Hilchos Issurei Mizbeiach 6:7

If olives and grapes are rendered ritually unclean, they are crushed in batches smaller than the size of an egg. The extruded liquids are then fit for libations. That’s because these liquids are considered separate from their foodstuffs and not part of them.

Hilchos Issurei Mizbeiach 6:8

The Sages made another rule when it comes to things that were consecrated: If seeds were rendered unclean, even if they were planted, what grows from them is not acceptable for libations. This is because planting won’t fix ritual impurity in cases of consecration. Similarly, even though firewood and frankincense are not foods, they can be rendered ritually unclean like food when it comes to offerings. In such cases, firewood and frankincense are rendered unfit for the altar because of impurity and may not be offered.