A growing market: vermiculite and perlite in horticulture

By Kasia Patel, Antonio Torrisi
Published: Friday, 21 March 2014

Reporter, Antonio Torrisi, and Senior Reporter, Kasia Patel, take a look at the uses of vermiculite and perlite in the horticultural industry.

Because of their specific mineral properties, both perlite and vermiculite lend themselves to a variety of commercial applications, such as in construction and packaging. One niche use is the application of perlite and vermiculite in horticulture, owing to the structure of both minerals, which allows them to control soil moisture and host mineral fertiliser.

Vermiculite is a hydrated magnesium-aluminium silicate, with typical composition being 38% to 46% silica (SiO2), 10% to 16% alumina (Al2O3), 16% to 35% magnesia (MgO), and other compounds such as calcium, iron, potassium and titanium oxide.

Owing to its lamellar structure, similar to that of mica, vermiculite expands 6 to 30 times the original volume of vermiculite concentrate when heated above 870¡ C through a process called exfoliation.

Exfoliated vermiculite is chemically inert, with a melting temperature of between 1200¡ C and 1320¡ C, non-combustible and a good insulator of electricity, heat and sound.

Horticulture accounts for at least 50% of vermiculite’s end market. Other market applications include building plaster; fire protection; refractory; friction linings; special coatings; animal feed; and packaging.

“The end use diversity of vermiculite does ensure some stability from a sales point of view. The agriculture and horticulture markets continue to perform very well,” Richard Knight, business manager at Palabora Mining Co.’s subsidiary, Palabora Europe Ltd, told IM.

In horticulture and agriculture, vermiculite is used for different purposes. It is used in the retention of soil moisture; acting as cation exchanger; and hosting a number of mineral fertilisers such as ammonium, potassium, calcium and magnesium.

When combined with peat, vermiculite promotes faster root growth in plants, controls the delivery of fertilisers, herbicides and insecticides, and protects plants from cold and drought.

At the beginning of 2014, the All-Russian Rapeseed Research Institute (ARRI) developed a new vermiculite, sodium carboxymethylcellulose (NaKMC) bio-nano-chip, to enhance soy-bean germination capacity from 92 to 99% with half the normal amount of protective fungicide, Topsin-M.

Substitutes for vermiculite in the horticulture market are perlite, peat, sawdust, pine bark and synthetic soil conditioners.

While perlite has a stable neutral pH, vermiculite’s pH can vary from 6 to 9, from neutral to slightly alkaline, owing to the presence of carbonate compounds associated with the mineral ore.

In the last four years, the vermiculite market suffered a contraction, because of rising vermiculite prices, as reported by the Canadian processing company, Perlite Canada Inc., in 2013.

Knight told IM that horticulture and agriculture markets continue to be strong and will see a growth in vermiculite demand. Ê

“The horticulture market is an exciting opportunity for Palabora vermiculite, which seems very well suited for this application and we are seeing increased growth in this area especially in the warmer countries where the climate is suited for greenhouses,” Knight said.

Jose Luis Fernandes, technical and sales manager at Brasil Minerios, told IM that the size of the market remained unchanged in the last three years, with 40% consumption in the horticulture/agriculture market and 40% in the building board market. He added that in the international markets, consumption was for the 40% coarse grade and 60% fine grade.

Brasil Minerios said that the economic crisis caused a 15% to 20% contraction in vermiculite demand in the last three years compared to 2007 and 2008.

According to Fernandes, the vermiculite market in Brazil and worldwide will increase at low rates. In Brazil, the construction market will be predominant, while the agricultural markets will see a moderate growth in demand, predominantly in fine grades.

New markets for fine grades of vermiculite are in water absorption and air pollution control in mines, used in ion-exchange columns, purification of waste water as well as for nuclear waste containment and removal.



Vermiculite prices

In the US, vermiculite prices ranged between $115/tonne and $460/tonne in 2011, depending on grade; according to the US Geological Survey (USGS). Prices increased to $145-525/tonne in 2012 and to $150-550/tonne in 2013, due to a difficulty in supply meeting increasing demand for coarse grades vermiculite.

