Written by Bria Metzger '20
Edited by Elana Balch '21.5
In the University of Wageningen in the Netherlands, a research team is endeavoring to throw off global fossil fuel dependency with the help of microscopic algae. A single cell under the lens of a microscope is not the first place most would think to look for the secret to sustainable energy, but every one of these photosynthetic organisms is its own private generator: on a foundation of energy from the sun, algae thrive off a basic combination of oxygen, carbon dioxide, and the nitrogen and phosphorus common to fertilizers. With these basic ingredients, these singular cells create the full suite of macromolecules necessary to survive. While it may seem counterintuitive to find anything single-celled at the vanguard of biomass production, the microalgae’s small size is actually a massive advantage — small, simple things scale up quickly. In the right environmental conditions, they can double their body mass several times per day .
The harvested microalgae biomass can be burned, harnessing the energy stored in the tissues of organisms for electrical generation. The lipid content of each cell comprises and average of 80% petroleum, which can be used to fuel transportation . Biofuels are relatively renewable compared to fossil fuels, since they bypass the 200 million year latency period of fossil fuels; this makes them a prime candidate to help smooth the transition to green energy infrastructure. They’re cleaner than fossil fuels, too, releasing far less methane and carbon dioxide. In addition to diminishing greenhouse gas emissions, biofuels are free of sulfur dioxide, a compound that can cause acid rain . Humans have been harnessing the energy stored in organic matter since the first deliberate fire. Now, however, we have the technology to capture the energy from crops, composting waste, and even single-celled organisms. This is where Robin Barten and RC Chin-On, two PhD students at Wageningen University, come in.
History divides biomass fuel development into three waves. The first wave used involved cultivating terrestrial plants like corn, which ultimately proved both unprofitable and contentious — the land and resources used to grow the biomass could be used to grow food crops, and food versus fuel was a dangerous debate. The second wave relied on agricultural, forest-harvesting, and wood-processing wastes alongside the inedible components of food crops — but converting these wastes into energy was costly and inefficient [1,7]. forest harvesting residue and wood processing residues and non-edible components from food crops. The dwindling availability of arable land, depletion of soil nutrients, and overdrawing of water resources suggested that terrestrially-sourced biofuels might actually end up contributing to the problem they were trying to solve. The third wave directs focus away from the land and draws it past the shoreline, where marine microalgae already float through the long sunlight hours. RC Chin-On’s project aims to design, test, and evaluate the performance of a novel floating biomass cultivator to be situated on Bonaire for the growth of algae for biofuels.
This design project aims to solve several problems of cost and efficiency at once. Most algal biomass cultivators currently use lagoons or long ponds, but these are susceptible to contamination from the atmosphere, where bacteria, fungi, and other organisms fall into the exposed ponds and outcompete the microalgae . Some cultivators have experimented with films to prevent contamination, but these decrease the amount of sunlight that reaches the algae. To bypass these constraints, Chin-On is adopting a photo-bioreactor structure: a three-dimensional, transparent, tube-like structure that slowly circulates the algae, along with all required nutrients, to receive as much sunlight as possible . By lingering in one area just long enough to photosynthesize, all algae maximize their time in the sun.
The next challenge is the delicate balance between heating and cooling. Bonaire, an island in the carribean, has consistently warm temperatures and long sunshine hours throughout the year, offering microalgae the right conditions to excel. However, the confined interiors of the photo-bioreactors themselves are prone to overheating. Although the algae thrive in warmth, they perish en masse above 50°C . Maintaining this temperature balance is an energy-intensive process that is typically powered by more traditional energy sources, which can offset the advantages of biomass energy. Chin-On’s project is investigating a floating cultivation system where part of the reactor is submerged — using the surrounding seawater as a perfectly renewable passive cooling mechanism .
To further these efforts towards passive cooling, PhD student Robin Barten is assaying dozens of strains of microalgae from Bonaire. Microalgae, for all their simplicity, have an incredible genetic diversity that allowed them to thrive in a vast range of environmental conditions . Barten wants to harness this natural diversity, and, with a nudge in the right direction, create a strain that will place the cooling demands of the photo-bioreactor squarely within the passive range. The aim of the project is to find the most thermotolerant strains, assess how well they perform under the parameters of the photo-bioreactor, and then optimize them even further through directed evolution .
Combined, Barten and Chin-On’s research projects imagine a sustainable, productive means of cultivating algal biomass. The entirety of the project is dependent, however, on another actor — Bonaire itself. The island offers its uniquely suitable climate, its evolutionarily fine-tuned algae, and, ultimately, its receptivity to the placement of the photo-bioreactor off its shores.
In interviews, project director René Wijffels, professor at Wageningen UR, has suggested that the algal cultivation could diversify Bonaire’s economy, which currently relies heavily on ecotourism. In addition to being harvested for biofuels, the nutritionally rich algae are an excellent protein and fat resource in fish feed. Wijffels explains how prior work shows that “half of the fishmeal in salmon farms can be replaced. Salmon is gradually becoming vegetarian. On Bonaire, algae meal can be used in shrimp farming or the cultivation of mahi mahi. ” In other words, Bonaire isn’t just the right project site for its sunny climate, heart algal strains, and available ocean space. It’s right because it’s primed to receive meaningful economic benefits. This thermotolerant bioreactor project series has drawn Bonaire and the Netherlands together across oceans in the shared interest of a more sustainable future, providing a case study of economic cooperation that could be a model for future environmental efforts seeking partnership alongside profit.