Demand for sand is killing rivers in Africa | Hacker News Reader

Demand for sand is killing rivers in Africa

bbc.com

109 pointsRed_Tarsius40 comments

Demand for sand (for concrete) is killing rivers... in Africa

In the US, dredging rivers or land near a waterway is pretty restricted. Sand is typically mined from open pits, see: https://en.wikipedia.org/wiki/Sand_mining#United_States

The situation is much the same[0] in many other parts of the world.

[0]: http://www.smithsonianmag.com/science-nature/world-facing-gl...

Does anyone know how much of it comes down to geology?

A lot of the accessible sand in the US is from glacial deposits.

Wisconsin is mentioned in the Wikipedia article as having a boom in sand mining and the surface geology there is nearly entirely a result of glaciers.

Ok we've sent the title above to Africa.

Isn't the river sand full of mud, in many cases? Can it really be washed that well?

Not only it can be washed perfectly but river sand (and gravel) tend to be much better for concrete when compared to "crushed" aggregates.

More or less the reason is that usually for a given size river ones are harder/more resistant, and have rounded edges (which also imply a bigger resistance) due to the cycles (wear, long time immersion, etc.) they were subjected to in the river.

And, as a final advantage, concrete made with rounded aggregates is usually easier to pump.

Mud is just soil in water, and drying and sieving soil is easy.

The New Yorker wrote a much better article about this months ago: https://www.newyorker.com/magazine/2017/05/29/the-world-is-r...

Also an article here on impact of sand mining on rivers in India:

https://www.nytimes.com/2017/03/01/magazine/sand-mining-indi...

For the French or German speakers here, there is an interesting 2013 Arte documentary on the subject:

French: https://www.arte.tv/fr/videos/046598-000-A/le-sable-enquete-...

German: https://www.arte.tv/de/videos/046598-000-A/sand-die-neue-umw...

(I didn't find an English version or English subtitles for it, sorry...)

It's available until September 18.

Industrial scale mining often has unintended consequences - there was a long running sand operation in California that caused erosion all around it on the coast unless you asked the company that was doing it. http://www.mercurynews.com/2017/06/27/controversial-beachfro...

Is there an alternative to using riverbed sand in concrete? Or an alternative to concrete for big buildings?

Crushing rocks down to sand is common. Here's the machinery.[1] The trick is to bang the rocks together. China seems to be making lots of sand for concrete. There are many manufacturers in China making rock crushers and sand-making machines.[2] China has plenty of mountain rock suitable for rock crushing.

Here's a marketing paper on making sand, and what to make for making concrete.[3]

[1] https://www.youtube.com/watch?v=1CpjRMICXNM [2] https://www.alibaba.com/showroom/vsi-crusher.html [3] http://www.metso.com/showroom/construction/new-type-of-crush...

Crushed concrete makes good concrete, but you'd still have to add sand.

Why not use riverbed sand and replace it with other sand?

It is really crazy how much sand is needed for modern development. It is a key component in a ton of different things.

Given that silicon's the second most abundant element on Earth, it seems like it should be trivial to mine without causing environmental damage.

Most of the sand is mined to make concrete (cement + sand + rocks + water = concrete). I think they use much smaller amounts of much higher purity sand for making silicon.

What about the Sahara desert? Seems like Africa has plenty of sand--why are they taking it out of rivers? Expensive to transport?

Addressed in the article:

>The sand used for construction comes mainly from riverbeds and oceans. Desert sand, it turns out, is too smooth for the mix.

It's actually quite striking if you handle Sahara desert sand its amazingly fine and smooth, I imagine other sand deserts where the sand is wind blown for eons is similarly smooth.

Middle Eastern countries are importing sand, even Dubai are importing from Australia. There's even the sand mafia.

http://www.bbc.com/capital/story/20160502-even-desert-city-d...

A lot of desert sand can be compared to powder. So in most cases this cannot be used.

More specifically, they would have to go further east to get the coarser sand.

Here's an idea - why not require the companies to replace the river sand with desert sand after mining it? Have they tried to use desert sand in the river?

This is Africa you're talking about. As much as that sounds like noble and a good idea, convincing local communities and especially businesses here is not going to happen unfortunately.

It's a consequence of being in the third world and having a "catch up at all costs" mentality. Besides, conservation and environmentalism just isn't as in-grained in most African cultures as it is in the west.

Even if you convinced the local government of putting such a law on the books, the odds of them being able to track and enforce such a law is next to impossible. Maybe in more developed countries like South Africa or Namibia, but not in most of the others.

Well why not have whoever is concerned about this sand thing fund an operation to go and bring sahara sand and dump it all along the riverbed? And the operation would be funded by local taxes on the companies extracting the resources. Solved.

Unless you're saying these governments have no negotiating power about their own land and resources? In which case this is just straight-up PLUNDER.

Oh so Africa is building long lasting concrete buildings and making life easier for everyone... something that most of the western world and a huge part of the developing world has already been using for a long time in the same way? No, let us tell you something much more important: how the freaking rivers are "dying".

Environmentalism is anti-humanism.

Did you read the article?

They are discussing offshoring this sand to other countries that can afford it, not to build useful African structures. An argument from "The world has already been using this for a long time" could be used for any number of grotesque and terrible acts (and has) so I will ignore that part.

The main complaint about the "rivers dying" is that it has a outsized impact on the poor who use those rivers for food and water (which is no longer available and which is no longer captured, respectively.)

While some people truly believe in the preservation of nature over humans, most of us "Environmentalists" want to save the environment because of the direct and indirect human suffering inappropriate exploitation of our shared resources cause.

Theres a lot of domestic construction going on in African countries. That growth is all using modern methods, which means lots and lots of pumped concrete.

Anti-environmentalism leads to concrete human and industrial harm. The classic example is having forested buffers between farmland. This is industrially necessary to avoid desertification. The USA learned this the hard way in the 30's. Some countries in Africa have also learned this lesson the hard way, others are still learning it.

This is a similar problem. When you dredge up some sand and a river disappears, you've made a mistake that has human consequences and it probably was not worth whatever you did with the sand.

>The classic example is having forested buffers between farmland. This is industrially necessary to avoid desertification.

I see. That must be the reason why Americans are starving and Africans are so fat because of too much they grow on their undesertified fertile farmlands.

Could you please stop posting flamebait comments on divisive topics? Those are the opposite of what we're trying for here. Please see https://news.ycombinator.com/newsguidelines.html.

Let's assume your points are 100% correct. If you make them by ranting, like you've been doing in these threads, you not only break the site rules, but discredit the truth. That's not in anybody's interest.

Did you reply to the wrong comment? That doesn't make any sense.

It is possible for two facts to be correct at the same time. Yes it is good that Africa has access to modern building materials. It is also bad that extraction is causing problems for rural communities. These two facts are not inconsistent.

All you have really proven is how much you dislike environmentalists. A debate that is quite colloquial to a few cossated western countries. In a lot places people actually live within touching distance of the environment. The pros and cons are just obvious to everyone. Young local men get paid to move sand, which is good. But farmers need water for crops and erosion is a problem. It becomes news outside because no one has a good solution. Just another intractable social problem.

Oh look, the 21st century looting of Africa for its resources. Just to think so many materials extracted from the continent and now sand.

This poor continent keeps getting jacked.

It's being used for local construction. Even if it wasn't, do you have the same sympathy for Australia which is a major source of many minerals? Continents aren't people. They don't have property rights. People do, and it's important for people to be able to exercise those rights to benefit their own lives.

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