Average prices of vermiculite sold by Palabora Mining Co., calculated from the ratio of total sales values and volumes, amounted to $326/tonne in 2012 and increased to $357.6/tonne in 2013.

Average prices of exported vermiculite in South Africa amounted to $186.7/tonne in 2011, according to data from the Department of Mineral Resources and Statistics of South Africa (DMRS); prices calculated from the ratio between total sales values and volumes.

Indian vermiculite exports were at $116.3/tonne in 2011 and increased to $140.7/tonne in 2012; calculated from the ratio between export values and export volumes reported by the IBM.

IBM data suggest that average vermiculite import prices from South Africa to India decreased from $289.8/tonne in 2011 to $240/tonne in 2012.

Fernandes said that prices of fine grades dropped by almost 20% compared to 2010, probably due to overproduction, while prices of coarse grades have shown little variation.

According to the USGS, after a ramp-up in the last few years, vermiculite prices are expected to stabilise in 2014.

“The price of vermiculite has been affected by the supply and demand scenario. We have seen increases of around 40% for some grades of vermiculite. Prices have reduced and stabilised to reflect the competitive environment,” Knight said.



Global vermiculite production

In the last few years, the vermiculite market has recorded several changes among global producers, with an increasing demand of coarse grade and an oversupply of fine grades, partly due to a downturn in the building sector over the last two years.

“The building sector is an important end use market for Palabora vermiculite and the downturn of this industry in the last couple of years has impacted on our sales,” Knight told IM.

According to the USGS, the estimated global production of vermiculite increased by 10.5% in 2013, reaching 420,000 tonnes from 380,000 tonnes in 2012.

The figures are still lower than those in 2011, when total production amounted to 542,000 tonnes.



South Africa

South Africa-based Palabora Mining Co. Ltd is one of the world-leading producers of vermiculite concentrate, with 133,000 tonnes produced in 2012 from its vermiculite mine in Limpopo.

The major producing country is South Africa, accounting for 31% of world production in 2013, with estimated reserves of 14m tonnes of vermiculite, according to USGS data.

Knight said that production in 2013 amounted to 130,000 tonnes, less than Palabora’s optimal plant capacity.

“Improved mine planning and more efficient recovery is giving us the right quantity of grades for the market. Our business plan is to be back to producing 150,000 tonnes in the next 18 months,” Knight told IM.

The company sold about 121,500 tonnes of vermiculite in 2013, compared to 115,000 tonnes in 2012.

Knight added that production capacity is around 200,000 tonnes and expansion of mining operations will extend the mine lifetime over 24 years.

“The European vermiculite market still remains a key market for Palabora with Asia and America markets still having opportunities for growth,” Knight told IM.

In December 2012, Anglo-Australian mining companies, Rio Tinto and Anglo American PLC, sold their respective 57.7% and 16% interests in Palabora Mining to state-owned Industrial Development Corp. of South Africa and a Chinese consortium, including private-owned Hebei Iron Steel Group, state-owned Tewoo Group Co. Ltd and private-owned General Nice Development Ltd.

According to the USGS, Palabora’s production of sufficient quantities of coarse-grained grades became increasingly challenging to meet a substantially increasing world demand in 2011.

Knight told IM that more efficient mining in the last few years has resulted in producing more medium and fine grades.

“In recent years, both these grades have been in short supply and our ability to now supply will definitely benefit our business,” he said.



Zimbabwe

Zimbabwe is another important producer of vermiculite in Africa from the Shawa mine, near the town of Dorowa, owned by the French mining company, Imerys SA.

The deposit, which extends over an area of 5.5km in radius, has an estimated lifetime of 30 years, with a processing plant production capacity of 50,000 tpa.

Imerys also owns a vermiculite deposit in Australia with an estimated minelife of 20 years.

Uganda

Uganda is the third major producer of vermiculite in Africa, with its East African Namekara mine hosting inferred mineral resources for 55m tonnes, 60% of which includes significant coarse and medium grades of vermiculite, according to the IBM.

