Experiences with mechanical pre- treatment of horse-dung ......mechanical thermic. Hans Oechsner and Matthias Mönch-Tegeder Experinces with mechanical pre-treatment of horse-dung

Der Landwirt als Energiewirt -

Biogaserzeugung in der

LandwirtschaftDr. Hans Oechsner; Dr. Matthias Mönch-TegederState Institute of Agricultural Engineering and Bioenergy,

University of Hohenheim

Experiences with mechanical pre-

treatment of horse-dung on a biogas plant

(190 kW)

Malmö, 10. September 2015

Hans Oechsner and Matthias Mönch-Tegeder

Experinces with mechanical pre-treatment of horse-dung on a biogas plant

3rd IBBA workshop, in Malmö, Sweden, September 10th 2015

2

Biological energy conversion efficiency

of different substratesE

nerg

y c

on

vers

ion

rate

(%

)

80%75%

68%

45%40%

15%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Umsetzrate GE zu Biogasenergie

Sugar

beet

Maize

silage

4-cut-

grassland,

intensive

2-cut-

grassland,

extensive

Wheat

straw

Silage of nature

protection area

Around 8000 Full scale biogas plants in Germany

Substrate use about 115 Mio. t FM per year, >50 % energy crops, costs

Alternative substrates?




3

Research project with horse manure,

funded by the Federal Ministry of Environment

Aims of the project:

To determine of digestibility of

this fibrous substrate

To increase the degradability and

efficiency

To optimize the managability in

the digester

To increase the methane yield

To use the horse manure as

energy source




4

Horse manure as feed stuff for biogas plants?

More than 1 Million horses in Germany

Manure production: 17 - 20 t per horse and year

50 – 70 % straw fraction (fluctuating)

Lack of space at the farms for storage and

disposal problems

Problems in the surroundig of towns

High costs of disposal

→ Energetic use in biogas plants

will be a chance

Häußermann et al., 2002; Beck, 2005; Winter, 2014




6

High fiber content causes

process engineering problems

Floating layer

Blockage of

leakage

possible

Increasing

viscosity –

energy

consumptionSlow conversion




7

Digestibility of horse manure

Material and methods

Substrate from 10 farms:

Used litter (straw, straw pellets, flax straw, wood shavings and

wood pellets)

Horse dung

Horse dung mixed with different litter materials

Fresh and stored manure

Analysis of composition

Weender and van Soest analysis

Concentration of trace elements

Analysis of biogas- and methane yields

Hohenheim Biogas Yield Test (HBT)

VDI-regulars 4630 (35 days)




8


Specific methane yield of different litter materials

0,205

0,247

0,067

0,021 0,017

0,000

0,050

0,100

0,150

0,200

0,250

0,300

Stroh Strohpellets Flachsstroh Holzpellets Sägespäne

Cu

mu

lati

ve

meth

an

eyie

ld[m

³ /

kg

VS

]

standardized: 1013 hPa, 273,15 K

Horse dung with straw straw pellets flax straw wood pellets w. shavings




9


Specific methane yield - age of manure

0,205

0,176

0,198

0,150

0,000

0,050

0,100

0,150

0,200

0,250

Einstreu Pferdekot Pferdemist "frisch" Pferdemist "gelagert"

Cu

mu

lati

ve

meth

an

ep

rod

ucti

on

[m³

/ kg

VS

]

Straw litter horse dung horse manure horse manure

fresh storedstandardized: 1013 hPa, 273,15 K

- 24 %




10


Results

Good digestibility of horse manure with straw

as litter

VS: Horse manure 198 m³ CH4 / t

- (Maize 330 – 350 m³ CH4 / t )

FM: Horse manure 80 m³ CH4 / t

- (Maize 100 – 120 m³ CH4 / t)

Insufficient decomposition with alternative

litter materials

Storage causes a considerable loss of

organic components and loss of methane

yield (24 % less)

Content of trace elements comparable with

grass silage




11

Conditioning of substrate

Plants or parts of plants with high fiber

fraction

Lignocellulose – hindering for digestion

Will it be possible, to enhance

anaerobic digestion by conditioning ?

