Green gold in waterways: Advancements in utilisation of aquatic weeds for biofuels and more

By Associate Professor Ts. Bridgid Chin Lai Fui

As global energy consumption continues to increase, concerns are mounting over the environmental effects of excessive reliance on fossil fuels. These circumstances highlight the imperative for conducting technical research on sustainable alternative energy sources.

The over-reliance on fossil fuels not only puts tremendous strains on a limited resource but also greatly increases the release of greenhouse gases that result in pollution and climate change. However, their use is not likely to be eliminated or diminished significantly any time soon due to the continually growing global population and expanding urbanisation. Hence, in such a scenario, the generation of energy from renewable biomass presents a potential and viable substitute for fossil fuels.

Biomass commonly refers to all organic materials originating from animals, plants, and microorganisms that are deemed suitable for converting into bioenergy. Among the varieties of biomass, lignocellulosic feedstock which includes aquatic plants, agricultural biomass, industrial and animal wastes is considered significant as it is easily available and cheap.

Leveraging biofuels derived from biomass for energy generation is regarded as a promising strategy. Specifically, the combustion of biofuels results in an equivalent amount of carbon dioxide (CO₂) emissions as absorbed during the growth of biomass. Consequently, utilising biomass-based fuels in energy production aligns with the assumption of carbon neutrality.

The primary biomass utilised for biofuel production is edible crops such as soybean, rapeseed, and corn, classified as ‘first-generation’. While this category currently dominates biofuel production, it faces numerous challenges due to escalating food prices, a threat to global food security, competition for land and water resources, and other issues associated with the food versus fuel dilemma.

Despite its current prominence, addressing these challenges is imperative for the sustainable evolution of biomass-derived biofuels. The viability of first-generation biofuels raises concerns due to inherent limitations. To address these drawbacks, researchers have introduced second-generation biofuels, utilising non-edible crop feedstocks such as cassava and jatropha.

Although the second generation of biofuels presents fewer issues compared to the first, non-edible crop feedstocks necessitate the use of fertilisers and pesticides, posing environmental challenges in their production. Furthermore, the production of second-generation biofuels involves complicated and costly technologies, posing a substantial hurdle to commercialisation.

Third-generation feedstocks, exemplified by marine algae, offer a solution to the challenges encountered by first- and second-generation biofuels. These feedstocks alleviate land and water stress by not requiring specific land or water conditions. Initiatives such as those at the National Renewable Energy Laboratory in the United States are dedicated to advancing biofuels derived from third-generation feedstocks. Notably, third-generation biofuels boast high lipid productivity, cost-effective nutrient requirements, efficient photosynthesis, shorter production times, and rapid growth rates.

Utilising third-generation feedstocks in biofuel production holds promise for reducing the carbon footprint compared to their predecessors. Current advancements include fourth-generation feedstocks, particularly metabolically-engineered algae, generating fourth-generation biofuels to enhance third-generation feedstock potential. Future research endeavours should further explore this innovative category.

Utilising aquatic weeds and macroalgae as third-generation feedstocks is feasible due to their distinct properties. The components of marine algae can undergo conversion into valuable products, including biofuels, pharmaceuticals, bioplastics, cosmetics, and dyes. Nevertheless, the increasing prevalence of macroalgal blooms on a global scale, notably in North America, East Asia, and industrialised coastlines in Europe, brings about environmental and socio-economic apprehension.

While excessive aquatic weed growth negatively impacts aquatic ecosystems, creating issues such as nutrient removal, disturbance of local ecosystems, and harm to aquatic animals, transforming nuisance seaweed into biomass offers a solution. This approach can yield valuable and economically viable products, addressing environmental, economic, and public health challenges associated with aquatic weed proliferation.

Aquatic weeds, also known as unwanted plants, which proliferate in bodies of water, pose a threat to aquatic life and the quality of the water. Utilising aquatic weed biomass as a biofuel feedstock offers numerous advantages compared to terrestrial energy crops. Unlike terrestrial crops, aquatic weed biomass does not necessitate the use of scarce resources like arable land and freshwater.

The rapid growth rate of aquatic weed biomass suggests the potential for higher productivity compared to many terrestrial energy crops. The global distribution of aquatic weeds further supports their utilisation as a biofuel feedstock for enhanced energy security. Additionally, aquatic weeds have undergone examination for various applications, including fertiliser production, medicinal properties, enzymes, and the synthesis of industrially significant chemicals.

Considering these applications alongside the biofuel production potential, the development of a sustainable biorefinery focused on aquatic weeds becomes a plausible and forward-looking prospect. Besides the production of biofuel production, aquatic weeds have considerable potential in producing bioenergy, implementation of wastewater treatment, carbon sequestration, production of biomaterials and bioproducts, and for habitat restoration and biodiversity as shown in the illustration below.

Various potential applications derived from aquatic weed as feedstock

In the natural process of phytoremediation, aquatic weeds aid in neutralising contaminants in water. These plants have the potential to absorb nutrients, heavy metals, and other pollutants from the water. Enhancing water quality via aquatic weeds may provide an eco-friendly and cost-effective solution for wastewater treatment. Furthermore, the fast growth of aquatic weeds could serve as a means of carbon sequestration from the atmosphere to mitigate climate change by reducing greenhouse gas emissions.

Additionally, these plant extracts have the potential to be used in the pharmaceutical, cosmetic, and agricultural sectors due to the wide variety of bioactive substances present in aquatic weeds.

Lastly, the preservation of biodiversity and habitat restoration can both benefit from the proper control of aquatic weeds. This is further evidenced by fish and aquatic creatures depending on some aquatic plants to supply them with vital habitats. Hence, establishing more balanced ecosystems could help conserve the variety of flora and fauna by eliminating the spread of these invasive species.

In conclusion, aquatic weeds are a viable and useful resource for the manufacture of biofuels and numerous value-added products due to their intrinsic qualities, which include their quick growth rate, ideal composition, and minimal land needs. These characteristics set aquatic weeds apart from several commonly used terrestrial biofuel feedstocks and highlight their potential for efficient and sustainable biofuel generation.

Associate Professor Ts. Bridgid Chin Lai Fui is the Student and Alumni Committee Chair of Curtin Malaysia’s Faculty of Engineering and Science. She is also an associate professor in the Chemical and Energy Engineering Department of the Faculty where she is actively involved in teaching, research, supervising research students, and providing academic leadership and administrative support for the Department. Her research focuses on converting lignocellulosic waste and plastic waste into value-added bioproducts and biohydrogen using green technology. Associate Professor Ts. Chin has received a number of international and national research grants and has authored and co-authored numerous academic journal articles and conference papers on related topics. She is currently working on a research project on the conversion of water hyacinth to syngas enriched hydrogen production via catalytic gasification process under a Curtin Malaysia Sustainability Research Grant 2021. She is a Chartered Engineer (CPEng) of Engineers Australia (EA), professional technologist under the Malaysia Board of Technologists (MBOT) and a Fellow of the Higher Education Academy, UK. Associate Professor Ts. Chin welcomes opportunities for partnerships and collaboration from interested parties and can be contacted by email at bridgidchin@curtin.edu.my.