By Cliò E. Agrapidis, PhD
The Long History of Biofuels
Biofuels might sound like a modern innovation, but they have been powering the world for millennia. Early civilizations lit their lamps with vegetable oils, and the first diesel engines ran on peanut oil. This long history reflects both their potential and the challenges they face. A look at their evolution reveals why the search for better biofuels continues today.
At the cusp between the 19th and the 20th century, the newly established combustion engine vehicle market saw the first diesel engines by Rudolf Diesel running on peanut butter oil, while Henry Ford designed his Model-T to run on hemp-derived biofuels. As the 20th century progressed, war shortages and oil embargoes kept biofuels in the spotlight as an alternative to fossil fuels.
From Crops to Algae: The Evolution of Biofuels
While first-generation biofuels were derived from crops like seeds, sugar canes, and beans, solving the food-vs-fuel dilemma led to the development of second-generation biofuels, mostly based on waste products, residue feedstocks, or energy crops. However, even second-generation biofuels have limitations, particularly in scalability and efficiency. During the previous decade, algae and microalgae have gained attention as alternative feedstocks for advanced biofuels. Nonetheless, several hurdles remain in order to turn microalgae-based biofuels into a cost-efficient operation able to support Europe towards its 2050 Climate Goals.
FUELGAE: Advancing Microalgae-Based Biofuels
To overcome these hurdles, the FUELGAE project aims to develop new advanced biofuels from microalgae. The main steps of this process are the microalgae growth in photobioreactors optimized for installment in proximity to specific industries, and the chemical transformation of the lipids from the microalgae into biofuel.
The Role of Catalysts in Biofuel Production
This final step requires a precise understanding of all the components involved in converting lipids into biofuel. One key component for these chemical reactions are catalysts. These molecules act as accelerators of chemical reactions, effectively reducing the time needed for the process completion, and, hence, the costs incurred in the procedure.
In industrial operations, such as those foreseen by the FUELGAE project, the choice goes to heterogeneous catalysts. These are made up of two components: an active phase and a support. The active phase is the material directly responsible for the catalytic activity. On the other hand, the support provides structural stability and enhances performance.
Photo: RTDS
Photo: RTDS
Choosing the Right Catalyst Support: Key Factors
Choosing the right catalyst support is fundamental as this choice impacts reaction efficiency. In fact, the catalyst support has direct consequences on the active phases’ accessibility, stability, and interactions with the reactants – the materials taking part in the chemical reaction. To ensure the highest efficiency, several factors must be considered when choosing a catalyst support:
- Surface area and dispersion. A high surface area maximizes the dispersion of the active phase and increases the number of available catalytic sites
- Thermal and mechanical stability. Unstable supports degrade under reaction conditions, leading to catalyst deactivation.
- Mass transfer and porosity. Porous supports improve reaction rates, while inadequate pore structure creates diffusion limitations, slowing down reactions.
- Chemical interactions. Reactive supports can enhance selectivity or lower the activation energy, while inert ones minimize unwanted side reactions
- Economic and Environmental Impact. Optimal supports reduce both catalyst replacement frequency and energy consumption, lowering operational costs. Durability plays a role in minimizing waste. Contributing to sustainability goals.
From Powder to Pellets: Optimizing Catalyst Structure
As FUELGAE aims to carry out industrial operations, careful consideration of the above points is necessary. Moreover, in an industrial setting, catalysts cannot be in powder form, as this might create blockage. Thus, understanding how candidate materials for supports perform in terms of, e.g., surface area and porosity is crucial.
With this goal in mind, FUELGAE researchers carried out an investigation of a mesoporous aluminosilicate (MSU-F), a candidate for catalyst support in industrial processes. This highly specialized study looked into how this catalyst transforms from powder to pellets (robust, shaped catalyst particles) under pressure. It focused on determining the lowest pressure at which the powder transforms into pellets while preserving the structural integrity of the catalyst.
Scientists found that the powder formed pellets at 20 MPa (~197 atm). The pellets formed at this pressure preserve the porosity of the original powdered material. On the contrary, higher pressure resulted in shrinking of the pores and distortion of the overall structure. This translates to the need for caution when preparing this material as a catalyst support in pellet form. Moreover, further study to determine the optimal pressure range for the pelletization process, especially the real lower limit for optimal pressure, can help in optimizing the pelletization process for industrial scale operations.
Towards a Sustainable Future with Advanced Biofuels
Biofuels have been known as an alternative to fossil-based fuels for at least two centuries. However, now more than ever there is a real need for a radical shift to renewable energy sources for transport. The production of biofuels from microalgae as envisioned by FUELGAE is not only a move towards independence from oil imports, but a necessary step towards a greener transport sector. Advanced biofuels already emit fewer greenhouse gasses than fossil fuels and first-generation biofuels. FUELGAE advanced biofuels take this a step further by including CO2 capture in the microalgae growth process and resulting in a genuine carbon-reducing final product, a necessary step towards a truly sustainable transport sector.
Photo: RTDS
