That is a good question.
Recycling and composting can cover up to 60% of waste economically, but municipalities have not found a solution for the remaining 40% of waste.
We can deal with 30% of the waste and thereby reach a percentage of 90%. This waste may be textiles, leftover lumber, plastic food packaging, old pairs of shoes, pizza boxes with leftover tomato sauce or old non-recyclable plastic toys. There is a large variety of material that can be turned into ethanol.