biological recycling and treatment processes

teach4waste I Mechanical-biological waste treatment I Slide 1

Biological recycling and treatment processes

- MBT

Klaus Fricke, Christiane Pereira, Andrea Pfeiffer and Bruno Aucar


Mechanical-biological waste treatment -learning objectives

The students should be able to:

• Understand the legal framework and its classification in

the waste hierarchy and to derive long-term perspectives

• Identify the objectives of the 5 main limit values from the

German Landfill Ordinance and draw conclusions for

process engineering

• Identify current and future requirements for the

performance of mechanical-biological pretreatment

processes prior to landfilling and integration of energy

recovery


Recycling

Energy recovery

Avoidance

Inc

rea

se

of

GH

G c

red

its Preparation

for reuse

Re

so

urc

ee

ffic

ien

cy

Inc

rea

se

in G

HG

em

iss

ion

s

Pre-treatment prior to landfilling

Incineration and MBT

Disposal

Waste hierarchy in the EU and Germany


Waste management objectives:

• Minimizing volume and mass of waste delivered to landfill

• Inactivation of biological processes → preventing landfill gas production and

settlement

• Immobilizing contaminants in the waste in order to reduce leachate emissions

• Separation of recyclable materials, Fe- and non-Fe-metals, plastics

• Production of alternative fuels e.g. RDF

Overall objectives:

Protection of

• Climate, water resources and soil

• Resources

Objectives of treatment before landfill


Mechanical, biological and thermal processes

• *66 incineration plants1) 20.2 Mio. t/a

• *32 energy recovery plants2) 5.8 Mio. t/a

• **36 MBT 4.8 Mio. t/a

Waste treatment before landfill

- Suitable procedures

1) Grate combustion technologies only; 2) Grate combustion and fluidized bed technologies

(Sources: *Quicker et al., 2018; **Ketelsen, 2019)


Parameter Reference Landfill class II

Incineration

plant

Landfill class

II

MBT

Ignition loss % in DM* 5

TOCsolid % in DM 3 18

TOCEluate mg/l 80 300

Respiration rate (AT4) mg O2/g DM 5

Gas formation rate (GB21) Nl/kg DM 20

Upper calorific value kJ/kg 6,000

*DM = Dry matter

Boundary values of DeponieV (German landfill ordinance) (2009)

Waste treatment before landfill

- Requirements for material to be landfilled


Emission parameter:

- respiration rate (AT4) ≤ 5 mg/g DM or

- gas formation rate (GB21) ≤ 20 l/kg DM

- TOCEluate ≤ 300 mg/l

Utilisation parameter:

- upper calorific value: ≤ 6,000 kJ/kg or

- TOCsolid: ≤ 18 % DM

Low gas emissions

Low concentrations of organics and in-organics in leachate

Low concentrations of plastics, textiles and paper/cardboard

Targets of boundary values of MBT waste in Germany:

Legal background landfill

- Germany

teach4waste I Biological processes - Introduction and history I Slide 8

• Kitchen waste

• Food waste

• Sewage sludge

• Garden waste wood-free

• Wood

• Paper and cardboard

• Bio-based plastics

• Nappies

• Nativ textile

Carbonate

Water of

cristalisation

Plastic

Rubberi

Lether

Hemicellulose

Lignin

Huminic substances

Glucose

Starche

Protein

Fat

Cellulose

Lo

ss

of

ign

itio

n

ae

rob

ic

de

gra

da

lble

an

ae

rob

ic

de

gra

da

ble

Raw material product of organic substances MBT- Species differentiated by microbial availability


Biological treatment

Anaerobic / aerobic

Municipal solid waste

Fe

Landfill

15 - 40%

HCF

5 – 8%

LVC >11 MJ/kg

Screening

100 mm Fe

> 100 mm

Reduction of oDM and H2O,

25 - 30%

> 30 - 40 mmScreening

30 – 40 mm

Sorting (optional) e.g.

