Technological problems in composting sites. Overview of composting technologies. Tallinn, May 18th 2011

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1 Fakultät Maschinenwesen, Institut für Verfahrenstechnik und Umwelttechnik, Professur TVT und Umwelttechnik Technological problems in composting sites Overview of composting technologies Tallinn, May 18th 2011 Dr.-Ing. Joachim Brummack Technische Universität Dresden Institute of Process Engineering & Environmental Technology

Aerobic degradation = 1principle- 3 powerful

composting conversion of various biowaste into

2 Aerobic degradation = 1principle- 3 powerful applications treatment of the biogenic part of mixed waste (MBWT) recovery of metal, refuse derived fuel and material for landfilling composting conversion of various biowaste into compost using self - heating production of renewable fuel Folie 2 von 33

For our understanding Biological degradation - an unavoidable incident, takes place inside of a wide range of ambient conditions A typical case of

3 For our understanding Biological degradation - an unavoidable incident, takes place inside of a wide range of ambient conditions A typical case of a spontaneous subsiding incident of degradation: wood chips after 5 weeks in a cold storage room (temperature 5 C) result: unusable! Folie 3 von 33

4 Therefore: We should look over a good practice, that is - short process time, - minimal first and operation costs, - lowest odor emissions, - good acceptability, - licensable, - good reputation of products and - best product properties. Folie 4 von 33

5 1. The process of aerobic degradation 1.1 Fundamental Basics Folie 5 von 33

6 Comparison of aerobic and anaerobic biodegradation substance-specific chemical reactions ( classical example: Glucose) aerobic (total formula) : C H O + 6 O ENZYME 6 CO + 6 H O; H = KJ/mol R T Composting is like a slow flameless burning! anaerobic ( total formula ): C H O ENZYME 3 CO + 3 CH ; H = KJ/mol R T combustion of Methane: 6 O + 3 CH 3 CO + 6 H O; H = KJ/mol R T summery reaction: C H O + 6 O 6 CO + 6 H O; H = KJ/mol R T Folie 6 von 33

7 Mass and heat balance of aerobic degradation Folie 7 von 33

8 Objectives of a aerobic process carbon dioxide + residual air air substrat water microorganisms water (vaporous) heat conclusion: It is not possible to realise all conditions without compromises Folie 8 von 33

9 model particle O 2 IM CH 4 Ideas of a stringent aerobic metabolism at instance of a model particle CO 2 CH... 4 anaerobic clusters inside of particle HO 2 O 2 HO 2 CO 2 CH... 4 Sms IM CH 4 IM CH 4 watercoat with solved Oxygen 1-2 mm depth of penetration of Oxygen= aerobic zone! detail: microorganism in watercoat substrat water soluble cellwall semipermeable membrane What thus can mean stringent aerobic in practice? IM and Methan have to completely consumed in watercoat, that means, we doesn t have this substances in exhaust gas. hydrolysis enzymes aerobic µo-cell substrat waterin soluble extracellular enzymes HO 2 CO 2 O 2 IM= intermediate metabolits= organic acids, higher alcohols... Folie 9 von 33

10 Rotting phases - a technical point of view point of contraflexure heat storage heat release 70 temperature of sanitation optimal temperature = maximum metabolic rate heap temperature in C initial phase thermophilic phase: decomposition phase thermophilic bacterias thermophilic fungi intensiv rotting time reconstruction phase: a mesophilic phase decomposition of persistant organic substances mesophilic bakterias & fungi maximum weeks (depended on used system) rebuilding phase: production of humins ph-value total rotting time months Folie 10 von 33

11 accumulated CO 2 - volume to characterization the conversion of aerobic degradation CO 2-volume in m i. N. Volumen CO 2 in m 3 i.n ideal developing real developing (windrow according to DAT-method) example of a defective developing rotting Rottetag day Folie 11 von 33

