‘Silver science’ turns aluminium scrap into clean energy source in farm-shed reactor

At the gates of a farm with the sign 'Keep Out', E&T is kindly greeted by a smiling cockney man wearing a T-shirt with five colourful test tubes printed on it. Alan Smith, 74, together with a team of other pensioners, runs a self-built hydrogen reactor in a former milking parlour in rural Essex.

Smith claims the little company Ecalox has engineered the world’s only zero-carbon aluminium hydroxide reactor. He made it his own and his colleagues' objective to establish hydrogen production from waste material – both to cut carbon emissions and to help recover the value of aluminium rubbish that is often dumped and under-appreciated within the global energy value chain.

With the current interest in clean energy provision, demand for hydrogen is booming around the world. As hydrogen plays a key role in everything from fuel to fertilisers, it is perceived as central catalyst for enabling greener energy to flourish, paving the way to a net-zero carbon economy. Being a highly flexible energy carrier, it is a powerful storage medium, its supporters argue.

Today's production of industrial hydrogen originates mainly from steam reformation of methane in fossil fuels, primarily from natural gas, although oil and coal are also used. Professor David Book at the University of Birmingham’s School of Metallurgy and Materials, explains that this is the cheapest way to produce hydrogen at the moment. The downside, he says, is that you have a lot of CO₂.

To a lesser extent, hydrogen can also be produced by electrolysis of water, according to the International Energy Agency. But affordability appears out of reach, at present at least. Smith thinks nobody has the price down below four dollars a kilo at the moment – even though by smart accounting some might claim they do, he adds.

To solve the global aluminium-recycling problem is Ecalox’s goal, he tells E&T. A huge quantity of aluminium still winds up in landfill instead of fulfilling its potential as an ingredient in energy production. “Just because cans are collected, it doesn't mean they are recycled," Smith points out. Only 10 or 15 per cent of the material is really being recycled globally, he reckons. In the EU rates are higher, around 60 per cent. But the smelting of the cans come with inefficiencies, causing further recycling issues.

Smelting cans produces a hard-to-recycle salt cake - the slack from the furnace - consisting of a mixture of aluminium oxides and aluminium nitrides, metal and salts. Salt cake recycling is yet not affordable enough, resulting in huge salt-cake mountains. 

Due to the large surface area of shredded cans, a lot of oxides are generated in the smelting process. As recycled drinks cans contain sugar syrup, carbon ends up in the aluminium when recycled, a problem that is also an issue for Smith and his team.

After months of intense research, the engineers found a solution for their reactor to deal with the carbon from the sugar syrup as well as with the denatured lacquer. At the end of each reactor cycle, which takes around four hours to complete, the end product is low-pressure hydrogen which the Ecalox team use to fire up a small generator in the corner of the barn-based laboratory. 

The key by-product is aluminium oxide. Decanted from the reactor into a bucket, this is white and odourless, but still needs some simple pre-treatment to increase its quality, the engineers concede.

The material looks almost like baby powder. Smith takes his finger, dips it into the white mass and licks it with his tongue. It is a demonstration of the material’s harmlessness. But despite its innocuous appearance, this material packs a punch. It is the main raw material for making new aluminium and sells for more than the cost of the low-grade scrap used as the input material.

While the low-grade aluminium scrap market remains very niche – the material can be hard to obtain and without a proper market price – aluminium oxide is in great demand in all sort of areas. It has applications in fillers, glass, catalysis, water purification, composite fibre, electrical insulation, body armour, as well as in paint – Smith points at three small paintings in one corner of the barn that used his aluminium oxide.

With $500 to $600-worth of aluminium scrap, Smith reckons his reactor could squeeze out $1,500-worth in aluminium oxide, plus all the energy it produces, he says. 

The catalyst for the hydrogen-water reactor is fully recoverable, and is said to be an inexpensive material but kept a business secret for now, though it is certainly traceable in public scientific literature, Smith admits.

"Because you get the aluminium and you use it to split hydrogen out in the water, you are oxidising it, so basically you burn aluminium in the reactor. Not only is it a very good raw material to make aluminium. In fact that is bauxite, the stuff they rip up tropical rainforests for, to get just that, with a CO2 penalty of 8-15 tonnes of CO2 per tonne of that [aluminium oxide]", he says. 

It would also just take five per cent of the energy to convert the aluminium oxide back into aluminium compared with the energy required for mining of the material. "It is a very virtuous process", Smith comments.

For every tonne of aluminium waste fed to the reactor tub, 4MWh of hydrogen energy is acquired from the process, Ecalox claims.

But hydrogen and aluminium oxide are not the only end products. Heat is another. So much so that Smith and his team had to deploy cooling systems to lower the reactor's temperature (see the cooling element in the process graphic).

"Because you burn aluminium, you get huge amounts of heat, which is worth another 4MWh per tonne,” Smith explains.

As each tonne of aluminium recovered has the same energy content as a tonne of gasoline, it seemed ridiculous to the team not to jump on the opportunity.

How does the reactor work?

The idea of obtaining hydrogen from the reaction with water is not new, and Professor Book told E&T that the process of using water and aluminium is well studied.

Having worked out the process to produce hydrogen and its valuable by-products, two problems remain in Smith's concept: how to obtain large quantities of scrap aluminium and the finance for setting up a hydrogen storage facility.

The former would be a significant challenge. Large quantities of aluminium scrapdo not lie around in the streets. The trade is very niche, he says, and volumes traded would be relatively low. "It is hard to get good figures. It is in the East-Enders brown envelope territory," Smith jokes.

The team used a market analysis by the University of Nottingham, who they are planning to collaborate with, to obtain more precise market figures. Smith adds that the university is also running a doctoral programme in hydrogen production, where he sees advantages for both parties in rolling out a low-cost alternative to carbon-intensive methods.

The first and immediate use case, Smith explains, might be in the context of a beverage packing plant. Can plants for beer and soft drinks produce enough scrap every day for our process to power the entire operation – and they could sell the aluminium hydroxide at a profit. This would make such a factory a zero-carbon operation.

At present, the team is looking for investment to expand its operation. They have an engineering partner who will help create the first containerised commercial plants. These can be located anywhere, make few infrastructure demands and will be able to produce hydrogen, electricity, heating, or cooling as required.

Smith is banking on only grabbing a small part of the aluminium scrap market, for now, at least. This could already be sufficient to help building a sizeable business. “If we only get a tenth of the landfilled post-consumer aluminium waste we would be able to process 50,000 tonnes a year, sell almost 100,000 tonnes of aluminium hydroxide and create a 400,000MW energy business on the back of it.”

In the Essex barn where Smith also built all the furniture, he and his colleagues spent much of the last year looking at the chemistry of the reactor process, tinkering with the science, refining the methods, and the end product while studying the aluminium scrap, hydroxide and oxide market, he says.

Despite, the chemistry being “relatively trivial”, Smith concedes, what no-one has done before us is to put together a whole business model and work out the chemistry that allows them to end up with a good quality product.

In recent months, signs suggest that the time for a hydrogen revolution in the UK is ripe. Whether it is in shipping – where hydrogen is promising the sector an allegedly attractive way to reach a zero-carbon future –, low-carbon vehicles or home heating systems, increasingly regulators are warming to the idea in the name of a greener economy.

Recently, the UK Department for Business, Energy & Industrial Strategy (BEIS) commissioned a review by the IET to evaluate risks in using hydrogen in Britain’s existing gas heating network.