• Plastic

• Paper/cardboard

• Glass

• Wood

• Textiles

< 100 mm

Filter material

MOL**

Shredding

Biogas

9 – 12%

Ferrous metals

2 – 3%

HCF*

20 – 35%

LVC >11 MJ/kg

MBT prior to landfill

- Flow chart, simplified

< 30 - 40 mm

Optional if anaerobic

digestion is integrated

*High Calorific Fraction

**Methane Oxidation Layer


Mass reduction by

• Sorting out recyclables and alternative fuels

• Loss of biological degradation (H2O, CO2, Biogas)

• Loss of drying

MBT performance

- Mass reduction

0,0

0,2

0,4

0,6

0,8

1,0

MBT MBT + removal of recyclables

[t]

/RDF


Higher installation density by

• Reduction of grain size through shredding and microbiological downsizing

• Separation of coarse grain fraction

• Separation of elastic waste components like plastics

Installation density on landfill

0,7

MBT performance

- Volume reduction on landfill by increasing density

0,7

0,9

1,3

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

Installation with caterpillar Installation withcompactor (thin layer)

lowly compacted

MBT material; installationwith compactor; thin layer;

highly compacted

[t/m³] Installation (bulk) density on landfill


MBT performance

- Need for reduction of volume on landfill

0,0

0,2

0,4

0,6

0,8

1,0

1,2

Untreated MBT (40% massreduktion)

MBT + removal ofrecyclables (70% mass

reduction)

[m³/t]

Required landfill volume per t waste

Compared to untreated waste, the demand for landfill capacity is lower by

58 up to 79 %

1,1

0,23

0,46


MBT performance- Reduction of gas potential

0

20

40

60

80

100

120

140

160

180

200

220

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Duration of treatment (weeks)

GB

21

(l/k

g d

m)

lower area

upper area

Limit value

20

Reduction of gas potential by aerobic treatment


MBT performance

- Reduction of landfill gas emission

MBT gas reduction rate 80 % !!

Reduction of landfill gas emission

200

40 40

50

100

150

200

250

MSW untreated MBT material MBT material +methane oxidation

[Nl/

kg

wa

ste

]


MBT performance

- Reduction of DOC

0

500

1000

1500

2000

2500

3000

3500

4000

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Duration of treatment (weeks)

DO

C-E

luat

(mg

/l)

lower area

upper area

300

Limit Value

Reduction of DOC during aerobic treatment


MBT performance

- Leachate emission (quantity)

0

10

20

30

40

50

60

70

80

Caterpillar Compactor

Le

ac

ha

teg

en

era

tio

n [

% o

f to

t. p

rec

ipit

ati

on

] Base

runoff

Base

runoff

Base

runoff

Compactor

after MBTuntreated waste

Surface

runoff


0

5000

10000

15000

20000

25000

30000

35000

40000

COD BOD5

COD BOD5

CODBOD5

MBT materialFresh waste

starting phase

Fresh waste

methane phase

[Nl/

kg

]

after MBTuntreated waste

MBT performance

- Leachate emission (quality)


Biological treatment

Anaerobic / aerobic

Municipal solid waste

Fe

Landfill

15 - 40%

HCF

5 – 8%

LVC < 11 MJ/kg

Screening

100 mm Fe

> 100 mm

Reduction of oDM and H2O,

25 - 30%

> 30 - 40 mmScreening

30 – 40 mm

Sorting (optional) e.g.

• Plastic

• Paper/cardboard

• Glass

• Wood

• Textiles

< 100 mm

Filter material

MOL*

Shredding

Biogas

9 – 12%

Ferrous metals

2 – 3%

HCF

20 – 38%

LVC < 11 MJ/kg

MBT prior to landfill

- Flow chart, simplified

< 30 - 40 mm

Optional if anaerobic

digestion is integrated

* Methane oxidation layer


Methane oxidation layer

(Source: Scheutz et al., 2009)

Me

tha

ne

ox

ida

tion

laye

r

> 1

20

cm

Gas diffusion

layer

Landfill body top

layer preferably

uncompressed

MBT output

- Methane oxidation layer (MOL)

Biological methane oxidation with methanotrophic bacteria

CH4 + 2O2 → CO2 + 2H2O + biomass + 210.8 kcal/mol


Efficiency of MBT treatment and methane oxidation layer

Landfill gas - Reduction rates

200

40 40

50

100

150

200

250

MSW untreated MBT material MBT material +methane oxidation

[Nl/

kg

wa

ste

]

MBT and MOL gas reduction rate 98 % !!


