Hello Aspirant, 

So IGNOU offers various courses and one amon them is:

1.Post Graduate Diploma in Environment and Sustainable Development (PGDESD). 

Minimum Duration: 1 year

Maximum Duration: 3 years

Course Fee : 5,500

Age: No bar.

Eligibility: Graduation from any recognised university.

2. Appreciation Course on Environment (ACE).

Minimum Duration: 3 months

Max Duration: 1 year

Course Fee: 1,400

Age: No bar

ELigibility: Graduation from any recognised university.

TO apply for these courses you can apply and register online through the official site of IGNOU. the second course which I mentioned is a certificate course basically but the first one if PG Diploma. 

Hope this answers you well. Good Luck.