Growing gains: Perlite and vermiculite

By IM Staff
Published: Friday, 07 July 2017

As two niche mineral sectors that have largely lacked innovation, Rose Pengelly, IM Correspondent, considers whether there could be more in store for vermiculite and perlite than tall buildings and tomatoes.

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Large areas of land in Almeria, southern Spain, are covered with greenhouse and polytunnels growing fruit and vegetables using perlite-based hydroponic systems. ANE, via Wikimedia Commons. 

With niche applications and supply controlled by just a handful of producers, perlite and vermiculite appear a world away from the highly liquid mineral commodities typically used to gauge economic confidence. 

But demand for these products is closely tied to some of the world’s most GDP-sensitive markets, including construction and crop production.

According to Chuck Vogelsang, technical consultant to the US-based Perlite Institute, perlite usage in particular is largely dictated by the strength of the economy.

"Perlite is used all over the world and most of it goes into the construction sector, so demand tends to be driven by the wider economy. A pickup in economic growth tends to lead to a rise in demand for perlite," he told IM.

Construction

Vogelsang cites the growth of Middle Eastern cities, which expanded rapidly on oil revenues in the 2000s, as an example of an economic event which caused typically stable perlite consumption to spike. During its various construction booms, the most notable of which lasted from around 2002 to 2008, Dubai saw huge surges in demand for expanded perlite for use in lightweight cements and insulation materials.

Lightweight cements are favoured in the Middle East since they can be supported by intricate and tremendously tall steel frames. The extreme temperatures of Middle Eastern desert climates also mean that insulation materials are indispensible in buildings. Thermal-acoustic ceiling tiles, commonly used in offices and other modern public buildings globally, can consist of up to 50% perlite and perlite-based masonry fill products are commonly used in both municipal and residential structures.

According to Vogelsang, the widespread use of perlite in construction materials began in the US around 30 years ago and the trend quickly spread to emerging economies, many of which have recently undergone swift urbanisation and construction.

But unlike other minerals, where sharp increases in consumption can push up their value due to temporary shortages, the price of perlite remains fairly steady, since suppliers are usually able to respond quickly to shifts in demand.

Perlite prices published by the USGS are averaged across all grades of perlite and therefore do not accurately reflect the varying cost of different grades of the mineral, however they do indicate broad price trends within the industry. "From what has been published, you can see that generically both prices and demand have been growing," Vogelsang points out (see table).

US perlite and vermiculite prices (2012-2016) 
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*Prices are average values in $/tonne, FOB mine. **Price ranges for concentrate in $/tonne, ex-plant.
Source: USGS 

"Capacity is fairly flexible. Turkey for example recently invested in a whole new perlite production facility solely to supply the Russian market, which has been consuming an increasing amount of perlite in the last few years".

Perlite also has a diversified end use profile, meaning that markets tend to balance each other and prevent significant volatility in supply or prices.

Similarly, vermiculite, which is also used in construction, benefits from having a wide range of other applications which contribute to an overall robust but stable industry performance. 

"Vermiculite is used in a multitude of end use markets, so when one market is flat another can be performing very well – not all the eggs are in one basket," Richard Knight, commercial manager at Palabora Europe, which distributes vermiculite sourced from its own mines in South Africa, told IM.

"That said, current vermiculite demand remains strong. In fact, we as a company are outperforming 2015/16.  The biggest market is building and construction and I believe that this will remain constant, but the horticulture market will grow – especially in areas of the world which are struggling to grow crops due to poor soil quality," he adds.

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Fields of gold: Vermiculite is used to help propagate daffodils,  one of the biggest commercial flower crops in the UK. Paul Pierce, via Flickr

 


Horticulture

One of the best-known uses for both perlite and vermiculite is in horticulture, which as well as ornamental plants and shrubs also includes certain kinds of food crops, such salad vegetables and fruits. Adding expanded perlite to water-holding growing media like compost provides aeration, which aids root growth. Likewise, adding vermiculite also helps improve drainage. 

Fruit and vegetable growers around the world are continually trying to maximise yields from ever smaller areas of land and with as little water input as possible and nutrients like perlite have played an important role in achieving these aims.

In Almeria, Andalucia, southern Spain, the fruit and vegetable industry has been transformed by the use of perlite-based hydroponic systems – growbags filled with the plant nutrient and watered by an irrigation network across large greenhouse and polytunnel complexes. 

The main crops grown using perlite are hydroponically grown tomatoes, bell peppers, and chillies. In hydroponic systems, roots are grown in troughs of perlite which is dampened with a fertiliser solution. This allows the right amount of water and oxygen to get to the roots. This growing medium can be replaced much more easily than soil, which tends to accumulate pests and diseases. 

According to research, growing plants hydroponically produces a heavier crop for the space used and a better quality product. Tomatoes, for instance, are less prone to splitting when grown hydroponically than if they are grown in soil.

Although the hydroponic revolution has brought with it concerns about environmental degradation and even allegations of modern slavery against the employers of migrant labourers that tend to the crops, this soil-free growing method has helped to make Spain the largest producer of fruit and vegetables in Europe. According to data from Eurostat, in value terms, Spain accounts for around 22% of all EU fruit and vegetable production and 34% of exports, more than any other European country.

"Southern Spain has become the vegetable basket of Europe, largely thanks to perlite," Vogelsang claims. 

As well as being a high volume consumer, the horticultural industry is also a relatively high-value market for perlite. According to Vogelsang, the price of horticultural grade perlite tends to be around 50% higher than the cost of material used in construction. 

Horticultural-grade perlite is expanded or "popped" to produce particles – or volcanic glass "bubbles" – that are around 1,000 microns in size by heating the mineral rapidly to temperatures of around 900°C.  

