Photosynthesis and respiration are the basis of life on earth. Civilizing progress went hand in hand with increasing energy consumption per capita and day. Heat engines and transistors convert fossil, nuclear and renewable energies into work performance and information processing, thus providing the energy services that create the wealth of industrial societies and free more and more people from heavy physical and monotonous mental work. These services can be illustrated by the number of energy slaves that serve each person of a society at a given time. An energy slave needs about three kilowatthours of primary energy per day. Polluting heat and particle emissions are its excrement. Particle flows can be converted into heat flows to reduce the production of entropy in the form those emissions, that are particularly harmful to the environment. The calculated pollutant heat equivalents in the retention and disposal of pollutants from coal and nuclear power plants show the associated approach in each case to the heat barrier, the outermost limit to industrial economic growth within the biosphere. Minimizing energy conversion and entropy production while leaving energy services undiminished is a powerful tool for emissions reduction and resource conservation. Examples of energy, emission and cost optimization by heat recovery, also in combination with solar energy, show what is possible, which competitive effects can occur between the considered technologies, and that the exploitation of the energy saving potentials of an energy supply system is favored by increasing energy prices.