I'd like you to put yourself in the shoes of a manager of a cement plant. From this viewpoint I'd like you to consider the concept of 'negative externalities' taking CO2 emissions as an example. explains your position on this issue.

I'll be endorsing particularly good answers. Good luck!

Task: From the viewpoint of a cement plant manager, explain the concept of 'negative externalities' taking CO2 emissions as an example and why it is difficult to tackle in absence of a system such as the European cap-and-trade system of emission rights.

Please note: I'm looking for succinct answers to this question.