DC Dredging talks about CO2 reduction and dilemma’s on sustainability at sea


DC Dredging talks about CO2 reduction and dilemma’s on sustainability at sea

Due to economic growth and a rising population, the demand for construction and infrastructure equally rises. These construction works require raw materials, such as sand and gravel, that are becoming more scarce on land. For this reason, more and more of the required raw materials are being sourced from the bottom of the sea. At the same time, offshore wind farms are being built at rapid speed to meet the demands for renewable power. This makes it more challenging to dig up the raw building materials from the sea, because the sea surfaces become crowded. DC Dreding, the Belgian dredging and sand extraction company, has the ambition to turn these dilemma’s into opportunities.

As a subsidiary company of the Belgian organization Groep De Cloedt, DC Dredging focuses on producing and offering raw construction materials such as sand, gravel and stone for the asphalt and concrete industry as well as railway construction and hydraulic engineering. A great number of raw materials that DC Dredging produces are being extracted from the sea. “We have five ships that extract sand and gravel from the sea. These raw materials are then transported to the main land”, says Dirk van Reijendam, who is hired by DC Dredging to further develop the organization. Van Reijendam is also responsible for the implementation of the CO2 Performance Ladder within the company.

“At DC Dredging, we noticed that we had less chance of being awarded a project in tenders where the CO2 Performance Ladder is being implemented as an award advantage. This triggered us to obtain a certificate.” The dredging company is momentarily working on obtaining its first certificate on the CO2 Performance Ladder at level 3. “Next to being awarded with projects and being able to register for various tenders, we realize that CO2 reduction is coupled with cost savings. That is why we expect the CO2 Performance Ladder to help us gain insights on the many possibilities to cut back carbon emissions resulting from our organization and projects.”

Dredging with less fuel

The fuel consumption of DC Dredging’s marine aggregate dredgers and ships result to the greatest number of carbon emissions. In order to save on fuel consumption and with it CO2 emissions, the dredger has developed a diesel electric aggregate dredger: the DC Orisant. This aggregate dredger is the first of its kind. The development of DC Orisant is made possible in collaboration with the Dutch firm Reimerswaal BV. “The diesel in this marine aggregate generates electricity which then drives the motors of the DC Orisant. Due to the generation of electricity, it requires less fuel than a marine aggregate dredger that solely runs on diesel”, Van Reijendam explains.

The marine aggregate dredger is provided with a power management system (PMS). This system ensures efficient consumption of power. “There are four generators and four electric motors on the ship. Depending on the power needed for the ship, the PMS will switch the generators on or off. By switching off one or two generators, there will be less fuel needed for the DC Orisant to sail compared to traditional marine aggregates. This enables us to save up on fuel consumption.”

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Next to the power management system, DC Dredging keeps track of the fuel consumption of its marine aggregates to sail efficiently. For this, the organization combines its sailing routes with insights on weather conditions and tides. “We strive to make the most of natural weather conditions to reduce the fuel consumption of our ships. If for example, there is an ebb current at sea, we will require less fuel, because we make use of the energy resulting from the current. This prevents us from wasting fuel.” Sustainable innovations such as the DC Orisant must contribute to the ambition of DC Dredging to cut back 5 percent of its carbon emissions in 2019 compared to 2017.

‘If there is no demand, there is no market’

Due to economic growth, the demand for more housing, offices and other construction works increases. “There were not enough houses built in the Netherlands for these past few years, which causes a shortage in the market. More housing must therefore be built. And what is required to build these houses? Raw materials”, says Van Reijendam. According to the advisor, sourcing raw materials on the main land becomes more complicated because of the scarcity of the materials. This problem is less prominent in the Netherlands, where there are rivers such as the Rijn, the Maas and the Waal, which are rich sources of raw construction materials on the main land. However, for other countries such as Belgium, there is no direct supply of sand on the main land. This creates a greater need to extract raw materials from the sea.

Van Reijendam expects that the need to extract raw materials from the sea will become even greater within the coming years. “It will become more complicated to extract materials from the main land. This requires permits from the government, that are difficult to obtain. A great deal of the accessible surfaces to extract materials on the main land is also being used as living quarters or other purposes. This contributes to the increasing necessity to extract the construction materials from the sea.” At the same time the advisor considers the environmental impact of raw materials extraction at sea. “We believe that more sand will be extracted from the bottom of the sea. In the meantime, the sea is being used for other purposes such as offshore wind farms, cables and pipes. On the long term, a fair division of the available spaces at sea is necessary to meet the demands of both raw materials as well as renewable electricity.” According to Van Reijendam, raw materials extracted from the sea is in high demand in the construction industry. “If there is no demand, there would be no market.”

Maritime Spatial Planning

The future of raw materials extraction from the bottom of the sea therefore requires efficient planning. Governments are constructing wind farms at rapid speed to adhere to the demands of renewables and contribute to climate goals. These wind farms require cables to transport the generated power to the main land. The cables take up a great deal of accessible space that is also needed for ships to sail and raw materials to be extracted. “Due to the construction of many offshore wind farms, the available surface areas for materials extraction at sea becomes smaller. In addition, sailing routes for freight shipping at sea will be diverted around the wind farms, which will remove even more surface area for sand extraction. Materials can still be extracted at those locations, but there is a greater risk of collisions with ships using the sand extraction areas as sailing routes. Ultimately, if an incident occurs, the ships in the sailing route will be given priority to remain and the firms extracting raw materials must clear the area”, Van Reijendam explains. “It is of utmost essence to make the relevant stakeholders aware of these circumstances.”

To tackle these dilemma’s at sea, the European Commission has come up with the concept of Maritime Spatial Planning. According to this concept, from 2020 onwards all EU countries must be held accountable for their activities at sea and the environmental impacts of these activities. With these regulations the dredging industries are obliged to communicate as a sector about the environmental impact of their business at sea. “On the one hand governments strive for economic growth for which raw construction materials are required, and on the other hand they wish to adhere to climate goals by building more offshore wind parks for renewables. This is why Maritime Spatial Planning must offer a solution that contributes to achieving both ambitions.”

To control the environmental damage caused by materials extraction at sea, the dredging companies are seeking opportunities in the circular economy. However, the possibilities of re-use and recycling of the raw materials are limited at the moment, according to Van Reijendam. “The stream of recycled materials such as gravel is not sufficient enough to eliminate the need for the extraction of gravel from the sea or from the main land. Moreover, recycling sand requires a lot of energy. In that sense, I believe that extracting and recycling sand from bricks for example, lead to more damage to the environment than extracting the same amount of sand from the sea.”

Van Reijendam: “The sea is becoming more crowded. These practices make it more difficult for us to extract materials from the sea, which means we need to cover greater distances to obtain the required materials. This leads to more fuel consumption and more carbon emissions, which is why we are aiming our efforts at the development of fuel efficient marine aggregates. We want to cut back CO2 where we can make a difference.”