Microbubbles are famed for their large surface area-to-volume ratio, with the promise of intensification of interfacial phenomena, highlighted by more rapid gas exchange. However, for bioprocessing, it has been recognised for many decades that surfactant-rich fermentation media hinders mass transfer and possibly other interfacial processes due to surfactant loading on the interface. This article focuses on the roles of microbubble size and bubble bank, dispersed microbubbles that are sufficiently small to be non-buoyant, in mediating other modes of interfacial transfer via collisions with microorganisms and self-assembled clusters of microorganisms and microbubbles. These provide a more direct route of mass transfer for product gases that can be released directly to the microbubble with ~10⁴ faster diffusion rates than liquid mediated gas exchange. Furthermore, secreted external metabolites with amphoteric character are absorbed along the microbubble interface, providing a faster route for liquid solute transport than diffusion through the boundary layer. These mechanisms can be exploited by the emerging fields of symbiotic or microbiome engineering to design self-assembled artificial lichen dispersed structures that can serve as a scaffold for the selected constituents. Additionally, such designed scaffolds can be tuned, along with the controllable parameters of microbubble mediated flotation separations or hot microbubble stripping for simultaneous or in situ product removal. Staging the product removal thus has benefits of decreasing the inhibitory effect of secreted external metabolites on the microorganism that produced them. Evidence supporting these hypotheses are produced from reviewing the literature. In particular, recent work in co-cultures of yeast and microalgae in the presence of a dispersed bubble bank, as well as anaerobic digestion (AD) intensification with dispersed, seeded microbubbles, is presented to support these proposed artificial lichen clusters.

Sustainability has been one of the main issues in the world in recent years. The decrease of resources in the world, along with the growing world population and the resulting environmental waste, present a fairly significant problem. As an alternative solution to this problem, insects are put forward as an ideal resource. Due to the enzymes and microorganisms in their intestinal microbiota, the biotransformation processes of insects are capable of converting wastes, organic materials and residues into valuable products that can be used for various industrial applications such as pharmaceuticals, cosmetics and functional foods. Some species of insects are in an advantageous position because of the simplicity of their lifecycle, the ease of their production and their ability to feed on organic materials to make valuable products. From a sustainability perspective, utilisation of the microorganisms or enzymes isolated from these microorganisms available in the microbiota of insects may allow novel insect-based biotransformation processes that promise a more sustainable world and novel green technologies.

10.1595/205651323X16838888587238

Measurement and control of process temperature is key to maximising product quality, optimising efficiency, reducing waste, safety and minimising carbon dioxide and other harmful emissions. Drift of temperature sensor calibration due to environmental factors such as high temperature, vibration, contamination and ionising radiation results in a progressively worsening temperature measurement error, which in turn results in suboptimal processes. Here we outline some new developments to overcome sensor calibration drift and so provide assured temperature measurement in process, including self-validating thermocouples, embedded temperature reference standards, and practical primary Johnson noise thermometry where the temperature is measured directly without the need for any calibration. These new developments will give measurement assurance by either providing measurements which are inherently stable, or by providing an in situ calibration facility to enable the detection and correction of calibration drift.

Flame is a natural phenomenon and is a basic element of any combustion process. The majority of flames consist of a gas; there is, however, a small amount of ionisation occurring in the flame. Despite the increased focus on combustion-free energy production such as wind, air and water power, and the refocus on nuclear energy now considered to be carbon-free, nonetheless combustion will remain, for the next few decades, the major energy and heat production route worldwide. Apart from carbon dioxide, which is commonly considered to be the major pollutant, there are other gases like nitric oxide and nitrogen dioxide which, although found in significantly lower amounts in the exhaust gases from combustion units, still present a large environmental impact and are a concern. There are however well-established technologies for removing combustion products from the exhaust gas, and the combustion process can in general be made CO₂ and environmentally neutral. Combustion optimisation is a route for further reduction of undesirable byproducts, fuel consumption minimisation and finally an overall energy and heat production enhancement. The key parameter in any combustion process is reliable flame and (post-) combustion gas temperature measurement and control. Various combustion environments such as waste incineration, internal combustion engines or solids explosions cause the appearance of various optical emission features in different spectral ranges not accessible to the human eye. A combination of modern and newly developed fast spectral optical techniques with extensive theoretical developments in spectral and heat radiative transfer modelling allows us to obtain detailed snapshots of what is happening in the combustion process. That also gives a possibility to establish a direct link to the industrial process control and pollutant emission reduction. In this article some examples of in situ flame and gas temperature measurements in various combustion environments and advanced spectral modelling are given and perspectives for further commercial instrumentation developments are discussed.