Schwarz et al., 2009

Micro fibre structure

physical

chemical biological

- hot water

- steam

- thermo-

pressure-

hydrolysis

- acid

- base

- oxidant

- enzymes- shearing strain

- pressure

thermicmechanical




12

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0 5 10 15 20 25 30 35 40

sp

ec

ific

me

tha

ne

yie

ld[m

3/k

g o

DM

]

Retention time [d]

Weizenstroh 1 mm

Weizenstroh 5 mm

Weizenstroh 10 mm

Wheat straw 1 mm

Wheat straw 5 mm

Wheat straw 10 mm

Wheat straw – different particle size

Effect of grinding

+ 30 %

Slotjuk, 2011standardized: 1013 hPa, 273,15 K




13

Mechanical pretreatment

Requirements

Text

Increasing of

particle surface

and

force up of

conversion rate

Optimizing of

viscosity

Reducing the loss

of organic

components

Prevention of

inhibiting effects

Low investment

costs and

low operating

costs

Avoiding process

engineering

problems

Taherzadeh und Karimi, 2008; Agbor et al., 2011




14

Systems used in full scale biogas plants

for mechanical treatment of substrate

Rotacut Ball Mill Cross Flow Grinder

Shredder Extruder Impact Reactor

FREY, 2014 FREY, 2014

JENZ GMBH, 2014 BTS BIOGAS GMBH, 2014 BTS BIOGAS GMBH, 2014

MÖNCH-TEGEDER, 2014




15

Mechanical pretreatment as possible solution –

cross flow grinder

• primarily recycling industrie

• working chamber diameter: 0.9 to 2.5 m

• connection power 55 to 315 kW

• number of rotation: 1200 /min

• working in batch or continuously

rotating chains




16

Mechanical desintegrated substrate

Maize silage 15 sec 30 sec

Horse manure 15 sec 30 sec




17

Wet sieving of the pretreated horse manure

- Variation of treatment time

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

<1,0 1,0≤ bis <2,0 2,0≤ bis <10,0 10≤

Shar

e o

f m

ass

fra

ctio

n

[%]

Size range [mm]

Horse manure control

Horse manure 15 sec.

Horse manure 30 sec.

> 10




18

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

0,40

0,45

0 5 10 15 20 25 30 35 40

Sp

ezif

isc

he

r M

eth

an

ert

rag

(N

m3

/ k

g o

TS

)

Verweilzeit (Tage)

Maissilage QZ 30 sec

Maissilage QZ 15 sec

Maissilage Kontrolle

Pferdemist QZ 30 sec.

Pferdemist QZ 15 sec.

Pferdemist Kontrolle

Maize silage 30 sec

Maize silage 15 sec

Maize silage control

Horse manure 30 sec

Horse manure 15 sec

Horse manure control

Mechanical disintegration –

different substrates

+ 16

bis

+24 %

0 bis

+ 6 %

Digestion time [days]

Specific

meth

ane

yie

ld[m

³/kg V

S]





19


Optic effectContinuously 10 cm gap

5 s

10 s 15 s

Untreated control

30 s




20


Specific methane yield – horse manure

Variation of treatment intensity

0,236

0,241

0,2470,249

0,257

0,249

0,200

0,210

0,220

0,230

0,240

0,250

0,260

0,270

0 10 cm 5 s 10 s 15 s 30 s

sp

ezif

icm

eth

an

eyie

ld[N

m³/

kg

VS

]




23


Energy consumption of cross flow grinder

11.6 11.3 11.813.8

10.7

14.8 14.0

16.3

20.5

15.2

0,0

5,0

10,0

15,0

20,0

25,0

En

erg

yco

nsu

mp

tio

n[k

Wh

/t F

M]

15

s

30

s

15

s

30

s

15

s

30

s

15

s

30

s

15

s

30

s

Maize Grass Total plant Horse Substratesilage silage silage manure mix

DM-content has an influence on energy consumption




24


Cognition

Significant influence on particle structure and - size

No significant effect on methane yield of green plant silage

Clearly significant effect for horse manure

Increasing of methane yield

Degradation kinetics

Optimal grinding effect at 15 s pretreatment

Energy consumption is depending on substrate type and

DM-content (10 - 20 kWh / t FM)

Mechanical desintegration only relevant for lignocellulosic material




25

Examinations in practical scale

Too little experience with lignocellulosic materials in

practical plants:

