Renewable and Nonrenewable Resources

Sort resources by timescale. Nonrenewable resources, like coal, oil, and natural gas, formed from buried organic matter over millions of years under heat and pressure; humans pump and burn them far faster than the Earth makes more, so every barrel used is gone for good on any human timescale. Renewable resources, like sunlight, wind, and flowing water, are replenished continuously by ongoing natural processes, usually within days or seasons, so using them today doesn't reduce what's available tomorrow. Potentially renewable resources sit in between: forests, fish stocks, and groundwater regenerate, but only at a finite rate, so they behave as renewable only if harvest or use stays at or below that rate.

This is why a wind turbine counts as renewable even though its gearbox and blades wear out in twenty or so years. Renewability is a property of the source, moving air, not of the machine built to capture it. The turbine is manufactured equipment with a service life, the same as any car or appliance; that's a separate question from whether wind itself regenerates fast enough to keep using.

On a national grid, this timescale split shows up directly as a renewable share versus a nonrenewable share of total generation, since each power plant draws on one kind of source or the other. The same logic explains why groundwater pumped faster than it recharges is treated as nonrenewable even while rain keeps falling: the resource's status depends on whether replenishment keeps pace with withdrawal, not on whether replenishment happens at all. Push the use rate past the regeneration rate and a 'renewable' resource starts draining like a nonrenewable one, which sets up the sustainable-yield math used throughout the rest of the unit.