Hungary's central bank is pulping wads of old notes into briquettes to help heat needy humanitarian organisations, a gesture that has warmed many bodies and hearts amid a deadly cold snap.

"It's a very useful charitable act, a vital aid for our foundation because we can save part of our heating costs," said Krisztina Haraszti, the head of a centre for autistic children in the impoverished northeastern town of Miskolc.

It helped the centre, which also provides aid to autistic adults, save between 50,000 and 60,000 forints (€180-€200) a month, which is a "considerable sum in this time of crisis," she said.

The central bank has been converting unusable notes into briquettes for the past four years.

The centre and another association dealing with handicapped children in the south-eastern town of Veszto are the institutions chosen to receive the briquettes this year.

There was palpable excitement when a truck from the central bank's cash logistics centre arrived Tuesday to unload four tons of compressed old notes at the centre for autistic children, which has been receiving them since September.

The monthly delivery is due to continue until March or April.

Since the briquettes have a high calorific value, "one only needs to add a few bits of wood and the rooms are really warm," said Haraszti.

The head of the central bank's cash logistics centre, Barnabas Ferenczi, said: "Our examination showed that the heating properties of these shredded currency briquettes are similar to brown coal so they are pretty useful for heating ... and resolve the problem to find fuel."

They can be used in boilers that use mixed fuel, he added.

When the initiative started, the notes were simply burnt. Then the centre decided to compress them into briquettes for better heating efficiency and got machines to transform the unusable cash.

"Approximately, 200 billion Hungarian forints are turned into briquettes that is useful for heating in poor regions.

"For the central bank, corporate social responsibility is an important thing. That's why we thought that since we destroy approximately 40 or 50 tons of currency every year, this thing can be useful for charities that have a problem finding fuel for burning."

It takes about 5 million forints (€17,000) to make a single 1kg briquette. The notes are cut into pieces of 1 to 5 millimetres and then the paper is compressed without any chemicals being added.

Every year, the central bank withdraws about a quarter of the notes in circulation and prints new money to replace the unusable and old currency.

The process of turning old cash into briquettes is held under tight security. People working here have to wear pocketless clothes.

The institutions are chosen they make bids for the briquettes. This year, some 20 organisations made a pitch.

The central bank just has one criterion: that the organisations chosen have no public debt.