The Design Process: Environmental Management in Design – Do More with Less

In the final article in his series aimed at giving new graduates a better understanding of the current design process, Tom Baxter reviews common standards and discusses the most obvious opportunities to boost sustainability during your future industrial design projects

AS A NEW graduate you may well take responsibility for providing information on emissions management for a new or existing chemical plant. That responsibility will need a thorough understanding of the associated regulations.

Chemical plants are regulated by emission standards to minimise their environmental impact. In the UK, these standards are primarily enforced by the Environment Agencies in the home countries. The key regulations include:

Environmental Permitting Regulations (EPR)

• Chemical plants require an environmental permit that specifies emission limits for pollutants that could harm air, water, or soil
• Permits are issued based on best available techniques (BAT); plants must use the best technology available to minimise emissions within economic and technical constraints

Industrial Emissions Directive (IED)

• The Industrial Emissions Directive (2010/75/EU) applies across the European Union and was adopted into UK law before Brexit. It sets out mandatory emission limits and environmental management standards for large industrial installations

Air Quality Standards Regulations

• The Air Quality Standards Regulations 2010 establish national air quality objectives and specify acceptable concentrations for various pollutants, ensuring they do not exceed levels harmful to human health and the environment

Compliance and Monitoring

• Compliance with these regulations requires continuous emissions monitoring, periodic inspections, and reporting to the relevant environmental agency
• If plants exceed their permitted emission levels, they may face enforcement actions, including fines and, in severe cases, closure
  These standards are designed to protect public health and the environment while allowing the chemical industry to operate within safe and sustainable boundaries.

Compliance and Variability

• BAT-Associated Emission Levels are tailored to individual processes, meaning limits can vary slightly based on a plant’s technology and location
• Local conditions, such as air quality requirements in sensitive areas, may also lead to stricter standards

CO2 emissions in the UK are regulated through a combination of legislative acts, trading systems (like the UK Emissions Trading Scheme (ETS)),¹ carbon pricing mechanisms, and sector-specific regulations. These frameworks aim to progressively reduce CO2 emissions, support low-carbon technology adoption, and achieve the UK’s net zero target by 2050.

Methane is a highly potent greenhouse gas, and emissions in the UK are regulated through a combination of sector-specific regulations and broader climate change policies. These regulations target key sources of methane, including the oil and gas industry, agriculture, waste management, and energy. With efforts to reduce methane emissions critical to meeting the UK’s climate goals, the government has established a regulatory framework aimed at curbing emissions through technological advancements, emissions trading, and best practices in various sectors.

There is much coverage of the role hydrogen will have in a net zero future. As a result of atmospheric interactions, hydrogen is also a global warming agent. There are currently no regulations in the UK that specifically target hydrogen emissions directly. There are several important regulations and policies that indirectly influence hydrogen-related emissions. These include:

• the UK’s Hydrogen Strategy promoting low-carbon hydrogen production
• The Climate Change Act and carbon budgets, which drive emissions reductions across the economy, including in hydrogen production
• carbon pricing mechanisms like the UK ETS, which encourage low-carbon hydrogen production technologies (green or blue hydrogen with CCS)
• health and safety regulations for hydrogen infrastructure to prevent leakage and associated emissions

Doing more with less

Now that the regulatory framework is understood we need to turn our attention to how can we work within the regulations to deliver chemical plants with an improved sustainability signature.

IChemE is aligned with the United Nations Sustainability Development Goal 12: “responsible consumption and production”. Of particular relevance to the chemical engineer is the caveat “doing more with less”.²

Figure 1 shows UK energy provision for pre-Covid 2017. Many of the concerning emissions are as a result of providing heat and power for industry, transport, and buildings.

A hugely important aspect of doing more for less is energy efficiency. Clearly if we use less energy, reduced harmful emissions is a consequence.

With respect to energy, the European Union sets out the following strategy:

“First, a more ‘circular’ energy system, with energy efficiency at its core, in which the least energy intensive choices are prioritised, unavoidable waste streams are reused for energy purposes, and synergies are exploited across sectors. This is happening already in combined heat and power plants or through the use of certain waste and residues. There is however further potential, for example, in reusing waste heat from industrial processes, data centres, or energy produced from bio-waste or in wastewater treatment plants.

“Second, a greater direct electrification of end-use sectors. The rapid growth and cost competitiveness of renewable electricity production can service a growing share of energy demand – for instance using heat pumps for space heating or low-temperature industrial processes, electric vehicles for transport, or electric furnaces in certain industries.

“Third, the use of renewable and low-carbon fuels, including hydrogen, for end-use applications where direct heating or electrification are not feasible, not efficient or have higher costs. Renewable gases and liquids produced from biomass, or renewable and low-carbon hydrogen can offer solutions allowing to store the energy produced from variable renewable sources, exploiting synergies between the electricity sector, gas sector and end-use sectors. Examples include using renewable hydrogen in industrial processes and heavy-duty road and rail transport, synthetic fuels produced from renewable electricity in aviation and maritime transport, or biomass in the sectors where it has the biggest added value.”

