Dansk Landbrugsrådgivning Landscentret More than biogas production Biogas Envi- ron- ment Agri- cul- ture Energy

Dansk LandbrugsrådgivningLandscentret

More than biogas production

Biogas

Envi-ron-

ment

Agri-cul-ture

Energy


Biogas rests on tree legs

Biogas

Energy EnvironmentAgriculture


Short status for Denmark, 2008

• About 60 farm scale biogas plants

• 5 percent of all manure in Denmark is digested (about 1.5 million tonnes)

• Additionally about 0.3 million tonnes of organic waste is digested and recycled to farmland

• 20 large shared biogas plants


Agricultural advantages, overview

• Improved utilization of nutrients

• Homogeneous and light-fluid slurry

• Reduced costs for transportation

• Large amount of declared slurry

• The slurry is free from disease germs and weed seeds


Environmental advantages, overview

• Reduced leaching of nitrate

• Lower surplus of phosphorus in the soil

• Reduced emission of green house gasses

• Reduced odour problems

• Controlled recycling of organic waste


Mixing and digesting slurry change the characteristic of the slurry

DM,

%

N-tot,

kg/t

NH4-N,

kg/t

P,

kg/t

K,

kg/t

pH NH4-N, %

Digested slurry

Pig slurry

Cattle slurry

4,8

5,0

7,5

4,4

4,8

3,9

3,5

2,9

2,4

1,0

1,1

0,9

2,3

2,3

3,5

7,6

7,1

6,9

81

74

61


Fertilizer value


Fertilizer value

0

10

20

30

40

50

60

70

80

90

100

Pig slurry Cattle slurry Digested slurry

Uti

lizat

ion

of

nit

rog

en,

% o

f co

mm

erci

al f

erti

lizer

Winter wheat Spring barley


Improved fertilizer effect of nitrogen- trials in winter wheat

0 20 40 60 80 100

Cattle slurry, injected

Pig slurry, injected

Digested slurry, injected

Cattle slurry, trailing hoses

Pig slurry, trailing hoses

Digested slurry, trailing hoses

N-utilization, % (fertilizer equivalent)


Ammonia evaporation in spring barley

0

10

20

30

40

50

2002 2003

NH

3-lo

ss, %

of

spre

ad N

H4-

N

Untreated pig slurry Digested pig slurry


Fertilizer plan for nitrogen for 1 ha grass

250250N-requirement, kg

170170N in slurry, kg total

6040N-utilization, %

10268N- in slurry, utilized, kg

34

17

-

-

Saved, kg

Saved, £

148182Mineral fertilizer

Digested slurryCattle slurryPer hectare


Digested slurry is low on germs

<5<5<5<5<5

1,300,000140,000690,000

9,000,00062,000

Mar. 18May 13July 15Sept. 9Nov. 11

AfterBeforeDate

Test results from Ribe Biogas,bacteria per ml. slurry (1998)

Lo

g10

ger

ms

per

ml s

lurr

y

Time, weeksSlurry tank, 6-8°C Mesofile biogas, 35°CTermofil biogas, 53°C

10

6

5

3


Digestion reduces odour


Digestion reduces odour

0

1

2

3

4

5

6

7

8

0 5 10 15 20

Days

Odour

units

Wind-direction

Untreatedslurry

Digestedslurry

5 minutes

12 hours


Odour concentration in air samples after spreading

0

200

400

600

800

1000

1200

20 minutes 260 minutes

Od

ou

r u

nit

s p

er

m3 o

f air

Untreated slurry Digested slurry


Concentration of VFA in slurry

0

200

400

600

800

1000

Iso-butanoicacid

Butanoic acid Iso-valericacid

Valeric acid

mg

per

litr

e s

lurr

y

Untreated slurry Digested slurry


Digestion reduces nitrate leaching

0 20 40 60 80 100

Digested slurry

Untreated slurry

Cattle slurry

Min. fertilizer

Nitrate leaching, kg N per hectare

Source: Grøn Viden


Digestion reduces emission of green house gases

• The total emission of CO2 is about 70 million tonnes

• Digestion of all slurry in biogas plants can reduce that with about 2.1 million tonnes

• That is equivalent to 3 percent!

• The reduction is a combination of lower emission of methane from manure tanks and a reduction of the use of fossil fuels

Sommer, Møller and Petersen, 2001

Documents

Dansk Landbrugsrådgivning Landscentret More than biogas production Biogas Envi- ron- ment Agri- cul- ture Energy