There are extant examples of simple chemical cycles that spontaneously produce more of themselves, repeating the cycle - yet are not life. The Citric Acid Cycle or Krebs Cycle is one. It produces products that are used in the starting phase of the next cycle. It also produces waste products, not used in the next cycle. "Overall, one turn of the citric acid cycle releases two carbon dioxide molecules and produces three NADH, one FADH2, and one ATP. The citric acid cycle goes around twice for each molecule of glucose that enters cellular respiration..." If this process were contained in a primitively-walled environment and surrounded with resources, it could keep churning out copies of itself endlessly.