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Biotechnology has emerged as an affordable, effective, and eco-friendly alternative to treat carbon disulfide ([CS.sub.2]) containing waste gases. Carbon disulfide is a chemical of widespread use both in the past and in the present. Its industry demand has dramatically changed over the last two decades and is expected to grow in future in step with those industries involving fibre, mining, rubber products, and the agro-chemical sector. This compound, classified as a hazardous air pollutant about 20 years ago, has been re-appraised, as increasingly restrictive pollution standards are expected to be introduced. An array of physical-chemical technologies for treating [CS.sub.2] containing air are already in use, but they have a series of drawbacks, such as high energy consumption (incineration, thermal oxidation), the immobilization of the contaminant solely from one phase to another (adsorption), and the generation of secondary by-products that require additional treatment (hydrolysis). Thus, technological research on affordable processing alternatives is of considerable interest for related industries using or producing [CS.sub.2]. The biological technologies whose efficiency is based on the activity of microorganisms to biodegrade air pollutants overcome many of the disadvantages of conventional techniques and are especially useful for the removal of relatively low concentrations of pollutants. In this paper, the main properties, sources, and uses of [CS.sub.2] are summarized, and alternative biotreatments for [CS.sub.2] are reviewed. Several applications of the technical and economical feasibility of biofilters and biotrickling filters are shown, although their widespread industrial application still requires further research. Key words: carbon disulfide, bioreactors, air pollution control, biotechnology, industrial emissions. La biotechnologie devient une alternative abordable, efficace et eecologiquement acceptable pour traiter les deechets gazeux contenant du disulfure de carbone ([CS.sub.2]). Le [CS.sub.2] est une substance chimique d'utilisation tresrepandue dans le passe; aussi bien que presentement. Sa demande industrielle a fortement change; au cours des deux dernieeres decades et l'on s'attend a ce qu'elle prenne de l'expansion dans le future, de concert avec l'engagement de ces industries dans les secteurs de la fibre, des mines, des produits du caoutchouc et du secteur agrochimique. Ce compose, classified comme dangereux polluant de l'air il y a environ 20 ans a ete reeevalue, car on s'attend a l'introduction de nouveaux standards de plus en plus restrictifs de pollution. On utilise deja un ensemble de technologies physico-chimiques pour traiter l'air contenant du [CS.sub.2], mais ils preesentent des probleemes comme une forte consommation d'energie (incineration, oxydation thermique) l'immobilisation du contaminant uniquement d'une phase a une autre (adsorption) et la generation de produits secondaires qui neecessitent un traitement additionnel (hydrolyses). Ainsi, la recherche technologique de procedes alternatifs abordables presente un inteeret considerable pour les industries utilisant ou produisant du disulfure de carbone. Les techniques biologiques, dont l'efficacite est basee sur l'activite de microorganismes degradant les polluants de l'air, evitent plusieurs des desavantages des techniques conventionnelles et deviennent particulieerement utiles pour eeliminer les contaminants a faibles concentrations. Les auteurs passent en revue et reesument les principales proprietees ainsi que les sources et les usages du [CS.sub.2], et examinent les traitements biologiques alternatifs. On presente plusieurs applications de la faisabilite technique et economique des biofiltres et des filtres par biotrickling, bien que leurs applications industrielles generaliseees demandent encore des recherches. Mots-cles: disulfide de carbone, bioreeacteurs, controle de la pollution de l'air, biotechnologie, emissions industrielles. [Traduit par la Redaction], 1. Introduction Carbon disulfide ([CS.sub.2], CAS Reg. No. 75-15-0) is also known as carbon bisulphide or dithiocarbonic anhydride (ATSDR 1996). Carbon disulfide is a colourless to faintly yellow liquid. The [...]

ABSTRACT The question of how to obtain the best inocula for conventional biofilters arises when an acclimation/adaptation procedure is to be applied. Bearing in mind that no standardized procedure for [...]

