The Dutch have a saying, "God made the world, but the Dutch made Holland," and anyone traveling through the country can see why. The Netherlands, about one-third of which lies below sea level, owes its continued existence to an intricate system of coastal fortifications, flood defenses and innovative water management technologies. And about one-sixth of the country consists of land that has been drained and reclaimed from the sea, lakes, marshes and swamps. The Dutch, in short, know quite a lot about keeping their feet dry in a delta.
One of the speakers at the recent Polymer Innovation Day, organized by the Dutch Polymer Institute in Papendal, the Netherlands, revealed that there is now a new weapon - made of biocomposite plastic material - that can be used in the ongoing process of dike reinforcement and shore protection. Called the "ground consolidator," it was originally developed to reinforce soft, weak ground. However, more and more applications are now being developed and tested, and civil engineering projects in which they are currently being deployed include biodegradable shore protection projects, which are aimed at preventing erosion; the creation of artificial reefs; and to improve the sliding stability of dikes.
What are they?
Basically, ground consolidators (GCs) are angular, hooked elements, formed of seven edges of a cube, which create a strong, interlocking, open framework that holds sand together when deposited in large quantities. A Dutch inventor called Jos Hoebe developed the innovative anchoring devices, and they are now produced and implemented in projects by a company called Anome BV, of which he is a partner.
Currently, there are two versions available: one is made of compostable biocomposite material, the other of a non-compostable bio reinforced PP. The choice of material depends on the application. One of the most interesting applications today is for biotechnical erosion control.
Lieuwe Boskma of Anome Projects, pointed out that in shoreland protection projects along rivers and lakes, the idea today is often to encourage vegetation to grow in order to establish a stable embankment and to create a wildlife habitat where plants and animals can thrive. However, this was not always the case. Biotechnical erosion control has only started to be recognized by civil engineers as an effective shoreland protection technique over the past decade or so. Conventional structural methods - bulkheads, revetments - were traditionally the preferred approach. Biotechnical erosion control, however, is a self-renewing, durable, and relatively low maintenance approach that keeps (human) disturbance to the environment to a minimum.
Developing vegetation, such as rushes and reed clumps that trap and stabilize sediments and sand, takes time. Ground consolidators promote the process, by holding sand in place, giving the vegetation time to take root and grow. And unlike the geotextile solutions and near-shore rocky breakwaters that are commonly used to provide erosion control while vegetative growth is established, using biodegradable ground consolidators means that they do not have to be taken down or removed: instead, they disappear.
Biodegradable GCs are currently made of PLA, reinforced with hemp and chalk and produced by means of injection molding. The non-degradable GCs used for dike reinforcements are made of PP, hemp and barium sulfate (filler), and are 100% recyclable as new GCs.
The patented slender, spatial design of the interlocking GCs and the innovative use of biocomposites are, according to Boskma, "a unique concept in geo-bioengineering." The mats or geotextile currently in use are invisible, but usually have a dense structure, which eventually impedes further growth, while breakwaters form an 'unsightly unnatural element' in the environment. Using GCs eliminates the problem: growth is encouraged while they gradually degrade, with no extra costs for removal required. And their use can be precisely adapted or 'tuned' for each project.
According to Boskma, GCs offer a feasible alternative to traditional technologies, and "they provide a sustainable solution in civil engineering that is at the same time ecologically and economically feasible. Instead of controlling nature, we are working with nature, with natural materials. What more do we want?"