Six fire engines and around 40 firefighters tackled a fire at an industrial unit on Newyears Green Lane in Harefield.
Around 15 tonnes of mixed waste was alight. There were no reports of any injuries.
The fire is believed to have been accidental and involved a lithium-ion battery.
A London Fire Brigade spokesperson said: "Lithium-ion batteries and electricals with hidden lithium-ion batteries should not be placed in the same bins as your regular rubbish or recycling. Instead, check with the retailer or your local authority's website for the safest way to dispose of lithium-ion batteries in your area and reduce the risk of fires occurring.
"Lithium-ion battery fires are a major risk. We’ve seen a growing number of fires at waste disposal sites that are believed to have been caused by a lithium battery.
"Although lithium-ion battery products that have been built to a poor standard are a higher fire risk, any battery is at risk of exploding and catching fire if it has been crushed or becomes damaged. Lithium-ion battery fires can be ferocious and can spread in seconds.
"Fires that we attend at sites like recycling centres and scrap yards can be very time consuming for our firefighters and often require a high level of resources to put the fire out. We’ve also seen the detrimental environmental and societal impact these fires can have on local communities."
The Brigade was called at 0304 and the fire was under control by 0610. Fire crews from Ruislip, Hillingdon, Harrow, Northolt and surrounding fire stations attended the scene.