Seabed mineral resources, an alternative for the future of renewable energy: A critical review

Highlights

• Global warming is the biggest problem humanity is currently facing, where CO₂ is the main gas contributing to climate change.

• The energy industry is the primary generator of CO₂; therefore, it is crucial to boost its decarburization and promote accelerated growth in the renewable energy market.

• Critical metals are indispensable for the manufacture of green technologies; however, there is a shortage of critical metals on the earth’s surface. Where China has a monopolistic position in the rare earth market, which prevents the accelerated growth of renewable energies, and generates political tensions between the countries involved.

• The seabed deposits have high concentrations of critical metals and are in various parts of the world. Unlike terrestrial deposits, these have high levels in a deposit so that they can be the solution to the supply and demand problems of these resources.

• The total environmental impact that could be generated by large submarine mining is still uncertain.

Abstract

Global warming is one of the most significant issues of today. Carbon dioxide is the primary contributor to climate change, and is mainly formed by the energy sector; thus, it is imperative to expand the total decarbonisation of this industry. Another global concern is the high demand and low supply of critical metals due to the constant growth of technological advances. These elements are essential for the manufacturing of advanced technology, green technology, and emerging industries. Currently, there is global tension and unrest over how the critical metals market is developing, with one example regarding China, which has an apparent monopoly on the mining, refining, and technical expertise associated with rare earth elements. China currently provides approximately 90% of the production of rare earth elements, causing conflicts with the European Union, the USA, and Japan due to their dependence on these raw materials. Another controversial case is the production of cobalt in the Democratic Republic of the Congo, which dominates in the global production (60% of the world’s production of Co). Despite this, the Democratic Republic of the Congo is one of the poorest countries in the world. The constant depletion of high-grade minerals from the Earth's surface forces the search for new alternative sources of the critical metals. The abundance of minerals within the sea is of relevance, with large deposits of marine nodules, ferromanganese crusts, and massive polymetallic sulphides. These are of great interest to the mining industry, as it is estimated that the largest reserves of various critical metals are found on the seabed, in addition to the largest reserves of cobalt, nickel, and manganese, and a considerable amount of rare earth elements. The exploitation of mineral resources from the seabed by the company Deep Sea Mining Finance Limited (DSMF) is currently being developed, which might promote the expansion of this market throughout the world. The wealth of minerals in the seabed may be a solution to the shortage of critical metals in the market, may decrease political tensions between countries worldwide, and may promote the large-scale deployment of renewable energy.

Introduction

Several types of minerals are found in the deep sea, including marine nodules, ferromanganese crusts, and massive polymetallic sulphides (Schriever and Thiel, 2013). Fe and Mn oxides (crusts and nodules) are formed by direct precipitation in seawater. They are mainly deposited on the flat parts and on the flanks of seamounts, where ocean currents prevent sedimentation (Konstantinova et al., 2017). These deposits are located in all oceans around the world (Marino et al., 2017a, Marino et al., 2017b). While polymetallic sulphides have been observed in a wide variety of volcanic and tectonic environments, at depths that vary between 3700 and 1500 m (Herzig and Hannington, 1995), they mostly occur in an oceanic ridge system that is almost 60,000 km long (Pandey, 2013). These are formed when seawater interacts with the heat of magma in the subsoil region (Hannington et al., 2011).

Diverse authors have highlighted the need to generate new options to overcome an eventual stagnation of the growth capacity in mining (ICSG., 2017, Toro et al., 2019a, Toro et al., 2019b), considering the significant challenges faced by the industry. The grade of the terrestrial deposits is continuously decreasing, for example, in the year 1900 the average of copper contained in the rocks was approximately 4%, while currently, the grades are close to 0.5% Cu (Mudd, 2009, Toro, 2020), with some cases reaching 0.26% (mch, 2012). In comparison, subsea polymetallic sulphide deposits have grades between 1 and 12% Cu, while manganese nodules also contain grades of 1% Cu (Hein et al., 2013). Land mining is exploited three-dimensionally, where significant amounts of surcharges are eliminated to find the mineral deposits. In contrast, the deposits of marine nodules and ferromanganese crusts are strictly two-dimensional, being on the seabed without overloading. On the other hand, massive polymetallic sulphides are three-dimensional and can be tens of meters thick; however, they are not exposed to overload (Hein et al., 2013).

The constant growth of technological advances is causing an expansion in the requirements for critical metals (Ros, 2018). Base metals are called “critical metals”, which are indispensable for the manufacturing of advanced technology, green technology, and emerging industries (Graedel et al., 2015, Pak et al., 2019). Researchers estimated that the largest reserves of many of these elements are located on the seabed, where the largest reserves of cobalt, nickel, and manganese are found in submarine deposits (mch, 2018), in addition to a considerable amount of rare earth (Pak et al., 2019).

Global warming is one of the primary concerns for industrial development, with carbon dioxide being the most significant contributor to climate change (Hofer et al., 2018, Lacis et al., 2010, Ming et al., 2014, Murakami et al., 2020). The energy sector produces substantial amounts of CO₂; hence, it is imperative to move toward decarbonisation (Greenpeace. , 2019, Lacis et al., 2010). This creates financial opportunities for mining due to the metal boom that decarbonization involves, and the large-scale deployment of generating renewable energy (West et al., 2019). Interestingly, Rietveld et al., (2019) projected a decrease in energy demands; however, the authors highlighted a reduction in the use of fossil fuels. Fig. 1 exhibits a prediction on the market of energy from different sources, where we highlighted how the consumption of electricity, biomass, and waste will grow, with a notable lessening of the use of oil.

Critical metals generate a positive perception for the development of technological advances, though their production causes controversy. An example is the effectively monopolistic status of China in the mining, refining, and technical knowledge for the production of rare earth elements (Jaroni et al., 2019). This has generated conflicts with the European Union, the USA and Japan due to their dependence on these raw materials (Rietveld et al., 2019). Another example is Cobalt production, as its supply is dominated by only one country, the Democratic Republic of the Congo. They produce nearly 60% of the world’s Cobalt, while no other country offers more than 6%. Despite this, the Democratic Republic of the Congo is one of the poorest countries in the world (Banza et al., 2018).

For the reasons previously stated, the mineral resources of the seabed are an interesting alternative that would allow the expansion in the supply of critical metals. They would also diversify the exploitation of reserves to avoid monopolistic concentrations in the production of these strategic elements.