Temperature is the most frequently measured process variable in almost all industrial sectors from the chemical industry to glass and ceramics, refrigeration and power generation. During many manufacturing processes, continuous temperature control is an important part of product quality assurance and a matter of avoiding malfunctions or detecting them at an early stage. Measuring points can be located at different places such as in containers, pipe systems, machines, ovens or reactors, whereby different gaseous, liquid or solid media, for instance, steam, water, oil or special chemical substances may be involved. In view of these extremely complex tasks, flexibility is one of the most important requirements for measurement technology and signal processing. And this is where thermocouples, which can be adapted to almost all measuring tasks due to their simple design, become relevant. The basic design and operating principle of thermocouples are described in this paper; issues relating to calibration, traceability and measurement uncertainty are addressed. Recent developments to improve temperature measurement with thermocouples are presented. New, drift-optimised thermocouples, novel designs and alternative calibration methods are described, and their advantages over conventional thermocouples or calibration methods are specified.

In May 2019 four of the seven base units of the International System of Units (the SI) were redefined and are now founded on defined values of fundamental physical constants. One of these was the kelvin which is no longer defined by the triple point of water but instead through a fixed value of the Boltzmann constant. In this paper the kelvin redefinition is introduced and the implications for temperature traceability and practical temperature sensing discussed. This will include outlining new approaches for temperature traceability, as well as discussing the rise of in-process calibration through practical primary temperature sensing approaches (where, in principle, no sensor calibration is required). These forthcoming changes are likely to have significant impact on everyone in the temperature calibration chain, whilst the advent of in-process temperature calibration should lead to step change improvements in process control, energy efficiency and product quality consistency and will help facilitate autonomous production.

Ammonia is a strong candidate as a hydrogen vector and has the flexibility to be used directly as a fuel or decomposed to form pure hydrogen. The format of an ammonia decomposition plant is only starting to emerge, with two types becoming significant: centralised locations feeding into the national gas network and decentralised units to supply fuelling stations, the chemical industry or remote applications. In this paper, we review the aspects critical to decompose ammonia in both cases. While the centralised cracking flowsheet can use equipment standard to current hydrogen production methods, the localised cracking unit requires a more innovative design. Energy and safety considerations may favour low temperature operation for decentralised applications, requiring high activity catalysts, while centralised industrial sites may operate at higher temperatures and use a base metal catalyst. Purification to deliver hydrogen suitable for fuel cells is one of the biggest challenges in developing the flowsheet.

This study aims to investigate the interactions between collagen and tanning processes performed by ecol-tan^®, phosphonium, EasyWhite Tan^®, glutaraldehyde, formaldehyde-free replacement synthetic tannin (syntan), condensed (mimosa) and hydrolysed (tara) vegetable tanning agents as alternatives to conventional basic chromium sulfate, widely used in the leather industry. Collagen stabilisation with tanning agents was determined by comparative thermal analysis methods: differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and conventional shrinkage temperature (T _s) measurement. Analysis techniques and tanning agents were compared and bonding characteristics were ranked by the thermal stabilisation they provided. Chromium tanning agent was also compared with the alternative tanning systems. The results provide a different perspective than the conventional view to provide a better understanding of the relationship between tanning and thermal stability of leather materials.

The principal possibility of processing the industrial poor collective concentrates of platinum group metals (pgms) using a hydrocarbonyl technology with the selective concentration of pgms from poor multicomponent chloride and chloride-sulfate solutions with the subsequent production of pure pgms is shown.

Industries face mounting challenges in the paradigm shift to a more circular economy. Research and development is increasingly focused on finding ways to turn waste into resources, recover energy and materials and make better use of resources extracted from the natural environment. At the same time industry and consumers seek to cause less harm in the form of pollution or CO2 emissions. In...

