Recycling old solar panels is challenging, but scientists from Singapore have found a way to upcycle the silicon inside and turn them into materials that can convert heat into electricity.
The team comprising researchers from the Agency for Science, Technology and Research (A*Star) and Nanyang Technological University (NTU) turned old solar panels into thermoelectric materials.
Such materials convert heat into electricity, and work in a similar way to how hydropower generation plants use water movement to drive turbines to generate electricity.
The joint study was published in the scientific journal Advanced Materials in March.
Dr Ady Suwardi, the deputy head of the soft materials research department at A*Star’s Institute of Materials Research and Engineering said that by moving heat from one side to another, thermoelectric materials generate electricity.
This can then be used for applications like cooling, added Dr Ady, who co-led the study.
The team found that impurities and defects in the silicon used to make solar cells actually enhance the performance of thermoelectric materials.
A solar panel is made up of many solar cells, also known as photovoltaic cells.
Separating the materials used to make solar panels and recycling each of them is a complex and costly process, said Associate Professor Nripan Mathews.
The team comprising researchers from A*Star and NTU turned old solar panels into thermoelectric materials. PHOTO: A*STAR
Prof Mathews, who is the cluster director of renewables and low-carbon generation (solar) at the Energy Research Institute @NTU (ERI@N), added that current recycling methods are able to recover only the glass and metallic support structures from solar panels.
Solar cells contain a complex mix of materials such as aluminium, copper, silver, lead, plastic and silicon.
Silicon, which is extremely pure, makes up 90 per cent of solar cells. However, this normally ends up in landfills.
This is because silicon has to be chemically treated and remelted to be recycled into pure silicon, said Prof Mathews.
He added that it is challenging, energy-intensive and expensive to recover the silicon to create new, functional solar cells.
“While silicon holds very little weight in the entire solar panel, it is the most valuable part of it, which explains why it is important for us to try and upcycle it,” said Prof Mathews.
Upcycling of solar panels (bottom) into valuable heat-harvesting electricity materials such as thermoelectric modules (top). PHOTO: A*STAR
The team is currently looking to pilot the technology for large-scale upcycling of waste silicon to create silicon-based thermoelectrics.
This can be used for high-temperature energy harvesting applications such as converting heat generated from industrial waste processes into electricity.
There are a number of research efforts ongoing in Singapore to see how solar panels can be recycled.
The NTU project, for example, is one of two currently supported by the National Environment Agency’s (NEA) Closing the Waste Loop funding initiative.
The $45 million initiative was launched in 2017 to boost research and development in areas such as the recovery of materials from waste streams.
The other project, a recycling programme led by Singapore Polytechnic (SP), aims to recycle solar panels on a commercial scale and recover more than 90 per cent by weight of the materials from the solar panels, said NEA.
In 2019, The Straits Times reported that Sembcorp and SP will also work together to develop a pilot recycling plant for solar panels.
However, the institutions declined to comment when asked for updates on the effort.
Another research effort by NTU spin-off EtaVolt, a solar tech firm, is working with the university on various other solar recycling projects, said its co-founder and chief executive Stanley Wang.
The project is not funded by NEA’s Closing the Waste Loop initiative.
Dr Wang said that the upcoming projects aim to recover materials from decommissioned solar panels so they can be recycled and reutilised as raw materials for battery, solar panel manufacturing and other industrial applications.
“This would allow us to recover the end-of-life value of these raw materials, which can potentially be given back to companies in the form of rebates to incentivise them to recycle their solar panels sustainably,” he added.
In his May Day Rally speech, Prime Minister Lee Hsien Loong spoke about the impact of soaring energy prices on Singapore and its people
The increase in electricity prices is due to a confluence of factors, such as the Russia-Ukraine war, Singapore’s lack of alternatives for electricity, and rising demand for electricity as the world recovers from the Covid-19 pandemic
With electricity costs expected to continue rising for at least a year, Singapore’s move towards greener energy sources has become more important than ever, some experts said
Solar panel sellers said they have seen an increase in enquiries as households look to generate their own electricity instead
Given the limitations on tapping solar energy especially among HDB dwellers, what are other ways for households to not only do their part for the environment but also go easy on their wallets?
SINGAPORE — Whenever the sun is blazing, Mr Arun Murthy gets excited, as a mobile application on his phone would show that his house is generating more electricity than it is using.
In mid-March, he installed 100 solar panels on the roof of his landed property in Bukit Timah.
Since then, the family’s monthly electricity bill has dropped from about S$1,200 to about S$370. Apart from meeting some of the house’s energy needs, the solar panels also generate excess electricity during the day that is sold back to Singapore’s power grid system operated by SP Group.
