Albert Barnes Commentary Leviticus 10:16

"And Moses diligently sought the goat of the sin-offering, and, behold, it was burnt: and he was angry with Eleazar and with Ithamar, the sons of Aaron that were left, saying," — Leviticus 10:16 (ASV)

The Law on the point in question was clear. See Leviticus 2:3, note; Leviticus 4:5, note; Leviticus 4:15 note. But on this occasion, though the sin-offering which had been offered by Aaron was for the people (Leviticus 9:15), its blood was not carried into the tabernacle. The priests might therefore have too readily supposed that their eating the flesh, or burning it, was a matter of indifference. Hence, Moses explains that the appropriation of the flesh by the priests is an essential part of the act of atonement (Leviticus 10:17).

It was burnt - It was consumed by fire in an ordinary way, not in the fire of the altar. See Leviticus 1:9.