Can Algae Save The World: Food, Filtration, Power, Light And Carbon Capture

Algae lamps that collect 150-200 times more CO2 in a year than trees may possibly light up streets.

Already popular for the manufacture of biodiesel, microalgae have applications in many areas. New technologies can  combine intensive production of biomass with extremely effective water and air sanitation.

But this is not the only reason that led the BioLets company to focus on microalgae. Director Yosu Ogarrio Tello explains that the material can also feed humans and animals, and is also an excellent fertilizer for farmland.

The exponential growth of microalgae is carried out in special enclosures, called continuous flow photoreactors. These structures ensure a supply of light, temperature and pH constant, and can produce the required biomass in just two days.

Two-day culture

Algae to the rescue of growers

During their growth, algae absorb significant amounts of metals, minerals, chemicals and organic matter. This is what gave Yosu Ogarrio Tello the idea of combining biomass production and purification of industrial effluents.

The process may be particularly suitable for coffee cultivation, which contaminates large quantities of water in separating the pulp from the coffee beans. Instead of using conventional filters, producers could simply use bioreactors for water purification and reuse. With microalgae, they would also have an excellent source of fertilizer for their crops.

Water filtration

The cleaning powers of algae are so effective that this technology could also be used during the early stages of production of drinking water. To be safe for consumption, water would then subjected to a process of chlorination and ultraviolet treatment.

The photoreactor was developed by BioLets developed in their pilot plant in Monterrey and is already the subject of a patent. Researchers are now working on new processes that will further improve the quality of filtered water.

Carbon Capture

The purification properties of algae are also being applied to air filtration. Biochemist and Shamengo pioneer Pierre Calleja has designed a microalgae lamp that uses algae both to provide its own electricity and to purify the air of CO2. The microalgae act as solar cells, using the natural process of photosynthesis to change the lamp’s battery, all while providing an exceptional level of CO2 absorption.

Calleja hopes to use the technology to develop streetlamps that can purify the air on busy motorways, to the tune of 1 tonne of CO2 per lamp per year. With car exhaust accounting for 25% of emissions, the implementation of these lamps could have a considerable impact on overall CO2 levels. Stanford engineers have generated electrical current by tapping into the electron activity in individual algae cells. Photosynthesis excites electrons, which can then be turned into an electrical current using a specially designed gold electrode. This study could be the first step toward carbon-free electricity directly from plants.

In an electrifying first, Stanford scientists have plugged into algae cells and harnessed a tiny electrical current. They found it at the very source of energy production – photosynthesis, a plant’s method of converting sunlight to chemical energy. It may be a first step toward generating high-efficiency bioelectricity that doesn’t give off carbon dioxide as a byproduct, the researchers say.

“We believe we are the first to extract electrons out of living plant cells,” said WonHyoung Ryu, the lead author of the paper published in the March issue of Nano Letters. Ryu conducted the experiments while he was a research associate for mechanical engineering Professor Fritz Prinz.

The Stanford research team developed a unique, ultra-sharp nanoelectrode made of gold, specially designed for probing inside cells. They gently pushed it through the algal cell membranes, which sealed around it, and the cell stayed alive. From the photosynthesizing cells, the electrode collected electrons that had been energized by light and the researchers generated a tiny electrical current.

Early research stage

“We’re still in the scientific stages of the research,” said Ryu. “We were dealing with single cells to prove we can harvest the electrons.”

Plants use photosynthesis to convert light energy to chemical energy, which is stored in the bonds of sugars they use for food. The process takes place in chloroplasts, the cellular powerhouses that make sugars and give leaves and algae their green color. In the chloroplasts, water is split into oxygen, protons and electrons. Sunlight penetrates the chloroplast and zaps the electrons to a high energy level, and a protein promptly grabs them. The electrons are passed down a series of proteins, which successively capture more and more of the electrons’ energy to synthesize sugars until all the electrons’ energy is spent.

In this experiment, the researchers intercepted the electrons just after they had been excited by light and were at their highest energy levels. They placed the gold electrodes in the chloroplasts of algae cells and siphoned off the electrons to generate the tiny electrical current.

The result, the researchers say, is electricity production that doesn’t release carbon into the atmosphere. The only byproducts of photosynthesis are protons and oxygen.

“This is potentially one of the cleanest energy sources for energy generation,” Ryu said. “But the question is, is it economically feasible?”

Minuscule amount of electricity

Ryu said they were able to draw from each cell just one picoampere, an amount of electricity so tiny that they would need a trillion cells photosynthesizing for one hour just to equal the amount of energy stored in a AA battery. In addition, the cells die after an hour. Ryu said tiny leaks in the membrane around the electrode could be killing the cells, or they may be dying because they’re losing out on energy they would normally use for their own life processes. One of the next steps would be to tweak the design of the electrode to extend the life of the cell, Ryu said.

Harvesting electrons this way would be more efficient than burning biofuels, as most plants that are burned for fuel ultimately store only about 3 to 6 percent of available solar energy, Ryu said. His process bypasses the need for combustion, which harnesses only a portion of a plant’s stored energy. Electron harvesting in this study was about 20 percent efficient. Ryu said it could theoretically reach 100 percent efficiency one day. (Photovoltaic solar cells are currently about 20 to 40 percent efficient.)

Possible next steps would be to use a plant with larger chloroplasts for a larger collecting area, and a bigger electrode that could capture more electrons. With a longer-lived plant and better collecting ability, they could scale up the process, Ryu said. Ryu is now a professor at Yonsei University in Seoul, South Korea.