Humankind’s Iron Age signifies another technological leap. Using knowledge gained from smelting soft copper and tin into bronze, we started smelting the vast quantities of iron that permeate the Earth’s crust. Out of the forges came wonderful fabrications such as nails, bolts, horseshoes, shields and swords. Forcing rocks into special utilitarian shapes facilitated the endavours of humans and made our species even more successful.

However, iron working was neither simple or cheap. A source of iron (like Magnetite – Fe3O4) had to be found and then mined. Then, the rock had to be purified by removing the oxygen and other unwanted material. A bloomery, or oven, heated the rock so as to force out the unwanted atoms. Introducing charcoal facilitates this process as the charcoal, or carbon, combines with the oxygen to make gaseous carbon dioxide and carbon monoxide which drifts away. The resulting sponge like mass, called a bloom, was again heated and hammered to continue with the removal of impurities and to shape the rock. The result, known as wrought iron, was well on its way to becoming an implement ready for humankind’s desires.

But this process had a high energy cost. Human labour dug the rock, carried it to the bloomery, and hammered the impurities out. Heating the rock (to about 1600C) required large quantities of wood. Most of all though was the charcoal cost. Charcoals is made by roasting wood. Therefore, wood was needed for both the roasting and to be roasted. This energy hungry process caused the denuding of the medieval European landscape.

The Cornwall bloomery consumed 340 acres of wood per year to produce 1000 tons of iron. Neglect the energy costs for the labour and the infrastructure. And, assume this bloomery used virgin, mature stands of trees with about 50 trees per hectare each about 50 metres in height. Using typical energy density values for trees, this results in 8e9 joules (8 GJ) of energy to produce one kilogram of iron.

In 2005 we produced approximately 1544 million metric tons of iron ore. If we still used trees as the energy (and chemical) source we’d need 72 million trees or 1.5 million hectares. Or, we would if this area of mature forest still existed. And, this is for one year’s worth of swords, ploughshares and every other iron implement.

The leaps we’ve accomplished with technology come at a cost. Maintaining a ready supply of iron gives us great quantities of durable goods. But iron will return to its oxidized state eventually. Hence their replacements require a continual energy supply. And, more people with more demands increase the requirements and thus the energy needs. Can we sustain the necessary energy supply to keep us at our desired technological level?

Cornwall

Before conception, each of us had no claim upon the Earth. With conception and the miracle of new life, we laid claim to huge numbers of atoms. Energy put these atoms into molecules and kept them moving and accumulating such that our human bodies evolved. At full life, we include about 75 kilograms worth of these unique little particles.

Eventually though, and hopefully after a long and full life, our bodies can no longer sustain themselves. Death signals the end of a journey that started long ago from two cells coming together.

Not so many years ago, upon death, a human body would lie on the Earth’s surface. Where-ever it fell, it would provide food to a host of other creatures. Some carnivore scavengers may take advantage but most of the body would feed little creatures, the detrivores. And, these little creatures would fall prey to larger creatures that would fall prey to even larger creatures and, in a grand circle, may provide food and energy for a new generation of humans.

If we prevent the detrivores from accessing the human body, its potential as food isn’t realized. Further, if we bequeath even more to the body, we reduce the amount available for other living things, whether small detrivores or new generations of humans. This legacy can only come from those with little view to or hope of future’s potential.