St. Louis Composting Inc. has acquired ECO Constructors, a local provider of storm water erosion control solutions. ECO, which has four employees and projected 2014 revenue of more than $1 million, has relocated its operations to St. Louis Composting's Valley Park headquarters but will continue to operate under the ECO Constructors name. ECO, which was founded in 2002 by Rob Carrothers, recently was awarded the erosion control contract for the $45 million Danforth Plant Science Center expansion. St.…