Biohydromet '14 Conference Diary

Biohydromet '14 was held at the St. Michael's Hotel, Falmouth, Cornwall from June 9-11, 2014. Two years ago, Biohydromet '12 was held in Falmouth, and in their summary of the conference MEI consultants Patrick d'Hugues, Sue Harrison and Chris Bryan felt it evident that bioheap leaching is one of the main targets for R&D and industrial applications, but tank leaching still has an important role. They highlighted the great potential for the use of biotechnology in the processing of secondary resources such as mine wastes and waste electronic equipment, and noted that emphasis should be given to co-processing of primary and secondary resources, as mining and recycling should not be seen as competitors.

Personally I found Biohydromet '12 to have been a very special conference, as it came at a time when rapid advances in our understanding of the science of microorganisms had in effect awoken biohydrometallurgy from its long slumber, looking as though it might start to realise its true potential and provide real benefits to the minerals industry. So we looked forward in anticipation to Biohydromet '14 to assess whether the hopes and aims of two years ago had been realised.

Monday 9th June

After thanking our sponsors, FLSmidth and International Mining, I welcomed the 65 delegates from 21 countries this morning and then handed over to Chris Bryan, of University of Exeter, one of our consultants, who summarised the last conference and looked ahead to what we have in store in the next few days. He remarked on what a pleasure it was to see so many of the big names in biohydrometallurgy - what a guest list!
Biohydrometallurgy is becoming more important in the minerals industry, accounting for the processing of over 15% of global copper and 3% of gold and there are some very exciting developments and planned operations, many in Europe. There are new applications to a wider range of resources and biohydrometallurgy is becoming important for the processing of wastes, and reprocessing of tailings. The future of biohydrometallurgy is therefore surely bright.

Barrie Johnson of Bangor University, UK, then got the conference off to a fine start with his keynote lecture on the potential use of bacteria to extract metals from oxidised ores. Biomining is traditionally practiced to accelerate the oxidative dissolution of sulphide minerals, but recent work has demonstrated that many acidophiles can accelerate the reductive dissolution of ferric iron minerals, such as goethite. This could be used to extract metals from oxidised ores, such as laterites and manganese nodules, at low (ca. 30°C) temperatures.

Barrie was also co-author of the second paper of the morning, presented by his colleague Rose Jones, who discussed the potential of a novel acidophilic bacteria for remediating metal-rich mine waters. A presentation by Suzanne Rea, of Australia's CSIRO, on the application of salt-tolerant bioleaching microbes for mining operations where fresh water is scarce, then took us to the morning coffee break.

Bangor University's Carmen Falagan, Barrie Johnson and Rose Jones,
with Patrick Nee of Universal Bio Mining, USA

Chiachi Hwang of Montana State University showed, by example of a spent gold heap leach, that a better understanding of the interactions between microbes and the local environment will allow improved design of in situ engineering configurations that stimulate microbial activities for more efficient metal recovery and subsequent site closure. Sabrina Hedrich, of the Federal Institute for Geosciences and Natural Resources, Germany, then discussed the abandoned Rammelsberg mine in Germany, an exploited ore deposit rich in zinc, lead, copper and silver, showing how it provides a potential habitat for microorganisms relevant in biomining.

Chiachi Hwang discusses the poster of Ioannis Vyrides
of Cyprus University of Technology

Prior to lunch, three papers dealt with various aspects of bioleaching. Currently more than 90% of the world’s copper is obtained through sulfide mineral processing. Among the copper sulfides, chalcopyrite is the most abundant and therefore economically more relevant, though averse to chemical leaching. Roberto Bobadilla-Fazzini of BioSigma S.A., Chile showed how Sulfobacillus thermosulfidooxidans strain Cutipay enhances chalcopyrite bioleaching under moderate thermophilic conditions in the presence of chloride ions. Yair Farber of the Israel Institute of Technology then discussed the bioleaching of silicate minerals by the soil bacterium Bacillus mucilaginosus under Fe-limited conditions.

Yair Farber (centre) with Dave Dew and Paul Norris (UK)

Arevik Vardanyan with Ioannis Vyrides

Arevik Vardanyan is our first ever delegate from Armenia and she presented the last paper of the morning, on behalf of the Institute of Microbiology, Armenia. The exceptional diversity of the ecogeographical conditions of Armenia and the richness of non-ferrous metals represent a great and valuable potential for investigation of the biodiversity of acidophilic chemolithotrophic bacteria as well as for isolation of new highly active strains and their communities. New acidophilic chemolithotrophic bacteria have been isolated from the Tandzut polymetallic ore of Armenia which are able to oxidize sulphur and its reduced compounds in the range of temperatures 20-400C. The isolated bacteria are able to oxidize copper concentrates only in association with Leptospirillum spp. bacteria.

