If you can do your job in four days for 32 hours a week instead of five days a week at 40 hours, then consider working four days a week instead of five. This way, you can save on the transportation energy and building energy that is used for a whole day per week, which would add up quite a bit if everyone adopted this. Other benefits would include a better work-life balance and happier and more productive employees. If you are an employee, make this case to your manager, and if you are managing a company, consider this new policy. There are studies that show that we are only productive part of the time when at work. But our culture has made it normal to work five days a week for eight hours per day. Are you really that productive every day for all hours? Most are not, depending on what exactly they do. But if you are a bus driver, for example, you drive a bus for your whole shift. This applies more to people working in an office.
With your extra day off, go for a hike and enjoy nature. Plant a tree. Do an activity that doesn’t spend a large amount of resources or energy so it has a positive impact on the environment.