The earth consists of a large array of elements, neatly represented in the periodic table, which are chemically or otherwise bonded in natural and human-intervened stocks and flows.

• Some elements and compounds are sequestered for long periods; others are more mobile. From a sustainability perspective, the anthropogenic flows relative to the natural flows is an indicator of degree of human intervention.For some (C, P, N, Mg), even massive intervention is minor compared to natural flows; for others (Pt, Au, Sn, W) human exploitation is a significant fraction of natural flows;
• Similar to fossil fuel use, the production of materials has increased exponentially in the last century, exceeding nowadays 70 Gt/yr, of which 40% are construction materials and another 40% biomass-related. Flows of ores and industrial minerals are much smaller (~ 5 Gt/yr, roughly half the size of fossil fuel mass flows) but of higher value and more widely used. Productivity in aggregate material use per unit of economic output has risen.
• Materials are part of commodity or supply chains, which are investigated in Material Flow Analyses (MFA) and input-output (I-O analysis. The resulting consumption-based indicator is called, in analogy with water and carbon, the material footprint(MF) for a country or region. The inclusion of trade flows can give a significantly different outcome.
• Commodity chains consist of stocks (ore deposit, in-use and end-of-life) which are connected by flows (mining output, discard rate etc.). A key indicator from a sustainability source and sink perspective is the fraction of throughput which ends up in the environment in too diluted form to be recovered or reused (dissipation rate). It differs widely for different elements.
• Commodity chains are confronted with depletion and cause environmental harm. The prime activity to mitigate both is to stimulate redesign, reuse and recycling. Another option, often occurring unintentionally, is the use of substitutes. An over-all scarcity index should contain both dissipation rate and substitution potential. Many analyses have been done to assess the scarcity of ‘critical’ materials (Ag, Co, In, Pt, Ni, Cr, Mo, rare earth, Cu, Cr, Pb…).
• The available resource is another indicator of scarcity. However, impending scarcity has historically for many elements been postponed by new discoveries by the few, globally operating corporations. However, mining has serious environmental implications, which become more serious obstacles with tighter environmental regulation and more ambitious preservation and bioreserves targets.
• Chemical substances are at the core of environmental pollution – and science – since they have been shown to cause all kinds of harm to human and ecosystem health. In particular the emissions of persistent chemicals need (more) research and regulation. Unfortunately, the number of new chemical compounds still grows and a large fraction is not (yet) classified.
• A key material in Modernity is plastic, an umbrella term for a range of (semi-)synthetic polymers. Their use has grown exponentially since mid-20^th century and is expected to keep growing. Like metals, their manufacturing requires a lot of energy (partly as feedstock) and their persistence and high dissipation rate are reason for alarm and urgent action.