91av

THE rich waters off the coast of Chile could soon be producing even more
plankton. In a bid to curb global warming, the Chilean government is considering
a proposal by an Australian oceanographer and a Japanese engineering company to
fertilise the sea with nitrogen. This would boost biological activity, and with
it the ocean’s capacity for absorbing carbon dioxide from the atmosphere.

Ian Jones of the University of Sydney’s Ocean Technology Group recently
patented his idea of piping fertiliser into the ocean to encourage the growth of
phytoplankton. As the organisms photosynthesise, they use up CO₂
dissolved in the water, causing the ocean to draw more out of the atmosphere.
Some of this carbon eventually falls to the ocean floor, locked up in the
skeletons of plankton and fish. So the effect of increased growth would be a
reduction in atmospheric levels of CO₂, the main greenhouse gas driving
global warming.

Jones presented his proposals for a pilot “ocean nourishment” plant to the
Chilean government last year and will unveil them publicly at an offshore
engineering conference in Houston, Texas, in May. His plans, drawn up with
consultants from Toyo Engineering of Tokyo, envisage a fertiliser factory on the
Chilean coast that would fix atmospheric nitrogen, powered by natural gas. The
fertiliser would be delivered to the ocean via a pipeline extending to the edge
of the continental shelf, about 100 kilometres out from the coast.

Jones’s partners at Toyo Engineering put the likely cost at between $5
and $15 per tonne of CO₂ captured—less than half the cost
of alternative methods, such as planting trees or extracting CO₂ from
the chimneys of power stations.

The capture of CO₂ can be monitored by existing satellite
measurements of plankton concentrations based on ocean colour, says Jones. This
would mean that Chile could claim carbon credits under the terms of the Kyoto
Protocol on climate change. The credits could be sold to industrial countries,
allowing them to increase their CO₂ emissions from burning fossil
fuels.

In the past, Norway has tried to boost fisheries by fertilising the ocean,
and researchers have tested seeding the ocean with iron to reduce CO₂
(91av, 13 January 1996, p 4 and 28 January 1996, p 13). But,
says Jones, more of the oceans are nitrogen-deficient than iron-deficient, and
iron-deficient areas are far from land and so could only be fertilised by
plane.

But others are not so sure his plan will work. “You need inordinate amounts
of nitrogen for this to work—a thousand times more than iron,” says Martin
Angel of Britain’s Southampton Oceanography Centre. “And I would be worried
about overloading the planet with yet more nitrogen, which is already a major
pollution problem in its own right.”