Cellphone recycling has increased sevenfold over the past three years, bringing in about NT$440 million (US$14 million) worth of rare metals annually, the Environmental Protection Administration (EPA) said on Saturday.

The government launched an advertising campaign three years ago to promote the recycling of cellphones, and by last year the number of phones recycled soared from fewer than 1 million units annually to more than 6 million units, the EPA said.

The EPA in 2006 began accepting phones for recycling through garbage collection services, convenience stores and phone service providers.

Phone sales picked up over the past decade, reaching a peak of 10.34 million units in 2014, but only a fraction of no longer needed phones were being recycled prior to 2009, it said.

About 1 million phones were recycled annually between 2009 and 2011, but after 2012 the number began to increase each year, it said.

However, only after the government began more actively promoting recycling was there a significant uptick in the number turned in, with about 5 million units per year recycled in 2016 and 2017, and 6.26 million last year, it said.

IMF statistics show that while Americans replace their cellphones every 21.7 months and the British do so every 22.4 months, they tend to hold on to old phones as backups, the EPA said.

However, Taiwanese generally do not, it said.

German researchers in 2016 said that newer cellphones invariably contain more aluminum than any other metal, with copper the second-most abundant, the agency said.

Taiwan can extract aluminum and copper from recycled phones, as well as gold, palladium, silver and tin, which are found in smaller quantities, it said.

Japanese Ministry of the Environment researchers found that it is possible to extract about 46g of gold and 275g of silver from a total of 1,000 recycled phones, so Taiwanese have recycled enough phones over the past three years to extract 250kg of gold and 1,485kg of silver, it said.

On average, NT$81.1 worth of such rare metals can be extracted from a single recycled phone, which would add up to about NT$440 million over the past three years, Department of Waste Management Director-General Lai Ying-ying said.

However, despite the growing number of Taiwanese who recycle unwanted phones, 60.7 percent of respondents surveyed by the Chung-Hua Institution for Economic Research last year said they prefer to hold on to old phones for backups.

Many said they felt safer holding on to old phones due to the personal information and photographs they contained, the institution said.

Just 19.8 percent of respondents said they resold or gave away old phones when they upgraded to a new one, and only 16.7 percent said they would recycle or discard old phones, the survey found.