The contribution of biogas plants to nutrient management planning

1
The contribution of biogas plants to nutrient
management planning

• Adviser Torkild Birkmose,
• DAAS, Denmark

Photo Torben Skøtt, BioPress
2
Biogas rests on tree legs
Energy
Environment
Agriculture
3
Agricultural advantages

• Improved fertilizer value of nitrogen
• Balanced P and K-balance in slurry
• Homogeneous and light fluid
• Full declaration of nutrients
• Free from germs and seeds
• Reduced costs for transportation of slurry

4
Environmental advantages

• Reduced nitrate leaching
• Reduced odour problems
• Reduced green house gas emission
• Controlled recycling of organic waste

5
Mixing and digesting slurry change the
characteristic of the slurry
6
Fertilizer value
7
Ammonia evaporation in spring barley
50
-N
4
40
30
-loss, of spread NH
20
10
3
NH
0
2002
2003
Untreated pig slurry
Digested pig slurry
8
Improved fertilizer effect of nitrogen- trials
in winter wheat
Digested slurry, trailing hoses
Pig slurry, trailing hoses
Cattle slurry, trailing hoses
Digested slurry, injected
Pig slurry, injected
Cattle slurry, injected
0
20
40
60
80
100
N-utilization, (fertilizer equivalent)
9
Fertilizer plan for nitrogen for 1 ha grass
Digested slurry
Cattle slurry
Per hectare
250
250
N-requirement, kg
170
170
N in slurry, kg total
60
40
N-utilization,
102
68
N- in slurry, utilized, kg
148
182
Mineral fertilizer
34 17
- -
Saved, kg Saved,
10
Digestion reduces risk of spreading diseases
11
Digested slurry is low on germs
6
Test results from Ribe Biogas, bacteria per ml.
slurry (1998)
Log10 germs per ml. slurry
3
After
Before
Date
lt5 lt5 lt5 lt5 lt5
1,300,000 140,000 690,000 9,000,000 62,000
Mar. 18 May 13 July 15 Sept. 9 Nov. 11
10
5
Time, weeks
Slurry tank, 6-8C
Mesofile biogas, 35C
Thermofile biogas, 53C
12
Digestion reduces odour
13
Reduction of odour compounds in the biogas reactor
14
Concentration of VFA in slurry
15
Carcass chamber for collecting air samples
16
Odour concentration in air samples after spreading