1. Digestate handling

2. Logistics of biomass for biogas
Co-substrates

3. Surplus of P in Danish agriculture
P Surplus
P Surplus
Plant Cattle Pig Mixed

4. What is this?

5. Typical composition of digestate
Total N
kg/ton
Total P K
Degassed slurry
5.0
1.0
2.0
Liquid fraction
4.5
0.3
Solid fraction
8.0
Birkmose et al. (2013). Biomasse til biogasanlæg i
Danmark

6. Logistics of biomass for biogas
Solid
Co-substrates
Solid fraction

7. Value of digestate Potential Value Kr/ton Degassed slurry 56 47
156
Degassed slurry
Liquid fraction
Solid 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 i
Danmark

8. Feedstock (chemical composition)
The goal
Feedstock (chemical composition)
Retention time
Temperature
Soil
Precipitation
Oxygen
NH3
N2O
CO2

9. 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

10. 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

11. 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

12. Application of fertilizer and N2O emissions
Bouwman (1996)