Australian mining company, Gulf Industrials Ltd, increased its production capacity at Namekara from 4,000 tpa raw concentrate in 2010 to 30,000 tpa in 2012. However, the company suspended production for ‘care and maintenance’ operations since October 2012.

According to the USGS, the company is planning to increase its capacity up to 50,000 tpa in 2014.

China

China is another producer of vermiculite, with 50,000 tonnes produced in 2013, accounting for 12% of global production, according to USGS data. Xinjiang Weili Xinlong Vermiculite Co. Ltd is the main producer in the country.

US

The US is the second largest producer worldwide, with 100,000 tonnes of concentrate produced in 2013 and reserves of up to 25m tonnes.

The country consumed 140,000 tonnes vermiculite concentrate in 2013, down 12.5% year-on-year, according to the USGS.

Imports, which were mainly from South Africa and China, increased from 53,000 to 57,000 tonnes in 2012, but decreased by 26.4%, to 42,000 tonnes in 2013.

WR Grace, one of the major US producers, sold its vermiculite mine in Enoree, near the city of Woodruff, South Carolina, to its subsidiary Specialty Vermiculite Corp.

The company previously ran the biggest US vermiculite mine in Libby, Montana, until 1990, when it closed operations owing to asbestos contamination in the area. The company filed for reorganisation under Chapter 11 of the US bankruptcy code in 2011 to resolve its asbestos-related liabilities and emerged from bankruptcy at the beginning of 2014.

Virginia Vermiculite LLC mines vermiculite in Louisa County, Virginia, with an average production between 35,000 and 40,000 tpa, according to the Virginia Department of Mines, Minerals and Energy.

Brazil

Brazil is also an emerging producer of vermiculite resources, with estimated reserves of up to 16m tonnes, according to the USGS.

In 2011, Brazil accounted for 9.3% of global production, with about 55,000 tonnes, according to the National Department of Mineral Production (DNPM). Production was concentrated in the state of Goias (84%), followed by Pernambuco (8.2%), Paraiba (6.7%) and Bahia (1.1%).

Brasil Minerios is the main vermiculite producing company in Brazil, with mineral reserves in Sao Luis, Goias, amounting to 4m tonnes, of which 1.2m tonnes are vermiculite ore.

With the development of its second vermiculite deposit at the Catalao project, near the state of Minha Gerais, the company will reach estimated mineral resources up to 20m tonnes.

Jose Luis Fernandes, technical and sales manager at Brasil Minerios, told IM that vermiculite production at Morro Pelado mine in Sao Luis in 2013 amounted to 60,000 tonnes, of which 40,000 m3 was expanded vermiculite. Vermiculite products were 50% coarse and 50% fine grades, with sales in America (50%), Europe (35%) and Asia (15%).

With the additional development of its Catalao project, Brasil Minerios aims to expand its production capacity to 200,000 tpa in 2016, when production will start at Catalao.

Processing improvements

Exfoliation of vermiculite concentrate traditionally takes place in a blast furnace, through an energetically intensive process, with waste being up to 8% of product not completely exfoliated.

In 2012, Brasil Minerios developed a unique hybrid wash screen-dry winnower method, which leads to high quality products and cost-effective improvements in exfoliation.

“These beneficiation techniques were developed to process our kind of raw material using natural resources, like sunlight and water,” Fernandes told IM.

New advanced exfoliation methods are based on microwave power, reducing energy costs and guaranteeing a more uniform heating of all concentrate flakes.

UK-based technology solution provider, E2V Technologies, in collaboration with the National Centre for Industrial Microwave Processing at Nottingham, developed a microwave-based process to exfoliate vermiculite, Prowave, which achieves yields of 80g/litre bulk density, compared to 110g/litre in blast furnaces.

Prowave can produce up to 12.5m3/tonne exfoliated vermiculite, compared with 9.1m3/tonne generated in blast furnace.

