Algae farms in river estuaries can dramatically reduce nitrogen concentrations and prevent environmental pollution

The culture reactor that served as the basis for the model. Credit: Meiron Zollmann

A new study from Tel Aviv University and University of California, Berkeley proposes a model according to which the establishment of algae farms in river estuaries significantly reduces nitrogen concentrations in the estuary and prevents pollution of estuarine and marine environments. The study was led by PhD student Meiron Zollmann, under the joint supervision of Professor Alexander Golberg of the Porter School of Environmental and Earth Sciences and Professor Alexander Liberzon of the Faculty of Mechanical Engineering at the Faculty of Engineering Iby and Aladar Fleischman , Phone. University of Aviv. The study was conducted in collaboration with Professor Boris Rubinsky of the Faculty of Mechanical Engineering at UC Berkeley. The study was published in the prestigious journal Communications biology.

As part of the study, the researchers built a large model algae farm to cultivate the ulve sp. green macroalgae in the Alexander River estuary, hundreds of meters offshore. The Alexander River was chosen because the river discharges polluting nitrogen from nearby upstream fields and towns into the Mediterranean Sea. Model data was collected over two years from controlled culture studies.

The researchers explain that nitrogen is a necessary fertilizer for agriculture, but that it comes at an environmental price. Once the nitrogen reaches the ocean, it disperses randomly, damaging various ecosystems. As a result, the state and local communities spend a lot of money to reduce nitrogen concentrations in water, in accordance with national and international conventions that limit the nitrogen load in the oceans, including in the Mediterranean Sea.

“My laboratory researches basic processes and develops technologies for aquaculture,” explains Professor Golberg. “We are developing technologies for growing algae in the ocean to offset carbon and extract various substances, such as proteins and starches, to provide a marine alternative to land-based agricultural production. In this study, we have shown that if algae are cultivated according to the model we have developed, in river estuaries, they can absorb nitrogen to comply with environmental standards and prevent its dispersion in water and thus neutralize environmental pollution. In this way, we are in fact producing a kind of “natural decontamination facility” with significant ecological and economic value since the algae can be sold as biomass for human use.

The researchers add that the mathematical model predicts agricultural yields and relates the yield of algae and chemical composition to the concentration of nitrogen in the estuary. “Our model allows marine farmers, as well as government and environmental agencies, to know in advance what the impact will be and what the outputs of a large seaweed farm will be – before creating the farm itself. “, adds Meiron Zollman. “Through mathematics, we know how to make adjustments for large farms and maximize environmental benefits, including producing the amounts of protein that are farmedly desired. “

“It is important to understand that the whole world is moving towards green energy and that algae can be an important source,” adds Professor Liberzon, “and yet today there is not a single farm with it. proven technological and scientific capacity. The barriers here are also scientific: we don’t really know what the impact of a huge farm will be on the marine environment. It’s like going from a vegetable patch outside the house to endless fields of industrial agriculture. Our model provides some answers, in the hope of convincing decision-makers that such operations will be profitable and respectful of the environment. In addition, we can imagine even more ambitious scenarios. For example, green energy: “If we knew how to use the growth rates of energy in better percentages, it would be possible to embark on a one-year cruise with a kilogram of seaweed, without additional fuel at the bottom. -beyond the production of biomass in a marine environment.

“The interesting link that we propose here is the cultivation of algae at the expense of nitrogen treatment,” concludes Professor Golberg. “In fact, we have developed a planning tool for the establishment of algae farms in estuaries in order to solve both environmental problems while producing economic benefits. We propose the design of algae farms in estuaries of rivers containing large amounts of nitrogenous residues linked to agriculture to rehabilitate the estuary and prevent nitrogen from reaching the ocean while growing the algae in it. – even for food. In this way, aquaculture complements terrestrial agriculture.

Reference: “Multi-scale modeling of intensive macroalgae culture and marine nitrogen sequestration” by Meiron Zollmann, Boris Rubinsky, Alexander Liberzon and Alexander Golberg, July 7, 2021, Communications biology.
DOI: 10.1038 / s42003-021-02371-z

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