Fire crews from Siducup, Orpington and Erith have spent over 12 hours at Waste4Fuel in St Paul's Cray fighting a blaze.
Four fire crews were called to the plant in Cornwall Drive at 1.30am on Monday- the site has a history of constant blazes.
Fire fighters are working with an on site team, using a mechanical digger to turn over the rubbish and apply water to the fire.
Mick McGurran, station manager at Sidcup told News Shopper: "The site is in our area but technically in the London borough of Bromley.
"We shared this shout with Orpington and have been going back every three hours in our own time to make sure the site is safe.
"We were there for over 12 hours for this latest shout and it's such a regular thing.
"Erith fire station has a car at the moment so they have been going back as well the check.
"This one was quite a bad one."