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Flow control for optimising growth of microorganisms

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01 Dec, 2024

This post was originally published on Sustainability Matters

Today, more than ever, enzymes and microorganisms are being used to increase sustainable production. This is particularly true in industries such as pharmaceuticals and (bio)chemicals. In these and other industries, researchers within universities, R&D organisations and other institutes, as well as within industry want to know under which conditions these biological cells grow. While it is essential and important to know how and under what conditions they grow faster, researchers need the full story. That means they are just as interested in what makes them grow slower or abnormally. It is also essential to learn about the influence of nutrients or additives to understand the underlying biological processes.

For research organisations the accurate measurement and control of low flows of liquids and gases is often required. What is low flow? The real values will be application dependent but might be as low as 0.014 to 0.7 mL/min of N2 to around 600 kg/h in liquid applications.

Bronkhorst excels in this arena and their customers are many and varied. In the area of biological cell growth, for one recent application the organisation sought to learn more about the conditions under which a population of microorganisms will grow. Flow control was used to give an accurate and steady flow of aqueous liquid while they varied an array of other parameters.

It was essential for them to investigate under which conditions a population of microorganisms can grow. For this they would vary one typical parameter, whilst other parameters, such as temperature, pressure and nutrient concentration, needed to be kept constant.

For this recent application, a research organisation contacted Bronkhorst. They had an application where they were struggling to stabilize the low flow in an aqueous stream — in this case their range was 30 to 200 mL/min. They had two reactors that needed to be kept in balance. They had tried to find a balance but were regularly emptying one of the reactors. To that end, their desire was that the liquid levels of two reactor vessels containing these microorganisms needed to be accurately and repeatably kept at a stable, constant value using flow control.

After consideration, Bronkhorst supplied two of their liquid mass flow instruments. In this case it was their mini CORI-FLOW series. The CORI-FLOW series uses the Coriolis effect which was first postulated as an explanation of the deflection of flowing air moving in a rotating system. In fact, the Coriolis effect is a mass inertia effect. A Coriolis-based mass flow meter is particularly suitable when you want to measure the mass flow of varying or unknown gas or liquid mixtures or for measuring supercritical gases. Besides measuring direct mass flows which eliminates inaccuracies due to the physical properties of the fluid, these devices are highly accurate and have a high repeatability. The Coriolis flow meter is the ultimate flexible, reliable and extremely accurate flow meter.

In this application, each CORI-FLOW was inserted in the circulation system in between the reactor vessels, with the aim to provide a continuous flow of aqueous liquid.

The main reactor was approximately 1 litre and the researchers allowed the micro-organisms to grow in the reactor within an aqueous environment. Regular sampling of the main reactor gave them information of the number of cells and the cell growth rate. The researchers also identified temperature as an important parameter. Too low temperatures will hold back the microorganisms and slow or stop them from growing, and too high temperatures are detrimental to the longevity of the microorganisms themselves.

For this sophisticated application, the liquid mass flow instrument with a control valve provides a signal to a control unit. That control unit is ‘in charge’ of a pump. The pump speeds or slows in response to the flow measurement and the control action, making for a very precise flow in this line. From there the liquid then flows from the main reactor to a second reactor. In this case the second reactor is much smaller than the main reactor and has a volume of about 200 mL. Using the same methodology, the fluid is again moved via the direct control pump scenario, described above, back to the main reactor. What is now set up is a continuous circulation, in which the flow is very steady. The process continues day and night for as long as the research requires.

While it sounds like smooth sailing, a further complication was identified. The microorganisms in this experiment were approximately 3 μm diameter. That provided a further challenge as all the microorganisms needed to be kept alive and they needed to be in perfect health (without any damage) during the process of circulation. For this Bronkhorst advised the researchers to use peristaltic pumps in their process to keep their microorganisms fit and healthy.

The Control Unit/s and setpoints were run within the research organisation’s systems; however, it was further determined that, in this application both the flow controller and pump combinations would best have the same capacities. This simplified the operation and helped the levels in both reactors remain at the same, stable value.

Bronkhorst’s flow meter range includes:

  • Thermal Mass Flow meters & controllers for gases and liquids
  • Coriolis Mass Flow Meters & Controllers for gases and liquids
  • Ultrasonic Meters for liquids
  • Pressure Controllers for gases and liquids
  • Control Valves and Control Electronica and accessories
     

In this case the correct flow meter was a Coriolis-based mass flow meter. This technology is particularly suitable when you want to measure the mass flow of varying or unknown gas or liquid mixtures or for measuring supercritical gases. The fundamental theory for a Coriolis meter is direct mass flow measurement. There are no estimations or assumptions or inaccuracies due to the physical properties of the fluid. A CORI-FLOW from Bronkhorst is thus highly accurate and they have high repeatability. For many users, the Coriolis flow meter is the ultimate flexible, reliable and extremely accurate flow meter.

The original article was published as an Application Note by Bronkhorst High-Tech B.V.

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Taking the electronic pulse of the circular economy

Taking the electronic pulse of the circular economy

In June, I had the privilege of attending the 2025 E-Waste World, Battery Recycling, Metal Recycling, and ITAD & Circular Electronics Conference & Expo events in Frankfurt, Germany.

