The artisan paper maker in north-west Tasmania has made a business out of using animal scats, cotton from rags and old bedsheets, and by-product from agricultural endeavours, such as fruit juice and hemp crops.
He works out of Burnie, a coastal city that originally sprung up around a paper mill that, at its peak, employed thousands of people.
Darren learned to make paper as a teenager through an unemployment support program.
Years later, he is still churning it out of a small workshop in Burnie.
In every batch of paper, he uses a cotton mix made out of materials gathered by a local disability enterprise which recycles old clothes and sheets and turns them into cleaning cloths.
In one of his quirkier mixes, he uses the scats from kangaroos and wombats, which he gathers himself in the wild. And has recently branched out into cattle dung.
"Scandinavia used elk poo, in China they used panda poo, Africa is quite well known, and even Thailand, using elephant dung to make paper, so that's kind of where we got the concept from," he said.
"As long as the animal is eating 100 per cent organic material — grass, hay, straw, that type of thing — it's basically mixing fibre with fibre."
Darren has a steady supply of apple pulp that he uses in one paper.
Director of juicing company Spreyton Fresh, Michelle Distill, said it was a good way for the company to put some of its leftover pulp to waste.
"[Darren] just rang up one day out of the blue saying, we're looking at making a range of papers using a little bit more different and diverse product. It turned out really well so he's added it to his paper-making mix," she said.
Like many agricultural companies, Spreyton is always looking for new ways to repurpose its by-product and diversify.
"I think it's like any business — if you don't continually try to grow and evolve, it stagnates," Ms Distill said.
"With any form of agriculture, often just having one point of sale or one use for something isn't enough."
Growing industries present new opportunities
As demand for different paper products grows, makers such as Mr Simpson are also seeing opportunity to put new by-products to use.
Recently, he got his hand on some husks from a hemp crop, something he had been interested in for a long time.
Laws around the sale of hemp food products were relaxed earlier this year, and many expect demand for the crop to rise in turn.
Historians say hemp was used in the earliest handmade papers in Asia thousands of years ago.
"Hemp's kind of got that journey with the history of paper and especially handmade paper," Mr Simpson said.
"And I've been able to get it so nice and white naturally, not using chemicals to bleach it."