Digestate handling
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Transcript of Digestate handling
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Digestate handling
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Logistics of biomass for biogas
Co-substrates
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Surplus of P in Danish agricultureP Surplus
P overskud i marken(kg P/ha)
(Grant et al., 2005)
P overskud i marken(kg P/ha)
P overskud i marken(kg P/ha)
(Grant et al., 2005)
P Surplus
Plant Cattle Pig Mixed
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What is this?
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Typical composition of digestateTotal Nkg/ton
Total Pkg/ton
Kkg/ton
Degassed slurry
5.0 1.0 2.0
Liquid fraction
4.5 0.3 2.0
Solid fraction
8.0 8.0 2.0
Birkmose et al. (2013). Biomasse til biogasanlæg iDanmark
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Solid
Logistics of biomass for biogas
Solid fraction
Co-substrates
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Value of digestatePotential ValueKr/ton
56
47
156
Degassed slurryLiquid fractionSolid fraction
True value is lower because of: 1. Difficulties and costs during storage, 2. Uncertain availability of nutrients, 3. Administrative and legistrative problems, 4. Increased demand for catch crops, 5. Odour, 6. Supply and demand
Birkmose et al. (2013). Biomasse til biogasanlæg iDanmark
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The goal
Feedstock (chemical
composition)
Retention time
Temperature
Soil
Precipitation
Oxygen
NH3
N2O
CO2
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Main environmental impacts associated with digestate handling
• NH3 emissions during storage and land application
• Formation of the greenhouse gas N2O ad CO2 after land application
• Nitrate leaching• Phosphorus loss
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NH3 volatilization
• High pH of digestate leads to high risk of ammonia volitilization
• Covered storage• Low dry matter content leads to fast
infiltration and therefore low ammonia volatilization
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N2O emission
• N2O is formed in two processes, nitrification and denitrification
• Nitrification requires ammonia and oxygen• Defitrification require nitrate, organic matter
and absense of oxygen
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Application of fertilizer and N2O emissions
Bouwman (1996)