Macquarie Asset Management is investing as much as €175 million ($190 million) in alternative fuel supplier SkyNRG as the aviation industry tries to become greener.

The Dutch fuel supplier has partnerships with airlines including Boeing Co. and Dutch airline KLM NV, and has anticipated long-term commitments of as much as €4 billion in sustainable aviation fuel purchases, according to a statement on Thursday. Macquarie’s investment came through its Green Investment Group Energy Transition Solutions Fund.

It’s the first venture into the SAF space for Macquarie’s green investment division, which has invested heavily in assets like grid-scale batteries, hydrogen, and metals in the past two years. Aviation has so far proved more difficult to decarbonize than other types of transport — SAF is currently the only feasible alternative to traditional jet fuel but can cost as much as five times more.

SkyNRG has been working on SAF capacity since 2010, according to its website.