The recent increase in the number of policies to protect the environment has led to a rise in the worldwide demand for activated carbon, which is the most extensively utilised adsorbent in numerous industries and has a high probability to be used in the energy and agriculture sectors as electrodes in supercapacitors and for fertiliser production. This paper is about the production of activated biochar from oak woodchips char generated by an updraft fixed bed gasifier reactor. Following this, using steam as activating agent and thermal energy from produced synthesis gas (syngas), the resulting highly microporous carbonaceous biomaterial was subjected to physical activation at 750ºC. The properties of activated biochar include adsorption or desorption of nitrogen to identify the physical adsorption and surface area measurement, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The biochar surface area, generated as a result of the gasification process, showed substantial improvement after steam activation. Also, significant discrepancies were obtained from the surface volume and areas of biochar byproducts from the gasifier and activated biochar obtained by steam activation after the gasification treatment (total pore volume 0.022 cm³ g⁻¹ and 0.231 cm³ g⁻¹, Brunauer–Emmett–Teller (BET) surface area 21.35 m² g⁻¹ and 458.28 m² g⁻¹, respectively). The two samples also yielded noteworthy differences in performance. As a consequence, it may be concluded that the kinetics of steam gasification is quicker and more efficient for the conversion of biochar to activated carbon. The pore sizes of the carbon produced by steam activation were distributed over a wide spectrum of values, and both micro- and mesoporous structures were developed.

The manufacturing industry must diverge from a ‘take, make and waste’ linear production paradigm towards more circular economies. Truly sustainable, circular economies are intrinsically tied to renewable resource flows, where vast quantities need to be available at a central point of consumption. Abundant, renewable carbon feedstocks are often structurally complex and recalcitrant, requiring costly pretreatment to harness their potential fully. As such, the heat integration of supercritical water gasification (SCWG) and aerobic gas fermentation unlocks the promise of renewable feedstocks such as lignin. This study models the technoeconomics and life cycle assessment (LCA) for the sustainable production of the commodity chemicals, isopropanol and acetone, from gasified Kraft black liquor. The investment case is underpinned by rigorous process modelling informed by published continuous gas fermentation experimental data. Time series analyses support the price forecasts for the solvent products. Furthermore, a Monte Carlo simulation frames an uncertain boundary for the technoeconomic model. The technoeconomic assessment (TEA) demonstrates that production of commodity chemicals priced at ~US$1000 per tonne is within reach of aerobic gas fermentation. In addition, owing to the sequestration of biogenic carbon into the solvent products, negative greenhouse gas (GHG) emissions are achieved within a cradle-to-gate LCA framework. As such, the heat integrated aerobic gas fermentation platform has promise as a best-in-class technology for the production of a broad spectrum of renewable commodity chemicals.

A sustained global effort is required over the next few decades to reduce greenhouse gas emissions, in order to address global warming as society seeks to deliver the Paris Agreement temperature goals. The increasing availability of renewable electricity will reduce our reliance on fossil fuels. However, some applications, such as long-haul aviation, are particularly challenging to decarbonise. The conversion of waste, biomass or existing CO₂ emissions into sustainable fuels via Fischer-Tropsch (FT) synthesis offers one solution to this problem. This paper describes some of the challenges associated with this route to these alternative fuels and how Johnson Matthey and bp have solved them.

Biofilms in industrial cooling tower systems are an important problem. The importance of the surface material in the response to an oxidising biocide (chloramine T trihydrate) was substantiated in our study. Polyvinyl chloride (PVC) cooling tower fill material, stainless steel cooling tower construction material and glass surfaces were compared by evaluating the bacterial loads on materials before and after biocidal treatment. The greatest logarithmic decrease in bacterial load was recorded as >3 log for glass after the first two months and for PVC after the second month. Actively respiring bacterial counts and adenosine triphosphate (ATP) measurements showed that there was no significant difference in the sensitivity of biofilm-associated cells to the biocide on the different surfaces. In addition, the effect of the biocidal treatment decreased with increasing biofilm age, regardless of the material.

C123 is a €6.4 million European Horizon 2020 (H2020) integrated project running from 2019 to 2023, bringing together 11 partners from seven different European countries. There are large reserves of stranded natural gas waiting for a viable solution and smaller scale biogas opportunities offering methane feedstocks rich in carbon dioxide, for which utilisation can become an innovation advantage. C123 will evaluate how to best valorise these unexploited methane resources by an efficient and selective transformation into easy-to-transport liquids such as propanol and propanal that can be transformed further into propylene and fed into the US$6 billion polypropylene market. In C123 the selective transformation of methane to C3 hydrocarbons will be realised via a combination of oxidative conversion of methane (OCoM) and hydroformylation, including thorough smart process design and integration under industrially relevant conditions. All C123 technologies exist at TRL3 (TRL = technology readiness level), and the objectives of C123 will result in the further development of this technology to TRL5 with a great focus on the efficient overall integration of not only the reaction steps but also the required purification and separation steps, incorporating the relevant state-of-the-art engineering expertise.

