dry anaerobic digestion of municipal solid waste and digestate ...

Depending on its characteristics, it could be either applied directly on the agriculture land
or treated by aerobic process of curing or composting. During its handling and
management, the digestate needs to be stored as well as dewatered. Thus, the main purpose
of Phase III is to find environmentally suitable options for digestate management. The
possible unit processes involved in digestate handling and management have been shown
in Figure 3.6. The unit processes shown in dotted boxes are the main sources of GHG
emissions from digestate management system. The processes used for management of
digestate in this study have been detailed in the following sections.
Figure 3.6 Possible unit processes of digestate management system
3.4.1 Storage of digestate
Liquid Digestate
Rich in N & K
The digestate after being withdrawn from the anaerobic digester was temporarily stored in
high density polyethylene (HDPE) plastic drums. The drums were kept covered and were
kept in shade to avoid NH4 volatilization as shown in Figure 3.7. The size of each drum is
150 L. All the withdrawn digestate of each run was collected in these drums and at the end
of the run it was dewatered by the sand drying bed.
3.4.2 Dewatering of digestate
Digestate
Liquid-solid separation or dewatering of the digestate was done, using simple filtration
system of sand drying bed (Figure 3.8 and 3.9).
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Storage
Dewatering
Composting
Land Application
Solid Digestate
Rich in OM & P
Curing