It said a digester tank was struck by the lightning at 7.20pm, causing the gases within the tank to ignite.
The company said no-one had been injured in the incident and it was working with emergency services to secure the site.
Our officers are currently at the scene of a fire at a waste plant near Yarnton, Oxfordshire.
It is believed that lightning struck gas containers at the site during bad weather this evening, causing a large fire. pic.twitter.com/Xy50berg1T
— TVP_WestOxon (@TVP_WestOxon) October 2, 2023
Videos began circulating on social media on Monday showing a large fireball and the sky in the area pulsing an orange colour.
Jack Frowde, 34, from Oxford, who works at Oxford University, said: “I was sitting in my kitchen when the whole room lit up with a brilliant white light, then followed by a huge crack which sounded like really heavy thunder.
“I looked out of the kitchen window and it was as if the sky was pulsating orange.
“I ran to the back to capture the orange glow as it faded after about 20 seconds.”
Stuart Hosking, in his 50s, from Oxford, an AI business director and former contestant on Big Brother, said: “We were pretty close. I thought it was the sun setting, until I saw the flickering and smoke.
“The lights flickered in the house then a flash, then a rumble like thunder, but a single bang.”
Oxfordshire Fire and Rescue Service and Thames Valley Police have been contacted for comment.