LISBON, Dec 19 (Reuters) - Portugal's Galp Energia expects to begin producing biodiesel and biojet fuel from waste in an industrial-scale unit it is constructing at its Sines refinery in 2026, the company, which is mostly an oil producer and refiner, said on Thursday.

In 2015 Galp participated in a 75%-25% joint endeavor with Japan's Mitsui to invest 400 million euros ($415 million) in the Hydrogenated Grease (HVO) plant, which will have a capability of 270,000 metric lots annually.

It will transform waste materials, such as used cooking oils, into renewable biodiesel and biojet fuel, likewise called sustainable air travel fuel (SAF), using green hydrogen produced by an electrolyser powered by wind or solar power.

Galp said in a declaration it got on Wednesday the 3 reactors to process biofuels, which will permit the HVO unit to "produce SAF and biodiesel in 2026 ... putting Galp at the leading edge of developing low-carbon options necessary for the energy transition".

Galp is likewise investing 250 million euros in a 100 megawatt (MW) electrolyser unit to produce green hydrogen to power the refinery in Sines. ($1 = 0.9637 euros) (Reporting by Sergio Goncalves