“Every month, we get a cheque from SP Group for selling our excess electricity, which we can use to offset our electricity bill from a private retailer… We have reduced our dependency on the grid by about 70 per cent,” said the 54-year-old chief executive officer of cybersecurity firm Invisiron.
As the family does not have a battery system to store excess electricity generated, the solar panels only fuel the house’s electricity needs when the sun is out in the day. On rainy days and at night, the home then relies on the national energy grid.
While installing the solar panels has meant lower electricity bills for the family, Mr Murthy said that the “primary reason” for doing so was to do his part for the environment.
Installing the S$54,000 solar panels on his roof also means less reliance on natural gas — regarded as the cleanest form of fossil fuel and is used to generate 95 per cent of Singapore’s electricity supply, but whose prices have skyrocketed recently amid a global energy crunch.
Since Mr Arun Murthy installed solar panels on the roof of his home, the family’s monthly electricity bill has dropped from about S$1,200 to about S$370.
Singapore’s electricity tariffs for April 1 to June 30 increased from the preceding quarter by around 9.8 per cent to S$0.27 per kWh, excluding Goods and Services Tax.
Earlier this month, in his May Day Rally speech, Prime Minister Lee Hsien Loong spoke about the soaring energy prices, which will set the country back by about S$8 billion a year, as he warned that Singapore must be prepared for more economic challenges ahead.
The increase in electricity prices is due to a confluence of factors, such as the Russia-Ukraine war, Singapore’s lack of alternatives for electricity and rising demand for electricity as the world recovers from the Covid-19 pandemic, experts told TODAY.
And with electricity costs expected to continue rising for at least a year, Singapore’s move towards greener energy sources has become more important than ever, some of the experts added.
Indeed, by reducing electricity consumption or turning to renewable energy, households now can not only do their part to save the Earth — but also go easy on their wallets
The increase in electricity costs during the past few months is a good opportunity for the Government to accelerate the adoption of green energy.
Dr Chua Yeow Hwee from the Nanyang Technological University’s economics division
Factors driving the surge in electricity prices
One reason for the rising electricity tariffs for the past two years is that 95 percent of electricity in Singapore is generated by natural gas, a byproduct of crude oil, said Associate Professor Chang Young Ho, head of the business and management minor at the Singapore University of Social Sciences (SUSS).
Because it is a byproduct, the price of natural gas is indexed to the price of crude oil. Hence, recent spikes in oil prices have caused energy prices to similarly jump.
He also noted that while the cost breakdown of generating electricity is not publicly available, industry experts have estimated that 60 to 70 percent of the total cost is related to fuel costs.
By reducing electricity consumption or turning to renewable energy, households now can not only do their part to save the Earth — but also go easy on their wallets.
“The recovery from Covid-19 has increased demand for oil, such as for use by industries, commercial and transport, so the price of oil increased,” said Assoc Prof Chang.
“The Ukraine-Russia war affected production and supply of oil (so) it also increased oil prices… As long as the war continues, the price is expected to increase,” he added.
Dr David Broadstock, a senior research fellow and the head of the Energy Economics Division at the National University of Singapore’s (NUS) Energy Studies Institute, said the decision by Europe and other countries to stop purchasing natural gas from Russia has forced them to search for new gas suppliers.
“At the same time, there are limits to how much gas supply chains can scale up without major new infrastructure development, which would also take some years to provide.
“This is a perfect recipe for natural price increases for natural gas, as those countries which are willing and able to pay higher prices may choose to do so to ensure a secure energy supply,” said Dr Broadstock.
He also noted that China’s demand for natural gas has been consistently growing as it searches for a cleaner fuel option as compared to coal. This is especially so during the winter season, which has created long-term pressure on markets.
While all these have resulted in the rise of oil and energy prices, Dr Broadstock said that key energy commodity prices have, to some extent, stabilised.
He added that the Energy Market Authority (EMA) had implemented mechanisms following local power market disruptions in 2021, which will help Singapore reach stable prices faster.
This would take about a year, other experts including Assoc Prof Chang estimated.
On April 4, Second Minister for Trade and Industry Tan See Leng spoke in Parliament about these mechanisms, which include a standby liquefied natural gas facility and requirements imposed on power generation companies to “bolster existing stockpiles and provide additional layers of fuel security to cope with the short-term shocks to global gas supply”.
They were introduced after “upstream production issues in Indonesia’s West Natuna gas field and gas pressure issues from South Sumatra in the fourth quarter of 2021 caused disruptions to our piped natural gas supplies,” said Dr Tan, who is also Manpower Minister.
“As a result, some companies had to purchase more liquefied natural gas at elevated global gas prices to make up for the drop in piped natural gas supplies.”