As vermiculite is transparent to microwaves, the final product is cooler (150¡C) than that processed in a furnace, it can be packaged almost immediately.

According to the E2V, the microwave method can reduce energy consumption by 90% and cut carbon dioxide emissions by 85%.

Perlite in horticulture

Perlite is a glassy volcanic rock with a pearl-like sheen. The mineral is generally composed of around 71 to 75% silicon dioxide, 12.5 to 18% alumina, 4 to 5% potassium oxide and between 1 and 4% sodium and calcium oxides, as well as trace amounts of metal oxides.

Because of its low density composition and relatively low price, a variety of commercial applications have been developed for perlite including in construction, fillers, horticulture and filter aids. Although it can be replaced with other competitive commodities in all its applications, approximately 15% of perlite produced globally is used in horticultural aggregate applications.

Functioning in the much the same way as vermiculite in horticulture, perlite is often used as a soil amendment owing to its high permeability and low water retention properties.

Various materials can be added to soil as an amendment, enhancing physical properties such as water retention and infiltration, drainage, aeration, structure and permeability. Perlite is particularly suited to clay soils with low permeability, while vermiculite, with its high water retention properties, is more suited to sandy soils, which have low water retention attributes.

When perlite is processed, it is heated to temperatures of around 871¡C (1600¡F), causing the mineral to expand as its particles pop like popcorn, leaving an extremely lightweight, snow-white material. The expanded perlite product consists of closed air cells covered in cavities, creating a very large surface area. It is this property that enables the perlite particle to trap moisture, making it readily available to plant roots when needed. The shape of the particle also adds additional aeration and improves drainage.

Used in both small-scale gardening and commercial growing, perlite also lends itself well to soilless growing thanks to its neutral pH and the fact that it is weed free. It is also ideal for carrying fertiliser, herbicides, pesticides and seed pelletising, as well as for container growing.

Several other positive traits include the fact that the mineral is organic and does not deteriorate, it insulates against extreme soil temperature fluctuations and it is sterile, clean and odourless.

Global perlite production

USGS figures indicate that the US is the leading consumer of processed crude and expanded perlite in 2012, however new data indicates that Greece, Iran, and Turkey have been producing more perlite that the US since 2008.

Although no reliable data is available for China, Greece and Turkey are believed to be the largest perlite producers, both producing around 800,000 tonnes of perlite in 2013. The third largest perlite producer is Iran, which produced 500,000 tonnes in 2013. Though the majority of global production remained stable, the US saw its production decline slightly from 396,000 tonnes in 2012, to 376,000 tonnes in 2013.

The US imports all of its perlite from Greece, with the majority provided by S&B Minerals. According to the USGS, production in the US has been decreasing since 2011, while imports have also been in decline. The estimated value of crude perlite produced in 2013 is $21.1m, with production from eight mines operated by six companies and led by New Mexico.

The primary end use for perlite in 2013 was in building construction products, which consumed 53% of all of the mineral produced in the US last year. This was followed by fillers, accounting for 15% of consumption, horticultural aggregate with 14% and filter aid with 10%.

Processing perlite

Crude perlite for use in plaster aggregates ranges from between 60 mesh to 12 mesh, while crude perlite expanded for use in concrete aggregate applications, ranges from between 16 mesh to 100 mesh. The majority of perlite ore used in horticulture is greater than 20 mesh.

Perlite mining uses open-pit methods and is transported to the plant site for crushing and drying. A primary jaw crusher is used to reduce the diameter of the ore, which is passed through a rotary dryer to reduce the minerals’ moisture content to less than 1%. The material is then passed through a secondary grinding phase using a closed-circuit system consisting of screens, air classifiers and hammer mills.

The mineral is subsequently stored until it is ready to be expanded using horizontal rotary or vertical stationary expansion furnaces. The processed ore is preheated to around 430¡C, which reduces the amount of fines produced at this stage of processing, or it is fed directly into the furnace at the expansion plant, where it is heated to around 760¡C to 980¡C.

