Not-for-profit mobile recycling company, MobileMuster, is urging Australian consumers to remember to recycle old mobile phones if they upgrade to Apple's new iPhone 5S or 5C smartphones.

According to MobileMuster recycling manager Rose Read, Australian consumers show significant interest in any major new smartphone release, but continue to store their old devices. He claims 23 million are being held onto.

"We know that most Australians hold onto their old mobile 'just in case they need it', but given that the majority of these old mobiles are considered to be outdated, and potentially pre-smartphones, Aussies are just holding onto old technology they are unlikely to every use again," Read said.

In encouraging Australians to deposit old devices at one of MobileMuster's 4000 drop-off points across the nation, Read said 90 per cent of materials inside a mobile can be recovered and made into new products.

In 2012, recycling reduced the need to mine 1165 tonnes of metal ore, and had the environmental benefit of planting more than 5600 trees.

Read also warns against donating old phones to developing countries as many of these have poor recycling facilities, meaning devices will be dumped in landfills or processed in a harmful manner.

"E-waste in developing countries is becoming such a big issue that just last month the WHO launched an inquiry into the potential health effects on local communities. We want Australians to stop, think and recycle in Australia with MobileMuster as it is industry-funded and the safest, most ethical way possible."

Alternatively, as a result of MobileMuster's partnership with the Salvation Army, consumers can leave their old mobiles in a Salvo store; MobileMuster will provide a donation for every kilogram of old mobile phones, batteries or chargers collected.