EMA has also modified market rules, allowing the agency to direct power generation companies to use gas from its standby facility, allowing the authority to manage the cost impact on consumers.
“These measures have ensured that we have sufficient fuel and electricity supply and stabilised the uniform Singapore energy price,” said Dr Tan.
However, experts said that the prices and impact on supply reinforce the need for Singapore to diversify its energy sources and improve its local production — which currently makes up just 5 per cent of the country’s energy supply.
Dr Chua Yeow Hwee from the Nanyang Technological University’s (NTU) economics division said: “The increase in electricity costs during the past few months is a good opportunity for the Government to accelerate the adoption of green energy.”
Dr Broadstock added: “The more power that can be produced locally, the more secure and predictable energy costs will become.
“However, there are limits to just how much solar energy can be deployed in Singapore. While more investment into solar will be very welcome, Singapore will inevitably need to explore additional energy resources.”
Dr Broadstock referred to recommendations made by a committee commissioned by EMA on March 22, which include importing renewable energy from verified resources — such as wind, large-scale solar and hydropower — which are abundant in other countries.
Viability of solar energy for households
Some households looking to cut their electricity bills without changing too much of their lifestyles can turn to generate their own electricity via solar power, which is the main renewable energy option here.
Professor Subodh Mhaisalkar, executive director of NTU’s Energy Research Institute, noted that solar panel technology has advanced over the years, reaching efficiencies of between 20 to 22 percent. This efficiency refers to the amount of electricity generated from solar energy that falls on the panel.
“Efficiencies used to be around 15 percent a decade ago, and we have seen a 30 percent improvement… it definitely makes sense from both sustainability and cost perspectives,” said Prof Mhaisalkar.
He noted that a barrier to getting these panels installed is the upfront cost, but solar leasing and favorable financing options have made installation a compelling value proposition.
Under solar leasing, a company pays for and installs a solar system from which homeowners can buy electricity.
Solar panel installation companies told TODAY that they have seen increased interest in their services this year, with more homes looking to do their part for the environment while saving money.
Mr Satish Prasath, founder and director of PMCE (Global), said his company used to receive about one inquiry a day for its residential services when it first started in December 2017, but that has increased to three queries daily this year.
The company has since outfitted 300 residential homes with solar panels. On average, households spend between S$18,000 and S$22,000, and the average home installs 30 panels. This would equate to about S$300 to S$400 saved a month, Mr Prasath estimated.
“We’ve installed panels in about 50 homes (so far) this year… people are concerned about the impact of the Ukraine-Russia war so they are looking for long-term solutions,” he said. His company had put up panels in about 95 homes for the whole of last year.
The panels have a warranty of 25 to 30 years, so homeowners stand to profit from installing them, he added.
The (solar) energy generated is often more than the household consumption, so when they sell to the grid, some of our customers even get negative utility bills each month because they’re owed money.
Mr Benedict Goh, chief investment officer of renewable energy firm UTICA
Mr Benedict Goh, a chief investment officer of UTICA, said another draw of solar panels today is the increased efficiency and return on investment.
“When we started selling goods related to solar panels in 2004, costs were much higher and the return on investment was around 10 to 15 years… people purchased to show off new technology, or because they wanted to go green,” he said.
“But now, it’s more efficient and costs (for the solar panels) have dropped by half of what they were in early 2010.”
Mr Goh said his company has done “hundreds” of installations, and inquiries for landed properties have increased by 30 percent in the past two to three years.
Solar panel installation companies told TODAY that they have seen increased interest in their services this year, with more homes looking to do their part for the environment while saving money.
“The energy generated is often more than the household consumption, so when they sell to the grid, some of our customers even get negative utility bills each month because they’re owed money,” he said, adding it can save customers between 40 and 80 percent of their monthly consumption bills.
Mr Christophe Inglin, co-founder and managing director of Energetix, added that residents stand to get a return on investment within four to six years, although that time frame is likely to be shorter as electricity prices increase.
Energetix focuses on installing solar panels for commercial projects, with residential installations making up less than 5 percent of its volume of sales. However, the company has also seen a spike in enquiries from homeowners.
While it would typically receive around two queries a month two years ago, the company now gets around six a week — mostly through referrals.
Mr Inglin declined to share the average number of panels installed but estimates a terrace house generates 10 to 15 kilowatt peak (kWp) a day, 15 to 25 kWp for semi-detached homes, and 20 to 60 kWp for bungalows.
However, while solar energy may provide future cost-savings, it has its own limitations.
For one, households still need to rely on electricity from natural gas as solar panels generate electricity only during the day. Dr Broadstock noted that many households’ demand for electricity increases at night — when people are back from work.
