Living peacefully with rightious happiness itself is a great contribution / Service to humanity .
A person not indulged in giving trouble to other creatures for his food - great service
Not judging others rather be compassionate - great service
Engaging into Spiritual book reading or clean & green activity in free time rather idle living or watching violence hours together - great service
..... this list goes on.
To conclude be happy in your own circumstances without creating pollution at mental and physical level .that itself a great service to humanity .