Green microalgae will reduce the environmental footprint of animal feed and food

Green Innovation 5. nov 2021 4 min Senior Specialist Malene Fog Lihme Olsen Written by Morten Busch

Clearing rainforests to grow soybeans and then transporting them to the other side of the globe to be used as animal feed must be stopped. Now researchers have found an alternative feed source in the form of a microalgae with protein content exceeding 50% and high content of essential amino acids. The algae are grown in 100-metre-long plastic tubes that can be placed anywhere and do not pollute the soil or involve deforestation. This method of production is not yet economically viable, but when it becomes profitable, it can replace the current sources of animal feed and eventually also be included in food for people.

The average person in Europe consumes more than 60 kg of soybean per year – without even realizing. Soybeans are a hidden source of protein in many people’s diets because many farm animals such as chickens are fed soybeans. Unfortunately, these protein-rich beans are often shipped from South America, where the land cultivated with soybeans has increased 15-fold in the past 50 years. The environmental footprint from the soybeans and ultimately such animals as chickens is enormous. Now researchers have discovered a useful and sustainable alternative protein source.

“Microalgae have emerged as a promising alternative in recent years. We tried to grow commercially available algae strains, but these were outcompeted by another strain that was found to both grow rapidly and have very high content of protein and essential amino acids. This is a huge benefit for sustainability, since these microalgae can be grown anywhere in long horizontal tubular reactors without polluting the environment,” explains Malene Fog Lihme Olsen, Senior Specialist at the Danish Technological Institute in Taastrup, adding:

“Based on these results, we joined forces with the Department of Geosciences and Natural Resource Management at the University of Copenhagen and several industrial partners in the ReMAPP project (2018–2022), supported by Innovation Fund Denmark. The goal is to make algae cultivation economically viable, so that it can soon replace soybeans in animal feed and perhaps eventually also become a source of protein for people.”


The discovery was made at a pig farm in Lolland. The research group had purchased several commercial strains outside Denmark to test which ones were best suited for cultivating high-protein animal feed at the northern latitudes in Denmark. Each time they tried to grow these strains on pig manure, the results were not as expected.

“We finally decided to try to determine which strain had emerged, since it was growing really well and apparently suited our latitude. Once we had identified it as the green microalgae Scenedesmus species, we then analysed the protein content, which turned out to be really high. More than half the dry matter is protein, and more importantly, 42% of the amino acids are essential,” says Malene Fog Lihme Olsen.

Essential amino acids are the ones essential for people, since we can only produce 11 of the 20 amino acids that comprise protein. We therefore need to eat these essential amino acids to produce the proteins we need to keep our body healthy and well. However, the essential amino acids are not the only component that make the algae nutritious.

“Algae can also contain large quantities of polyunsaturated fatty acids, which are essential for blood pressure regulation, kidney function and the immune system. We cannot make these compounds ourselves and must therefore obtain them through food. They are a main reason why eating a lot of fish is recommended, and fish contain these essential fatty acids because they consume microalgae,” explains Malene Fog Lihme Olsen.

20 times more protein than soybeans

Nutrition is not the only benefit of Scenedesmus and similar species. The microalgae can be grown in long horizontal tubular reactors and thus can be cultivated almost anywhere. They therefore do not necessarily compete with other types of agriculture and do not involve deforestation.

“In addition, we can use industrial sidestreams to supply the microalgae with nutrients, carbon dioxide and surplus heat, since we can channel manure and carbon dioxide from biogas and other substances through plastic bags to feed the microalgae. In fact, about 1.8 kg of CO2 is used to produce 1 kg of algae solids, so we can capture quite a bit,” says Malene Fog Lihme Olsen.

In addition, microalgae are very adaptable to variation in light conditions, temperature, salinity and growth media. These properties can increase the potential for choosing different algae species that can be grown almost all year round, even at northern latitudes.

“With the right approach, microalgae as new protein crops will have far higher annual protein productivity than conventional protein crops, with up to 20 times more protein than soybeans and 40 times more than corn,” explains Malene Fog Lihme Olsen.

The microalgae Scenedesmus can be grown in long horizontal tubular reactors and can be cultivated almost anywhere. They therefore don't necessarily compete with other types of agriculture and do not involve deforestation.

Tastes good

Although the new research clearly shows that the microalgae will be a huge benefit both nutritionally and environmentally, the researchers say that there is still a long way to go before they reach people’s dinner tables.

“The first challenge is production, since we still do not have the tools to harvest the microalgae profitably. With sedimentation and agglomeration techniques, we can concentrate the microalgae into 10–30% of their original volume, thus greatly reducing the cost of the subsequent concentration, so we are well on our way. In addition, microalgae’s cell walls pose a challenge, since they are difficult to digest, so we must either learn how to degrade them mechanically or enzymatically or must refine the microalgae so that they become easier to digest,” says Malene Fog Lihme Olsen.

The current inefficiency of production also means that producing the microalgae for either animal feed or food for people is not yet profitable. However, Malene Fog Lihme Olsen thinks that the accounting is somewhat imbalanced.

“The overall environmental accounts for soybean production do not look good. There are many transport and deforestation costs – especially related to climate. So when we eventually become more skilled at producing and calculating environmental accounts that include both economic and environmental factors, we are optimistic that we can benefit from these algae,” explains Malene Fog Lihme Olsen.

The remaining obstacle is purely psychological: will people eventually be willing to replace meat with insects or microalgae? Initially, however, the microalgae are not intended as food for people but as feed for animals such as chickens.

“We are in ongoing discussions with the appropriate authorities, such as the Danish Veterinary and Food Administration, about future challenges with relevant permits, and all our preliminary experiments indicate no health problems with eating meat from animals such as chickens fed with microalgae. In fact, initial experiments suggest that the microalgae taste good, so this may eventually even become a selling point,” says a smiling Malene Fog Lihme Olsen.

Outdoor cultivation of a novel isolate of the microalgae Scenedesmus sp. and the evaluation of its potential as a novel protein crop” has been published in Physiologia Plantarum. In 2016, the Novo Nordisk Foundation awarded a grant to the Department of Geosciences and Natural Resource Management of the University of Copenhagen for the project Harnessing the Energy of the Sun for Biomass Conversion. The project, which also received funding from the Villum Fonden, is a collaboration between the University of Copenhagen and the Danish Technological Institute.

To accommodate the future demands for an increasing protein supply for food and feed, there is an unmet need for new crops and technologies capable of...

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