Congratulations on being chosen to undertake a Capstone Project.
Since your mentor has recommended this solution, perhaps you could also ask for advice about sources of funding to support your project work: maybe there is some sort of bursary or hardship fund you could apply for within your place of education?
Guessing you are somewhere in North America, the cost would be about 35 USD, 46 CaD. Perhaps when split between the members of the team that is worth finding for the sake of the boost you might get to your careers? Could you earn it by car washing, baking cookies, etc?
Or try to interest other people who might back your project: commercial waste disposal operators; local authorities; local 'green' campaign groups.
Good luck with your project.