Alternative water: Iceberg harvesting

The idea that large icebergs could be collected from polar regions and transported to arid countries to provide a new source of water has been speculated by some people, and ridiculed by others, since at least the early 19^th century.

Interest in harvesting icebergs to provide a new large-scale alternative source of water increased during the 1950s and peaked in the late 1970’s. More recently, icebergs have again been suggested as a potential way of overcoming water shortages during the Millennium Drought in Australia, and as a possible water source for Southern Africa.

While large-scale commercial iceberg harvesting has never been adequately tested, short-distance iceberg towing is routinely used in the energy industry to move icebergs away from sea-based oil rigs. A few commercial operators also harvest iceberg ice to produce small quantities of water for bottling and selling as boutique water from a ‘novel’ source.

The real issues with towing icebergs for long distances are the practicality and cost of safely towing something weighing 300,000 tonnes or more through the Southern Ocean. Based on the predicted melt losses as the icebergs reach warmer water (50 to 80 per cent), only icebergs in the 300 – 350 million tonne range could be considered economically viable. Such weights would require tugs with a towing capacity well beyond any existing vessel (see Figure 1).

Then there is the practicality of getting something with almost 90 per cent of its mass below the waterline close enough to the coastline to an offshore melting treatment plant with piping infrastructure to feed into the urban water supply.

Are icebergs a viable option for supplying Adelaide and other regions of South Australia?

Iceberg harvesting is not regarded as a viable and cost-effective source of water for South Australia because:

• Harvesting icebergs commercially at a large scale (e.g. to provide tens to hundreds of gigalitres of water) and towing them thousands of kilometres across open ocean is unproven.
• A large scale iceberg harvesting trial would be extremely expensive and risky, this may explain why a large scale trial has never been undertaken.
• Other much cheaper and proven alternative water supplies, with lower associated risks, are already available.
• The energy requirements and greenhouse gas emissions associated with iceberg harvesting, including the energy that would be consumed to tow icebergs across thousands of kilometres of open ocean, are considerable.
• Icebergs might fragment during towing resulting in greater melt loss. Shepherding multiple smaller ice fragments to Australia would be difficult and potentially dangerous to towing vessels and any other ships in the vicinity. At this stage no obvious and adequately demonstrated technical solution has emerged.
• If the icebergs were wrapped in plastic it is likely the wear and tear of such a covering on the long journey would mean that some plastic would break away into the ocean to be eaten by whales and fish which mistake floating plastic for jellyfish. Plastic that sinks to the sea floor is known to suffocate and kill seagrasses.
• The environmental implications of mooring or grounding icebergs in South Australian waters would need rigorous investigation to allow regulators and the public to be satisfied that there would be no environmental harm.

More information

Iceberg water is low in salinity, making it potentially suitable for use in many applications. Most icebergs of the volume that might be most amenable for considering for towing to Australia (one to several gigalitres range) are likely to be produced from the fragmentation of large icebergs of many square kilometres in surface area.

Even small icebergs of the order of 1-3 gigalitre in volume are very heavy (approx. 1-3 million tonnes weight) and weigh several or more times the weight of the world’s largest shipping vessel (see Figure 1).

The South Australian Government previously looked into the viability of iceberg harvesting for water supply in the 1980s ((South Australia Water Futures: 21 Options for the 21^st Century, Engineering and Water Supply Department, 1989) and again during the early 2000s. On both occasions iceberg harvesting was deemed to be a highly speculative option with no certainty that it would deliver a lower cost water source compared to most other alternatives. The latter assessment estimated iceberg-sourced water supplies would cost about $19 per kilolitre, or $37 per kilolitre in today’s value. It also found that because of capacity constraints, such as limitations on the likely availability of capable towing vessels, probably only a few gigalitres of iceberg water per year would be available – assuming the feasibility of long-distance iceberg towing could even be proven. Adelaide’s current water demand is in the order of 150 to 200 gigalitres per annum.

Related media and research

• The Many Failures and Few Successes of Zany Iceberg Towing Schemes - The Atlantic
• Dubai firm dreams of harvesting icebergs for water - phys.org
• Antarctic icebergs distributions 1992–2014

Figure 1: Illustration of the comparative size of a small iceberg

Left: The Prelude FLNG (floating liquefied natural gas) (silhouetted above) is the world’s largest floating vessel and five tugs were needed to tow her from South Korea where she was built to 200km off the northwest coast of Australia. Even when fully loaded, the vessel’s weight is less than half that of a ‘small’ one gigalitre iceberg.

Right: An approximately similarly scaled two gigalitre iceberg. About 100 icebergs of two gigalitre each in size per year would need to be harvested, towed, moored and melted to fully meet the equivalent of Adelaide’s current water demand.