Earth's biosphere, what we commonly refer to as “Nature” or “Life” is constantly perfecting the art of reuse. Countless species that include plants, animals, and microbes ingest, process, and expel mass and energy, most of which can over time be used by others.
Mass exists either as atoms, joined atoms (called chemical compounds, found in one or some combination of gas, liquid, or solid), or unbound subatomic particles. Life is primarily concerned with chemical compounds, which may under specific circumstances be either inert or reactive. While inert compounds stay unchanged in the presence of others, reactive compounds join with others to form new ones, and in the process either absorb or release energy. Energy itself exists in any of several forms: chemical (exchanged between atoms), nuclear (exchanged between particles that form atoms), electromagnetic (carried by massless light particles), and gravitational (embodied in space and time, which connect everything to everything else). From a purely theoretical perspective, mass, energy, space, and time are likely to be manifestations of the same thing, ultimately indestructible and eternal in some larger sense that none of us will ever be able to comprehend.
Within the confines of our experience, however, Life “uses” mass and energy to maintain, propagate, and modify itself. Maintenance preserves the individual, propagation preserves the species, and self-modification includes not only reproductive experimentation (evolution) but also changing one's immediate physical and emotional condition. The grunt work of performing these functions is done by cells: biological micro-machines evolved over eons to build, tear apart, and move mass throughout an organism while managing the energy required doing so. When too many cells become disabled from wear and tear, reproductive errors or catastrophic external “modification,” the organism loses integrity and its parts are either disassembled for use by other organisms or more randomly broken down by non-biological processes for potential use over a much longer period of time (such as oil). Even artifacts, buildings and machines built by humans to control how they feel, will eventually be available for use, in some other form, by someone or something else.