40 °

56 °

sgs engineers

Reduction of slope stability

screening to < 60 mm leeds to reduction of reinforcing material (fibres) from > 25 %

(w/w) to < 5 %(w/w)

reduction of tensile strength

Reason:

plastics are able to take up tensile forces

18 °

3.01.0

MBT performance

- Slope stability


Consequences for construction:

• as a result of the homogeneity of MBT material

large differences in settlement are not to be

expected

• final surface sealing system can be installed

earlier

• Higher viability of surface sealing system

Total settlement MBT

[%]

Untreated waste

[%]

- primary settlement (load) 15 - 20 35 - 50

- secondary settlement (biol. processes) < 5 15 - 30

MBT performance

- Surface settlement


MBT landfill operation- Emplacement technologies

For distribution: bulldozer / tracked loaders

For compaction: - compactor

- pad foot roller

- and vibrating smooth roller


Aftercare

- Period of time and costs

MBT Landfill MBT Landfill

• Gas collection not necessary

• Shorter period of time for leachate collection and treatment

Period of aftercare of untreated waste > 30 years

Period of aftercare of MBT pre-treated waste < 30 years

Lower costs of aftercare


Generation of fuels from waste in MBT - Increasing the calorific value through drying

0

5.000

10.000

15.000

20.000

25.000

30% 40% 50% 60% 70% 80%DM-content

Lower calorific value

Ho* paper 15.500 16.500 17.500 Ho cardboard 17,500 19.000 20.500 Ho diapers 23.000 27.300 31.000

kJ/kg DM

*upper calorific value


Dryers - Overview technologies

Thermal dryers

• disc dryer

• paddle dryer

• thin film dryer

Thermal dryers

• drum dryers

• fluid bed dryer

• belt dryers

• ascending pipe dryer

Convection

dryer

Conduction

dryer

Solar

dryers

Solar dryers,

combination of solar

dryers with

supporting heat

supply

Aerobic

dryer

Aerobic dryer,

combination aerobic

dryer with

supporting heat

supply


Air temperature 30 °C

30 g H2O/m3 air

Air temperature 50 °C

82 g H2O/m3 air

Drying - Aerobic drying


…increases the quality of separation processes:

• Screens

• Air classifier

• Ballistic separator…improves the product

quality

Pre-processing / waste treatment - Water content and processing properties

Low water content reduces adhesive effects (protein) between waste particles...


• MBT is based on existing and well known technology, like mechanical treatment

stages, composting, aerobic drying, fermentation

• MBT is a fairly flexible system approach which can be adjusted to local

conditions and treatment targets

• Because of the dynamic development of waste amount, waste composition and

the recycling markets, the recycling and treatment technology has to be highly

adaptable. This flexibility can be achieved by MBT due to:

- Its ability for modular construction, therefore easily adaptable in size

- High flexibility of treatment goals, therefore adjustments resulting from

changes in markets and demand are possible

Key Advantages of MBT


• MBT can be adjusted in order to optimise the energy yield from waste, including

the production of renewable energy via AD and heat and power via RDF

combustion

• Recyclable materials like plastics, paper or glass can be separated with

automatic and/or manual sorting systems

• MBT reduces the waste volume - this minimizes the demand for landfill capacity

which maximises the landfill’s resource and lifespan

• GHG mitigation in a very large scope is possible. Compared to other GHG

mitigation options, its costs are relatively low

Key Advantages of MBT


Lessons learned

• Name the objectives of the pre-treatment of residual waste

• Explain limit values and their respective protection objectives

• How are those being implemented by the MBT technology?

• Which are the different concepts of MBT? Draw a process flow with the most

important process steps

• Which are the objectives of drying waste?

• Which biological type of drying waste exists? On which physical basic principle is

it based?

• Sample calculation

• Which products and material streams are being discharged by the MBT?

• Explain the climate effect of landfilling untreated and treated waste - both

thermical and mechanical-biological

biological recycling and treatment processes

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