Take one Pope, 1500 ministers and a racecourse full of the faithful, add 300 kilos of flour, 300 litres of water and 120 litres of wine, and what have you got?

Answer: holy communion for half a million people.

These are the logistics organisers are juggling with as they plan Pope Benedict XVI's huge July 20 mass at Sydney's Randwick racecourse, the final event of the church's week-long World Youth Day (WYD).

"Mass was not meant to be celebrated by quite so many people, so the challenges are great but not insurmountable," said Father Peter Williams, WYD director of liturgy, as he visited an inner Sydney bakehouse busy making one million communion hosts, or altar bread, for the event.

Half a million of the hosts will be used at the final mass, and the rest at other WYD events, including the opening mass celebrated by Sydney's Catholic Archbishop, Cardinal George Pell, which is expected to attract up to 180,000 people at Darling Harbour on July 15.

"We have doubled our production. We are now making 45,000 hosts a week to meet the July contract," said Rod Silber, business development manager for the Ozanam Bakehouse at Stanmore, a St Vincent de Paul Society operation providing supported employment for people with physical and mental disabilities.

"There is not usually a large market for communion hosts.

"It's something I can safely say will never happen again."

Bakehouse supervisor Aida Santos said the hosts were being made in plain, wholemeal and low gluten varieties, each 100,000 of them requiring some 30 kilos of flour and 30 litres of water.

Father Williams said bishops, priests and deacons would serve as ministers of communion at the mass, as well as commissioned laymen, seminarians and brothers and sisters from religious orders.

The Pope will administer holy communion to 24 young people he will confirm on the day.

The communion, planned to take 30 minutes, is so vast that many hosts will be "pre-consecrated" at other masses around Sydney.

Randwick will be divided into a grid system so that the hosts can be quickly ferried in 1,800 ciboria -- round metal communion bowls - to designated staging points and tents
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AAP