Singapore households have a dismal recycling rate of just 19 per cent and up to half of all items put into the blue recycling bins at the foot of every housing block go to waste because people dump trash like used diapers or soft toys into them, the National Environment Agency (NEA) told The Straits Times.

Such poor recycling practices not only complicate the process at materials recovery facilities - where workers manually separate plastic from paper, and paper from glass - but also increase the cost of maintaining the facilities, say public waste collectors.

Food waste, in particular, is corrosive and attracts pests like rats, said a spokesman for Veolia, one of Singapore's four collectors. On average, 35 per cent of the 12,000 tonnes of waste the company collects each year must be discarded.

At SembWaste, the average contamination rate is higher, at around 40 per cent of the 16,000 tonnes of waste collected each year, peaking at 50 per cent on bad days.

Such items end up wasting even more resources than regular trash.

FUN FACTS ON RECYCLING

• Recycling 1,000kg of paper saves 17 trees. • Recycling an aluminium can saves 95 per cent of the energy used to make a new one. For a glass bottle, 30 per cent of the energy is saved. • Recycling a single plastic bottle can conserve enough energy to light a 60-watt bulb for up to 6 hours.

Said Mr Lim Chin Khuang, senior vice-president of asset management at Sembcorp Environment: "First, you are bringing in waste into a recycling plant, which should not be the case, and this waste will have to be reloaded onto a truck and sent to the incineration plant.

"This is counterproductive."

Tips on recycling

Q What can be deposited in those blue recycling bins found in housing estates? A Paper, plastic, metal cans, glass and clothes. This includes plastic and glass bottles, jam jars, plastic bread wrappers, biscuit boxes, liquid soap bottles and refill packs, milk tins, egg trays and cereal boxes. Q What cannot be recycled? A Bulky items like furniture, items with composite materials like mechanical pencils and shoes, and anything contaminated with food waste - even sweet wrappers. Tissue paper, styrofoam, disposable plastic cups and containers, window glass, cassette tapes as well as ceramic and porcelain items cannot be recycled economically and are not accepted. Light bulbs, fluorescent lamps and electronic waste like computers and home appliances cannot be deposited in the blue bins and must be taken to special designated recycling stations. Q How can I recycle? A Have a separate bag to collect recyclable items. For containers, empty them of all contents and rinse them. When your bag is full, deposit the items in the recycling bin. • For more information and to find the closest recycling bin or station, download the myENV mobile app, available on the Apple and Google Play stores.

As it stands, Singapore's only landfill on Pulau Semakau is expected to run out of space by 2035, and is under tremendous strain, said the NEA. Last year, the Republic disposed of 8,284 tonnes of waste a day - enough to fill 16 Olympic-sized swimming pools.

Under the Paris Agreement, there is a need for the Republic to curb its emissions, and recycling is an important part of that process.

The authorities have made recycling easier. While existing blocks have the blue bins, all HDB developments launched from 2014 have recycling chutes in each block, with throw points on every floor.

But while the industrial sector recycles 77 per cent of waste produced, household recycling rates have fallen from 22 per cent in 2010 to 19 per cent last year.

They fall far short of those in places like Taiwan, where household recycling rates are more than double.

There, recycling is law, and this has produced results. A government-run fund financed by manufacturers and sellers subsidises collection and recycling industries. Residents are also required to separate their trash into general refuse, recyclables and kitchen waste. This has pushed household recycling rates from 5 per cent in 1997 to over 50 per cent today.

Ms Jeanne Stampe, Asian finance and commodities specialist at the World Wide Fund for Nature, said: "Attitudes needs to change and we must learn that recycling is not an inconvenient option but an absolute necessity."

She asked if households fully understand what to do with their recyclables, noting that perhaps clearer instructions from the Government and manufacturers are necessary.

The lack of awareness is clear at SembWaste's Materials Recovery Facility in Tuas, where the stench of rotten food wafts through the air.

Houseflies attack a 3m-tall mountain, sampling remnants of what might once have been someone's lunch, now smeared on plastic, metal and paper collected for recycling.

Here, workers in orange overalls sort through 16,000 tonnes of recyclables collected each year.

Although items are supposed to be relatively clean and dry, such as magazines and plastic bags, the men have to sort through soiled diapers, dirty tissue paper and food waste, which makes their job more difficult and far more unpleasant.

Some items are not suitable at all - such as lightbulbs or mattresses, which have too many components to be recycled easily.

At a recent visit, 20 were hard at work, sorting through the load dumped by a truck minutes earlier that included bags of plastic bottles, cardboard and tin cans.

The bags were placed in a machine called the bag splitter, which broke them apart and dropped the items onto conveyor belts.

Next to the conveyor belts, in sweltering heat, men wearing helmets, masks and gloves, picked out the items, placing them into different containers rhythmically.

Paper, right bucket. Glass, left bucket. Plastic, container across.

After the first round of sorting to pick out larger items, the remaining recyclables go through a magnetic separator that removes ferrous materials, and then a machine called the ballistic separator.

This segregates flat from rounded objects, placing them on two different conveyor belts where they go through another round of sorting by material type.

The sorted recyclable materials are tied up in bales weighing between 200kg and 300kg and transported to local recycling plants or overseas, to countries such as Indonesia and Malaysia.

At these plants, recovered paper is turned into recycled paper while plastics are turned into pellets and used to create new plastic products such as cups and coasters, or placed in shipment crates to protect the items within.

The men's job at the local facility is a critical part of the recycling process. But it is arduous.

According to the NEA, the contamination across all four public waste collectors - SembWaste, Veolia, Colex and 800 Super - is between 30 per cent and 50 per cent.

Mr Seah Tiong Han, 71, who has been on the secondary sorting line at the SembWaste facility since 2008, said the smell used to put him off but, after so many years, it no longer bothers him.He urged the public to think twice before they dump trash into the blue recycling bins as that renders all efforts useless.

For example, a perfectly good piece of cardboard - dirtied with food - will now join the trash at the incineration plant.

A Veolia spokesman said contaminants like the toxic components of electronic waste, used diapers and tissues also pose a health hazard to the workers.

While the Government has not taken the hard line, the NEA stressed that people need to be more mindful about what they throw into the recycling bins.

"In a worst-case scenario, the thoughtless behaviour of one person can render an entire bin of recyclables non-recyclable, wasting the efforts of many," said NEA.

Mr Lim said getting the contamination rate down to 20 per cent would be a "major milestone".

"We have to press on because the aim is to minimise waste" he said. "Can you imagine 16,000 tonnes of recyclables going to the landfill every year?"

WATCH THE VIDEO

Find out what happens to recyclable waste after it is collected. http://str.sg/4ojD