Chemicals from algae: just a gimmick?
For green chemistry academics, microalgae can be a surprisingly contentious topic. Microalgae, by the way, refers to single-celled plants that grow in the water and are the very bottom of the aquatic food pyramid. Algae, on the other hand, is a poorly-defined term that can mean basically any plant that grows in the water, including giant kelp as well as microalgae. When chemists do anything with algae, it is usually microalgae they are talking about. But what do chemists actually do with algae?
Left: Microalgae viewed through a microscope. Right: Big, fat regular algae.
Chemists have recently moved past the dream of pressing algae to extract oil for fuel, which captivated venture capitalists around the world from about 2005–2012. Instead, we've shifted to working out how to transform algae into chemicals that can be used to make plastics, solvents, and other useful things. At a conference I recently attended, a researcher from China gave an excellent presentation on his group's advances in extracting useful chemical compounds from microalgae. The presentation sparked a lively debate (well, lively by academic standards—a bit of a snoozefest from a normal perspective).
Wake me up when you're done arguing.
The argument was this: is growing algae to use as a feedstock actually worth it? It sounds like a cool idea on the surface. Most of our chemicals today are made from petroleum, but fossil fuels are running out and global warming is an urgent problem. Algae can take carbon dioxide and convert it to chemicals, trapping it temporarily and neatly sidestepping the rising price of oil. Plus, there are a number of start-ups left over from the algae tech boom of the early 2000's, and they're hunting for something to do with their algae farms—turns out making money from algae fuel is not as easy as it sounds.
TerraVia, formerly Solazyme, started out making fuel from algae and ended bankrupt.
Source: YCharts via The Motley Fool.
So what's the problem? If algae can produce 10 to 100 times more oil per acre than conventional crops, and has plenty of usable bits—nutritious fatty acids, colorful pigments, and gains-inducing protein—why are we not seeing algae fields (or photobioreactors, if you're fancy) taking over the world?
The difficulty lies, as always, in two things: the money, and the life cycle assessment.
Money
Start-ups in algaculture (like agriculture, but for algae) run into one of two monetary problems: their complicated photobioreactors are expensive and prone to fouling, or their simple outdoor algae ponds cannot generate high-value products.
Photobioreactors don't pay for themselves—at least, not right away.
Source: Ralf Reski, University of Freiburg.
While photobioreactors, like the ones in the image above, look very cool and futuristic—great for impressing investors—they are a very new technology, and the kinks have not been worked out. Seemingly basic questions like the best size, shape, and light source for a photobioreactor are still being studied. Algae also has a nasty tendency to clog the reactors it's grown in, which slows production and can break the expensive equipment. Finally, trying to harvest it when it's ready is a thorny and expensive issue. All of these issues are pricey stumbling blocks for start-ups trying to turn a quick profit.
Open algae ponds aren't as pretty, but they do scale well.
Source: Cyanotech Corp.
Growing algae in open ponds, as nature does, is considerably cheaper and easier. The technology is more mature—commercial algae farms have been doing this since World War II, and many wastewater treatment plants include algae ponds. Construction and maintenance is relatively simple. The downside is that in an open system, rogue microbes can wander in and hijack the pond for their own use. The ponds have to be kept extremely salty to kill off invaders, but the salt also kills off more temperamental species of algae. Only the sturdiest of algae can thrive in these conditions. Unfortunately, the sturdiest of algae are not the money-making ones. These species don't produce convenient chemical compounds, and are limited to low-value applications like food supplements. In short, this technology does not make a lot of money.
Life Cycle Assessment
Aside from the monetary issues, is algaculture actually environmentally friendly? The best way to find out whether a "green" technology is good for the environment is to perform a life cycle assessment (LCA), which looks at the energy and materials that go into a product, and the waste that comes out.
Life cycle assessment looks at environmental impact from cradle to grave.
Source: NIST.
When the only product being made from algae is biofuel, the LCA results do not look good. Algae comes out ahead of other fuel crops—switchgrass, canola, and corn—in land use and eutrophication potential (a specific type of water pollution). In every other category, algae has a worse environmental impact. The energy use, greenhouse gas emissions, and water use are all higher in algaculture than conventional agriculture, regardless of where the algae is grown. This is mostly because of the high demand for concentrated fertilizer and carbon dioxide to feed the algae as they grow.
However, making more products from the algae changes the picture. Co-products such as biomethane, protein, and succinic acid can be made from algae with a lower environmental impact than their conventional counterparts. So, if you're farming algae as a "green" crop, you should be choosing carefully what to turn it into—otherwise, the only green is in the color.
Verdict
It may seem like the odds are stacked against algaculture technologies, for the time being. However, there are a number of interesting options out there for reducing the cost and environmental impact of algae production, and improving its feasibility.
People are only getting more interested in microalgae and photobioreactors. Data from Scopus.
First, scientists and engineers all around the world are furiously researching how to fix the technological problems with algae and photobioreactors. The number of publications about each topic, which is a rough indicator of how popular the topic is and how much money is going into it, has been increasing pretty steadily since 1991. The recent surge of funding and publicity for algae-related startups means this number will probably continue to increase for the next few years, and we will hopefully see improved reactors being scaled up soon, as well as a number of new high-value applications for microalgae.
There have already been solutions proposed to the problem of the high environmental footprint. Existing flue gas from power plants or off-gassing from waste sites can be harnessed to grow algae, reducing greenhouse gas emissions and increasing profitability of those enterprises. Instead of adding expensive fertilizer to clean water, contaminated municipal wastewater could be used as a source of nitrogen and phosphorus. These co-location approaches benefit both the waste source (power plants, wastewater treatment facilities) and the algae grower, generating profit while releasing cleaner air and water into the environment.
Algal blooms are a major environmental problem around the world, killing rivers like this one in China.
Source: Felix Andrews (Floybix).
A little more crazy, but currently being explored by academics, is the option of taking algae directly from lakes and oceans with algal bloom problems. In fact, there's even a company that is currently producing polymers from algae harvested from at-risk lakes and ponds: BLOOM Foam. It's only a partial solution, as you're limited to whatever algae strain you find in nature, but it neatly sidesteps a lot of cost and environmental issues.
Finally, the high capital cost of photobioreactor technology can be overcome by producing high-value products. The right strain of algae can make beautiful pigments, omega-3 oils, sterols for pharmaceutical applications, cosmetic ingredients, or even polymer precursors for biodegradable plastics—all of which are bio-derived, natural, and biodegradable.
There's still a lot to come in the algaculture sphere, and I am excited to see what researchers and entrepreneurs come up with next. In the meantime, at least we have these weird outdoor running shoes made from algae.
BLOOM Foam's collaboration with Vivobarefoot has gifted the world with this crazy shoe.
Source: Vivobarefoot