Speaking in the ITAD & Circular Electronics track on a panel with global Circular Economy leaders from Foxway Group, ERI and HP, we explored the evolving role of IT asset disposition (ITAD) and opportunities in the circular electronics economy.

The event’s focus on advancing circular economy goals and reducing environmental impact delivered a series of insights and learnings. From this assembly of international expertise across 75+ countries, here are some points from the presentations that stood out for me:

1. Environmental impact of the digital economy

Digitalisation has a heavy material footprint in the production phase, and lifecycle thinking needs to guide every product decision. Consider that 81% of the energy a laptop uses in its lifetime is consumed during manufacture (1 tonne in manufacture is equal to 10,000 tonnes of CO2) and laptops are typically refreshed or replaced by companies every 3–4 years.

From 2018 to 2023, the average number of devices and connections per capita in the world increased by 50% (2.4 to 3.6). In North America (8.2 to 13.4) and Western Europe (5.6 to 9.4), this almost doubled. In 1960, only 10 periodic table elements were used to make phones. In 1990, 27 elements were used and now over 60 elements are used to build the smartphones that we have become so reliant on.

A key challenge is that low-carbon and digital technologies largely compete for the same minerals. Material resource extraction could increase 60% between 2020 and 2060, while demand for lithium, cobalt and graphite is expected to rise by 500% until 2050.

High growth in ICT demand and Internet requires more attention to the environmental footprint of the digital economy. Energy consumption of data centres is expected to more than double by 2026. The electronics industry accounts for over 4% of global GHG — and digitalisation-related waste is growing, with skewed impacts on developing countries.

E-waste is rising five times faster than recycling — 1 tonne of e-waste has a carbon footprint of 2 tonnes. Today’s solution? ‘Bury it or burn it.’ In terms of spent emissions, waste and the costs associated with end-of-life liabilities, PCBAs (printed circuit board assembly) cost us enormously — they generally achieve 3–5% recyclability (75% of CO2 in PCBAs is from components).

2. Regulating circularity in electronics

There is good momentum across jurisdictions in right-to-repair, design and labelling regulations; recycling targets; and voluntary frameworks on circularity and eco-design.

The EU is at the forefront. EU legislation is lifting the ICT aftermarket, providing new opportunities for IT asset disposition (ITAD) businesses. To get a sense, the global market for electronics recycling is estimated to grow from $37 billion to $108 billion (2022–2030). The value of refurbished electronics is estimated to increase from $85.9 billion to $262.2 billion (2022–2032). Strikingly, 40% of companies do not have a formal ITAD strategy in place.

Significantly, the EU is rethinking its Waste Electrical and Electronic Equipment (WEEE) management targets, aligned with upcoming circularity and WEEE legislation, as part of efforts to foster the circular economy. A more robust and realistic circularity-driven approach to setting collection targets would better reflect various factors including long lifespans of electronic products and market fluctuations.

Australia and New Zealand lag the EU’s comprehensive e-waste mandated frameworks. The lack of a systematic approach results in environmental degradation and missed positioning opportunities for businesses in the circular economy. While Australia’s Senate inquiry into waste reduction and recycling recommended legislating a full circular economy framework — including for imported and local product design, financial incentives and regulatory enforcement, New Zealand remains the only OECD country without a national scheme to manage e-waste.

3. Extending product lifecycles

Along with data security and digital tools, reuse was a key theme in the ITAD & Circular Electronics track of the conference. The sustainable tech company that I lead, Greenbox, recognises that reuse is the simplest circular strategy. Devices that are still functional undergo refurbishment and are reintroduced into the market, reducing new production need and conserving valuable resources.

Conference presenters highlighted how repair over replacement is being legislated as a right in jurisdictions around the world. Resources are saved, costs are lowered, product life is extended, and people and organisations are empowered to support a greener future. It was pointed out that just 43% of countries have recycling policies, 17% of global waste is formally recycled, and less than 1% of global e-waste is formally repaired and reused.

Right to repair is a rising wave in the circular economy, and legislation is one way that civil society is pushing back on programmed obsolescence. Its global momentum continues at different speeds for different product categories — from the recent EU mandates to multiple US state bills (and some laws) through to repair and reuse steps in India, Canada, Australia and New Zealand.

The European Commission’s Joint Research Commission has done a scoping study to identify product groups under the Ecodesign framework that would be most relevant for implementing an EU-wide product reparability scoring system.

Attending this event with the entire electronic waste recycling supply chain — from peers and partners to suppliers and customers — underscored the importance of sharing best practices to address the environmental challenges that increased hardware proliferation and complex related issues are having on the world.

Ross Thompson is Group CEO of sustainability, data management and technology asset lifecycle management market leader Greenbox. With facilities in Brisbane, Sydney, Melbourne, Canberra, Auckland, Wellington and Christchurch, Greenbox Group provides customers all over the world a carbon-neutral supply chain for IT equipment to reduce their carbon footprint by actively managing their environmental, social and governance obligations.

Image credit: iStock.com/Mustafa Ovec

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