The profit model of the landfill site for stale garbage mainly relies on government subsidies. After a certain period of operation, the generated biogas can be collected and utilized to generate certain income. However, overall, the key income still depends on government subsidies.

For general enterprises investing in renewable resources, construction waste is not real waste, but a gold mine misplaced. After sorting, crushing, and screening construction waste, it is processed into recycled aggregates of different sizes and specifications using appropriate construction waste crushers. The cost of purchasing construction waste is very low, and some even do not need to spend money. The purchase cost per ton of construction waste is 10 yuan, and the product of each ton of construction waste is calculated at 70%. Each ton of construction waste can produce 0.7 tons of sand and aggregate. Based on the current market price of sand and aggregate, the price per ton is approximately between 60-100 yuan. So, if we calculate at a low price of 60 yuan per ton, in addition to the cost of 10 yuan, the gross profit per ton is also above 30 yuan. Assuming a production rate of 100 tons per hour and an 8-hour workday, after deducting worker wages and utilities, if calculated at 5000 yuan per day, one would conservatively earn 20000 yuan per day, which can be recovered in two to three months.