Maputo — The Mozal aluminium smelter on the outskirts of Maputo on Wednesday began its controversial "by-pass" operation, whereby pollutants will be emitted from the two fume treatment centres (FTCs) without passing through filters, while the FTCs are rebuilt.
A Mozal spokesperson confirmed to AIM that the "filter by-pass" did indeed begin on Wednesday morning and will last for 137 days.
Several environmental groups, backed up by much of the Mozambican media, have campaigned against the by-pass, demanding that the government revoke the authorisation for the by-pass that was granted in May by the Environment Ministry.
But Mozal insists that, although emissions will certainly increase during the four and a half months of the by-pass, they will not reach dangerous levels, remaining within the limits set by World Health Organisation (WHO) guidelines.
A Mozal statement issued on Tuesday night declared "After revisiting all data in light of stakeholder concerns, MOZAL remains confident that the by-pass will not harm the environment or human health".
Mozal added "The project team is fully prepared to continue the repairs and improvements required within the strict environmental parameters set out for the project".
Mozal and the Environment Ministry both say that rebuilding the FTCs is essential because the current state of the buildings is dangerous. The FTCs have suffered severe corrosion blamed on sulphuric acid, which threatens their structural integrity.
The corrosion was noted in November 2009, and Mozal has suggested it resulted from "sub-optimal engineering" by the contractor who built that part of the factory. It is not clear whether the problem could have been detected earlier - some of Mozal's critics believe that the company is to blame for poor maintenance.
The FTCs are part of the carbon plant which makes the anodes that are essential for the electrolytic furnaces where the raw material, alumina, is transformed into molten aluminium. The carbon plant cannot just be turned off, while the FTCs are rebuilt, since without a continual stream of anodes, the whole factory will soon grind to a halt.
In theory, Mozal could import anodes - and indeed it has, on occasion, imported "top-up" anodes. In 2009, it imported 7,000 over a period of nine months. But replacing the anode production of the 137 days of the by-pass with imports looks almost impossible. For the carbon plant produces 1,000 anodes a day - thus the level of imports required is not a few thousand over nine months, but 137,000 over four and half months.
Since 22 anodes can fit into a container, over 6,200 containers would be required, implying a constant stream of trucks between Maputo port and the smelter. This heavy traffic would itself be an environmental hazard. The Mozal management thus ruled out massive imports on logistical grounds.
Since aluminium production is a continuous process, 24 hours a day, 365 days a year, there can be no question of shutting the whole smelter down for a few months and restarting it. The risk of closing the factory down is that the electrolytic furnaces and the molten aluminium they contain will solidify. Mozal puts the cost of one ruined furnace at 300,000 US dollars, and the smelter contains around 540 furnaces.
The main pollutants trapped by the FTC filters, and which will now be released directly into the atmosphere are hydrogen fluoride, dust particles, and tars. The studies ordered from independent consultants, both by the government and by Mozal, suggest that none of these emissions will exceed the WHO limits during the period of the by-pass.
Nobody has to take Mozal's word for it, however, since there are now monitors from the Swiss company SGS placed around the smelter measuring the emissions. The SGS team arrived in mid-October, and began by measuring the reference state of emissions - that is, the emissions when the FTC filters are working.
By comparing this with the emissions during the by-pass period, the monitors will tell by exactly how much emissions have increased with the filters off. They will also be able to measure cumulative impacts.
For it is one thing to say that dust concentrations will not exceed 40-50 micrograms per cubic metre over a 24 hour period (a prediction from South African environmental consultant Sean O'Byrne), and something rather different to predict a build-up of dust particles over days or weeks.
Mozal has promised to release the results of the SGS monitoring on a regular basis. The SGS monitors are credible, since SGS is the largest company in the world providing testing, inspection, verification and certification services, and its findings are generally regarded as reliable.
But Environment Minister Alcinda Abreu announced in the Mozambican parliament, the Assembly of the Republic, on 6 November that if anyone else wanted to undertake their own monitoring, they were welcome to do so.
Mozal emissions do not come only from the FTCs. Gases and particles are also released from the four Gas Treatment Centres (GTC) that scrub gases from the "potlines" (the rows of furnaces), and from the vents in the potline roofs themselves. These continue functioning as normal, and are completely unaffected by the FTC by-pass.
