What digestate is

F. Adani, January 24-25F. Adani, January 24-25

What digestate is.F. Adani, A. Schievano, G. D’Imporzano,

F. Tambone, B. Scaglia Di.Pro.Ve.

Università degli Studi di Milano, Via Celoria 2, 20133 Milano

[email protected] website: http://www.diprove.unimi.it/


Digestate is not Ingestate

Biological process determines chemical and biological modification of raw

materials (ingestates)

Therefore…………

Anaerobic digestion is a biotechnology


Looking for the Identikit!!!!

So… what is digestate ?

? ?


Degradation

The AD process affects:

Nutrients

Organic matter quality

Xenobiotics

Organic load


Degradation: TS and VS mass balances;

Organic load: BOD5 and COD.

OM quality: biological stability, wet chemical and spectroscopic analyses.

Nutrients: mass balance and speciation.

Xenobiotic content: direct detection.

Our approach


OM reduction of 60-70%

DegradationMass balance

100 %

35% ± 10%

0

10

20

30

40

50

60

70

80

90

100

OM

%

Ingestates Digestates

F. Adani, January 24-25F. Adani, January 24-25Abbattimento COD e BOD

Organic load

152 ± 16

68 ± 11

0

20

40

60

80

100

120

140

160

CO

D

gO 2

L-1


79 ± 10

40 ± 12

0

10

20

30

40

50

60

70

80

BO

D

gO 2

L-1


COD

BOD


OM qualityOM quality

Biological stability OM Biological stability OM degradability degradability Degradation processes determine a

concentration of recalcitrant molecules.

Biological tests

- Anaerobic test;

- Aerobic test.


Anaerobic test: potential Anaerobic test: potential biogas productionbiogas production

ABP

0

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60 70 80 90 100

days

ml

bio

gas

*gT

S-1

It is a good test but it requires time ( 60 dd).


Anaerobic test (ABP)

646 ± 76

221 ± 56

0

100

200

300

400

500

600

700

AB

P m

3 bi

ogas

g-1

TS



Aerobic test: liquid state Aerobic test: liquid state respiration indexrespiration index (SOUR) (SOUR)

…..it allows a strong time reduction (20h)

OD Cumulata

0

100

200

300

400

500

600

00:00 02:24 04:48 07:12 09:36 12:00 14:24 16:48 19:12

tempo prova

OD

Cumulated O2 up-take in 20h


Aerobic test

219 ± 60

90 ± 28

0

50

100

150

200

250

OD

20 m

gO2

g-1

TS



y = 2.319x + 73.760

R2 = 0.713

0

200

400

600

800

1000

0 50 100 150 200 250 300 350

OD20 (mgO2 gTS-1)

AB

P (

Nm

L g

TS

-1)

ingestati

digestati

A case study……….


Correlation ABP vs SOURCorrelation ABP vs SOUR

R2 = 0.710

0200400600800

10001200140016001800

0 100 200 300 400 500

OD20 (mg O2 gTS)

AB

P (

Nm

L g

TS-1

)


Wet analysesWet analyses

Spectroscopic analysesSpectroscopic analyses

OM qualityOM quality


CS (%TS)

cell soluble

70-90% 40-70%

OM qualityMacromolecular composition


ADL (%TS) (Lignin, cutin,

suberan, sterol)

effetto concentrazione

2-8% 10-35%

OM qualityMacromolecular composition


OM qualityCPMAS 13C NMR Spectroscopy

Ingestate

Digestate


Pig slurry

Digested Pig slurry


OM quality

PCA analysis


OM qualityPCA analysis

IngenstateIngestate

Digestate

Biosolid

Compost

-2.

-1.5

-1.

-.5

.

.5

1.

1.5

-1. -.5 . .5 1. 1.5 2.

Fact.1 63.8%

Fa

ct.2

3

1.9

%

Ingestate

Digestate

Biosolid

Compost

-2.

-1.5

-1.

-.5

.

.5

1.

1.5

-1. -.5 . .5 1. 1.5 2.

Fact.1 63.8%

Fa

ct.2

3

1.9

%

Predig. swinemanure

Freshswinemanure

Biological stability+ -


Total N (% TS)

Nutrients: quantity

2-5% 5-12%


N-NH4 (% TS)

0-2% 2-8%

Nutrients: quality


Organic N

Costante 2-4%

Recalcitrant???

Nutrients: quality


XenobioticHeavy metals

0.5100.08Cr VI (mg/kg s.s.)

-100.05As (mg/kg s.s.)

-7501.16Cr III (mg/kg s.s.)

500250074.83Zn (mg/kg s.s.)

230100049.58Cu (mg/kg s.s.)

14075018.16Pb (mg/kg s.s.)

10030012.48Ni (mg/kg s.s.)

1.5101.19Hg (mg/kg s.s.)

1.5200.21Cd (mg/kg s.s.)

Compost limits

Bio solid limit

ValueElemento

Example of digestate analysis:

Metal


absent

Hygienic parameters

Parameter Digestate Legge 99/92 Reg. CE 1774/02

Fecal coliform (MPN/g TS) 100 10.000 n.i.

Vital Helminthes eggs Absent Absent n.i.

Salmonella Absent < 100 Absent

Escherichia coli Absent n.i. < 1000

n.i. = not indicated


Digestate: the Identikit

OM

Low organic load

Medium biological stability

Presence of humus-precursor molecules

Nutrient content

High N content;

High agronomic value.

Xenobiotic content

Very Low


Amendment properties

Fertilizer properties

Hygienic product

High quality

Digestate: the Identikit


Digestate needs to be qualified……….


…….… a proposal.… a proposal

Limits needed for:Limits needed for:

Biological stabilityBiological stability Hygienic parametersHygienic parameters Heavy metal contentsHeavy metal contents

1.1. Environmental and human protection:Environmental and human protection:


..…. a proposal..…. a proposal

Parameters should be indicated:Parameters should be indicated:

N-tot and N-NHN-tot and N-NH44;; P;P; K;K; OM.OM. Moisture contentMoisture content

2.2. Agronomic use: Agronomic use:


Thank you Thank you Dipartimento di Produzione Dipartimento di Produzione

VegetaleVegetale Università degli Studi di MilanoUniversità degli Studi di Milano

Documents

What digestate is