And while they can combine solar power with chargeable batteries, Dr Broadstock said battery technologies can be unsafe, which makes their use in residential and high-density urban environments like Singapore “challenging”.
The installation of solar panels is also subject to a building’s structural limitations, be it for a landed property or a HDB flat.
According to the Building Construction Authority’s (BCA) handbook for solar photovoltaic systems, there are constraints whereby standard development control guidelines apply — for example, if solar panels are to be installed on the rooftop of an attic, attic guidelines would apply.
Apart from possibly requiring an electrical installation license, BCA said in its handbook that existing buildings may require a professional structural engineer to carry out an inspection of the roof structure and calculate the structural loading.
“If the roof is unable to withstand the loading of the solar photovoltaic system, structural plans will need to be submitted to BCA for approval before a building permit can be issued for commencement of installation works,” the authority said.
It also noted that the solar panels are exposed to the threat of lightning strikes and hence, require proper lightning protection.
The installation of solar panels is also subject to a building’s structural limitations, be it for a landed property or a HDB flat.
LANDED PROPERTIES
For landed properties, the existing roof’s material and the angle it is it can make it expensive, unsafe and inefficient to install solar panels.
Mr Prasath said: “About 30 to 40 percent of homes that enquire are unable to install the panels.
“Some roofs have tiles that are glued directly to it, so it can become unsafe for us to clear up some tiles and place our brackets for solar panels on top. It may compromise the roof’s integrity.”
He added that roofs which are at a 45 degree angle or have protruding windows would not be suitable for solar panels.
CONDOMINIUMS
For condominiums, homeowners seeking to install solar panels will need to get approval from their management committees — commonly known as Management Corporation Strata Title, or MCSTs — and the authorities, and the green light is given on a case-by-case basis depending on various factors.
Both Mr Prasath and Mr Goh said that their companies have received inquiries from condominium homeowners interested in installing solar panels, but faced difficulties in getting the necessary approvals.
Condominium homeowners interviewed said that even if they manage to get the green light from their MCSTs to install solar panels,they are unsure if authorities require additional approvals.
Approvals aside, cost savings for condominium owners are also limited because they are ineligible to sell excess electricity to the national grid.
Their apartments also need to be on the top floors with roof access belonging to them, and where there is enough sunlight to generate electricity.
Mr Prasath added that another obstacle is that condominiums often use submeters, which allows condominium homeowners to track their individual consumption.
“Solar panel systems require testing and commissioning by SP Group before they can be connected to the grid, which (SP Group) only does for buildings connected to master meters such as (landed homes) and private-owned industrial buildings,” he said.
SP Group did not reply to TODAY’s queries.
HDB FLATS
For HDB flat homeowners, their options are further limited as solar panels not only take up space, but also require direct sunlight to generate a significant amount of electricity for home usage.
In 2020, a HDB resident made the news when he put up solar panels — reportedly weighing 10kg to 20kg — on top of a clothes-drying rack and an air-conditioner.
HDB told the media then that said such installations outside flats are not allowed as they may affect the structural integrity of the building, and can pose a risk to the public. It also reiterated that installations outside of a flat are prohibited unless approved by the town council.
Dr Chua from NTU’s division of economics noted that households on high floors can still tap solar energy in a limited fashion, such as hanging small solar panels at their windows and using them to power their mobile phones or laptops.
Smaller solar power generators are also readily available in the market. Such generators can cost anywhere from several hundred dollars to a few thousand dollars.
Mr Goh from UTICA, which sells such products, said they are commonly bought by hikers and campers looking to tap solar energy while outdoors. Some residents have also bought these generators to place in their balconies to power their mobility devices and other gadgets at home.
As part of a Government initiative to harness solar energy, HDB has to date installed solar panels on about 2,700 blocks and plans to reach 8,400 blocks in the next “two to three years”. In total, this will produce enough electricity to power 95,000 four-room flats.
On how these panels will benefit residents, the Ministry of National Development (MND) said in a written parliamentary reply on Jan 10 that the energy generated is “first used to power common services in HDB estates, such as lifts and lights”, and any excess solar energy will be channeled to the national grid.
“Town Councils managing these HDB blocks will enter into a service agreement with the solar vendor to pay for the solar energy consumed, at a preferential rate not higher than the retail electricity tariff rate,” MND added. “This may help the Town Councils in mitigating the rising cost of energy.”
How to save on electricity bills
For now, there remain significant limitations as to how individual households can turn to renewable energy as an alternative power source.
Nevertheless, consumers can still take matters into their own hands, in terms of reducing their electricity consumption.
For example, Ms Valerie Khoo, a 27-year-old wealth management consultant, said she does not use a fan or air-conditioner on cooler days but instead, leaves her windows open at night while she sleeps.
