1. A method for transporting bulk products for a planning period, comprising: (a) receiving a data set comprising: (1) identification of multiple origin and destination locations; (2) a set of voyages between the locations; (3) information relating to the market value of the voyages; (4) identification of multiple vehicles for carrying bulk products between the locations; (5) information relating to the cost of transporting the bulk products on the vehicles; (b) formulating, by a computer, a mathematical model for vehicle assignments comprising an objective function for total net profit margin and multiple constraints; wherein the objective function for total net profit margin comprises the sum of the individual net profit margins for each combination of feasible voyage-vehicle pairs, wherein the net profit margin for each feasible voyage-vehicle pair comprises the market value and the incurred costs for the feasible voyage-vehicle pair during the planning period; wherein the multiple constraints include constraints relating to the origin and destination locations, constraints relating to the voyages, and constraints relating to the vehicles during the planning period; (c) populating the mathematical model with data from the data set or parameters calculated from the data set; (d) obtaining, by a computer, a solution to the mathematical model for vehicle assignments, wherein obtaining a solution comprises (i) identifying feasible voyage-vehicle pairs available for transporting bulk product during the planning period based on temporal and physical vessel/voyage constraints, wherein identifying feasible voyage-vehicle pairs includes performing a forward projection in time to determine when a given vessel can perform a given voyage, (ii) optimizing maximum cargo revenue for each identified feasible voyage-vehicle pair, wherein optimizing maximum cargo revenue includes determining the maximum total amount of cargo each feasible voyage-vehicle pair can transport, and (iii) determining an assignment of vehicles that contains the optimal combination of identified feasible voyage-vehicle pairs during the planning period that yields the highest total net profit margin; (e) assigning vehicles to perform the set of voyages based on the solution to the mathematical model for vehicle assignments; and (f) physically transporting the bulk products based on the vehicle assignments.