Channel assignment in CRAHN (Cognitive Radio Ad Hoc Network) is defined as a critical issue during any kind of communication to be executable. It is a problem of determining an optimal mapping between the accessible licensed channels and the cognitive radio channels such that the performance of CRAHN is optimized. The objectives of the channel assignment in this concerned network are to assign the available channels to cognitive radio interfaces of cognitive nodes to achieve proficient spectrum utilization, to diminish the interference among cognitive or secondary nodes, and to curtail the interference to PUs (primary users). Thus, motivates the necessity for optimization during spectrum sensing in a cognitive radio system. This paper has narrowly focused on optimized spectrum allocation problems by developing new algorithms under a platform of Non-dominated Sorting-based Genetic algorithm (NSGA-II), Heuristic Harmony Search (HS), Cuckoo Search (CS), and Multi Objective Bat Algorithm (MOBA) by weighted sum method. The assessment of optimal solutions in terms of true pareto-fronts has been discussed towards ensuring eco-friendly environment in context with channel allocation.