Grinding down waist before making compost?

Your teacher is an idiot.

Get some good books on composting.

Composting is a wonderful work. I ran a house with four members, two adults and two young ones. Composting was the most amazing management skill. However composting is only one part of management. You have to also stop buying plastics and milks and meats. If you have these then you have to dispose of them in another way. Recycling is the complement to composting. There is a big difference between creating compost which is a powerful product and producing land fill.

Dump sites sort thier garbage into compostables and recyclables.

Composting is amazing. You can build composting toilets to reduce the amount of water.

Do not let anyone smuggly misdirect you waiting for you to fail and become frustrated the way your shop teacher is behaving. Research. Experiment and be willing to be taught by those who have been doing it for a long long time.

Good luck.