Heating the perlite at high temperatures causes the water in the mineral to be released as steam, and allows the particles to expand by 4 to 20 times their original size. Perlite particles are then collected from a cyclone classifier system, which enables them to cool as they are transported. As particles are collected, the cyclone classifier system removes the excessive fines and discharges gasses for air pollution control either using a baghouse or wet scrubber.

New processing facility in New Orleans

Despite an apparent 5% decrease of crude perlite bought or sold in the US in 2013, Governor Bobby Jindal and the CEO of IT Minerals LLC, Jose Domene, announced this month that the company is to invest $4.5m in Louisiana to establish a perlite importing, processing and exporting facility at the Port of New Orleans.

The company produces lightweight aggregates and fillers for polymer-based products, construction products, insulation, filtration, textile, cryogenic, horticulture and gardening products, and estimates that around 6,000 tonnes of product will be processed in the first year of operation. Processing is then expected to be ramped up to 12,000 tonnes in the second year.

“As we explored our options for setting up our new facility, we found one that offered all the conveniences we were looking for: energy, logistics, land and a friendly business environment,” Domene said, adding that he expects IT Minerals’ investment in the area to increase in the future.

The project, which will begin in the first quarter of 2014 and is expected to be completed by the third quarter, will enable the company to import raw materials from igneous rock quarries in north central Mexico by rail to Louisiana; the company already imports and processes raw minerals from Mexico, Brazil and South Africa.

Building a new processing facility at the Port of New Orleans will allow IT Minerals to add value to its imported perlite ore, which will then serve US markets, followed by the Caribbean and Central and South American markets.

The facility will use a natural gas-fired furnace processing method to heat and reform minerals at the plant for various applications, which will then be stored and prepared for export to commercial customers.



Perlite in filtration

US speciality minerals producer, EP Minerals, produces perlite for another niche application; the filtration market. The company commissioned a new perlite plant in the Midwest US in early 2014, allowing it to expand its business into new regions. In terms of sales, perlite accounts for around 5% of EP’s business, though its main focus is diatomite, followed by clay. The company sources perlite from its own deposits in Nevada, and has chosen to play a large part in a small area of perlite application, concentrating on uses in filtration.

“In terms of our existing plants and our new plant in Blair, it will be a growing part of our portfolio, and also because we’re filtration experts, perlite serves many end uses with the biggest in construction and horticultural applications, but we play in

a small space in perlite, which is filtration,” Gregg Jones, president of EP Minerals, told IM.

In some cases EP also acts as a distributor where it buys product from factories around the world and sells into filtration applications where the company has the technical knowledge to help the customer with the use of the product.

“There’s very specific processing that needs to be done to make it suitable for the filtration industry, so it’s fairly complex,” Jones told IM. “But what we know about the filtration industry gives us a unique advantage in terms of how to manufacture the product to make it suitable for its end use.”

In terms of the biggest demand drivers for perlite in filtration applications, Jones said that the mineral continues to find unique applications in the filtration area where it adds value to the end customer. In some more demanding filtration applications customers may opt for diatomaceous earth, while other customers find that perlite will add more value depending on what product is being filtered, where the customer is located and what kind of equipment the customer has.

“In the filtration space it’s more of a technical solution that drives the use of the product, and that’s where our expertise comes into play,” he told IM.

Towards the end of 2013, EP Minerals announced that prices of perlite and cellulose products would be increased affecting all regions. The price increases followed a similar announcement by fellow producer, Imerys.

Speaking to IM about the price increases, Jones explained: “It’s basically inflationary costs in our business whether it’s in the mining of the ore, just general costs, costs of energy, all the things we mentioned in our press release, but it’s basically just inflationary pressure we experience and we pass through to our customers.”

In terms of the outlook for perlite, EP Minerals expects to continue to see growth in business, which is why it has invested in its new perlite plant.

“Perlite is very much of a local business, meaning you can’t ship it very far because of its light density, so you tend to service a local market close to the expander. The expander in the Midwest is going to give us a nice opportunity for our business and we will continue to focus on the sale of the product around the world,” Jones said.