A flexible combined heat, power and fuel production concept, FlexCHX, is being developed for managing the seasonal mismatch between solar energy supply and the demand for heat and power characteristic of northern and central Europe. The process produces an intermediate energy carrier (Fischer-Tropsch (FT) hydrocarbon product), which can be refined to transportation fuels using existing refineries. The FlexCHX process can be integrated into various combined heat and power (CHP) production systems, both industrial CHPs and communal district heating units. In the summer season, renewable fuels are produced from biomass and hydrogen; the hydrogen is produced from water via electrolysis that is driven by low-cost excess electricity from the grid. In the dark winter season, the plant is operated only with biomass in order to maximise the production of the much-needed heat, electricity and FT hydrocarbons. Most of the invested plant components are in full use throughout the year with only the electrolysis unit being operated seasonally. The catalytic reformer plays a key role in this process by converting tars and light hydrocarbon gases into synthesis gas (syngas) and by bringing the main gas constituents towards equilibrium. Developmental precious metal catalysts were used, and an optimal reformer concept was established and tested at pilot scale. Reforming results obtained at pilot gasification tests with commercial nickel catalysts and with the developed precious metal catalysts are presented.

PLATInum group metals Recovery Using Secondary raw materials (PLATIRUS), a European Union (EU) Horizon 2020 project, aims to address the platinum group metal (pgm) supply security within Europe by developing novel and greener pgm recycling processes for autocatalysts, mining and electronic wastes. The initial focus was on laboratory-scale research into ionometallurgical leaching, microwave assisted leaching, solvometallurgical leaching, liquid separation, solid phase separation, electrodeposition, electrochemical process: gas-diffusion electrocrystallisation and selective chlorination. These technologies were evaluated against key performance indicators (KPIs) including recovery, environmental impact and process compatibility; with the highest scoring technologies combining to give the selected PLATIRUS flowsheet comprising microwave assisted leaching, non-conventional liquid-liquid extraction and gas-diffusion electrocrystallisation. Operating in cascade, the PLATIRUS flowsheet processed ~1.3 kg of spent milled autocatalyst and produced 1.2 g palladium, 0.8 g platinum and 0.1 g rhodium in nitrate form with a 92–99% purity. The overall recoveries from feedstock to product were calculated as 46 ± 10%, 32 ± 8% and 27 ± 3% for palladium, platinum and rhodium respectively. The recycled pgm has been manufactured into autocatalysts for validation by end users. This paper aims to be a project overview, an in‐depth technical analysis into each technology is not included. It summarises the most promising technologies explored, the technology evaluation, operation of the selected technologies in cascade, the planned recycled pgm end user validation and the next steps required to ready the technologies for implementation and to further validate their potential.

The main objective of this study was to evaluate the performance of a self-developed filler micro-embedded with Pseudomonas putida (P. putida) for toluene removal in a biofilter under various loading rates. The results show that the biofilter could reach 85% removal efficiency (RE) on the eighth day and remain above 90% RE when the empty bed residence time (EBRT) was 18 s and the inlet loading was not higher than 41.4 g m⁻³ h⁻¹. Moreover, the biofilter could tolerate substantial transient shock loadings. After two shut-down experiments, the removal efficiency could be restored to above 80% after a recovery period of three days and six days, respectively. Sequence analysis of the 16S rRNA gene of fillers in four operating periods revealed that the highly efficient bacterial colonies in fillers mainly included Firmicutes, Actinobacteria and Proteobacteria and that the abundance of Bacteroidetes increased significantly during the re-start period.

Oil fields harbour a wide variety of microorganisms with different metabolic capabilities. To examine the microbial ecology of petroleum reservoirs, a molecular-based approach was used to assess the composition of bacterial communities in produced water of Diyarbakır oil fields in Turkey. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments was performed to characterise the bacterial community structure of produced water samples and to identify predominant community members after sequencing of separated DGGE bands. The majority of bacterial sequences retrieved from DGGE analysis of produced water samples belonged to unclassified bacteria (50%). Among the classified bacteria, Proteobacteria (29.2%), Firmicutes (8.3%), Bacteroidetes (8.3%) and Actinobacteria (4.2%) groups were identified. Pseudomonas was the dominant genus detected in the produced water samples. The results of this research provide, for the first time, insight into the complexity of microbial communities in the Diyarbakır oil reservoirs and their dominant constituents.