12 1.2 Properties of the rotting material Folie 12 von 33

13 most important properties: - moisture content - C/N/(P) ratio - ph-value on start (and during process) - pressure loss (of the fixed bed) - Particle shape and size - homogeneity regarding composition and particle size aspects of the daily experience relevant aspects of basic dimensioning (selection of equipment) As economical point of view it is not practicable to determine all properties for each input material! Only simple (but good) auxiliary means and step by step a lot of experiences are needed. Folie 13 von 33

14 moisture content for a lot of cases in practice optimal moisture content: % 2 different functions of water: - essential for metabolism - cooling liquid (evaporative cooling) water loss by saturated exhaust gas! rule: the more the merrier, but too much is terrible moisture regulation perfect material: wood chips dry wet adjustment of an optimal moisture content of too wet material (e.g biowaste) water store for a long-time process without wetting Folie 14 von 33

15 C/N-ratio a critical parameter Adjustment is difficult to realise optimal (on beginning): C/N = : 1 common mixed municipal biowaste C/N= : 1 two potential cases too much nitrogen excrements of poultry and animals insufficient nitrogen old (dead) wood C/N-ratio C/N= 2 10 : 1 C/N= : 1 solution? note mixing with wood chips ammonia emissions anavoidable no direct solution using as structure material and water storage in composting Folie 15 von 33

16 ph - value to the beginning: simply expressed: content of organic acids ph=7 minimum during process: ph=6 In finished compost: ph=8 developing of ph-value during rotting process ph=7 only in very young substrate ph-value ph= 5 6 critical value, danger of acidification note: strong acidification (ph<5) take place (unavoidable) during times of compilation, transport and storage adjustment of ph-value: dry leaves as natural buffer material Folie 16 von 33

500 mm lenght: 3 000 mm usable for particle sizes up to 50 mm fixed bed from waste etc.

17 pressure drop, pore volume (1) typical global parameters, only limited measurable pore volume optimal value: vol % possibility to measure the pressure drop (for flow trough) column: material: HD-PE diameter: 500 mm lenght: mm usable for particle sizes up to 50 mm fixed bed from waste etc. grid: mashes 20 mm volumemeter (Rotameter) air pump air gauge functional principle flow through column ready for filling Folie 17 von 33

18 pressure drop (2) Diff.Druck [Pa] different a herunter lines shows pressure b herunter drop according to compression c herunter set results of such experiments: - design of material - design of aeration Vpkt/A [m³/h/m²] mixing with structure material to reduce the pressure drop and compression set during process example (waste probe MBWT) Folie 18 von 33

acceptance of our understanding) by a intensive pre-treatment with addition of structure and buffer

19 right pre-treatment of rotting material - more than 50 % of a successful rotting process Biowaste with high content of water as soon as sugar, fat can only treated by a good aerobic process (under acceptance of our understanding) by a intensive pre-treatment with addition of structure and buffer material. Such biowaste are better used in a two-step plant with an anaerobic first step. Folie 19 von 33

20 2. technics & technology of composting Folie 20 von 33

21 detail: torn wheel of turner compost turner - ready for scrapping Folie 21 von 33

22 2.1 Overview Folie 22 von 33

23 Classification of intensive and post-rotting using of expensive sytems - only reasonable at high reaction rates respectively high biological activities initial phase thermophilic phase: decomposition phase thermophilic bacterias thermophilic fungi reconstruction phase: a mesophilic phase decomposition of persistant organic substances mesophilic bakterias & fungi after this-not possible to accelerate biological degradation by means of technics rebuilding phase: production of humins intensiv rotting time maximum weeks (depended on used system) total rotting time months closed reactors operating time: (7-14 days) boxes, containers, drums, towers half open methods operating time: 4-12 weeks rotting halls, tunnels, lines post - rotting open air windrows post - rotting open air windrows open air methods operating time: arbitrarily different aeration methods with/without turning post - rotting open air windrows Folie 23 von 33

