Biogas-E: Practical investigations towards digestate application in Flanders

Belgian-based Biogas-E leads a research group focusing on the implications for the new manure legislation. 

Under the current Flemish manure legislation, all digestate originating from co-digestion of co-substrates with animal manure is being labelled as ‘animal fertiliser’. As a consequence animal manure is created from other (non-animal) sources when it undergoes anaerobic digestion, which makes it more difficult to use the digestate as an organic fertiliser. A possible alternative for the new manure legislation (MAP-5) is to make a differentiation between ‘animal fertiliser’ and ‘other fertiliser’ based on the animal nitrogen input, as is the case in several other European countries. Under the so-called ‘pro rato’ system the share of ‘other fertiliser’ could be used as a replacement for fossil based fertilisers while avoiding competition with fertiliser products from Flemish animal production.

The Flemish government is willing to incorporate this principle in legislation, yet requires thorough follow-up to proof that the natural environment is sufficiently protected from nutrient losses to ground and surface water.

For this reason the ‘pro rato’ system is being investigated at full practical scale by a research group consisting of Biogas-E, Ghent University (ECOCHEM), INAGRO and VCM. The practice investigations pay attention to agronomic (fertiliser efficacy), environmental (leaching and spreading of nutrients, reduction of GHG emissions) as well as economic effects (for both digestion plants and farmer).

The practice investigations are conducted within the framework of the European project Interreg IVB Biorefine (

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Source: De Keulenaere, B.1,2 & Meers, E.1,2

1 Biogas-E, sectoral knowledge platform for biogas in Flanders, Belgium
2 Applied Environmental Chemistry, Ghent University, Belgium