Technically speaking, maintenance is a capital investment.
Use of some rare natural consumable (lubricating a machine with whale oil?) would still require a) labor b) capital and c) paying rent to whoever owned that slice of nature. So consumption, broadly, may take from nature, but the returns (if there are any) go only to people - as rent, interest, or wages. If there are no returns, then it is just consumption proper.
Technically speaking, maintenance is a capital investment.
Use of some rare natural consumable (lubricating a machine with whale oil?) would still require a) labor b) capital and c) paying rent to whoever owned that slice of nature. So consumption, broadly, may take from nature, but the returns (if there are any) go only to people - as rent, interest, or wages. If there are no returns, then it is just consumption proper.