“With the (electricity) price increase, we’ve been a bit more conscious and my mom nags at us more about not using the air conditioner unless its really too hot,” she said.
Her family of four spends about S$120 a month on electricity for their five-room flat. Apart from ensuring they turn off the lights when not in use, they also chose a two-tick refrigerator — the highest energy rating available for her nearly 650 litre fridge when it was bought in 2018.
Apart from her parents and younger brother, Ms Khoo lives with the family’s two dogs. The food for her dogs takes up half the space in the freezer, she said.
The ticks system by the National Environment Agency (NEA) rates the energy efficiency of household appliances, with five ticks being the most efficient, and one tick being the least efficient. This is displayed on the energy label, which also shows consumers the annual energy cost of the appliance.
Ms Valerie Khoo does not use a fan or air-conditioner on cooler days but instead, leaves her windows open at night while she sleeps.
Ms Khoo said that while the family is keen to save electricity, the cost of big-ticket items has to justify the long-term savings, and be within their means, before they decide to buy a pricier appliance with a higher energy saving rating.
Like some other consumers whom TODAY spoke to, Ms Khoo said her electricity-saving habits have been shaped over the years, motivated by a desire to not just reduce her electricity bill but also to reduce her carbon footprint.
By using energy-efficient appliances and adopting good energy consumption habits, households will enjoy lower utility bills whilst contributing towards climate action.
National Environment Agency
Responding to TODAY’s queries, NEA noted that small habits can help reduce electricity costs — for example, simply using a fan instead of an air-conditioner can save households around S$384 a year based on electricity tariffs of S$0.26 per kWh.
“Based on an earlier household energy consumption survey conducted by NEA, cost-savings is the key motivating factor that households consider when deciding on the purchase of more energy-efficient appliances,” the agency said.
“By using energy-efficient appliances and adopting good energy consumption habits, households will enjoy lower utility bills whilst contributing towards climate action.”
To help inform consumers’ purchasing decisions, NEA said they can use its online Life Cycle Cost Calculator to check yearly energy costs and compare these with upfront costs for electrical appliances.
NEA also said its “enforcement checks” at retail outlets have shown that there are appliances with higher ticks that are not more expensive than those with lower ticks.
“With rising electricity prices, the higher cost of a more energy-efficient appliance can be quickly recouped and the owner saves even more over the appliance’s lifespan,” it said.
Under the government’s Climate Friendly Households Programme, one-, two- and three-room HDB households can register for S$225 worth of e-vouchers to offset the purchase price of resource-efficient appliances.
For example, households may get a S$150 e-voucher for the purchase of an energy-efficient refrigerator, or a S$25 e-voucher for LED lights.
Nevertheless, consumers can do more beyond opting for appliances that are more energy-efficient, experts said.
Mr Tan Tsiat Siong, lecturer at SUSS’ School of Business, said households should not just replace damaged appliances with more energy-efficient ones but do so with their older appliances as well.
Amid higher electricity prices, energy-efficient appliances can bring about long-term savings, Mr Tan reiterated.
He added that the simple actions of turning off switches when not in use, not leaving chargers on when devices are fully charged, and unplugging cords when not in use, can help reduce electricity consumption.
Likewise, Prof Mhaisalkar from NTU’s Energy Research Institute said homeowners can minimise energy losses through simple steps such as by ensuring their windows are sealed well when using an air conditioner or relying on natural ventilation instead.
Dr Broadstock from NUS’ Energy Studies Institute suggested setting the timer on appliances such as water heaters to help eliminate unnecessary energy consumption.
Households should also watch out for appliances with standby modes, which he dubs as “electricity vampires”.
“These constantly ‘suck’ a little energy from the socket even when on standby, hence the name ‘vampire’. Turning these off when they are not being used will help to reduce some power consumption,” he said.
He added that when it comes to saving electricity, a “reasonable guiding principle” is to look for options to reduce energy consumption without reducing quality of life and even gaining “co-benefits” in ideal situations.
“For example… take an extra 15 minutes to walk around your community after dinner, reducing the energy used at home while getting health co-benefits,” said Dr Broadstock.
Perishables such as fruit and meat are often at the mercy of harmful bacteria, especially when left for a long time outside the refrigerator.
To salvage such food items, scientists have created a biodegradable packaging material that can kill harmful bacteria and fungi that sprout on fresh produce.
The packaging also extends the lifespan of strawberries by up to a week. Berries kept in ordinary boxes stay fresh for only four days.
The material – which resembles plastic – was created by researchers from Nanyang Technological University (NTU) and Harvard T.H. Chan School of Public Health in the United States.
The material is made from corn protein, starch and other naturally derived substances, and is infused with a cocktail of natural antimicrobial compounds such as the oil from thyme, and citric acid.
