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Life Cycle Assessment of Biogas from Separated slurry Processes F.11 to F.14: Handling the raw slurry input for biogas: from in-house storage to storage at the biogas plant.
F.11 In-house storage of raw slurryThe assumptions and Life Cycle Inventory data for the storage of slurry in the housing units are the same as for the reference scenario (section A.2, Annex A), and thereby the same as described in section F.2. F.12 Storage of raw slurry in pre-tankThis process is identical to the process described in section F.3. Therefore, the same life cycle data applies here. F.13 Transport of raw slurry to biogas plantFor the transport of untreated slurry to the biogas plant, a distance of 5 km is assumed between the farm and the biogas plant. This distance is based on the fact that farmers transporting raw slurry are located nearby the biogas plant, so it pays-off to transport raw slurry rather than separated slurry. As transport distance is not anticipated to have a considerable influence on the environmental impacts in the overall scenario (based on the results obtained by Wesnæs et al., 2009), no sensitivity analysis was carried out for a greater transport distance. The slurry is transported by trucks. The transport is modelled by use of the Ecoinvent process “Transport, lorry >32t, EURO3” (Spielmann et al., 2007; table 5-124, p.96). F.14 Storage of the raw slurry at the biogas plantThe raw slurry is stored at the biogas plant for a rather short time, since the storage capacity available at the biogas plant is limited. Therefore, no emissions were considered for this temporal stage. The composition of the raw slurry is therefore the same as the ex pre-tank slurry and is presented in table F.18 below. Table F.18. Raw slurry composition at the biogas plant, just before entering the digester (slurry from fattening pigs)
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