24 Assortment of highly engineered systems closed reactors static reactors dynamic reactor box tunnel non portable, reinforced concrete container portable rotting drum not usable for treatment of municipal biowaste because autogeneous crushing! during process neither possibility to regenerate structure economical limited process time: days half open methods static rotting line,- tunnel composting regeneration of structure by rotation economical limited process time: days using capillary tubes Brikollare - method forced aeration, internal turning 4-12 weeks intensiv rotting 4-6 weeks process time Folie 24 von 33

25 Assortment of open air systems (1) Folie 25 von 33

26 Assortment of open air systems (2) Folie 26 von 33

27 Assortment of open air systems (3) Folie 27 von 33

28 Summary of open air systems advantages - not expensiv (if not under a roof) - choise under a lot of different solutions - high flexibility - short implementing time disadvantages - exhaust air emission over complete surface of the heap, coating with membranes or carded webs not possible - non forced systems with low aeration efficiency - subject to changes in weather, if not under a roof - not possible to collect and treat emissions - in case of using aeration tubes, danger of void-blockage Folie 28 von 33

29 2.2 open air systems Folie 29 von 33

30 Any details for instance of an open air system (1) windrow with perforated aeration tubes during built-up Folie 30 von 33

31 Any details for instance of an open air system (2) blower-box with allocation Folie 31 von 33

32 Any details for instance of an open air system (3) blocked hole open hole detail: real situation of perforated aeration tube Folie 32 von 33

33 Any details for instance of an open air system (4) bumptious tarpaulin (semipermeable membrane) required aeration flow is greater than permeabilty! Folie 33 von 33

34 Any details for instance of an open air system (5) consequences: incorrect high temperatures becomming of Malliard-products (danger of stink!) solution only: addition of neutral structure material balanced heat balance! leakiness bumptious tarpaulin (semipermeable membrane) Folie 34 von 33

35 An alternative solution - Dome Aeration Technology - (1) exhaust air exhaust pipe cover inlet air (ambient conditions) inlet air (ambient conditions) rotting material channel dome outline of the windrow structure of a Dome Aeration windrow Folie 35 von 33

36 - Dome Aeration Technology (DAT) - (2) delivery air cannel cannel delivery air dome critical areas for aeration= control points delivery air cannel cannel delivery air dome delivery air cannel cannel delivery air flow pattern of a DAT - windrow Folie 36 von 33

37 - Dome Aeration Technology (DAT) - (3) no diffussive surface emissions aeration by natural convection exhaust air (temp. max. 70 C, water saturated) monitoring of composition is possible weatherproof cover energy saving simple setup any pros of the DAT Folie 37 von 33

38 - Dome Aeration Technology (DAT) - (4) working DAT-windrom (sewage sludge, pre-treated with wood chips Folie 38 von 33

39 - Dome Aeration Technology (DAT) - (5) DAT is absolutely a good solution, but: It s never possible to circumvent the nature! Remember capture 1! built-up of a DAT-windrow, covering of a finished segment with compost Folie 39 von 33

40 2.2 closed reactors Folie 40 von 33

41 computer-operated valves to biowasher/ biofilter exhaust air exit exhaust air reactor wall (insulated) gate filling rim rotting material blower circuit air air-water heat exchanger coldwater from evaporative cooler aeration device blower inlet air principle of Herhof Rottebox (rotting box,unportable) Folie 41 von 33

42 gate and filling rim (opened) box during filling Herhof Rottebox aeration device on the top Folie 42 von 33

43 rotting container, portable Folie 43 von 33

44 3. final summery Folie 44 von 33

45 To the end: aerobic treatment of waste in headlines composting is a ecological solution for a lot of kinds of biowaste biowaste with a high moisture content needs expensive pre-treatment for biowaste with a high energy content, an anaerobic process as a first step is the better solution from the ecological point of view, a high energy consumption of the sophisticated systems is a problem Folie 45 von 33

46 Thank you for your attention the last picture: melted data logger after application in a overheated post rotting windrow

The Biology of Composting

The Biology of Composting Mark King, Sustainability Division mark.a.king@maine.gov MAINE DEPARTMENT OF ENVIRONMENTAL PROTECTION Protecting Maine s Air, Land and Water Systems Covered First We ll Discuss