Principles 1 and 2 sit alongside doing more with less and, to my mind, they are a sound basis for a new chemical engineer to focus their thoughts.

Fresh minds

In your chemical engineering training, you have been given skills to establish energy usage and how to transform energy – heat to work and work to heat. Also, you should be familiar with the energy requirements of key items of equipment and unit operations. Furthermore, you will have been trained in the opportunities to use low-grade heat and apply heat integration techniques.

Let’s say you are working on the design for a chemical plant and the basis is a direct copy of a previous design. When there is a clear need to do more with less, you should ask, is a direct copy good enough? The industry needs graduates with fresh minds questioning custom and practice.

Although the energy consuming chemical industries seem very diverse, they all use the same items of equipment and unit operations.

Take pumps, ubiquitous across industry. According to the British Pump Manufacturers Association: “pumps are the single largest user of electricity within industry across the European Union, consuming over 300 TWh pa of electricity, which in turn accounts for over 65m t CO2”.³ Factor in a study of industrial facilities commissioned by the US Department of Energy (DOE)⁴ which found that “a pump’s efficiency can degrade as much as 10% to 25% before it is replaced”, and that “efficiencies of 50% to 60% or lower are quite common”. The DOE also states that “because these inefficiencies are not readily apparent, opportunities to save energy by repairing or replacing components and optimising systems are often overlooked” – it’s a no brainer, the chemical engineer must target energy efficient pumps, from our central heating boiler pumps to the massive pumps in industry.

Similarly with distillation. According to the DOE,⁵ distillation is a low thermal efficiency unit operation that consumes 40% of the processing energy used in refining and continuous chemical processes. A big target.

We put heat in at the bottom and take heat out at the top and there is tremendous scope for efficiency improvements in distillation. This can be achieved through heat integration, optimising reflux, efficient mass transfer devices, side heaters, using mechanical vapour recompression, and advanced control systems.⁶

Furnaces are also huge users of energy. Here you should be considering stack losses, air ingress, fuel to air ratio, and burner maintenance.
Compressors are also large energy users and the design of the compressor and how it is operated is key to delivering more for less. Often compressors are operated with unnecessary discharge recycling leading to unnecessary energy consumption.

For both pumps and compressors, the application of variable speed drives can deliver reduced energy consumption.

The list of energy saving opportunities are vast.

Many energy-saving opportunities are self-evident to chemical engineers. However, justifying them is another matter. Investment decisions will seek to find a balance between capital cost, operating cost, reliability; revenue, safety, and environment.

Herein lies the quandary. Many energy-efficient options result in more equipment, hence increased capital cost and more complexity. More complexity generally means more leak paths (making the plant less safe), more manpower, and reduced reliability. While energy reduction will generally reduce operating costs, discounted cash flow makes it much less important to the accountant. The upshot is that many energy-saving opportunities are difficult to justify.

In my view, how we put a price on environmental burden (EB), particularly greenhouse gas emissions, must change to allow the chemical engineer to deliver on more for less.

The IChemE Sustainability Working Group has produced an excellent document – “The sustainability metrics” – recommending sustainable progress metrics for use in the process industries.⁷ The publication introduces a set of indicators that can be used to measure the sustainability performance of an operating unit. These metrics help engineers address the issue of sustainable development. They also enable companies to set targets and develop standards for internal benchmarking, and to monitor progress year on year.

The section on environmental indicators is particularly useful. As shown, a potency factor of 1 is used for CO2 and other greenhouse gases have potency as a result of their CO2 equivalence. To my knowledge this has not been widely adopted by industry. I would also suggest that IChemE look to producing a bottom-up guidance document covering the energy-saving opportunities associated with the major unit operations and equipment that are common across our industries. That would give the new engineer a running start in identifying energy efficient options.

Finally, you can’t fail to notice that Figure 1 shows that we throw away more energy than we use. Now there’s a target for new graduates.

References

1. UK Emissions Trading Scheme markets: https://bit.ly/3B3Rqfb
2. UN SDGs: Goal 12: https://bit.ly/3CJthep
3. Optimising energy consumption in pumping systems - Plant & Works Engineering: https://bit.ly/3ZtCfV1
4. Test for Pumping System Efficiency; Industrial Technologies Program (ITP) Energy Tips - Pumping Systems Tip Sheet 4: https://bit.ly/49bRm9H
5. Douglas C White: Optimize Energy Use in Distillation, Chemical Engineering Progress: https://bit.ly/3CInHcm
6. TCE: Distilling Knowledge: Distillation Improvement Opportunities: https://bit.ly/4eV2TLP
7. IChemE: The sustainability metrics: https://bit.ly/4g3TOS2