Biogeochemical transformations
Biogeochemical transformations means those changes in chemical compounds and substances which naturally occur in ecosystems. Examples are the carbon, nitrogen, and phosphorus cycles in nature, in which these elements are incorporated from inorganic substances into organic matter and recycled on a continuing basis.
Source
23 CFR § 777.2
Scoping language
In addition to those contained in 23 U.S.C. 101, the following definitions shall apply as used in this part: