The cement industry uses a variety of secondary materials and fuels, thus fulfilling the role of “scavenger” in industrial ecology (IE). The use of wastes in cement production has been advocated to reduce cement production costs and to achieve the degradation and immobilization of hazardous compounds. In dealing with hazardous elements contained in the wastes, this development has side effects such as relatively significant stack emissions of heavy metals and leaching of hazardous compounds during the life cycle of cement‐derived products. Emissions and leaching potential may be substantially lowered by reducing levels of hazardous elements in wastes before they are included in cement production and by selectively capturing mercury from stack gases. An analogy to metabolic functions of selective uptake, sequestration, and selective excretion is presented.

Summary: The release of hazardous substances is a matter of concern for nanotechnology. This may include some nanoparticles, reactants, by‐products, and solvents. The use of low‐hazard solvents may reduce the hazards from nanoparticle production and nanomaterial processing. The hazards of inorganic nanoparticles may be reduced by modifying their chemical composition, surface characteristics, or structure. In nanomedicine, optimizing the balance between persistence and excretion and preventing the release of toxic degradation products may reduce hazard. In applications of fixed inorganic nanoparticles, the focus should be on preventing the release of such particles and of hazardous compounds during the product life cycle. When, after exhaustion of known hazard reduction options, significant hazard remains, other approaches merit consideration.

Substitutability of natural capital by human-made capital would seem to be limited. When human-made capital substitutes natural capital, there are currently commonly long-lasting negative impacts of such substitutions on constituents of natural capital. Long-lasting negative impacts on natural capital can be considered at variance with justice between the generations. In view thereof, there is a case to define (environmental) sustainability as keeping natural capital intact for transferral to future generations. A major problem for such conservation regards natural resources generated by geological processes (virtually non-renewable resources), especially regarding geochemically scarce elements. Substitution of virtually non-renewable resources by generating equal amounts of renewables has been proposed as a way to conserve natural capital. However, renewables substituting for fossil carbon compounds are currently associated with negative impacts on constituents of natural capital to be transferred to future generations. The same holds for the substitution of widely used geochemically scarce virtually non-renewable copper by abundant resources generated by geological processes. Though current negative impacts of substitutions on natural capital can be substantially reduced, their elimination seems beyond the scope of what can be achieved in the near future. The less strict “safe operating space for humanity”, which has been used in “absolute sustainability assessments” is, however, not a proper alternative to keeping natural capital intact for transferral to future generations.