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Extracting raw materials from the seabed is costly and potentially quite damaging to the marine environment. Wenbin Ma developed a framework to weigh up all the factors.

Extracting raw materials from the seabed is costly and potentially quite damaging to the marine environment. Wenbin Ma developed a framework to weigh up all the factors.

Lees in het Nederlands

With resources becoming scarce on land, companies are looking to the seabed for extracting valuable raw materials. Currently, little commercial deep sea mining is being done. Explorative missions, on the other hand, are plentiful. Most of them cover subjects such as the commercial or technical viability of particular mining methods or the effects of seabed disturbance on deep ocean species.

Economic and environmental factors are clearly interrelated: minimising the environmental impact puts constraints on the technologies that can acceptably be used. Today, however, little is known about this interrelationship. This is where PhD student Wenbin Ma’s research comes in.

Economical factors
“In terms of economics, many factors play a role: the depth of the sea, the abundance of raw materials, the technologies used, and so on,” says Wenbin Ma, who received his MSc from Wuhan University of Technology, a partner institution of TU Delft. “I decided to focus on three lifting models: hydraulic pumps, air pumps, and buckets.”

Using data from various sources, Ma constructed a theoretical model to evaluate these technologies under different circumstances. In general, it appeared that hydraulic pumps perform much better, mainly because they can operate in deeper seas – in theory, that is, Ma warns, because the only data available is from small scale testing and one can never be sure whether these hold after upscaling operations.

Environmental aspects
“With respect to the environment, I modelled four aspects,” Ma explains. “These are, one, direct physical disturbances and, two, the resulting sediment plumes, clouds of material dispersing in the water. Then, three, there is the disposal of tailings, the material fractions that are not useful. One question that arises is what should be done with these? Finally, four, there is disturbance of species, which depends on the other three aspects.”

“Let me give an example of the type of models I made. Sediment plumes are a serious issue. Larger particles will sink to the bottom fairly quickly, where they may disturb species living there. Smaller particles may remain suspended for a long time and spread over an area much larger than the actual mining site. They influence the amount of light that reaches the bottom and may impair the hunting ability of deep ocean species that use sight to hunt. My model calculates the diffusion, so you can assess the consequences of mining activity.”

Priority
Apart from his own calculations, Ma also interviewed several experts in the field to bring economic and environmental aspects together in one model to answer questions like given environmental legislation and constraints, is mining operation X likely to be profitable? One of Ma’s recommendations is that minimising plume release should be a priority for technology development.

Though the model is a good start, it is not the final answer. Ma asserts that “I would really love to do fieldwork to validate my model. Unfortunately that is very expensive, but hopefully a company will be interested in pursuing this research further.”

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