Lab experiments found that when the material detected rising humidity levels and enzymes from harmful bacteria, its fibres released minuscule amounts of the antimicrobial compounds that got rid of the bacteria.
The compounds can kill bacteria or fungi growing on both the food and the material. Dangerous microbes that thrive in food include E.coli and listeria, which causes one of the most serious forms of food poisoning.
The packaging is suitable to hold food items such as raw meat, fish, fruit, vegetables and ready-to-eat meals, said Professor Mary Chan, the director of NTU’s Centre for Antimicrobial Bioengineering who co-led the project.
She added that the team’s aim is to replace conventional plastic packaging with the new material that will also double the shelf life of produce.
“Vegetables are a source of wastage because even if they are refrigerated, they will continue to respire, leading to spoilage after a week or two. With the anti-microbial packaging, there is a chance to extend their shelf life… and also make the vegetables and fruits look fresh with time,” she said.
Prof Chan noted that while there is anti-microbial packaging already available in the market, the team’s material is believed to be the only one that is both biodegradable and able to release the bacteria-killing compounds only when needed, such as when there is a rise in humidity.
This means that the food will not be overly exposed to anti-microbial compounds.
A comparison of strawberries that have been protected by the packaging (left) and those which have not. The packaging was found to extend the lifespan of strawberries by up to a week. ST PHOTO: ALPHONSUS CHERN
The new material was made through a process called electro-spinning – where the corn protein, the antimicrobial compounds with cellulose and an acid are drawn into tubes using electric force, and turned into fibres.
Harvard T.H. Chan School’s Adjunct Professor Philip Demokritou, an environmental health expert, noted that the new packaging would help to manage the triple threats of food safety, food waste and unsustainable packaging.
The research team’s project was published in October in the peer-reviewed journal ACS Applied Materials & Interfaces.
Packaging waste, including plastics, makes up about one-third of domestic waste in Singapore, and is a key waste stream.
As part of the nation’s efforts to reduce packaging waste, producers of packaged products and retailers, such as supermarkets with an annual turnover of more than $10 million, will be required to submit data and develop plans to reduce, reuse or recycle their packaging materials by March 31 next year.
The researchers hope to scale up their technology with an industrial partner, and to commercialise their food packaging within two years.
They are currently working to fine-tune and optimise the material’s manufacturing process and its functionality. They are also looking into other types of biopolymers – beyond corn protein – to create different forms of sustainable packaging.
NTU’s School of Chemical and Biomedical Engineering principal research fellow Suresh Kumar Raman Pillai and Centre for Antimicrobial Bioengineering director Mary Chan. ST PHOTO: ALPHONSUS CHERN
Prof Chan said their material will cost about 50 per cent more than ordinary plastic packaging.
ComCrop – a local company that pioneered urban rooftop farming – had assessed the viability of the scientists’ packaging material.
ComCrop chief executive Peter Barber said: “As ComCrop looks to ramp up products to boost Singapore’s food production capabilities, the volume of packaging we need will increase.
“The wrapping’s antimicrobial properties could potentially extend the shelf life of our vegetables.”
He added that the new packaging has to be made cost effective.
“The first three things Singapore supermarket consumers will check are: price, price and price,” said Mr Barber.
Local scientists have invented a cheap, rechargeable, and a fully biodegradable paper battery that can someday be used to power wearables of the future.
This battery is made by screen printing an ink layer of manganese on one side of a sheet of strengthened paper, and a layer of zinc and conductive carbon on the other.
Developed by a team from Nanyang Technological University (NTU), it can hold a substantial amount of charge. For instance, a 4cm by 4cm printed paper battery about 0.4mm thick can power a small electric fan for at least 45 minutes.
Bending or twisting the paper battery does not interrupt the power supply.PHOTO: NTU
Bending or twisting the battery does not interrupt the power supply, and larger battery sheets can be printed and cut up and used as individual, smaller batteries of different sizes and shapes for different uses.
Professor Fan Hongjin from the NTU School of Physical and Mathematical Sciences and the study’s co-lead author, said: “(The versatility of use, durability and efficacy of these batteries) make our paper batteries ideal for integration in the sorts of flexible electronics that are gradually being developed.”
Beyond the potential ergonomics of these batteries, the researchers said these batteries cost at least 10 times less to manufacture in the lab as compared with lithium-ion (Li-ion) batteries, the world’s standard for rechargeable batteries.
The paper batteries are made up of electrodes screen-printed on to both sides of a piece of cellulose paper reinforced with hydrogel.PHOTO: NTU
This is because the primary electrodes use manganese and zinc, which are much cheaper and more common metals than lithium.
The entire battery can be safely degraded underground within a month, with the metals contributing to the mineral culture in the soil.
