Risicobeoordeling van contaminanten in afval- en reststoffen bestemd voor gebruik als covergistingsmateriaal

A number of wastes and by-products were reviewed for their suitability as substrates for co-digestion with animalmanure to produce biogas and a digestate for use as a fertiliser. The review included 21 substances proposed byLTO Noord (Dutch Farmers Union – Northern Netherlands) and Biogas Branche Organisatie (BBO, the Dutch BiogasIndustry Association) for inclusion in Annex Aa of the Fertiliser Act. At the request of the Ministry of EconomicAffairs a further 6 substances were added (21+6). In addition, 119 substances were re-reviewed in connection witha change to the reference composition for animal manure. The review focused on the possible adverseenvironmental effects of using the digestate as a fertiliser and followed the protocol for assessing the value andrisks of waste used as a fertiliser, version 2.1. The risk assessment included the inorganic contaminants (Cd, Cr, Cu,Hg, Ni, Pb, Zn, As) and organic contaminants (dioxine, PCBs, PAHs, mineral oil, residues of crop protectionproducts) as required by the Fertiliser Act. For all the wastes and by-products, data on composition were collectedfrom the literature and from analyses provided by stakeholders. Expert judgment was used where data were notavailable or were insufficient to conduct a risk assessment as prescribed by the protocol. Criteria for expertjudgment were developed for such situations. Two alternative risk assessment methods were developed for theresidues of pesticides and biocides, based partly on expert judgement. These methods were compared with themethod prescribed by the protocol. These three methods reflect different policy judgements; the protection level setby policymakers will determine which method should be used. The 21+6 substances were evaluated in accordancewith the protocol and using the three methods for evaluating the residues of pesticides and biocides. The resultswere compared with registered co-digestion materials in Flanders, Denmark and Germany. Recommendations aregiven to support policy decisions on the choice of alternative risk assessment method to be used to permit the codigestionof wastes and by-products in biogas production that produce an agronomically and environmentallyacceptable digestate for fertiliser use