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When wondering if there’s any way out of the climate crisis I find myself pinning my hopes on a fairly small number of basic materials, where the massive steps forward in our recent understanding allow us to do things that have never been possible before, Nathan Wrench, Cambridge Consultants’ head of sustainability innovation, writes.
Silicon is one such material: it has spawned an industry that has changed information, communication and is now changing energy – photovoltaic arrays are the nearest thing to a silver bullet we have. Lithium (and Related materials in batteries) is another.
There are many opportunities for materials manipulation at the molecular level. The semi-permeable membranes made from polyamide (or PETFE) are another class of materials that is vital. I also have a side-bet with graphene.
But the reality is that, by the middle of this century, we’re going to need to be able to desalinate water on a previously unimagined scale. Fossil water – the ancient water stored in the underground aquifers that is extracted to irrigate the fields that produce our food – is running out.
Nearly a century ago, the technology that saved agriculture in the US was the centre pivot irrigator. Gasoline-powered pumps pulled water from the underground and turned deserts green again with massive circular fields. However, the water tables are not inexhaustible. The water there was once rain and is not being replenished. In most large arable areas, water tables are declining at a rate of 3m per annum.
Farmers are chasing the water levels downwards – drilling a kilometre down in some cases. The water that rises hundreds of metres underground is becoming less salinized and more plentiful.
Already, desalinated water has been used in the Middle East for irrigation. This trend will continue using techniques such as Red Sea Farms’ “saltwater greenhouses” which are amazing. Graphene is used in the membranes that filter salt from seawater. If it can be produced in sufficient quantity and quality, it will result in thinner membranes with lower pressure requirements.
This will dramatically lower the energy cost and make it possible to water high-value crops within controlled agricultural environments. If that can be halved – or better – then we’ll see it spread, possibly even to commodity crops in open fields with drip irrigation (centre-pivots are are cheap in capital expenditure terms, but wasteful in terms of evaporation losses).
For the rest though, we’re probably going to see photovoltaic solar energy used for reverse osmosis. Solar energy is cheap and plentiful – it’s as near infinite a resource as makes no difference, if it can just be ScaledIt is possible to do this quickly. We are left with hydrogen.
Natural gas (methane) is used to make hydrogen. Natural gas has a similar climate change impact to coal. This is because so many methane vapors out during exploration and extraction, distribution, use, and use. Methane has a global warming potential (GWP) of 28 over 10 years, which is all that is available for us to act on. Nitrous oxide has a greater GWP of 310, while carbon dioxide has a GWP of 1. The carbon from the methane is then removed (steam reforming) and the CO2 is released to the atmosphere. This is why hydrogen has a higher global warming potential than natural gas.
The prime current application for hydrogen is oil refining – it is used to terminate the molecular ends and stop them fraying when you take long-chain molecules (like bitumen from tar sands or heavy crude) and divide them up into shorter lengths like gasoline or kerosene. Other large-scale (existing) uses of hydrogen include ammonia production in agriculture and as a feedstock for chemical production. The switch from ammonia production to low-carbon hydrogen would have a significant impact on oil consumption.
It is now possible to make hydrogen using electrolysing water (green hydrogen). Saudi Arabia spends billions to do this. Australians seem equally interested. When people talk about hydrogen as a solution, they often envision a future in green hydrogen that is abundant and cheap. Those days may come, but current production volumes are miniscule – a drop in the ocean of current black hydrogen production. Priority for green hydrogenShould be to reduce oil refining’s carbon intensity (I admit this is counter-intuitive).
Long-range air travel could also use green hydrogen – I don’t see any other viable long-term alternative. However, the problem remains that combustion at high altitude is a bad idea, when it’s done at volume. The sad truth is that eventually, air travelNeeds to be reduced by a lot.
Hydrogen is also being considered for heating, but I am increasingly of the view that hydrogen shouldn’t be used for this purpose. The best case is that it works and can be used for something more valuable – so why not attack that market first? The worst thing about it is that the noise it makes can delay electrification, which, when accompanied with insulation and draught exclude, is the real solution to heating.
Don’t get me wrong – I like hydrogen. Hydrogen is a really little molecule with enormous internal energy, which is why it’s good for getting a Zeppelin off the ground. Unfortunately, this same activity makes it hard to keep it in your Zeppelin – it leaks out through any seal or membrane. Even if you can solve the leaks, you’re still left with hydrogen being a second-rate fuel. Its internal energy makes it big – high volume – compared to its calorific value. You can waste as much as half of the energy you use to compress and transport it than you would get back if your just burn it.
But in terms of home boilers, you might manage to get up to a 20 per cent hydrogen/80 per cent natural gas ratio without losing too much in leaks, pressure drops etc – but it’ll never be 100 per cent. The combustion engineers I’ve spoken to all hate burning hydrogen. It’s dangerous because the flame is not visible. It doesn’t radiate much heat either, so you don’t feel it’s hot until your hand is actually in the flame…and then it’s super-hot and horrible.
Replacing 20 per cent of your gas from a material with a higher GWP than the natural gas you’re replacing doesn’t make sense: hydrogen is not a solution for climate change. It’s a massive decarbonisation problem first and foremost, and will continue to be so for a long time. Before we can decarbonise other sectors, we must invest in eliminating CO2 emissions from hydrogen production.
For domestic heating, better insulation is better. Heat pumps. Where there isn’t room for an individual heat pump, I’m very much in favour of heat networks. My old village is being served by a colleague who is building a district heat network.Swaffham Prior)… quite brilliant I think.
My main objection to hydrogen is its use by bad actors in the fossil fuel sector as a bait-and-switch. This sounds paranoid – but remember that these are the people who have spent the last 30 years denying the reality of climate change. It should be alarming to see these same people describe hydrogen (made of fossil fuels) now as a solution.