Assistant Professor Lee Seok Woo from the NTU School of Electrical and Electronic Engineering and the study’s co-lead author said: “We believe the paper battery we have developed could potentially help with the electronic waste problem, given that our printed paper battery is non-toxic and does not require aluminum or plastic casings to encapsulate the battery components.”
These batteries serve as an improvement over current Li-ion batteries that are commonly used.
Li-ion batteries contain toxic substances that when crushed, may leak and contaminate water sources. Furthermore, exhausted Li-ion batteries need to be disposed of safely because they can cause fires in the event of a leak.
The team is now focused on optimising the battery, which is in its early stages of development and sees the battery is integrated with printed-on sensors at scale.
The scientists from NTU who developed the batteries are (from left) Dr Li Jia, Assistant Professor Lee Seok Woo, Professor Fan Hongjin and Dr Yang Peihua. PHOTO: NTU
Prof Fan said: “As we move towards the future of the Internet of Things, many more of our everyday objects will need to be embedded with sensors that need to be powered in order to communicate with other objects.
“We believe that our battery is contributing to that future.”
Three devices that may benefit from paper batteries
1. Electronic medical skin patches
Sufferers of chronic health conditions can wear a skin patch with sensors to measure vital signs or a drug delivery system that supplies medication when necessary.
For instance, an asthma patient’s breathing patterns can be monitored round the clock by a medical patch that keeps track of wheezing. The patch can inform its wearer that they are about to get an asthma attack and remind them to use their inhaler.
Other uses might be insulin patches that can administer insulin at regular intervals based on blood glucose levels measured. Paper batteries can keep these patches thin and unobtrusive to wear.
2. GPS-tracking stickers
Although tracking devices, such as Tile and Apple’s Airtags, are becoming more mainstream, they are relatively bulky additions and can trace only objects large enough to hold them, such as bags or wallets.
In the future, small GPS-tracking stickers integrated with thin paper batteries can be stuck onto small items – such as pens.
3. Thinner wearables
Most smartwatches today are relatively bulky as they require higher-capacity rechargeable lithium-ion batteries that can be the size of an SD memory card or bigger.
If powered by thin, flexible paper batteries, smartwatches can have more creative configurations, such as batteries fitted into watch straps.
And as the metaverse, a 3D virtual environment, becomes increasingly important, demand for thinner and lighter virtual reality headsets and augmented reality glasses for everyday use will rise.
A new light brown paper made of sunflower pollen can automatically fold itself into a food container or straw when exposed to moisture in the air, breaking the mould for single-use packaging.
The intelligent pollen paper – created by scientists from Nanyang Technological University (NTU) – is created by adding potassium hydroxide to sunflower pollen grains.
After 24 hours, the pollen transforms into a gel that is moulded onto a petri dish, for example, and left to dry overnight. The dried pollen paper is then peeled from the mould.
The pollen paper can vary in thickness from 20 to 200 micrometres, similar to that of a strand of hair – but it is far from fragile.
In fact, pollen is known as the diamond of the plant kingdom as it is one of nature’s most durable materials, said the research team’s co-lead, Professor Cho Nam-Joon from NTU’s School of Materials Science and Engineering.
Prof Cho’s research includes turning pollen into plastic and metal alternatives.
The pollen paper can be made thicker or layered if it were to be folded into a container or straw. It can be used as a greener alternative to materials such as plastics and styrofoam for disposable products and packaging.
Pollen is also abundant and can be degraded in nature gradually.
“If we make the paper thicker, its properties will be more plastic-like. The original raw material itself is very strong. So, by modifying that, it can be stronger,” said Prof Cho.
The pollen paper comes to life when it is exposed to humidity, and after some toner – a powder that works like printer ink – prints lines and patterns on the brown paper. Toner acts as the ink in office and home laser printers.
To apply toner on the pollen paper, it goes through an ordinary printer, just like writing paper.
The pollen paper is then exposed to different humidity levels in a controlled environment.
While the pollen paper is sensitive to moisture in the air and curls up, the inked parts do not respond to water. These opposing behaviours cause the flat paper to morph into three-dimensional shapes as humidity drops.
How the paper folds or twists depends on the printed pattern.
For example, a piece of pollen paper cut into an outline of a box would automatically fold into a box when the folded hinges are printed with barcode-like vertical lines.
A strip of paper printed with diagonal lines would curl into a straw.
Pollen paper with an ink pattern printed on it. PHOTO: NANYANG TECHNOLOGICAL UNIVERSITY
Prof Cho said: “Products can be produced without manual folding, reducing the skill and time necessary for fabrication. The whole process is also eco-friendly and scalable.”
