By dr. Maja Berden Zrimec
The use of waste streams in biomass production can create a closed-loop system that minimizes waste and pollution. One of the most attractive opportunities for multiple industries is the use of algae, which can grow in various wastewaters and become a source of additional jobs and income. Wastewater treatment with algae is an important step to recover valuable resources, such as nutrients and energy, which can be used to create various products. The use of algae in wastewater treatment can replace energy-demanding technological oxygenation with oxygen from algae. Oxygen is used for bacterial degradation, while algae use the resulting nutrients and organic carbon for biomass production.
Biogas plants can also use algae technology to treat the liquid phase of anaerobic digestate. Liquid digestate is frequently treated as wastewater, even though it is a rich source of nutrients for agriculture. The use of algae in biogas plants can stabilise the liquid phase of anaerobic digestate into biomass, reducing storage and transport logistic costs and greenhouse gas emissions. Nutrients from digestate can be recovered and cycled on site, making this approach an innovative way to improve the quality of digestate liquid fraction, use excess heat, and reduce odour.
Macroalgal biomass with recovered wastewater nutrients can be stabilised for agricultural use by composting or pyrolysis. Composting uses macroalgae cultured in heavily loaded wastewater as an ideal source of nitrogen, while agricultural crop residues can be used as the source of carbon. Slow pyrolysis transforms the biomass into biochar. Biochar produced from macroalgae biomass improves the retention of nutrients from fertilisers in low-quality soils and enhances plant growth and nutrient uptake. Biochar can also increase the cation exchange capacity and bind labile nutrients and trace elements from water.
In agriculture, seaweed biochar can be used for the sequestration of carbon in soil, soil amelioration, remediation of degraded soils, and improvement of soil fertility. It can also be used as a source of bioenergy and in the treatment of contaminated wastewater. The large surface area of biochar is also beneficial for soil microbiota, as it offers sites for their stabilization and growth, increasing their abundance and changing the type of microorganisms that are favoured.
Biorefineries for specific products
A biorefinery approach can enhance the sustainability of microalgae production by utilizing the biomass more efficiently and preventing waste. EU Horizon projects like SABANA, Water2Return, and Saltgae projects have demonstrated large-scale microalgae-based biorefinery concepts to produce high-value and low-value products, recover nutrients from waste streams, and avoid waste. Algae biomass contains essential amino acids, essential fatty acids, vitamins, and other beneficial compounds, making them an ideal source for various products like biofuels, bioplastics, cosmetics, biostimulants, biopesticides, aquafeed additives, and more.
The use of microalgal biomass, cultivated in waste streams, for hydrogen production, bioethanol, and biosorbents also offers promising potential. Biohydrogen production can be achieved through the dark fermentation process where anaerobic microorganisms convert biomass into hydrogen and CO2. Algal biomass also contains high amounts of carbohydrates, making it an excellent feedstock for bioethanol production. Additionally, algal biomass can be used as biosorbents for metal ions in industrial effluents (i.e., textile industry) and later used as fertilizers for soil, contributing to the soil’s nutrient content.
While the biorefinery model is still in the early stages of development, the use of algae biomass offers a potential solution to sustainability challenges while providing valuable products. Algae cultivation is not only environmentally friendly but also cost-effective, which makes it a promising approach for future sustainability initiatives.
Algae integration into existing technological systems
Algae systems present attractive opportunities for multiple industries because they can grow in most wastewaters that are not toxic. The systems can be seamlessly added to the existing technology as side streams, thus not requiring any changes in the current installation, be it in the wastewater treatment system in the sewage plant or industrial technology systems. An addition of algal raceway pond can complement or even replace the secondary and tertiary treatment of wastewater, substantially reducing the production of unwanted sludge (not allowed to be agriculturally used in many countries).
They can be added to the existing technology system as the side-streams (not requiring major restructuring), which makes them appealing to the industrial operators. In the case of biogas plants, they can be installed on-site to treat the digestate and recycle nutrients, significantly lowering the storage and transport costs as well as environmental footprint. Additionally, their production can be a source of additional jobs and income.
Business models with algae grown in wastewater or digestate
To fully realize the potential of algae grown in wastewater or anaerobic digestate, innovative business models are needed that can capture the value of these products. Here are some possible business models:
- Algae production and processing for specific industries: Companies can focus on producing algae for specific industries, such as aquaculture or biofuels. By optimizing their production and processing methods for these specific markets, they can create high-value products that meet the needs of those industries.
- Integrated systems for wastewater treatment and resource recovery: Companies can develop integrated systems that use algae to treat wastewater and recover valuable resources, such as nutrients and biofuels. By offering a complete solution for wastewater treatment and resource recovery, these companies can provide value to municipalities, industrial facilities, and agricultural operations.
- Circular economy partnerships: Companies can partner with other businesses and organisations to create circular economy partnerships that leverage the value of algae and wastewater. For example, a food processing company could partner with a wastewater treatment facility to use the algae produced in the treatment process as a source of animal feed.
- Carbon credits and offsets: Companies that use algae for carbon sequestration or biofuel production can generate carbon credits or offsets that can be sold on carbon markets. This can provide a new revenue stream for companies and incentivize the development of sustainable practices.
- Direct-to-consumer products: Companies can develop direct-to-consumer products, such as fertilisers or biostimulants, that use algae grown in wastewater or anaerobic digestate. This can provide a way to capture value from these products without relying on traditional supply chains.
Overall, innovative business models are needed to fully capture the potential value of algae grown in wastewater or anaerobic digestate. By focusing on specific industries, developing integrated systems, partnering with other businesses, generating carbon credits, or developing direct-to-consumer products, companies can create sustainable and profitable businesses that contribute to a circular bioeconomy.
Find out more with VCG.ai
If you would like to check how algae could fit in your business, use VCG.ai to find out how to include algae solutions into your value chain!
We are grateful to colleagues from Algen, algal technology centre, llc for sharing their knowledge and experience from their projects: Cronus, BioRural, Water2Return, LIFE AlgaeCan, Saltgae and AlgaeBioGas.