The afternoon session began with two papers from the University of Cape Town (UCT). Rob van Hille discussed the effect of thiocyanate on BIOX® organisms and Sue Harrison the effect of acid stress on selected mesophilic bioleaching micro-organisms, which is critical during the start-up of heap bioleaching. Stoyan Gaydardzhiev of the University of Liege, Belgium, then presented observations on the bioleaching of carrolite with a mixed culture of acidophilic bacteria.

A further paper from UCT, presented by Rob Huddy, provided an insight into the building blocks of the Metallosphaera hakonensis biofilm. The results highlighted the differences in the thermophilic mineral-microbial-interfacial environments created as a function of inoculation conditions and across tank and heap bioleach systems for processing mineral sulphides.

Rob Huddy, Rob van Hille and Sue Harrison

The last paper of the day was presented by Fabian Giebner of the TU Bergakademie Freiberg, Germany who introduced three new methods to quantify biomass and activity of microbial leaching cultures.

After a quick coffee, it was time to unwind and network, with the usual 6 mile coastal path walk, ending up, slightly damp at Falmouth's 17th century Chain Locker pub, where many delegates sampled real Cornish ale for the first time (see also posting of 9th June).

At Swanpool Beach

At the Chain Locker

Tuesday 10th June

For some years now biohydrometallurgy has been one of the process options evaluated by the mining industry for base metal sulfide and sulfidic-refractory precious metal projects. However, the difficulties of process selection are increasing substantially, because of declining ore grades, complex mineralogy, deep deposits, and environmental and societal pressures. Biohydrometallurgy is likely to play an increasing role in future mines, because the technology offers various processing methods and there is opportunity for innovation. Corale Brierley, one half, with husband Jim, of Brierley Consultancy LLC, USA delivered a fine keynote this morning highlighting how it is the obligation of researchers and practitioners of biohydrometallurgy to create new application approaches and to innovate methods effective in bioprocessing ores of the future. Her presentation looked at the mines of the future and addressed how advances in biohydrometallurgical processing might be commercially used.

She based her presentation on the bioheap leaching of copper ores, and highlighted some interesting facts, such as that 50% of all copper mined in the world was in the last 25 years, and that 18-20% of global copper production is now by bioleaching. She stressed that the growth in renewable energy is set to dramatically increase copper use.

Corale Brierley with Pieter Van Aswegen, Jim Brierley and Jan Van Niekerk

The keynote provided a perfect curtain-raiser to a day of excellent presentations discussing innovations in biohydrometallurgy.

Chalcopyrite (CuFeS2) is the most abundant copper-containing mineral in the lithosphere, but is known to be highly recalcitrant to effective bioleaching. Often only 20-30% of its copper content is leached by conventional bioleaching bacteria, though it has been shown that more efficient extraction can be achieved at elevated temperatures (~80°C) or low redox potentials (EH ~650 mV). Although copper occurs as Cu(I) and iron as Fe(III) in chalcopyrite, little attention has been given to redox transformations of these two metals that occur during (bio)leaching, so it was interesting to hear Carmen Falagan, of Bangor University, UK discuss her work on the bioleaching significance of copper speciation during the abiotic and microbial dissolution of chalcopyrite.

Sue Harrison of UCT, South Africa then discussed the effect of physicochemical conditions on the growth and activity of Acidithiobacillus ferrooxidans on low grade chalcopyrite ore, with particular emphasis on heap leaching systems, where quantifying microbial growth and activity in both the flowing solution and in the mineral associated phases is important.

Sabine Kutschke of the Helmholtz-Institute Freiberg, Germany, took us up to the coffee break by describing the German-French project EcoMetals, which focuses on metal production from Cu- bearing primary and secondary resources in Europe. The objectives are the development of alternative methods in mineral processing involving biohydrometallurgical methods, their up scaling, the determination of economical and sustainable performances, the demonstration of bioprocesses for treatment of mineral processing wastes, and the life cycle assessment as well as the sustainability assessment for the proposed technologies.

Sabine Kutschke (right) with Fabian Giebner
and Simone Schopf of TU Bergakademie Freiberg

Finland is one of the largest gold producers in Europe. In Finnish ores, gold is often inside sulphide crystal lattices and requires pretreatment prior to cyanide leaching. Bio-oxidation is a pretreatment process that improves gold availability to cyanidation and thus results in economic and environmental savings in the overall process, as described by Sarita Ahoranta of Tampere University of Technology, Finland.