Coating the morphed paper with petroleum jelly or chitosan – a natural sugar found in the shells of crabs and shellfish – will prevent the product from unravelling due to humidity changes, and lock it in shape.
NTU president Subra Suresh, who co-led the research, said: “We combined easy-to-process pollen grains and cost-effective digital printing to develop a moisture-sensitive (material) that can morph on demand into… complex shapes depending on the patterns we print.”
(From left) Professor Cho Nam-Joon, NTU President Subra Suresh, and NTU research fellow Zhao Ze examining the pollen paper. PHOTO: NANYANG TECHNOLOGICAL UNIVERSITY
Prof Cho said this is the first time pollen is used to develop self-folding materials. The research team’s method was published in the scientific journal Proceedings Of The National Academy of Sciences of the United States of America last month.
Packaging waste, including plastics, makes up about one-third of domestic waste in Singapore. Last year, about 200,000 tonnes of disposables – including carrier bags and takeaway containers – were thrown away here.
The NTU team is now working on optimising its pollen paper and method so that companies can eventually use the technology to manufacture greener products, including humidity sensors.
Having worked with wastewater and sewage sludge for seven years, I have developed not only a selective loss of smell (anosmia), but also true respect for wastewater.
Just look at the coronavirus pandemic and we can appreciate how wastewater has become a surveillance tool to detect possible Covid-19 infections.
Scientists at Nanyang Technological University (NTU) and the National University of Singapore (NUS) routinely test wastewater at the student hostels on campus as a precautionary measure to screen for circulation of the virus in the population.
And there is a lot more to wastewater than that.
Wastewater recycling is crucial because there is water scarcity in different parts of the world, even in an economically and technologically advanced country such as Singapore.
This is, after all, one of the most water-stressed countries in the world. For Singapore, as a tiny city state with a limited water catchment area and no other natural water resources, every drop counts – even wastewater.
Wastewater recycling has undeniably become the norm instead of the exception in many countries, including Singapore.
The Republic consumes about 1.9 million cubic m of water a day, with the non-domestic sector accounting for more than half of this demand.
Research to upcycle and return wastewater constituents to the circular economy is key to ensuring the sustainable use of water, more so on the industrial front.
For wastewater to be reused, it has to undergo strict treatment to meet all the regulations, and this is a complex and costly process.
Wastewater treatment processes also produce sludge that needs to be treated before it can be safely discharged to a landfill or incinerated (typically, the ash generated from the incineration will end up in a landfill too).
A common sludge treatment method is anaerobic digestion (AD) – a biological process that not only treats the sludge by removing the undesirable organics in it, but also reduces the volume of sludge that needs to be discarded or incinerated.
This is aligned with the Singapore Green Plan 2030, which aims to reduce waste sent to the landfill by 30 per cent, with a target of 20 per cent reduction by 2026.
Microbiome to the rescue
Research to improve the efficiencies of wastewater treatment has been rigorously conducted in Singapore and beyond.
Since wastewater treatment typically involves biologically driven processes collectively called “digestion”, a good understanding of the microbiome – microorganisms that exist in a particular environment – that drives this process is needed.
For example, a study at SCELSE, a biofilm and microbiome research centre hosted by NTU and NUS,
assesses the ability of the AD microbiome to function at a shortened digestion time of five days instead of 30 – six times faster – to speed up the digestion process for greater efficiency.
This microbiome is sensitive to changes in its environment. So, the scientists are also looking to improve its ability to withstand disturbances in order to minimise downtime and failure of the digesters (huge vessels where biological reactions take place), which can be costly to rectify.
Upcycling
We can also upcycle wastewater.
This fashionable term refers to the creation of something new out of waste or old materials.
I used to associate wastewater with “destroying” and “removing” instead of “creating” or “generating”. But research has opened my eyes to the potential of wastewater to generate valuable products.
For example, AD converts sludge and other biowaste to clean gaseous methane, which can be used by other microorganisms to produce safe protein-rich microbial biomass as a source of animal feed or food.
Although there is still some way to go, such renewable energy sources can be used instead of conventional fossil fuel, and thus support the Singapore Green Plan.
Sludge can also be used to produce other value-added products, such as volatile fatty acids (VFAs).
VFAs can be turned into biopolymers like polyhydroxyalcanoates – plastics that are more biodegradable than their petrochemically derived counterparts.
Upcycling is taken to a whole new plane too when we produce single-cell protein from wastewater that food and beverage industries would have discarded.
These microbial proteins can then be used to produce fish food.
So, with all these potential gains, we stand to benefit if we do not dismiss wastewater.
But all this boils down to our ability to conserve water, since wastewater can be generated only if there is clean water to begin with.
So, start appreciating every drop and plop that comes your way.
