Personal fitness trainer Balan Gopal gets a kick out of turning trash into something useful.
Among other things, the 43-year-old father of two has made a lamp out of an empty 2-litre milk bottle and turned a netting he collected from a construction site into a bag that holds his gym shoes while allowing them to be aired.
So when he saw last year that coffee shops were throwing away used coffee grounds, he lugged bags of them back to his three-room Housing Board flat in Balestier, to the horror of his wife, Madam Chan Lan Foong, 43.
She is a vice-president in a bank and the couple have two sons, aged 11 and eight.
He researched online and read that coffee grounds can be used as a base for growing oyster mushrooms, one of his favourite foods.
One thing led to another and, within a few months, he found himself growing other vegetables and herbs.
Today, there are herbs such as basil and mint growing in 15 recycled soft drink bottles that he has secured to the railing outside his flat.
There are also herbs sprouting from about 150 small transparent plastic cups at the railing outside his in-laws' place two doors away. There, he also grows oyster mushrooms in 12 soft drink bottles as well as vegetables such as bak choy and kangkong in a styrofoam box.
He harvests the plants about two to three times a month and his mother- in-law, who cooks for his family, uses them in her dishes. He gives any excess to his appreciative neighbours and also uses the various herbs to brew tea for his family.
"It's so nice to eat what you grow. They taste fresher and sweeter than the ones you buy," he says.
He now has more than 20 types of edibles and hopes to grow more varieties of food with different harvesting times so that they can eventually supply most of his family's meals.
It is not an expensive hobby, says Mr Gopal, who reckons that he has spent about $300 so far, mainly on plants and seeds.
He relies heavily on recycled materials. Besides coffee grounds, he also collects fruit peels from a fruitseller in a nearby hawker centre.
Sometimes, he even lifts the covers of rubbish bins and scans them for plastic bottles and bags of decomposed vegetables.
Back home, he washes the bottles and uses them to hold his plants. He feeds the fruit and vegetables to earthworms, hundreds of which are housed in two big containers outside his flat. He then uses their castings, or manure, to fertilise his plants.
But it took some trial and error before he got things right.
"So many plants died in the first couple of months, I lost count," he recalls.
Other mistakes he made in the early days include leaving the coffee grounds outside for more than a month and adding fish guts that had not fully decomposed to fertilise his plants.
Both gave off a stench that, according to his wife and children, rivalled that from a rubbish truck.
Madam Chan says she thought initially that her husband was going through a mid-life crisis.
But she has since come to appreciate that his "crazy ideas" do work.
Mr Gopal, who will start an online business (www.herbinacup.com) next month selling eco-friendly products he created, says he is passionate about growing his own food because he wants to challenge himself. He says: "I wanted to show people that it's possible to grow your own food in built-up areas like HDB flats."
He also wants to teach his children the basics of growing food and that "food does not grow in supermarkets".
His sons now help him harvest, prune and propagate his plants. Troy, his older boy, says: "I want to grow my own food too when I grow up, so that I don't have to waste money buying it."
A version of this story appeared in the April 2015 issue of The Life e-magazine in The Straits Times Star E-books app, with the headline "Herb garden in HDB corridor".