Danube sludge peril: Brown trouser time or not?

Millions of tonnes of “red sludge” flowing into the Danube: sounds like Hungary's got something of an environmental problem, doesn't it? And indeed they do, but it's a short-term one, not the long-term disaster that the likes of Greenpeace (hey, surprise!) are telling us all it is.

It isn't actually “red sludge”, the technical term is red mud and it's created during the Bayer process. It's an inescapable part of the manufacture of aluminium. Essentially, take bauxite, the ore, mash it up and boil it in sodium hydroxide (also known as caustic soda or lye) and about half the aluminium oxide (alumina or Al₂O₃) falls out. You can also extract gallium at this point - and indeed that's where we get all of the stuff that goes to make gallium arsenide chips for our phones.

What's left over is this red mud and it's, well, essentially, dirt in caustic soda. The dirt part is nothing very special, a mix of iron oxide (40% perhaps), alumina, titanium oxide and silicates (what we usually know as “sand”). There's not an allotment in the country that doesn't contain these materials; the problem is that suspension of caustic soda they're swishing about in. This can give people some very nasty burns (its pH is 13 as it comes out of the plant), in fact it can even kill through such burns, as well as drowning people - as happened to some unfortunates in Hungary.

The usual treatment method is simply to lagoon the stuff in lakes, such as the one that just burst, and let the weather take care of the sodium hydroxide part over the decades. Eventually, cover with topsoil and plant it. When it does burst out, of course, slightly less indifference is called for.

Thus the stories of pouring plaster of paris and vinegar into streams and rivers: these are attempts to neutralise the alkaline nature of the sludge rather than anything else. Even if pH neutralised, a flood of such a suspension isn't going to do much for the riverine ecology - but sufficiently diluted it will do no more harm than a heavy load of silt coming downstream. By this logic, rather than preventing the red mud from reaching the Danube, we should be allowing, even encouraging, it to do so. Dilute it away, in short. Seawater is better for this than fresh (one such Bayer plant simply dumps its red mud into the Gulf of Corinth to no obviously ill effect), but river water will work.

As to claims that the land will be irretrievably damaged, well, it'll be highly alkaline, this is true, but we know how to acidify such soils: using a nitrogen-based fertiliser works, as farmers who use too much of such fertiliser find out as their soils become progressively acidic. And there's nothing other than the caustic soda in the mud to worry: it is in fact used in some places as an addition to soils which are too acidic, so as to raise their pH level.

As to heavy metals and radioactives (again, much mentioned in more hysterical reports currently) well, yes, you'll get either if you process a million tonnes or so of any rock. The important question though is not whether they are there, it's in what concentrations are they there. And the concentrations are, well, how about less than in some garden soils? Much less than, say, the gardens of Chilcompton in Somerset, where you should not eat the cabbages because of the lead and other heavy metals content. But uranium content of a couple of parts per million - or a vanadium, chrome or arsenic reading of a couple of parts per million - these are the sorts of levels which you probably don't want in your drinking water. While this is true, we're surrounded by those sorts of levels all the time - they make up the very dirt under our feet.

Yes, of course, a flood of such stuff ripping through villages is a disaster, not least for those who didn't survive it. But a long-term threat to the ecosystem? Nah, it's just something for the more excitable greenies to shout about.

But despite such complacency, isn't there something else we can do with this stuff than just letting it be rained upon? Actually, yes there is. We've known for decades that you can extract all those lovely valuable metals such as iron, aluminium, titanium, even the rare earths (which will make the greenies happy as these are what power windmills, CFLs and those electric cars) and make use of them. Unfortunately, the value of the metals extracted is less than the cost of extracting them; so to do so would not a wise economic move on anyone's part. We thus have, in red mud, a problem, a waste, rather than a resource.

Which brings us to a point economists keep trying to tell environmentalists: humans don't consume resources, humans create resources by inventing the technologies to make use of them. In this particular case we may well be (we'll have to see how my own research and pilot plant works out in the next couple of years) on the verge of making that switch. The big change has come in the technology of iron making. Despite red mud being 40% or more iron oxide, you can't just shovel it into the old style blast furnace, as the residual alumina in it will destroy the lining of said blast furnace. However, new technologies (direct reduction for example) seem to sidestep that problem, allowing us to use this waste from alumina production as a source for the making of pig iron. And then once we've done that we can extract the alumina and caustic soda, then the titanium dioxide and even the rare earths, leaving, at the end of the process, some sand. We still don't know whether this is an economically sound method: that's the point of doing research after all. But we do know that it can be done.

One reason not many people have worried about this is that there haven't been any great disasters with red mud. Now there has been one, even if not a great or long-term one, perhaps more resources will be devoted to investigating the question. In fact, perhaps I should be out there with the Greenpeace folks, screaming that this is the end of the Danube as we know it? After all, my financing application went in four months ago and decision day is only six weeks hence...