Recent trends in anaerobic digestion of macroalgae for blue carbon derived biofuels – a review
This week, we take a closer look at the pre-print of the paper to be soon published in Process Safety and Environmental Protection. The study was led by Dillirani Nagarajan from the Institute of Aquatic Science and Technology, of the National Kaohsiung University of Science and Technology in Kaohsiung, Taiwan.
Macroalgae, commonly known as seaweeds, are among the majorly cultivated species in the aquaculture industry because of their intensive use in the food and pharmaceutical industries. Macroalgae have now also been revisited, due to their superior carbon sequestration potential in the marine habitat, as “blue carbon” stock in the ocean sinks. Considered as the third-generation feedstock for biofuel production through anaerobic digestion (AD), especially bioethanol and biomethane, macroalgal biomass could represent a viable, sustainable, and eco-friendly alternative to chemical methanation. In this review, the authors examine the increasing interest in using marine algae as a sustainable biomass source, emphasizing its potential in oceanic carbon fixation and blue carbon donor for biofuel, and urging further innovation and research to overcome current challenges and scale up production.
The authors discuss the irrefutable evidence supporting maximal carbon capture, transport, and sequestration in both ocean shelf and sediments by macroalgae, due to their fast growth and minimal land use (Figure 1 illustrates the macroalgal carbon fixation and sink potential). They also discuss the technical aspects of AD, focusing on challenges like lignin content and digestion efficiency, reviewing various pretreatment methods to enhance yields and the evidence on factors affecting AD performance.
Figure 1
The review also connects AD to “blue carbon”, noting how macroalgae biofuels can store carbon and reduce fossil fuel dependence, contributing to carbon sequestration goals (Figure 2 illustrates the scheme of anaerobic digestion of seaweeds). Further technological innovations, including advanced techniques improving macroalgae AD efficiency and integrating biofuels into circular economies are discussed.
Figure 2
The authors also discuss challenges such as high production costs, low digestion efficiency for certain species, and environmental risks like nutrient imbalances and invasive species, suggesting future research should focus on improving feedstock consistency, pretreatment methods, and scaling up operations, while also assessing the sustainability of macroalgae-based biofuels.
Here’s a short wrap-up of the key insights from this review:
- Macroalgae are a promising, sustainable feedstock for biofuels, offering advantages like rapid growth and no land requirements.
- Macroalgae-based biofuels can sequester carbon and reduce fossil fuel reliance, supporting blue carbon goals.
- The high lignin and polysaccharide content of some macroalgae species complicates their digestion: pretreatment methods can improve biogas yield and process efficiency.
- Innovations in bioreactor design and enzyme use are improving the efficiency of macroalgae anaerobic digestion.
- Future studies should focus on feedstock consistency, cost reduction, and scaling up sustainable production systems.
Read the full paper here: Recent trends in anaerobic digestion of macroalgae for blue carbon derived biofuels – a review