1. A computer-implemented method to plan and schedule bulk material distribution for the transportation of bulk materials from supply terminals to demand terminals, comprising: providing a computational system; executing, using the computational system, a plurality of computer-executable instructions, the executed instructions providing a method comprising: a) obtaining input data specifying a plurality of requirements to be satisfied for a marine transportation schedule of a plurality of ships to meet predetermined objectives represented by an objective function, b) determining a current feasible schedule from said input data, the current feasible schedule comprising a ship schedule for each of the plurality of ships, c) evaluating said current feasible schedule to determine a current objective function value based on the predetermined objectives, d) iteratively generating alternative feasible schedules, the iterative generation method comprising: selecting a first ship and a second ship from the plurality of ships, the first ship having a first ship schedule in the current feasible schedule and the second ship having a second ship schedule in the current feasible schedule; modifying the first ship schedule and the second ship schedule to generate an alternative feasible schedule; evaluating the alternative feasible schedule to determine an alternative objective function value based on the predetermined objectives; and selecting the current feasible schedule or the alternative feasible schedule to become the current feasible schedule based on the current objective function value and the alternative objective function value, and e) generating, after said iterative generating of the alternative feasible schedules, an operational plan for ship scheduling based on the current feasible schedule, wherein the objective function comprises at least a first constraint for generation of bulk material at a supply terminal, a second constraint for a maximum amount of bulk material at a supply terminal, a third constraint for reduction of bulk material at a demand terminal, and a fourth constraint for a minimum amount of bulk material at a demand terminal.