A Perspective on Best Available Carbon (BAC) as Feedstock for the Chemical Industry

Biobased Chemicals

Author

Caroline Randall

Marketing Manager

The petrochemical industry is a significant global consumer of carbon and a notable producer of carbon emissions contributing to climate change. This report explores the potential for the industry to make a progressive move towards more sustainable carbon choices through the use of BAC.

Best Available Carbon for a More Sustainable Carbon Economy

Sustainability isn’t a destination, it’s a journey. Therefore, the concept of sustainable carbon is not a concrete definition of what carbon source is the most sustainable, but rather a developing and constantly evolving view of what would be described as ‘Best Available Carbon’ (BAC). BAC means the available carbon that could be used in manufacturing, which minimises GHG emissions and any other negative impacts on the environment, whilst also importantly maintaining the economic and technical viability of specific manufacturing processes. Although the focus is placed on CO2 emissions, the careful management of carbon is required to avoid undesirable and unintended knock-on consequences in other areas of planetary health, such as water availability, air and water pollution, toxicity and biodiversity. The idea of BAC sits within the established concept of ‘best available techniques’ (BAT), where advanced and proven techniques are used for the prevention and control of industrial emissions and wider environmental impacts caused by industrial installations. These available technologies have been developed to a scale that enables their implementation under economically and technically viable conditions. In a similar way, the concept of BAC should consider the economic and technical viability of the carbon sources required for specific manufacturing processes.

Through consideration of BAC there is the potential for the industry to make a progressive move towards more sustainable carbon choices.

Given that around 96% of all manufactured goods are currently reliant on chemicals, when chemical products inevitably become more sustainable in the future, there will be a huge multiplier effect, with downstream products benefiting considerably. The chemical industry could therefore be a hidden climate hero, as it has the potential to act as a key enabler for the defossilisation of many other industries.

Planetary Health Under Threat

The health of the planet we all call home is under threat, with Earth’s natural systems and boundaries increasingly breached on a daily basis.¹ Human health and well-being are intricately linked to the health of the planet, which is under threat from reduced air and water quality, climate change, biodiversity loss, and pollution from toxic materials.² At our present consumption rate, by 2050 three planets will be required to meet both our resource needs and to absorb our society’s waste.³

The climate emergency is one of the greatest societal challenges of our time, caused primarily by the human induced release of fossil-derived greenhouse gases into the atmosphere – with carbon dioxide (CO2) making up ~70% of all emitted GHGs.⁴ As GHG emissions continue to rise, so too does the temperature of the planet, causing wildfires, flooding, food scarcity, disease outbreaks and droughts.⁵

Global emissions of climate changing fossil GHGs must therefore be reduced by significant volumes, as quickly as possible.⁶

Carbon and Chemicals

Chemicals play a crucial role in modern life, and we are likely to encounter them every day – from the chemicals used at work, to products found at home e.g., paints, detergents, and pesticides for use in the garden.⁷ The chemical industry provides us with goods that we often take for granted and it is an essential part of the UK economy.

Currently, roughly 90% of the feedstocks used to make chemicals worldwide are derived from fossil resources, such as crude oil, natural gas and coal.⁸ As such, the chemicals and plastics sectors are responsible for up to 10% of global GHG emissions⁹,¹⁰, and given that emissions resulting from the use of fossil carbon are the main cause of anthropogenic climate change, there is a very real need to significantly reduce the impact of these industries on the planet. While the UK rightly emphasises the reuse and avoidance of fossil-based feedstocks, the chemicals and materials industries are inherently reliant on carbon-based feedstocks. Unlike the energy sector, the chemicals sector cannot be “decarbonised” – instead, this industry must be “defossilised”.

Hidden Emissions

The chemicals and downstream manufacturing industries use fossil carbon in three ways: (1) as a source of fuel for industrial heat and steam, and in the supply of electricity, (2) as a transport fuel to move raw materials and products from location to location, and importantly, (3) as a source of carbon atoms, in the form of feedstocks from coal, crude oil, and fossil (natural) gas to produce the tens of thousands of chemicals manufactured by the chemical industry.

It is widely recognised that the combustion of carbon as fuel, during transportation and manufacturing processes, results in the production of CO2 (a greenhouse gas), with well-known and studied implications for climate change.¹¹ Less recognised however, are the CO2 emissions associated with the use of carbon within manufactured products. This is known as ‘embedded carbon emissions’¹² and includes carbon that is released during the production of raw materials, through processing and transformations, and from the disposal of products after their use. In the context of the petrochemical industry, the carbon emissions associated with the use of carbon as a material vastly outweighs its use as fuel.

