Enabling decentralized pre composting of organic household waste - - PowerPoint PPT Presentation

Enabling decentralized pre‐composting of organic household waste with a novel high‐rate bioreactor

• M. Sakarika, R. Baetens, K. Vinck, M. Spiller, K.C. Vrancken, G. Van Barel, E. Du Bois, S.E. Vlaeminck

The Urban pre‐Composter

Fate of organic household waste in Flanders

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(Roels et al., 2017)

composting 40% conversion to animal feed 28% incineration 24% anaerobic digestion 6% landfilling 2%

[Reference period: 2015]

Cost breakdown composting

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(Kaza et al., 2016)

collection and transport 74% composting process 26% [Reference period: 2009]

• Household organic waste: vegetables, green, fruit (VGF)
• Urban household organic waste: mainly kitchen waste
• Composition of waste disposed in the collection points of the Flanders:

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Urban household organic waste composition

vegetables 35% fruit 35% bread 15% prepared dishes 6% meat, fish and poultry 4% dairy products (yogurt) 4% sauces, herbs and spices 1%

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Organic household waste High capacity requirements for centralized composting High transportation requirements Collection point

Conventional organic waste flow

Air pollution Odor Noise Mobility problems (traffic)

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Organic household waste Reduced capacity requirements for centralized main composting Collection point Reduced transportation requirements

Novel organic waste flow with the Urban pre‐Composter

Decentralized, high‐rate pre‐composting Goal: max. mass and volume reduction in 2 weeks Requirements:

• space limitation  compact (high‐rate)
• practical  allow for loading/unloading
• minimal use of resources (bulking agents; water)

Challenges in composting kitchen waste

Kitchen waste  67‐85% moisture2

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2(Nair et al. 2006); (Yang et al. 2013)

[picture from: www.thebulletingredients.com]

lack of structure poor oxygen diffusion addition of structure material high leachate generation

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Research objectives

• 1. Develop a prototype Urban pre‐composter and validate achievable mass and volume

reduction of kitchen waste

• 2. Extrapolate to efficiency gains in the overall kitchen waste treatment (pre‐composting

+ main composting)

• 3. Characterize final compost quality

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nozzle for optional wetting with leachate air outlet pipe leachate collection reservoir leachate drainage tube static barrel (200L) waste load/unload point motor to rotate agitator aerator inlet points agitator

Reactor design

• Continuous loading drum bioreactor with forced aeration and internal agitation
• Capacity: kitchen waste from 44 persons (4.5 L/person)

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Design 1: straight scraper with internal void (Runs 1 and 2) Design 2: battlemented scraper with internal bars (Runs 3 and 4)

Agitator design

static barrel (200L) waste load/unload point motor to rotate agitator agitator

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Urban pre‐composter performance

10 20 30 40 50 60 70 Fresh weight Volatile solids (VS) Moisture Volume % Reductions Run 1 Run 2 Run 3 Run 4 Kitchen waste Formulated Real Sawdust No Yes No Agitator design 33% reduction batch in 28 days (Yang et al. 2013)

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Water balance

• Minor water removal from leaching
• Moisture content 56‐75% above 55%, so no need for moistening3

3(Nair et al., 2006)

20 40 60 80 100 Run 1 Run 2 Run 3 Run 4 % Evaporation Leachate Waste

Passive aeration 50 100 150 200 250 300 Run 1 Run 2 Run 3 Run 4 Andersen et al., 2011 Amlinger et al., 2008 2 4 4 7 130 270 Leachate generation (mL/kgFM) Active aeration

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Leachate generation

• Low amounts of leachate
• Can be added to compost (negligible moisture content increase 0.8‐1.1%)  no separate collection
• Upscaling: trade‐off between energy use (aeration; evaporation) and leachate production

Worse case: 400 persons generate 3.5L vs 135L

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Research objectives

• 1. Develop a prototype Urban pre‐Composter and validate achievable mass and volume

reduction of kitchen waste

• 2. Extrapolate to efficiency gains in the overall kitchen waste treatment (pre‐

composting + main composting)

• 3. Characterize final compost quality

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Overall treatment: pre‐composting + main composting

• High‐rate conversions during pre‐composting
• 42% and 71% of overall mass and volume reduction potential achieved in 21% of the time

20 40 60 80 100 Fresh weight reduction (%) Volume reduction (%) Time (days) pre‐composting main composting +16% Fed‐batch, 67 days (Amlinger et al., 2008)

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Research objectives

• 1. Develop a prototype Urban pre‐Composter, and validate achievable mass and volume

reduction of kitchen waste

• 2. Extrapolate to efficiency gains in the overall kitchen waste treatment (pre‐composting

+ main composting)

• 3. Characterize final compost quality

Parameter Unit Produced compost VGF compost composition4 Requirements for solid

• rganic

fertilizers5 Total solids (TS) %gTS/gproduct 26.8 70 >40 C/N ‐ 11.8 12 <15 N %gN/gproduct 0.85 1.2 2.5 P %gP/gproduct 0.13 0.13 0.44 K %gK/gproduct 0.07 0.42 0.83 N/P/K ‐ 1/0.15/0.08 1/0.11/0.35 1/0.18/0.33

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Compost quality

• Final moisture removal is needed
• C/N ratio indicates near mature compost after 68 days
• Good N/P ratio

4VLACO; 5(European Commission, 2016)

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Organic household waste Reduced capacity requirements for centralized main composting Collection point Reduced transportation requirements

Conclusions

Urban pre‐composting (400 PE: 2.5 m3)

33% mass reduction

• Successfully demonstration of the effectiveness and feasibility of urban pre‐composting at semi‐

technical scale (200L)

• No bulking agent addition, no need for separate leachate collection  no additional cost for logistics

and management

• 42% and 71% of the overall mass and volume reduction potential achieved in 14 days
• The urban pre‐composter lowers overall costs of organic waste management

Thank you for your attention!

Myrsini.Sakarika@UAntwerpen.be – Siegfried.Vlaeminck@UAntwerpen.be

Financial support by

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Back‐up slides

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Neighborhood level waste collection

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Sorting streets for 400 persons (250 families)

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Composting of real kitchen waste

2 4 6 8 10 12 14 10 20 30 40 50 60 Run 4 Mass (kg) Time (days)

Mimicking of realistic feeding (fed‐batch)  not full reduction potential (compared to batch process)