Designing a Biomanufacturing Process to be Circular

Article by Sanchari Ghosh

Sanchari Ghosh highlights ten ways in which you can incorporate process circularity in biomanufacturing

BIOMANUFACTURING describes processes that use a biological aid to commercially produce bioproducts across a variety of applications such as food, fuel, pharmaceuticals, and consumer goods. Processes come in different shapes and forms, including microbial fermentation, enzymatic conversion, cell cultivation, and cellular agriculture. Using a feedstock and a biological conversion step that is less harmful and less emissions intensive than fossil fuel-based petrochemical processes, the environmental impact and commercial attractiveness of biomanufacturing can be further increased by incorporating principles of process circularity.

A circular process employs the four Rs – reusing, reducing, removing, and recycling – to efficiently use energy, raw materials, and other process inputs to minimise or eliminate harmful process outputs like waste and greenhouse gas emissions.

Figure 1: The four Rs of a circular process

However, implementing circular practices in biomanufacturing are complex and can be technically challenging. In addition, companies must also consider additional challenges such as the cost and length of time needed to set up circular technologies, maintenance and upkeep costs, and integration of resources within and outside the plant. Companies that can move forward and incorporate process circularity into biomanufacturing processes will be able to increase their positive impact on the environment, gain process efficiencies, and better utilise process input and output materials. Additionally, they will likely generate less emissions and waste, which will contribute towards minimising the carbon footprint and boosting process safety. Incorporating these processes may also help lower plant costs over time.

Here are ten ways to incorporate process circularity into biomanufacturing:

1. Heat integration

Heat integration makes a chemical plant more energy efficient by matching heat sources and sinks. It is an engineering tool commonly used during the development and optimisation of chemical processes. The principle of heat integration promotes process circularity by reusing energy that would otherwise be wasted. Heat integration has a cost trade-off because it lowers overall utility requirements but can also become capital intensive due to the use of more equipment like heat exchangers.

2. Plant co-location

Plant co-location is the practice of building a plant near to another plant to share resources. Co-location of a biomanufacturing facility can serve many different purposes, for example, for renewable energy integration, wastewater treatment, or feedstock production. Co-location of a plant makes a process more circular by reducing harmful greenhouse gas emissions and costs associated with transportation and storage of raw materials, utilities, or waste.

3 Raw material recycling

Recycling raw materials is a simple way to incorporate process circularity into biomanufacturing processes. Enabling recycling streams is a common method to optimise chemical processes by lowering raw material costs and enhancing product recovery. Used raw materials like water, which is typically heavily utilised during fermentation, or solvents, can be processed and recycled back to other process steps. Other raw materials like certain catalysts, membranes, and resins can be regenerated and reused for set periods of time.

4. Waste utilisation

Certain waste streams in a bioprocess can be reused to enhance circularity. One way is by valorisation or upgrading waste into a valuable product. Waste valorisation reduces the carbon footprint of the process but can become expensive depending on the process complexity of waste processing. Biomass wastes can be converted to other products or returned to the soil using a microbial consortium via bioremediation, with examples including anaerobic digestion and composting. Bioremediation is usually a lower-cost option compared to chemical or thermal treatments and promotes ecological diversity but has long and variable operating times and can be challenging to implement.

5. Product disposal

A biomanufacturing process that generates a product that will ultimately be returned to the environment after use. Biodegradation is a blanket term for the breakdown of a product into its components when it is disposed into the environment. The rate of biodegradation depends on the ease of decomposition of the product and can be enhanced by making it compostable, which is when a product is fully decomposed into organic components. An alternative for circular product disposal is by recycling it as feedstock or repurposing it to create another product. Composting or recycling a bio-based product reduces greenhouse gas emissions and the overall process carbon footprint and saves costs that would otherwise be needed for end-of-life disposal.

6. Sustainable process design

Sustainable process design of a biomanufacturing facility enhances process circularity by increasing process efficiency and reducing process steps and raw materials. Sustainable process design can be implemented in a variety of ways. For example, by designing process steps at similar temperatures and pressures so temperature and pressure step changes, and the equipment used to achieve them, are minimised. Another example is to minimise raw material inputs and instead repurpose existing process outputs. It might even be feasible to combine processing steps for consecutive unit operations depending on their complexity and operating conditions.

