The traders quoted in the article note that it's common for the shoes to get repeatedly shipped around, half of what they buy is not good enough for resale, and

The traders quoted in the article note that it's common for the shoes to get repeatedly shipped around, half of what they buy is not good enough for resale, and I'm sure a large portion of the shoes don't sell and get junked anyway. So the carbon footprint is much larger than local recycling in Singapore.