Hong Kong businessman Kennedy Tam always wanted to travel the world. When he died suddenly of a stroke in 2010, his wife Freda decided death would not stand in his way.

Since that day, Freda has taken Kennedy on trips to New York, Canada, Shanghai and Turkey.

"We are always together. Even at work he is always near me," said Freda, 48.

As she talks, Freda looks lovingly down at the necklace around her neck. "This is Kennedy," she says. "He is my diamond."

She is not speaking metaphorically. When he died at the age of 52,Kennedy was cremated and his ashes made into a synthetic diamond.

It's an option more people in Hong Kong may have to consider in future as the city, with its rapidly ageing population of 7.1 million and annual death rate of 50,000, faces up to a shortage of places to bury its dead.

Burial plots are scarce in the city - one of the world's most densely populated spaces - and often exorbitantly expensive, with permanent spots starting at 36,000 US dollars, or around 770US dollars for a short-term stay of six years in a government plot, after which the body has to be exhumed and the remains cremated.

The other main option of keeping cremated ashes in urns at a columbarium - a storing place for urns - is less expensive, costing around 330 dollars at a government facility. However, the price rises to between 6,200 and 42,500 US dollars at a private columbarium.

But with 90 per cent of people choosing cremations, even this option is unable to keep pace with demand and there are an estimated12,000 deceased people now on waiting lists for columbarium places.

The government says a new columbarium will be ready by summer which will provide some 43,000 niches - roughly equivalent to the number of cremations in one year.

It has also identified 24 potential new columbarium sites. However, many of these have already met with opposition in the community because of the belief that presence of the dead drags down property prices due to their bad feng shui.

Recently, the government began promoting other options, such as remembrance gardens for scattering ashes and an internet memorial service in the absence of real grave.

In 2007, it lifted a 22-year ban on scattering ashes at sea, and began offering free boat trips for the purpose. Since then, sea burials have increased fourfold, from 160 in 2007 to 660 in 2011.

But these numbers are a drop in ocean when you consider the death rate, says Professor Lily Kong of the Department of Geography at the University of Singapore.

"Space is at a premium and the growing death rates present a challenge to the city authorities in accommodating the dead amidst the challenges of housing the living," Kong said.

Kong, who has studied the subject, said the biggest obstacle for alternatives like sea burials was cultural practices and beliefs.

"The notion of returning to the earth upon death is deeply entrenched in Chinese belief systems," Kong said.

"Without a proper burial, the traditional Chinese belief is that the soul will not rest, giving rise to a 'hungry ghost' rather than a venerated ancestor."

Moving away from burials to cremations had involved a "significant cultural shift", but taking the further step of disposing of the ashes at sea presented even greater cultural obstacles, with many people believing it showed "disrespect and lack of care for one's ancestors", said Kong.

A funeral director, speaking on condition of anonymity because of the sensitivity of the subject, said sea burials were unpopular because people did not like the idea of a parent or spouse floatingaround in the sea.

"They prefer to have a place to visit, something real, and to keep their loved ones close," he said.

Space burials, in which ashes are shot into space, have also proved unpopular in Hong Kong for similar reasons, he said, adding he knew of only one in the last 10 years. (DPA)