Use of dredged sediments as a sustainable material
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Sediment is dredged from the bottom of rivers and harbours to keep inland shipping and marine traffic possible. All over the world hundreds of millions of cubic meters of sediment is dredged annually. Human activity surrounding those rivers and harbours are a source of pollutants that are ingrained in the sediment. A huge part of the dredged sediment is classified as waste and is dumped in sea or on land. There are however many valuable resources present in sediments that now go to waste. Dredged sediments consist predominantly of eroded rock and soil in the form of sand, silt and clay. Those are non-renewable resources used in applications ranging from building materials to plant growing media. Organic matter and heavy metals present in dredged sediments can be used for beneficial purposes. This review paper aims to address why dredged sediment is not completely used as a resource and whether these barriers can be overcome. There are several reasons why not all dredged sediment is used. These include the inconsistent composition of the dredged sediment, the common occurrence of pollutants in sediment and the high cost associated with using dredged sediment compared to other sources. Construction materials are held to high standards, as buildings and roads should be safe. The variable nature of dredged sediment causes construction materials made from them to have different attributes. High costs also are a barrier in the use of dredged sediments. Steps needed to prepare dredged sediments for use results in higher prices compared to similar resources. These barriers lead to a low demand for dredged sediments. Cost would go down with increased use of dredged sediments, as processes will become more efficient and new methods of cleaning will be tried. Regulations from the government could help streamline this process, by standardising test for sediment compositions and lifting the ‘waste’ classification of dredged sediments.