technical digestate treatment - biogaz europe

Technical digestate treatment- advantages, limitations, costs -

Biogaz Europe, Nantes, 25. and 26.10.2011

Helmut Döhler, Sebastian Wulf


• Aims of digestate treatment and operating principles

• Treatment Techniques and Model Biogas Plant

• Costs of treatment technologies

• Comparative assessment

• Pilot project Italy

• Conclusions

Content

Introduction

Technologies

Products

Comparitiveassessment

Pilot project

Conclusions

Reasons for digestate treatment

• „Export“ of nutrients

• Reduced costs of storage and application

• Production of a tradeable fertilizer– storable and transportable fertilizers

• Reduction of environmental effects– Improved nutrient utilization– Reduced gaseous emissions– Odour reduction– Inactivation of pathogenes and weed seeds

Nach Weiland, KTBL 2001, verändert

Introduction

Technologies

Products


Pilot project

Conclusions

treatment technologies

physical chemical biological

separation

drying

evaporation

membranetechnologies

flocculation

precipitation

composting

nitrification /

denitrification

stripping

Elimination of nutrients

Principles of digestate treatment

Introduction

Technologies

Products


Pilot project

Conclusions

Model biogas plant

CHP (500 kWel / 650 kWth)

treatment

50 % cattle slurry50 % maize silage

Output: 20.000 m³ digestate

DM Ntot NH4-N P2O5 K2O [%] [g/kg]

7,75% 5,6 3,6 2,1 6,17

application to arable land in vincinity of biogas plant

(330 ha)

distant to biogas plant (20 km)

Introduction

Technologies

Products


Pilot project

Conclusions

Treatment 1 - Application (and storage)

Introduction

Technologies

Products


Pilot project

Conclusions

Treatment 2 – Separation and application

Foto: Ahrens, FAL

Introduction

Technologies

Products


Pilot project

Conclusions

! Separation is precondition for all following treatment technologies

separation(press-screw separator)

solid phase

(2.500 t/a) approx. 30% DM

liquid phase

(17.500 t/a )

biogas-plant

biogas

(20.000 t/a)substrate

Treatment 2 – Separation and application

Introduction

Technologies

Products


Pilot project

Conclusions

Treatment 3 – Drying

Foto: Ahrens, FAL

Introduction

Technologies

Products


Pilot project

Conclusions


dried solid phase

(920 t/a) approx. 80% DM

liquid phase

(17.500 t/a )

biogas-plant

biogas


drying of solid phase

exhaust air

Treatment 3 – Drying

Introduction

Technologies

Products


Pilot project

Conclusions

Spectrum of filtration techniques

Treatment 4 – Membrane technology

Introduction

Technologies

Products


Pilot project

Conclusions

ultrafiltration(UF)

Flocculationadditive

separation(decanter) shaking

screen

solid phase

(3.900 t/a)

concentrate

(5.000 t/a)

reverse osmosis (RO)

antiscalantacid

concentrate - recirculation

permeatedirect discharging

quality

(8.700 t/a)

biogas-plant

biogas

substrate

Treatment 4 – Membrane technology

Introduction

Technologies

Products


Pilot project

Conclusions recirculation

Treatment 5 – Evaporation


solid phase

(3.900 t/a)

concentrate

(6.100 t/a)

evaporation plant- two-stage -

acid

condensate

(10.000 t/a )

biogas-plant

biogas


(Photo: www.guetling.com)

Introduction

Technologies

Products


Pilot project

Conclusions

Treatment 6 – Stripping


solid phase

(2.500 t/a)

ASS

(650 t/a)

NH3-strippingwaste water

(14.200 t/a )

biogas-plant

biogas


P-precipitation

(optional)

P-K- sludge

(2.900 t/a)

Introduction

Technologies

Products


Pilot project

Conclusions

nutrient concentrations in treatment products

0

5

10

15

20

25

30

35

40

45

50

liq

uid

so

lid

liq

uid

so

lid

liq

uid

so

lid

liq

uid

so

lid

liq

uid

so

lid

liq

uid

nu

trie

nts

[k

g/

t]

Norg NH4-N P2O5 K2O

applicationseparation

belt dryermembrane

evaporationstripping

80,6 kg/tIntroduction

Technologies

Products


Pilot project

Conclusions

0%

20%

40%

60%

80%

100%

application separation belt dryer belt dryer(100% heat)

membranetechnique

evaporation stripping

digestate solid phase liquid phase / concentrateprocess water dischargable water/ air

Mass balance of products

Introduction

Technologies

Products


Pilot project

Conclusions

1,50 2,003,84 3,81

5,864,55 5,25

0,360,41

0,77 0,91

2,08

1,551,382,57

3,48

4,501,84

0,82

1,47

0,66

2,012,24

2,112,06 1,47

1,34

1,36

2,362,35

2,232,11 1,62

1,41

0,70

-4,40 -4,40 -4,26 -4,08 -4,40 -4,40 -4,38

-9

-5

-1

3

7

11

15

application separation belt dryer belt dryer100%

membranetechnology


€/m

3 dig

es

tate

fix costs energy (el.) energy (th.) consumables application

transport nutrients heat bonus net costs

Specific costs of treatment

Introduction

Technologies

Products


Pilot project

Conclusions

1,84 2,59

7,268,29 7,46

10,52

6,81

-9

-5

-1

3

7

11

15

application separation belt dryer belt dryer100%

membranetechnology


€/m

3 dig

es

tate



Specific costs of treatment

Introduction

Technologies

Products


Pilot project

Conclusions

5,623,66 2,95

-9

-5

-1

3

7

11

20.000 40.000 80.000 20.000 40.000 80.000

€/m

3 dig

es

tate



Specific costs of treatment – effect of plant size

Introduction

Technologies

Products


Pilot project

Conclusions

Without treatment Membrane technology

Pilot project Italy

Introduction

Technologies

Products& Costs

Conclusions

Pilot project Italy

Introduction

Technologies

Products& Costs

ConclusionsSeparation (decanter and srew press)

Ultrafiltration

Reverse Osmosis

Zeolite Filter

Ammonia Stripping

Drying

Pilot project Italy

Introduction

Technologies

Products& Costs

Conclusions

Summary and Conclusions- technical aspects -

• separation is without technical risks

- no reduction of residue volume for application

costs of application is increased

only useful in case of local need

• drying of solid phase

- well established in other fields of application

- adaptation to digestate drying is well advanced

- profitable pathways of utilization for dried product arenecessary

Introduction

Technologies

Products


Pilot project

Conclusions

- complete use of heat bonus can make drying profitable(only if no other option of heat use)

• Membrane technologies are furthest advanced

• Treatment technologies for liquid phase are not „state of theart“ yet

- challenge: reduction of energy demand and wear-out

- several reference plants

• Evaporation and stripping not so far advanced in permanent operation

- Pilot plants are in implementation

- profound assessment of reliability a.profitabilitynot yet possible

- technical risks still high

Summary and Conclusions- technical aspects -

Introduction

Technologies

Products& Costs


Pilot project

Conclusions

• Cost efficiency strongly depends on conditions of biogas plant

Treatment can be useful:

- in areas with high nutrient surplusses

- for large biogas plants

- in areas focussing on living and recreational quality

- if there is a (also local) market for treatment products

Summary and Conclusions-

Introduction

Technologies

Products


Pilot project

Conclusions

Technical digestate treatment- advantages, limitations, costs -


Helmut Döhler, Sebastian Wulf


Merci beaucoup pour votre attention !

Thank you for your kind attention !

Vielen Dank für Ihre Aufmerksamkeit !

technical digestate treatment - biogaz europe

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