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Digestate handling.

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Presentation on theme: "Digestate handling."— Presentation transcript:

1 Digestate handling

2 Logistics of biomass for biogas

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)

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