Royal Caribbean Group will spend the summer testing a biofuel blend on two ships sailing in Europe.
Celebrity Cruises' Celebrity Apex and Royal Caribbean International's Symphony of the Seas will use a mix of marine fuel oil and biofuel for three months, according to the company.
The biofuel usage is part of a trial to collect data about the fuel's capabilities and supply chain.
The Apex will depart from Rotterdam and the Symphony of the Seas from Barcelona using a biofuel blend, which will reduce both ships' carbon emissions.
The fuel is produced by purifying renewable raw materials like oils and fats and combining them with fuel oil, Royal Caribbean Group said.
After the summer trial, Royal plans to scale up the use of alternative fuels on Europe cruises.