The Botswana Public Officers Pension Fund, page-7

The article did have some errors in it but that is down to the writer. As for the 50k litres bringing even 2mw online would displace much more then that so 10mw would be a huge saving. The article was written around government savings, however as goodenuff pointed out Tlou have already removed one diesel generator onsite and replaced with gas. This replacement was RNSd to save 50k litres of diesel per year so perhaps this is where the writer has got the figure from. Tlou also plan to install a second unit thus saving costs on 100k litres per year.
Regardless, the fact remains - the writer has actually understated what will be achieved.