11 pm #

    http://www.discountsildenafilonline.com/ generic viagra http://www.wwwgenericsildenafilonlineusa.com/ sildenafil viagra pills

  45. Wayne Stevens March 14, 2017 at 12:15 pm #

    http://www.cheapsildenafilonlinestore.com/ viagra generic online

  46. Jane Graham March 14, 2017 at 12:28 pm #

    http://www.cheapsildenafilonlinestore.com/ reviews of generic viagra

  47. Ryan Gray March 14, 2017 at 12:31 pm #

    http://www.cheapgenericviagraonlineus.com/ viagra online

  48. Alice Gonzalez March 14, 2017 at 12:36 pm #

    http://www.cheapgenericviagraonlineus.com/ generic viagra online

  49. Elizabeth Ortiz March 14, 2017 at 12:42 pm #

    http://www.discountsildenafilonline.com/ sildenafil citrate http://www.wwwgenericsildenafilonlineusa.com/ generic viagra online canada

  50. Rachel Bell March 14, 2017 at 12:42 pm #

    http://www.cheapsildenafilonlinestore.com/ discount viagra

  51. Janice Thomas March 14, 2017 at 12:52 pm #

    http://www.cheapsildenafilonlinestore.com/ buy cheap viagra with fast worldwide shipping

  52. Emily Hamilton March 14, 2017 at 1:08 pm #

    http://www.cheapsildenafilonlinestore.com/ generic viagra

  53. Kimberly Baker March 14, 2017 at 1:43 pm #

    http://www.cheapsildenafilonlinestore.com/ viagra online

  54. Deborah Foster March 14, 2017 at 3:46 pm #

    http://www.cheapgenericviagraonlineus.com/ cheap viagra

  55. Patrick Cole March 14, 2017 at 7:01 pm #

    NOB864 vrupqgvgfyfg, lplyhpllnmes, hifnhygiuesf, http://wccchbsqjlwr.com/

  56. Aaron Green March 15, 2017 at 1:54 pm #

    http://www.discountsildenafilonline.com/ discount generic viagra http://www.wwwgenericsildenafilonlineusa.com/ generic viagra

  57. Douglas Mcdonald March 15, 2017 at 2:43 pm #

    http://www.cheapsildenafilonlinestore.com/ generic viagra online pharmacy

  58. Keith Barnes March 15, 2017 at 7:06 pm #

    http://www.cheapsildenafilonlinestore.com/ cheap viagra

  59. Barbara Daniels March 16, 2017 at 6:29 am #

    http://www.cheapgenericviagraonlineus.com/ discount viagra online

  60. Kathleen Cox March 16, 2017 at 11:40 am #

    http://www.cheapgenericviagraonlineus.com/ cheapest viagra online

  61. Mary Taylor March 18, 2017 at 5:40 pm #

    http://www.discountsildenafilonline.com/ sildenafil citrate http://www.wwwgenericsildenafilonlineusa.com/ order generic viagra cheapest price

  62. Janet Perez March 18, 2017 at 10:35 pm #

    http://www.cheapgenericviagraonlineus.com/ cheap generic viagra

  63. Marilyn Wallace March 19, 2017 at 3:33 am #

    http://www.cheapsildenafilonlinestore.com/ reviews of generic viagra

  64. Wayne Hunter March 19, 2017 at 5:19 am #

    http://www.cheapgenericviagraonlineus.com/ cheapest viagra

  65. Louise Alexander March 20, 2017 at 3:14 am #

    http://www.cheapgenericviagraonlineus.com/ discount sildenafil

  66. Kathleen Price March 20, 2017 at 11:20 am #

    http://www.cheapgenericviagraonlineus.com/ viagra vs cialis

  67. Theresa Morales March 22, 2017 at 11:20 am #

    http://www.cheapgenericviagraonlineus.com/ viagra online

  68. Karen Henry March 25, 2017 at 7:51 pm #

    http://www.cheapgenericviagraonlineus.com/ generic viagra

  69. Lawrence Diaz March 25, 2017 at 11:31 pm #

    http://www.cheapgenericviagraonlineus.com/ sildenafil

  70. Philip Foster March 28, 2017 at 1:19 pm #

    http://www.discountsildenafilonline.com/ generic viagra online http://www.wwwgenericsildenafilonlineusa.com/ order generic viagra cheapest price

  71. Martin Morris March 28, 2017 at 9:15 pm #

    http://www.cheapgenericviagraonlineus.com/ cialis vs viagra

  72. Ralph King March 31, 2017 at 3:10 am #

    http://www.cheapgenericviagraonlineus.com/ buy viagra

  73. Aaron Hughes April 2, 2017 at 6:28 am #

    http://www.cheapgenericviagraonlineus.com/ viagra alternative

  74. Brenda Clark April 3, 2017 at 2:12 pm #

    http://www.discountsildenafilonlinefast.com/ reviews of generic viagra tablets http://www.cheapsildenafilonlinestore.com/ discount viagra online http://www.discountsildenafilonlineusa.com/ buy discount sildenafil online pharmacy usa http://www.discountsildenafilonlinecanada.com/ viagra generic

  75. Eric Evans April 5, 2017 at 9:35 pm #

    http://www.cheapgenericviagraonlineus.com/ cheap generic viagra online

  76. Judith Perez April 8, 2017 at 12:18 pm #

    comment2, kamagra oral jelly cvs, :OO,

  77. Jane Carter April 24, 2017 at 9:07 pm #

    http://www.discountsildenafilonline.com/ viagra online http://www.wwwgenericsildenafilonlineusa.com/ order vagra generic

Leave a Reply