Metals, Energy and Sustainability

Copper was the first industrial metal and for over 7000 years has been one of our most essential metals. Coal resources have only been developed in the last few hundred years although the contribution of coal to human welfare has been just as significant. This introductory chapter explains the title of the book and the essential properties of copper and coal that stimulated our demand for both. When steel hulled ships were introduced, there was no longer a need for copper sheathing of wooden hulled ships; however, the Age of Electricity was beginning and copper was in even greater demand. Today there is increasing demand for copper in wind farms and electric cars.

Copper deposits occur in rocks of all ages and are formed as a result of geological processes that concentrated copper initially dispersed through large volumes of magma or rock. The majority of copper deposits were created by hydrothermal processes when metal sulfides were precipitated from hot waters in fractures and permeable rocks in the subsurface and at seafloor hydrothermal vents. Copper minerals can also crystallise in magma chambers or form as a result of secondary enrichment processes when primary copper deposits are weathered. Porphyry copper and associated skarn, vein and replacement deposits are the most important type of copper deposits accounting for some 60% of current world copper production. Sediment-hosted stratiform copper deposits in sedimentary basins account for some 20% of historic world copper production and were some of the earliest copper ores mined. Volcanic-hosted massive sulfide deposits occur in submarine volcanic rocks and are observed forming today at seafloor hydrothermal vents. Magmatic nickel-copper sulfide deposits in igneous rocks have a very different origin than the hydrothermal copper deposits that dominate current and historic world copper production. This type of deposit forms when mafic and ultramafic magmas separate a metal-sulfide magma that sinks to the bottom of the magma chamber or flow conduit.

Copper sulfide orebodies exposed at the surface are subject to weathering processes and typically show a progression from an iron-rich cap through leached rock to oxidised ore that contains copper minerals such as malachite, azurite, cuprite and chrysocolla. Copper liberated from the breakdown of sulfide minerals may also be precipitated as native copper and secondary sulfides such as covellite and chalcocite in the vicinity of the water table. The most common copper minerals in primary ores are chalcopyrite, bornite and tetrahedrite-tennantite. The earliest metalsmiths exploited near surface deposits of copper oxide and carbonate minerals, which were easier to mine and not as difficult to smelt as the underlying sulfide ores.

Coal is a combustible sedimentary rock composed of the altered remains of plants that accumulated in vast swamps and peat bogs. Increasing temperature and pressure as a result of gradual burial beneath overlying sediments subsequently transformed the plant remains into coal. Significant coal formation first occurred some 360 million years ago during the Carboniferous Period. Coal varies greatly in its physical and chemical properties because coal type and rank are independent variables that reflect depositional environment and coalification history, respectively. Humic coals are the most common coal type that form largely from woody plant remains. Sapropelic coals are less common and dominated by non-woody plant materials. Coalification is the process that produces coals of different rank, with higher rank coals having a higher carbon content and higher calorific value than low rank coals.

We will never know who first smelted copper. Nevertheless, archaeometallurgy has made considerable progress in identifying where, when and how our first industrial metal was made into tools. Stone tools had served us well; however, copper proved to be more versatile especially when combined with tin to make bronze. The technology for mining copper ores and extracting copper progressed slowly for the first five thousand years but gathered pace in the first century AD as the Roman Empire expanded and introduced new technology.

As Europe emerged from the Dark Ages, production of copper began to increase, firstly from Mansfeld Land in Germany. By 1650, the largest European production was coming from the Falun Mine in Sweden. In the 1780s, the reverberatory furnace and Welsh coal enabled Swansea, known as ‘Copperopolis’ at this time, to become the world’s leading copper producer.

North of Huelva on the Iberian Peninsula, the mines at the headwaters of the Rio Tinto had drawn Phoenician merchants to Spain and were a major sources of copper for the Roman Empire. There was little mining activity in the Rio Tinto region after Roman mining ceased around the year 400 until 1725 when Liebert Wolters, a native of Stockholm, formed one of the first joint stock companies in Spain to develop the mines of Guadalcanal, Cazalla, Aracena, Galaroza and Rio Tinto. In 1873, after many unsuccessful attempts to make the Rio Tinto Mine profitable, it was bought by a syndicate led by Hugh Matheson for the equivalent of £3,850,000. Rio Tinto Company developed one of the first modern mines.

In the latter half of the nineteenth century, rich copper ore bodies were discovered in the United States, firstly around Lake Superior in the east and then from Arizona in the south to Alaska in the north. The U.S. became the dominant world copper producer and remained so for almost 100 years until surpassed by Chile. The U.S. surpassed Britain as the major coal producer in the last years of the nineteenth century and remained the dominant producer until surpassed by China in the 1980s. At the centre of the copper mining story was Bingham Canyon.

The War of the Pacific between Chile, Peru and Bolivia that erupted in 1879 was primarily fought over the right to mine saltpetre in the Atacama Desert. However, the Copper Man is testament to copper mining in the region some 1500 years ago. The mega-mine Escondida produces over one million tonnes of copper annually mostly as concentrate, although around 320,000 tonnes were in cathode form in 2015. Chile produces some 30% of the world’s copper, and one mine Chuquicamata holds the record for total copper produced. The story of Chuquicamata, ‘Chuqui’ to the local population, encapsulates the history of copper mining in Chile.

Although sustainability was popularised in the late twentieth century, it was also a concern in the late eighteenth century as evidenced in the writings of Thomas Malthus. In his sixteenth century text, De Re Metallica, Georgio Agricola also addressed the environmental impacts of mining. Although copper mining on the Iberian Peninsula took place over thousands of years, no single copper ore body will last forever. The question ‘is copper mining sustainable?’ is addressed by examining previous research into the question and exploring various methods researchers have used. The statement that an activity is sustainable if it enhances or at least does not decrease human welfare now or in the future implies that the relative cost of producing copper will not increase. More precisely, ‘will the future cost of producing copper including environmental cost increase or decrease?’ U.S. data indicate that in the past technological advances have reduced the energy required to mine and concentrate copper ores even though ore grades have decreased. In 2002, the cost of producing copper was less than in 1954. An econometric model predicts that the unit cost of producing copper in the U.S. in 2020 will be less than in 2002. What happens after 2020 is less predictable.