7. Carbon capture, utilisation, and storage (CCUS)

Sanchari Ghosh

Carbon capture is the process of removing existing or future CO2 from the atmosphere. CO2 can be captured directly from the air or from plant emissions, and either utilised or stored for future usage. The implementation of CCUS technologies in biomanufacturing processes can greatly improve process circularity by reducing or fully offsetting CO2 emissions or going one step further and becoming a carbon negative process. Some drawbacks of CCUS technologies are its high cost and technical complexity which can make it challenging to scale up. However, carbon capture technologies are becoming increasingly commercially attractive due to their effectiveness in removing CO2 from the atmosphere while being cost- and energy-effective.

8. Plant construction

Building greenfield (from scratch) biomanufacturing facilities are expensive and take a long time. Alternatives to building from the ground up are brownfield or retrofit projects that refurbish old facilities to fit a new process to an existing plant. These alternatives enhance process circularity by more sustainable land use and revitalising the local economy. However, such projects could still require long construction times, contain unsafe and contaminated property, and result in an increase in plant capital costs depending on the condition of the existing facility.

9. Co-production

Commercial biomanufacturing facilities are expensive to build and should be operated according to their processing capacity. One way to do so while reducing manufacturing costs is by co-producing multiple, low-volume products. Companies with modular processes can use the same facility to manufacture different products depending on customer demand, or even share a facility with another company that uses similar bioprocessing steps. Such strategies promote process circularity by reutilising finite resources like land and equipment and reducing/removing the plant’s idle time.

10. Feedstock choice

Feedstock choice in a biomanufacturing process should be intentional to maximise environmental and economic benefits and minimise pre-processing costs. The use of recycled and waste/circular feedstocks promotes process circularity by repurposing renewable resources and lowering emissions and costs associated with fresh feedstock processing and handling steps. Using a combination of feedstocks in a bioprocess has the potential to introduce circularity by reutilising resources that would otherwise be wasted and benefits the process by reducing supply chain dependency. However, multiple feedstock utilisation is a challenging strain and process engineering endeavour, and feedstock variability could impact process performance depending on its quality and composition.

Examples at work

Raízen, the world’s largest producer of sugarcane ethanol, produces ethanol and bioenergy from a waste feedstock and converts process byproducts to biogas via anaerobic digestion.

Archer Daniel Midlands (ADM), another key player in bioethanol production, decarbonises its bioethanol processes by capturing CO2 during the corn-to-ethanol fermentation step and storing it underground for future use.

Braskem, one of the largest biopolymer producers in the world, uses circular practices to produce 100% recyclable bio-polyethylene from sugarcane by consuming CO2, making it a carbon negative process.

Unibio sustainably produces animal proteins from methane gas by using waste feedstocks, a specialised bioreactor that is designed to be energy efficient, and less land and water for agricultural protein production.

Aemetis produces renewable fuels and chemicals by integrating its facilities in multiple ways; examples include feedstock reutilisation, byproduct upgrading, plant co-location, and energy integration between its biogas, cellulosic ethanol, and biodiesel and sustainable aviation fuel (SAF) facilities.

Lanzatech offers another form of integration by co-locating its carbon recycling technology with existing plants around the world to remove and reutilise waste emissions to make products like ethanol, SAF, polyethylene, and n-octanol.

Waste-to-energy (WtE) is a popular technology to recycle wastes, typically municipal solid wastes (MSW), for electricity generation. Hitachi Zosen INOVA is a WtE company that thermally treats MSWs to generate power in over 1,000 plants all over the world. They have envisioned a “plant of the future” by designing an integrated ecosystem that is centred around a WtE plant and includes integration with anaerobic digestors, biogas upgrading facilities, carbon capture technologies, recycling facilities, and power plants.

Pros and cons of implementing circularity in biomanufacturing

The major advantages and disadvantages of incorporating circular practices into biomanufacturing are summarised below. This list is not exhaustive, and the advantages and disadvantages are labelled as “potential” as it depends on how successfully the circular practices are applied.

Furthermore, the pros and cons are often dependent on each other due to trade-offs. For example, a biomanufacturing process with a circular practice that makes it safer and generates less waste may also have been expensive and complex to construct. There are several metrics used to measure the degree of success of implementing circular practices (eg reduction in capital and operating costs, greenhouse gas emissions, raw material usage, water, and energy consumption). These metrics can be quantified by tools used to evaluate process feasibility such as techno-economic analysis and life cycle analysis.

The benefits of circular biomanufacturing to the consumer also come with their own trade-offs, cost again being at the forefront. However, many will see that as a small price to pay for goods that are sustainable, traceable, and produced in a socially responsible manner.

Article by Sanchari Ghosh

Bioprocess development engineer for a leader in biochem sustainability

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