Lucy McTaminey with Amanda

Europe is increasingly looking at its own mineral reserves as a route to supply independence. However, given extensive historic mining activity, remaining ore deposits tend to be complex and low grade. Therefore, increasingly sophisticated processing options are required. Lucy McTaminey of Camborne School of Mines, UK described how a complex sulphide ore containing arsenopyrite in tight association with sphalerite was targeted. Fine grain chalcopyrite was disseminated within the sphalerite matrix, a condition known as chalcopyrite disease. Bioleaching tests were devised to test the ability to selectively leach the zinc at low temperature.

Sophia Kostudis is wired up
for her presentation

Following on from this Sophia Kostudis of the Helmholtz Institute Freiberg, Germany described the heterotrophic bioleaching of the German Kupferschiefer copper ores, which are not amenable to leaching due to their high carbonate content, using microorganisms adapted to mid and higher pH ranges.




In heap bioleaching processes, air is often injected into the heap to accelerate the leaching efficiency. Chen Bowei of the General Research Institute for Nonferrous Metals, China, described how simulated heap bioleaching of a pyritic chalcocite ore was conducted at 40 °C with elevated CO2 and N2. The results indicated that the limitation of oxygen could change the bioleaching microbial community and the elevation of CO2 and N2 is favourable for the growth of sulphur-oxidizer and iron-oxidizer separately, which could be used for the regulation of the role of microorganisms in mineral bioleaching.

Chen Bowei (right) with co-authors Li Wenjuan and Yang Limei

Following lunch, Paul Norris, of the University of Exeter, discussed the influence of anoxic conditions on mineral sulfide ore bioleaching, with emphasis on heap leaching, where excessive iron precipitation could affect the access of leaching solution to mineral surfaces and impact channelling.

The use of oxygen is a well-known practice in high-temperature bioleaching reactors, whereas air is usually preferred in medium and low-temperature operations. Anne Guezennec, of BRGM, France, described an investigation of the use of oxygen-enriched atmospheres in bioleaching reactors at 40°C in order to improve the global heat balance of the system.

Mondo Minerals is the world’s second largest talc producer and owns two talc mines, namely Sotkamo and Vuonos, in central Finland. Mariekie Gericke, of Mintek, South Africa, discussed the option to use bioleaching for the production of nickel as a metal hydroxide product (MHP) from nickel-cobalt-arsenic containing flotation by-products of the talc industry. The results show that nickel and cobalt recoveries in excess of 95% could be achieved and that stable iron and arsenic precipitates and good quality MHP could be produced.

Mariekie Gericke with co-authors Pieter Van Aswegan of PMet Consulting,
South Africa and David Dew of Dewality Consultants, UK

An interesting day concluded with a paper from Nadja Gelhaar of TU Bergakademie Freiberg, Germany on the effect of different media-compositions on sphalerite bioleaching.

After a quick coffee it was the long, but worthwhile, coach ride to St. Austell for the conference dinner at the world famous Eden project (see also posting of 11th June). We were privileged, as usual, to have exclusive use of the Eden Project with dinner in the Mediterranean biome, used in filming of the 2002 James Bond film Die Another Day.

Wednesday 11th June

Jan van Niekerk, of BIOMIN, South Africa, opened a day containing an interesting eclectic mix of papers. BIOMIN has been successfully delivering the BIOX® process, for the treatment of refractory gold concentrates for over two decades. To date 12 successful BIOX® plants have been installed in 8 countries spanning 4 continents, confirming the technical and commercial viability of the process. BIOMIN introduced a second technology in 2010, the ASTER^TM process, for the biological destruction of cyanide and thiocyanate. Two commercial ASTER^TM plants are currently in operation in South Africa and Kazakhstann. Jan showed how the delivery of a successful commercial biooxidation project is dependent on the integration of the technology with the specific requirements of the project.

Jan's paper was followed by an interesting presentation by Naoko Okibe, of Kyushu University, Japan, who discussed the biooxidation of Alaskan refractory gold ore concentrates containing arsenopyrite and pyrite as major sulfide mineral components. The role of individual microbes in biooxidation cultures containing toxic As(III) was discussed.

Naoko Okibe (right) with Sabrina Hedrich at Eden Project

Stoyan Gaydardzhiev of the University of Liege, Belgium discussed the possibilities for Co(III) dissolution from a cobaltiferrous copper ore ore through simultaneous bioleaching of pyrite. A bacterial consortium involving three different acidophilic chemolithotrophs was adopted for the pyrite bioleaching and the concentration of ferrous iron was found to be a key factor for cobalt solubilisation.