Best Available Carbon for a More Sustainable Carbon Economy

Sustainability isn’t a destination, it’s a journey. Therefore, the concept of sustainable carbon is not a concrete definition of what carbon source is the most sustainable, but rather a developing and constantly evolving view of what would be described as ‘Best Available Carbon’ (BAC). BAC means the available carbon that could be used in manufacturing, which minimises GHG emissions and any other negative impacts on the environment, whilst also importantly maintaining the economic and technical viability of specific manufacturing processes. Although the focus is placed on CO2 emissions, the careful management of carbon is required to avoid undesirable and unintended knock-on consequences in other areas of planetary health, such as water availability, air and water pollution, toxicity and biodiversity.¹³,¹⁴ The idea of BAC sits within the established concept of ‘best available techniques’ (BAT)¹⁵, where advanced and proven techniques are used for the prevention and control of industrial emissions and wider environmental impacts caused by industrial installations. These available technologies have been developed to a scale that enables their implementation under economically and technically viable conditions. In a similar way, the concept of BAC should consider the economic and technical viability of the carbon sources required for specific manufacturing processes.

Any view of carbon sustainability and ‘best available carbon’ sits within a consideration of carbon cycles, climate change, and the need to maintain a balance of carbon (in various forms) across the planet’s geosphere, biosphere, atmosphere and hydrosphere. The use of fossil resources extracted from the geosphere, ultimately results in the transfer of carbon in the form of CO2 into the atmosphere and hydrosphere, which cannot then be easily returned to the geosphere [Figure 1].

This transfer of carbon lies at the heart of climate change, with increasing concentrations of CO2 ultimately ending up in the Earth’s atmosphere.

Given the importance of petrochemicals and derived materials, around 96% of all globally manufactured goods are understood to contain petrochemical products. It is therefore unrealistic to expect that any significant reduction in petrochemical use will take place in the near future, regardless of how desirable it would be. On the contrary, the production of petrochemical-derived goods is in fact expected to increase significantly over the coming decades.

Figure 1. Current and future carbon flows

Petrochemical production takes place at large scale through mature value chains that are inextricably linked to the refining of fossil oil and gas. The scale and value of petrochemical production means that any change to established processes and raw materials will inevitably be a slow one. Therefore, it is foreseeable that fossil resources will continue to be the predominant source of carbon for the manufacturing of chemicals and materials for several decades to come.¹⁶

The development and deployment of carbon capture and storage (CCS) technologies¹⁷ can, to an extent, mitigate the fossil GHG emissions resulting from petrochemicals production. However, carbon leakage during CCS means that fossil carbon will continue to enter the atmosphere. It is also worth noting that the carbon emissions associated with the production of specific chemicals can be significantly influenced by feedstock choice (e.g. emissions associated with coal based methanol production can be three times higher than typical processes based on natural gas).18 Fossil carbon could therefore be a BAC source in the near- to medium-term, however, targets for reducing its use through research and technology development are essential.

Fortunately, alternative carbon sources also exist, and alternative carbon flows can be envisaged where carbon moves from the atmosphere (either directly, or via the biosphere) into the technosphere, where it is recycled as part of a circular economy. In addition to fossil carbon, BAC can be derived from three other sources, the atmosphere (atmospheric carbon), the biosphere (biogenic carbon) and the technosphere (recycled carbon) [Figure 2]. These alternative sources offer the opportunity to reduce, and even halt the extraction of fossil resources, preventing any additional fossil-derived GHGs from entering the atmosphere. The use of these resources means that carbon remains above ground, creating a circular carbon economy where feedstocks are regrown (as biomass from the biosphere), recycled, captured and utilised (as carbon in multiple forms from the technosphere), or extracted (as CO2 from the atmosphere).

