- Renewable energy sources can be replenished within a human lifetime. - Biomass is organic material from plants or animals (like wood, crops, waste) that can be burned directly or converted into biofuels (like ethanol or biogas). Since plants can be regrown, biomass is considered renewable. - Coal, petroleum (crude oil), and kerosene (a petroleum product) are fossil fuels. They were formed over millions of years from ancient organic matter and are being consumed much faster than they are naturally replenished, making them non-renewable resources.