Batch Brewing Company has created a pork-roll beer to pay tribute to the area's Vietnamese cuisine. Photo: Louie Douvis

When the zombie apocalypse comes, Doug Bremner and his beer-brewing mates will probably be just fine. Self-sufficient? You bet. They have, after all, just created a beer from little more than coriander seeds, orange zest… and yeast collected from their belly buttons.

And if that's not up your alley, how about a refreshing glass of whale vomit ale, made using ambergris, taken from the digestive tract of whales? It's all on offer at this year's Great Australasian Beer SpecTAPular (GABS), in Sydney's Australian Technology Park on May 27-28.

Both beers came about because of their brewers' sheer ingenuity. Belly Button Beer, made using yeast collected from the midriffs of Bremner and his co-founders, Brendan Baker and Matthew Boustead, was dreamed up after the men heard of an American brewery marketing a "Beard Beer", made from yeast isolated from the chin hair of brewers. "We tried it and liked it," says Bremner, "and it all started from there. We started talking about other places yeast might naturally occur… and bellybuttons were one of them."

Ambergris being sliced up to add to 'Moby Dick' Ambergris Ale. Photo: Supplied

Bremner, Baker and Boustead had been toying with the idea of a spontaneously fermented brew for a while - the idea being that, without using active yeast, natural microbes in the air are left to ferment the beer, giving it a sort of "terroir" normally associated with cheese or wine. "We had always planned to isolate our own unique yeast from that," says Bremner, "and really figure out what the natural yeast of the brewery would taste like. Then we thought about belly button beer and just decided, 'Well, we already have some pretty unique yeast going on.'"

Speaking of unique, at Robe Brewing in South Australia, owner Maris Biezaitis was intrigued when friends found some ambergris - commonly known as whale vomit and highly prized for its pungent but earthy scent - on a nearby beach. "I knew it was used in making perfume and was very expensive - it's worth almost its own weight in gold, literally - and I wondered if you could use it in cooking, or brewing beer." The brewers added it to their amber ale and now are selling the brew as 'Moby Dick' Ambergris Ale.

They say the resulting taste is of caramel and fruit. The famed smell? "It can be a bit off-putting," admits Maris. "But once people get over the idea of 'whale vomit' beer, they often quite like it. I would say it's for people who appreciate challenging tastes."

Pre-fermentation of Moby Dick Ambergris Ale, by Robe Town Brewery. Photo: Supplied

Both breweries are quick to point out that their beers are safe to drink. Belly Button Beer's yeast has been isolated and checked regularly by the brewers for any contaminants. As for the taste? "It reminds me of a Hoegaarden," says Bremner, referring to the popular Belgian beer. "It has clove and spice flavours, with a sort of creamy banana undertone. We set out to make a German witbier, which is traditionally spiced with orange zest and coriander seed. They both complemented the yeast really nicely." All the other ingredients, says Bremner, were intended to highlight the taste of the yeast, rather than mask it.

While there's been quite a bit of fanfare over Belly Button Beer, with American talk shows on the phone and even The Smithsonian running an article on it, it's had its fair share of detractors, too. Even hardcore craft beer nerds, says Bremner, turned their noses up at the idea. "I'd say the split is 20 per cent up for it, 80 per cent still grossed out." For those 20 per cent who want in, though, you'd better get in quick. The brewers, for whom 7 Cent is still a side project in addition to their full-time jobs as engineers, will only have around 10 kegs left after GABS.

If you're not quite up for Belly Button Beer or Whale Vomit Ale, there's plenty more happening at GABS. Sydney-based Doctor's Orders are pulling a squid ink and algae ale, and Marrickville's Batch Brewing Co will pay tribute to the many Vietnamese restaurants in their suburb with a pork roll beer (brewed with cucumber, carrot, coriander, chilli and pork broth).

Possibly not to everyone's taste? Photo: Supplied

More of a sweet tooth? Maybe Black Hops Brewing's trifle beer is more your style - it's been made with sponge cake, Aeroplane jelly, toasted coconut, flagons of sherry, Madagascan vanilla and plenty of fresh fruit. Not quite apocalypse fare, but we'll take it.