Effects on process biology

Influence on substrate utilisation

Demand on process engineering

Necessity of pretreatment




26

Usability of horse manure in practical scale

Research biogas plant „Unterer Lindenhof“

Electrical power: 186 kWel

Digestervolume: 800 m³ Netto

Temperature: 40.0 °C




27


Research biogas plant „Unterer Lindenhof“

Period of investigation: 160 days

Use of Cross Flow Grinder MeWa Bio-QZ 900 at digester 1

Identical mass and ratio of feed in both digesters

Analyse of biological parameters

Continuously investigation of gasvolume and gas composition

Calculation of degradation efficiency

Methane yield of digestate with HBT

Calculation of methane yield by using of substrate input




28


Ration of feed

Maize silage12%

Grass silage

8%

Whole plant silage10%

Crushed grains

3%

Horse manure

18%

Solid manure

8%

Liquid manure

41%

26 %

33 %Feed

amountHRT OLR

[t/d] [d] [kg/m³ d]

Digester 1

pretreated10.5 ± 2.0 78.8 ± 14.1 2.9 ± 0.5

Digester 2

control10.4 ± 2.3 79.5 ± 15.6 2.8 ± 0.6

Pretreatment at digester 1




29

Horse manure in practical plant

With and without mechanical pretreatment

0

200

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100 120 140 160

Bio

gas

yie

ldp

er

day

[Nm

³ /

d]

Duration

Fermenter 1 (Bio-QZ)

Fermenter 2(unaufbereitet)

with pretreatment

0.272 m³/kg VS

0.200 m³/kg VS

without pretreatment

Mönch-Tegeder, 2013




30

Use of horse manure in practical scale

Degradation efficiency

0.306 0.272

0.200

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

Berechnet Fermenter 1 (Bio-QZ) Fermenter 2 (unaufbereitet)

Cu

mu

lati

vesp

eci

fic

met

han

eyi

eld

[Nm

³ /

kg V

S]

- 26.5 %

- 11.2 %

Calculation Digester 1 Digester 2

over HBT and input pretreated Control





31


Costs of pretreatment

Definition: investment 104,800 €; interest rate 5 %; machine life 8 a;

electricity consumption 11 kWh / t FM; electricity costs 20 ct / kWh ;

price of maize silage 40 € / t 31

186 kW

30 % liquid manure;

30 % horse manure;

40 % maize silage

30 % liquid manure;

50 % horse manure;

20 % maize silage

Total input t / d 16.5 17.9

Solid Input t / d 11.5 12.5

Input horse manure t / a 1,825 3,285

Amortisation € / a 15,720 15,720

Maintenance costs € / a 2,000 2,000

Electricity costs € / a 9,235 10,038

Pretreatment costs

of horse manure€ / t 14.8 8.4

Cost saving because

of maize substitution€ / a 24,150 67,150




32


Cognition

Process biology

Stable operation (low concentration of VFA)

Increase of DM-content in digester (+3 %)

Substrate efficiency

Quality of horse manure is essential

Nearly complete utilisation of energy content with pretreatment

(89 %)

Insufficient degradation without pretreatment (65 %)

(In reference to HBT-yields)

Process engineering

Neither problems in digester 1 detected (with pretreatment)

Floating layer in digester 2 (without pretreatment)

Reduced demand of process heating (4.750 kWhth / month)

Energy consumption of Bio-QZ: 11,3 ± 1,3 kWhel / t FM, to allow

the use of a substrate, which yields > 300 kWh/t FM electric

energy




33

Conclusions


Horse manure with straw as litter can be well used as cosubstrate in

biogas plants

Quality of horse manure (composition and age) have a big influence on

biogas yield


For the use of green plant silages, pretreatment has no positive effect

on digestibility and gas yield

For the use of fibrous substrates, pretreatment has a crucial effect on

gas yield and degradation kinetics

Usability of horse manure in practical biogas plants

Use of horse manure is only feasible with pretreatment

Substitution of 7.8 Mio t maize could be possible in Germany, if 50 % of

available horse manure is digested

156,000 ha is equivalent to 13 % of momentan used crop area for

biogas production

Extension of substrate spectrum possible




34

Thank you for Your attention!

Contact:

Dr. Hans Oechsner

[email protected]

Tel. ++49 - 711 459 22683




37

Daniel-Gromke et. al, 2013; Fachverband Biogas e.V., 2013; Gömann, 2013

Use of substrates in Biogas plants

7720 Full scale biogas plants in Germany

Substrate use about 115 Mio. t FM per year

10 % of arable land

Liquid manure38%

Solid manure5%

Biowaste and residues

4%

Maize silage39%

Grass silage5%

Whole plant silage

4%Other energy crops

5%

Energy crops53%

Documents

Experiences with mechanical pre- treatment of horse-dung ......mechanical thermic. Hans Oechsner and Matthias Mönch-Tegeder Experinces with mechanical pre-treatment of horse-dung