Post on 24-Dec-2015
Dansk LandbrugsrådgivningLandscentret
More than biogas production
Biogas
Envi-ron-
ment
Agri-cul-ture
Energy
Dansk LandbrugsrådgivningLandscentret
Biogas rests on tree legs
Biogas
Energy EnvironmentAgriculture
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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)
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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
Dansk LandbrugsrådgivningLandscentret
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