A couple of months ago my son’s dislike of school dinners reached the tipping point, and outweighed his parents’ refusal to find an extra 10 minutes each morning. We did the unthinkable and switched to packed lunches.

A shelf in the kitchen quickly filled with colourful packages, each containing smaller packages. The drink cartons came with plastic straws, in tiny film sleeves stuck to the composite carton with a dab of glue. We bought them in trios, swathed in more plastic. And all the while the calls to cut plastic waste were growing and growing. Our treat shelf began to feel like a shelf of shame.

Could we manage a week of plastic-free packed lunches – and maybe change our habits for good?

First, a cold-eyed audit of the usual lunchbox. There’s a roll, wrapped in greaseproof paper, a raw carrot, peeled and wrapped in foil, a piece of fresh fruit, an individually wrapped treat – often a Soreen mini malt loaf or a Bear fruit yoyo – and a carton of juice. The lunchbox itself is plastic, and I am attracted to some stainless-steel multi-compartmental containers that would look nice in photographs. But the zero-waste consultant Rachelle Strauss tells me: “The most sustainable choice is to buy nothing.” So we stick with what we have got.

Next, the drink carton. I would love to know how many environmentally minded parents still send their children to school with a drink carton in their lunchbox, as I have done unthinkingly for weeks. It is such an easy fix to switch to a refillable sports bottle. We are saving packaging and money. My son, Gabriel, who is eight, is happy not to be using straws and doesn’t seem to miss the juice.

But the rolls are a problem. We buy them from a supermarket, wrapped in plastic film. Most mass-produced bread now comes in bags that can be recycled, so why not rolls? The loose rolls in the supermarket have gone hard by the time I get there at 5pm, and I know that a hard roll is bound to come home. I bike to my local baker’s. It’s shut.

So day one starts with a sandwich, using up last night’s chicken. I fold it up in a reusable beeswax wrap, and buy some compostable baking paper for emergencies. There’s an extra piece of fruit instead of the treat. The treats are a sticking point: Soreen says the plastic film wrapping of its mini loaves is not recyclable. In our lunch hours my husband picks up popping corn loose from Whole Foods, and I start to collect ingredients for carrot and pineapple muffins.

Good and wholesome and no waste in sight: the contents of Gabriel’s new-look lunchbox. Photograph: Linda Nylind/The Guardian

Day two begins with us popping corn at 7am. How much corn do you need to pop for a child’s lunch? We’ll have to come back to you on this, as our best guess fills a large bowl. Luckily there are people in the world who are happy to graze on popcorn for breakfast, and some of them live in my house. Fruit is a couple of slices of mini watermelon, bought whole and unwrapped in Sainsbury’s.

After school we cycle to Bulk Market, one of five shops that sell loose produce within two miles of home. We scoop dried organic apricots (70p for 100g – cheaper than some supermarkets), banana chips (55p/100g), oats (25p/100g) and giant chocolate buttons (£1.20/100g) into paper bags and make a note to bring containers next time. We also grind peanut butter, but that’s just for fun: ours is a nut-free school. I pick up some compostable cake cases, and buy loose peaches and plums at the greengrocer. But when we get home and I open the lunchbox, I find two large U-shaped crusts that have to go in the compost. Not plastic, but I still feel guilty.

On day three, we get up early to bake pineapple and carrot muffins in the compostable cake cases. Unlike many items, which break down only in industrial facilities, these are certified to be suitable for home composting. It is hard to believe that a few weeks ago I refused to get up early to make a packed lunch, and now I am rising to bake muffins.

Meanwhile, Waitrose replies to say that it’s “looking at alternative packaging (including home compostable materials)” for its rolls. I still don’t understand why they can’t stack them in a recyclable bread bag but apparently this might be “so they don’t get squashed (which can lead to food wastage).”

Still, the house smells amazing. We cut the sandwiches into triangles to avoid the U-shape crusts (don’t ask me why children find this more palatable, but they do). I had to buy plastic-wrapped cheese, but the pouch is resealable and we will use it to store dried apricots. We drop apple rings into the gaps in the box and scrub the carrot instead of peeling it, in line with the waste-reduction charity Wrap’s injunction to “eat as much of the food as you can”.

Nine-year-old Gabriel measures out the ingredients for homemade malt loaf. Photograph: Linda Nylind/The Guardian

When we started this project, I thought that a plastic-free lunch would be a manageably contained way to live more conscientiously. But the dozens of decisions and calculations we are making – are compostable cake cases better than silicone ones? Where can I find a bread roll? – are rippling well beyond the confines of the lunchbox. I have become hypersensitive to waste. To bake the muffins, I open a new bottle of oil and drop the tiny plastic seal into the bin with a heavy heart.At lunch, I stare sadly at the sandwiches in Pret, in their partially recyclable cardboard and plastic containers, and walk away.

I am keen to see if the crusts have come back after school. They haven’t – the whole lunchbox has been left in class. I remember Rachelle Strauss’s advice about not buying new: “Look around your house and ask yourself what you could use.”

We pack the next lunch into an old ice-cream tub; we are not doing this for Instagram. But the treats are running low. It turns out that bulk shopping leads to bulk snacking. I puree some apples to make apple flapjacks. They are very flat jacks, but never mind.

The lunchbox treat is our most challenging item – and the most fun. In future, we could make fruit leathers to replace the Bear yoyos, and core and slice apples to dry our own rings. I would like to make a tortilla to replace the sandwich. I have found a recipe for malt loaf. Gabriel gives a thumbs-up as far as he can above his head. But at lunch I go to the sushi place and stare sadly at the individually wrapped nigiri.

And then the week ends.

“What? We can’t stop just because we’ve done a week,” Gabriel says. He says he has not missed the malt loaves and yoyos. He hopes other children may feel the same. And I have learned that I can get up in time to make two packed lunches. I order myself a highly attractive stainless steel multi-compartmental bento box.