Although horticulture is one of the handful of applications where perlite competes with vermiculite, the sector comfortably accommodates healthy market shares for both minerals.

Perlite and vermiculite are both used to improve drainage and lighten the texture of growing media, especially compost. While not often added to soils, they are best suited to heavy clay soils which are prone to waterlogging. They can also help very thin, sandy soils, as they act like a sponge to hold onto a small amount of water.

Both perlite and vermiculite are used in horticultural research, such as, for example, in the testing of different fertiliser blends. 

During summer months, perlite is mostly used to help grow bedding plants for gardens. Compared to grit or sharp sand, which can also be used to improve drainage, perlite is lighter, which reduces transport costs, and is porous, meaning it can hold a small amount of water to keep compost moist. 

The result is that delicate seedlings and cuttings are able to establish strong roots prior to planting out.

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The construction booms in Middle Eastern cities like Dubai generated significant demand for perlite for use in lightweight cement and insulation materials. Leandro Neumann Ciuffo, Via Flickr

Competition

In the markets where they compete, the choice between perlite and vermiculite is largely determined by the economic value of the end use product. Vermiculite is typically more expensive than perlite, meaning that perlite is preferred for lower value applications where the respective performance benefits of each mineral are similar. 

Perlite is preferred for applications such as filter-aids, since its use can be extended. "If you’re filtering something like apple juice, you end up with a lot of pulp and apple skin from the filtering which has to be disposed of. Because perlite is inert, this waste can be used in animal feed – which represents an important secondary market for perlite," Vogelsang told IM.

Another advantage of using perlite is that, unlike vermiculite, it is never contaminated with asbestos – a problem which affected some vermiculite producers which mined the mineral in the US’ Mid-West states, notably Montana, towards the end of the last century.

This led to a backlash against vermiculite usage in North America and although suppliers in other parts of the world benefitted slightly, Palabora Europe’s Knight says that the asbestos issue has tainted the vermiculite industry as a whole.

"Unfortunately, we never seem to shrug off the asbestos label, due to one event in the 1990s.  But Palabora actually benefits from the issue, as we give strong guarantees about our vermiculite to customers."

"We have very rigorous testing processes, which are actually being used by the global industry as an example of 'best practice’.  But, we must never be complacent about the dangers of asbestos," he adds.

As well as competing with one another in some areas, perlite and vermiculite consumption is also coming under pressure from the increasing popularity of alternatives.

In horticulture, both minerals can be substituted with grit or sharp sand for lightening heavy soils. For ornamental gardening purposes, these camouflaged alternatives are preferable to perlite, which is shiny and white and can be visually unappealing.

A recent competitor material to perlite in horticulture is biochar, a type of charcoal, which has proven very effective in developing countries in improving the moisture-holding ability of thin, sandy soils, while adding nutrients. 

The main, obvious, advantage is that charcoal can be produced very cheaply and easily. There is a lot research into the benefits of biochar, but results are contradictory, partly because the product is highly variable. 

In the vermiculite market, Palabora Europe has noticed the rise in alternatives. "World vermiculite consumption has decreased and this is mainly due to substitution and new methods in end use markets," Knight told IM. "Conversely, we have more commercial mines, vying for a much smaller piece of cake.  

This has created a much more competitive market, which I believe has benefitted customers, as suppliers have had to improve their offerings." 

Knight says that suppliers like Palabora Europe, which are currently leaders in the vermiculite industry, cannot afford to take their foot of the quality control pedal if they are to hold on to market share, but some factors are more difficult to manage than quality. 

"For us logistics plays a huge role and our supply chain is constantly being reviewed" he notes, hinting that costs have to be squeezed wherever possible to ensure price competitiveness. 

R&D

Both perlite and vermiculite are used to produce speciality products tailored for specific end uses. But according to Vogelsang, in the perlite sector, research and development (R&D) is not a market driver. Prohibitive freight costs mean that consumption of expanded perlite tends to be local to the source and there is little incentive to invest in expensive R&D for products that will not reach mass markets.

In the perlite ore market, raw ores are traded over long distances to buyers which then convert them into products – a model which similarly fails to foster innovation.

Knight is more optimistic about the scope for R&D in the vermiculite industry. "Vermiculite is a technical product and customers require high exfoliation levels and to a homogenous product, so quality is very important." 

"Whenever I speak to people about vermiculite, there seems to very little known about its huge potential in many different areas.  Is that the fault of the vermiculite miners who have not educated the end use market, or the exfoliators keeping their niche markets to themselves? Whatever the blocker is, vermiculite still has some very valuable uses which could be realised if more research and development was carried out."

Knight sees the construction industry as a prime target for innovation, saying that vermiculite-based materials could be exploited to help make new buildings greener, in terms of carbon footprint and energy efficiency.

"We at Palabora Europe are very keen to work with universities, academic bodies to discover or dig deeper into the attributes of this very specialised mineral, which covers so many end uses," he adds.

Vermiculite in commercial flower production

Vermiculite has a minor use in propagating Narcissus, or daffodils, as well as tulips, and snowdrops grown commercially for sale as cut flowers or to gardeners for planting. 

In a process called twin-scaling, bulbs are cut into pieces and incubated in moist vermiculite, where they develop small bulbs that can be grown on. This is slightly quicker than waiting for bulbs to multiply naturally. 

Research conducted at the UK’s University of Warwick’s Crop Centre is attempting to find alternatives to vermiculite that are less complicated and messy to use, such as on damp paper or mineral wool.

So far, however, this research has not yielded a viable alternative to vermiculite.