HIGHLIGHTS● Potassium-rich mining waste addition can improve the mineral nutrient of traditional sludge fertilizer.● Potassium-rich mining waste addition can improve the air permeability of compost, promote the reproduction of thermophilic bacteria and shorten the composting period.●...

This paper examines a vertically differentiated duopoly model where firms are distinguished into three dimensions: marginal cost, product quality and the level of product substitutability. I hereby replenish Zanchettin (2006) result in an enlarged parameter space context, and propose more...