Figure 2. Best Available Carbon

Significant quantities of carbon reside in the millions of tonnes of products that are already traded and used within the global economy, with ~400 million tonnes of plastics entering the economy each year.¹⁸ This carbon represents the potential from the recycling of chemicals and materials. Mechanical recycling reduces demand for virgin polymers, however when mechanical recycling is not possible, chemical recycling allows for the deconstruction of polymers back to starting feedstocks (e.g., chemical monomers or chemical feedstocks) which can then be turned back into useful chemicals. Although ideally avoided, technospheric carbon can be combusted or oxidised through chemical or biological processing, but carbon capture and utilisation (CCU) provides a means of preventing GHG emissions from entering the atmosphere and keeps carbon circulating throughout the economy.

Each form of recycling has its own merits and disadvantages and requires systemic approaches to ensure that the right feedstocks are used for different products and materials. Technospheric (recycled) carbon is widely accepted as a BAC category which will grow in importance.

However, despite the desire to develop a circular economy¹⁹ no recycling system can run perpetually, and the loss of some carbon via oxidation to CO2 to the atmosphere is inevitable. Additionally, not all chemical products can be recovered and recycled, as large volumes of carbon are lost during use (e.g. personal care, household cleaning products and total loss lubricants). Therefore, the chemical industry will require virgin (make-up) carbon, either extracted from the atmosphere or sourced in the form of biomass.

In terms of biomass, the use of carbon contained within the biosphere predates human civilisation, with plant and animal materials being used to construct shelters and provide clothing. The development of new chemistry, and in particular industrial biotechnology²⁰, results in increased opportunities to utilise biomass for the production of biochemicals and synthetic materials. The challenge in using biomass feedstocks, however, lies in ensuring that the volumes harvested do not damage our ecosystems’ ability to maintain their regulating and cultural services. Sustainably managed biogenic carbon constitutes an important renewable carbon source.

The final category of BAC is atmospheric carbon, where CO2 is extracted through direct air capture (DAC). While the direct capture of atmospheric CO2 essentially provides an unlimited supply of carbon for manufacturing, the effort, energy and financial cost of recovering such a dilute source of carbon from the atmosphere raises questions around the commercial viability of its use, and whether/when it could be a considered a BAC source.²¹, ²² Furthermore, the conversion of CO2 into the wide spectrum of chemicals currently manufactured by the chemical industry will require access to large volumes of low-cost, low-carbon electricity, which for the foreseeable future could instead be used in more efficient ways.

Assessing Best Available Carbon

Determining what constitutes BAC requires the careful consideration of multiple factors, addressing economic, environmental and social sustainability. Technoeconomic appraisal and lifecycle analysis are necessary to assess the range of impacts associated with each carbon source.

Each carbon source is chemically different, ranging from reduced fossil hydrocarbons, to oxidised carbon in CO2. Furthermore, biogenic carbon encompasses many forms, both chemically and physically – available as vegetable oil, carbohydrates, or as various components within lignocellulosic materials. Physically, biogenic carbon may be associated with high moisture materials, such as animal and food wastes, or may be available as relatively dry material, such as cereal grains. The appropriateness of each carbon source must be evaluated against its intended product and the subsequent conversion processes expected to be used.

BAC may also vary by geographic location. This is because the availability and impacts of a specific carbon source may vary by region, particularly if considering the use of biogenic carbon. Accessing biomass may be restricted by competing land requirements (e.g. for food or feed), or it may be constrained by environmental factors such as the need for irrigation. The use of CO2 feedstock is likely to be reliant on the availability of low cost, low carbon, renewable energy, and the availability of renewable electricity can vary by region (both due to a region’s ability to generate electricity, in addition to its electricity demand).

Final Remarks

The petrochemical industry is a significant global consumer of carbon and a notable producer of carbon emissions contributing to climate change. The majority of the petrochemical industry’s fossil carbon emissions do not result from energy consumed by the industry for the production of its products, but in the sourcing and disposal of its raw materials and products respectively. The disposal and treatment of petrochemical products is to a large extent beyond the control of the industry; however, the industry does have a level of control over the choice of its raw materials.

Through consideration of BAC there is the potential for the industry to make a progressive move towards more sustainable carbon choices.

Through the use of BAC, the carbon intensity of products can be reduced, and the use of sustainable non-fossil carbon eliminates the possibility of fossil carbon emissions being generated at the end of a product’s life.

Given that around 96% of all manufactured goods are currently reliant on chemicals²³,²⁴, when chemical products inevitably become more sustainable in the future, there will be a huge multiplier effect, with downstream products benefiting considerably. The chemical industry could therefore be a hidden climate hero, as it has the potential to act as a key enabler for the defossilisation of many other industries.

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