Bioleaching is considered a sustainable and effective alternative to conventional micromachining and extracting processes for recovering valuable metals from electronic waste. Nevertheless, the industrial scaling-up of these applications is limited by several factors. Among these factors, the use of free cells and low microbial density have been reported to reduce process efficiency. Recent research has therefore focused on bacterial immobilization on different support materials as a solution for increasing microbial density inside the bioreactor and protecting microorganisms from toxic compounds. Furthermore, biomass immobilization facilitates biomass replacement whenever required. The increasing amount of metals in the solution is also a factor to be controlled, as it can inhibit bacterial activity. This study set out to assess the suitability of two hydrogels, polyvinyl alcohol (PVA) and biocellulose (BC) as support materials for Acidithiobacillus ferrooxidans (A. ferrooxidans) immobilisation, and to analyse the effectiveness of the active material generated for use in metal bioleaching processes. In addition, an assessment was conducted of the influence of the amount of dissolved copper (0-20 g Cu2+/L) on the time required for complete Fe2+ oxidation to Fe3+. The two hydrogels tested, PVA and BC, were viable as support materials for A. ferrooxidans immobilisation. Both active materials successfully transformed all the Fe2+ contained in the nutrient medium to Fe3+. Nevertheless, BC was specifically selected for further studies because of its higher efficiency (shorter oxidation time needed for complete iron transformation), longer integrity maintenance, and higher resistance to dissolved copper up to 20 g Cu2+/L. [ABSTRACT FROM AUTHOR]

Every innovation seeks to become a profitable business, with this considered to be the engine for economic prosperity. When an innovation is revolutionary, its long-term consequences can be revolutionary too. The Haber-Bosh process for ammonia synthesis is arguably the twentieth century’s most significant innovation, and its importance to global food production and its impact on the environment are not expected to diminish over the coming decades. The historical case of the ammonia synthesis process invented by Fritz Haber and the ensuing innovation provides an incomparable opportunity to illustrate the interactions across contemporary needs, prominent scientists, political concerns, moral dilemmas, ethics, governance and environmental implications at a time when the concept of sustainability was still in its infancy. Despite its high economic and environmental costs, no cleaner or more efficient sustainable alternative has so far been found, and so replacing this “old” innovation that still “feeds” a large part of the world’s population does not appear to be on the cards in the near future. [ABSTRACT FROM AUTHOR]

The use of microorganisms to remove metal from a workpiece is known as biological machining or biomachining, and it has gained in both importance and scientific relevance over the past decade. Conversely to mechanical methods, the use of readily available microorganisms is low-energy consuming, and no thermal damage is caused during biomachining. The performance of this sustainable process is assessed by the material removal rate, and certain parameters have to be controlled for manufacturing the machined part with the desired surface finish. Although the variety of microorganisms is scarce, cell concentration or density plays an important role in the process. There is a need to control the temperature to maintain microorganism activity at its optimum, and a suitable shaking rate provides an efficient contact between the workpiece and the biological medium. The system’s tolerance to the sharp changes in pH is quite limited, and in many cases, an acid medium has to be maintained for effective performance. This process is highly dependent on the type of metal being removed. Consequently, the operating parameters need to be determined on a case-by-case basis. The biomachining time is another variable with a direct impact on the removal rate. This biological technique can be used for machining simple and complex shapes, such as series of linear, circular, and square micropatterns on different metal surfaces. The optimal biomachining process should be fast enough to ensure high production, a smooth and homogenous surface finish and, in sum, a high-quality piece. As a result of the high global demand for micro-components, biomachining provides an effective and sustainable alternative. However, its industrial-scale implementation is still pending. [ABSTRACT FROM AUTHOR]

A laboratory scale bioreactor has been designed and set up in order to degrade hydrogen sulfide from an air stream. The reactor is a vertical column of 7 litre capacity and 1 meter in height. It is divided into three modules and each module is filled with pellets of agricultural residues as packing bed material. The gas stream fed into the reactor through the upper inlet consists of a mixture of hydrogen sulfide and humidified air. The hydrogen sulfide content in the inlet gas stream was increased in stages until the degradation efficiency was below 90%. The parameters to be controlled in order to reach continuous and stable operation were temperature, moisture content and the percentage of the compound to be degraded at the inlet and outlet gas streams (removal or elimination efficiency). When the H2S mass loading rate was between 10 and 40 g m-3h-1,the removal efficiency was greater than 90%. The support material had a good physical performance throughout operation time, which is evidence that this material is suitable for biofiltration purposes. [ABSTRACT FROM AUTHOR]