Stoyan Gaydardzhiev (right) with Chris Bryan and Arevik Vardanyan

From 1942 to the ‘60s, oil was produced by pyrolysis of shale in Kvarntorp, Sweden. This generated some 40 million m3 of metal rich pyrolysed shale and discarded fines that were piled on site. Viktor Sjöberg of Örebro University, Sweden presented the results of a study focusing on a low cost heterotrophic leaching of vanadium, manganese, iron and molybdenum from the fines by addition of woodchips and steel slag in outdoor 1 m3 reactor systems at low liquid to solid ratio.

Viktor 2nd right at last nights Eden dinner with Clara Costa
and husband Joao and Ann Grandin

After the morning coffee break Patrick d'Hugues of BRGM, France discussed the co-processing of sulfidic mining wastes and metal-rich post-consumer wastes by biohydrometallurgy and Jarno Mäkinen, of VTT Technical Research Centre of Finnland, the effect of pre-treatment and parameters for bioleaching of printed circuit boards, important as a large amount of WEEE is generated nowadays, with only limited technologies available for recovering valuables from this waste.

Patrick D'Hugues (right) with Cecile Leycuras, Neilish Syna and Paul Norris

Two papers on the use of biotechnology in froth flotation took us to the lunch break. Previous work from the Pontifical Catholic University of Rio de Janeiro, Brazil has demonstrated the effectiveness of bacterial strains as flotation reagents on hematite beneficiation, and Mauricio Torem discussed the evaluation of Rhodococcus ruber as a biocollector, showing that, due to its high hydrophobic properties and fast bacterial growth, it is a potential bioreagent in the iron flotation industry.

Amir Nazari, of McGill University, Canada, then introduced work on the flotation of copper-loaded hydrophobic bovine serum albumin-coated bubbles. Copper adsorption was carried out using a novel technique where a stable colloidal system containing microscopic protein-coated bubbles (less than 10 microns) is dispersed through the aqueous solution, resulting in increasing both specific surface area and contact time between extractant and metal ions. Column flotation, a mature method used to float hydrophobic minerals, was then adopted to remove the microbubbles by means of attachment to the surface of larger air bubbles.

Jon with Amir Nazari and co-author Kristian Waters at Falmouth's Chain Locker

Three papers on the removal of arsenic from mine waters followed the lunch break, and brought the technical sessions to an end.

The discharge of As-containing acid mine drainage may cause contamination of water sources with heavy metals, and Anna Kaksonen, of CSIRO Land and Water, Australia discussed the biotreatment of As-containing acid mine drainage using sulfate reducing granules in an upflow anaerobic sludge blanket reactor.

Anna (right) and colleage Suzy Rea enjoying the steamy Rain Forest at Eden with Marieke Gerieke

In gold mining, arsenic often co-occurs with ammonium deriving from the degradation of cyanide used for gold recovery. Stefano Papirio of Tampere University, Finland, introduced work assessing the feasibility of maintaining nitrification in the presence of arsenic. Candidatus Nitrospira defluvii and other species belonging to Nitrospirae were the main nitrifying microbial species, tolerating high As levels and making nitrification a potent process for ammonium oxidation in mining waters. A further paper from Tampere University, presented by Sarita Ahoranta, discussed the sorption of arsenic onto biogenic iron precipitates from mining waters.

Sarita Ahoranta and Stefano Papirio with Jarno Makinen (left) 

The finale to the conference was an excellent panel discussion on the future of biohydrometallurgy, chaired by MEI Consultants Patrick D'Hugues of BRGM France and Sue Harrison of University of Cape Town, with panellists Pieter Van Aswegen of PMet Consulting, South Africa, Paul Norris of University of Exeter, UK, and Jim Brierley of Brierley Consultancy, USA. This one hour session covered many important aspects of the future role of biohydrometallurgy, and these will be highlighted in future blog postings.

Panellists Paul, Jim and Pieter

This has been a superb conference with a fairly small but very distinguished audience from academia, research institutions and industry, with a wide range of different disciplines. Sue Harrison summarised the conference, which has covered innovative technologies and the challenges for existing processes, including important trends, such as expanding the range of minerals treated by biohydrometallurgy. The biotreatment of tailings and WEEE is also becoming more important, as are remediation and water issues. One of the great challenges is transferring scientific developments from academia into industry, concerns which have been expressed at other recent MEI Conferences. She also felt that in future conferences we must address not only technological, but also social issues.

Things are obviously changing rapidly in biohydrometallurgy, which is set to become a very important part of the mineral processing toolbox. So we look forward now to Biohydromet '16, which will be held in Falmouth again in June 2016.

The Proceedings from Biohydromet '14 are available from MEI, and selected papers will be published in a special Biohydrometallurgy issue of Minerals Engineering after peer-review.