What are the roles of environmental inspectors with regard to prosecution of environmental offenders?

Subject to the Constitution, and section 29 of the Office of the Director of Public Prosecutions Act and the directions and control of the Director of Public Prosecutions, an environmental inspector may, in any case in which he considers it desirable so to do—
(a) institute and undertake criminal proceedings against any person before a court of competent jurisdiction (other than a court martial) in respect of any offence alleged to have been committed by that person under EMCA.
(b) discontinue at any stage with the approval of the Director of Public Prosecutions, before judgment is delivered any such proceedings instituted or undertaken by him/herself.

Ref: EMCA Section 118

Question

Explain the roles of an environmental inspector in prosecution of offendors and give reasons why each is necessary.