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

In 2015 Galp participated in a 75%-25% joint venture with Japan's Mitsui to invest 400 million euros ($415 million) in the Hydrogenated Vegetable Oil (HVO) plant, which will have a production capacity of 270,000 metric tons annually.

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

Galp said in a statement it received on Wednesday the three reactors to process biofuels, which will enable the HVO system to "produce SAF and biodiesel in 2026 ... placing Galp at the forefront of developing low-carbon options vital for the energy transition".

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