"You pick something up but you don't know what to do with it.
It has stuff in it, so you've got a choice. You can either throw it in the bucket and recycle it or you can throw it in the bucket altogether," he says.
A classmate at St Ninian's Primary in Cardenden, Fife, expands on the options. "If you throw stuff for the bucket people, they take it to a junkyard. Then that gets really big," Rhiannon says. "Instead, you can reuse it, like we've reused these bottles and stuff to make junk monsters."
At this point children and monsters are called to the set of the film commissioned by the P3P4 teacher as part of St Ninian's Primary's first eco-school project.
"We're making a DVD starring all the junk monsters the children have made in class," explains Aileen Main. "We will show it at assembly so the whole school can see what we've been doing and get the message about litter and recycling."
Rushes screened on the class laptop are impressive, with squads of sturdy monsters converging on a waste-paper bin and depositing the litter they have picked up. Missing arms on a few of the litter collectors might seem like a handicap, but the magic of modern technology masks the odd missing appendage.
"We can stick the litter on to those with a bit of tape," explains David Griffin, of Glasgow-based Media Arts and Services Scotland. "Filming will take us a few hours of working with the children in groups. We are animating every monster they've made."
Twelve frames, each subtly altered by the pupils, are needed to make each second of film.
"We have done a lot of work with schools, after-school clubs and community groups since we left art school three years ago," says Stacey Matthew.
"From what I've seen, this is about the youngest age group that gets what animation is all about."
The monsters were completed only just in time for filming because the pupils put a lot of effort and creativity into them, explains Ms Main. "I wanted to give them some kind of hands-on project to get across the idea of recycling rubbish," she says. "They came up with loads of ideas: plastic bottles for feet, CDs for ears, pipe-cleaners for arms and hands, bottle tops for noses, coloured tissue paper for their hair."
But there is a limit to how much rubbish generated by a class can be turned into monsters.
"We have separate bins for different waste materials - paper, cardboard, plastic, clothes, CDs - which lets the children see the sheer amount of rubbish that piles up. At the end of the week, it all goes to be recycled,"
The monster project has touched many areas of the curriculum: maths through litter surveys and charts, language through interviews and poster work, expressive arts through designing and making the monsters and ICT through animation.
"The kids absolutely love it and it is helping them to become that bit more responsible," says Ms Main. "Small things like this can make a big difference."
That is the point of becoming an eco-school, says the headteacher, Janette McRae: "It is very nice to have a litter-free school but that is not the main aim. We want children who will grow up to be good and well-informed citizens."
Some environmental issues are beyond the experience of young children, but this is where good teaching plays its part, says Ms McRae. "It's about having high expectations and not treating them as if they can't understand.
They know all about recycling now and they talk about it a lot."
This is not confined to school, of course, but some environments are more intractable than others: "I've got two sisters at home," confides young Rhiannon, "and they are pretty messy."
Media Arts and Services Scotland, tel 0141 632 5243