More than biogas production

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More than biogas production
Biogas
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Biogas rests on tree legs
Energy
Environment
Agriculture
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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

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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

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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

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Mixing and digesting slurry change the
characteristic of the slurry
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Fertilizer value
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Fertilizer value
100
90
80
70
60
Utilization of nitrogen,
of commercial fertilizer
50
40
30
20
10
0
Pig slurry
Cattle slurry
Digested slurry
Winter wheat
Spring barley
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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)
10
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
11
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,
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Digested slurry is low on germs
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Digestion reduces odour
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Digestion reduces odour
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Odour concentration in air samples after spreading
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Concentration of VFA in slurry
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Digestion reduces nitrate leaching
Source Grøn Viden
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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