Microalgae and whey offer sources of bioenergy.

Method used by researchers obtains biogas and other value-added products derived from waste

When biologist Maria Paula Giulianetti de Almeida proposed conducting a study with microalgae and her doctoral advisor, Professor Gustavo Mockaitis, from the School of Agricultural Engineering (Feagri) at Unicamp, added anaerobic digestion to their proposal, all that was left was to define the waste. When they both came face to face with the excessive disposal of cheese whey in Brazil, taking into account the difficulty of obtaining official information about the product and the effects of dumping whey on the environment, they had no doubt that this should be the waste subject of the research.

As a result, they proved the concept that it is possible to use cheese whey to obtain, in addition to biogas, other value-added products, from the modified biogas production process. “All of this with the foot on the ground in low-cost application”, highlights Mockaitis, especially in the case of medium and small dairies or cheese producers, without access to the technology to reuse all the whey. In practice, the main contribution of the research consisted in offering a way to treat the whey so that these producers can obtain value-added products.

In large dairies around the world, this utilization is already happening. “The technology exists, but it’s expensive. A large-scale industry has milk, cheese, and whey. If you look at the label of a chocolate, a cream cheese, a yogurt, or a whey protein , you will read 'whey' or just 'whey,' because they add whey to the products or create new products, such as 'dairy blend' instead of cream,” says Almeida.

“We performed anaerobic digestion of the whey, a dark fermentation process – or acidogenic fermentation, without hydrogen production – in which we focused on acids such as acetate. Then we fermented the acetate with microalgae,” describes the researcher, who identified high concentrations of acetic acid and other molecules of added value.

Biorefinery

For Almeida and Mockaitis, the process could become efficient if it were part of a biorefinery, such as an oil refinery in which, since the refining process, many byproducts are processed. “By processing the initial residue, you can produce microalgae biomass and numerous other components through fermentation processes, which can be precursors to bioplastics or be used in the pharmaceutical, cosmetics and food industries.”

Claiming to be passionate about algae, the scientist from Minas Gerais had already worked with microalgae in the production of biofuel during her master's degree. According to the researcher's hypothesis, the anaerobic digestion process with microalgae, avoiding the production of methane, generates other components, such as volatile acids and biohydrogen, among several molecules. “The microalgae itself is a possible source of energy, because it is in itself a biomass that can be converted into bioenergy,” adds the advisor.

According to Almeida, an anaerobic digestion process aims to produce biomethane. “The microorganisms undergo an acid pre-treatment in order to divert methane production to the production of more complex molecules with added value, such as volatile acids. Among them, we take acetate, a component produced in greater quantity, and feed it to the microalgae culture, which grew. We observed an interaction between the microorganisms and produced a little biomass,” the researchers described.

Discard

It is common for small and medium-sized producers to use cheese residue as soil fertilizer or in animal feed, but much of the excess whey often ends up being discarded in rivers and streams. “Water washes the problem away.” Whey, which is a protein, is very acidic and can acidify the soil, says Almeida. Excess of the product in the soil and water, therefore, can cause serious damage to the environment. The production of 12 kilos of cheese requires 100 liters of milk and generates 87 liters of whey, for example.

According to the researcher, whey production in the world increased by 5% between 2023 and 2024 and tends to grow, “even though we are moving towards a substitute, because there is still a large consumption of dairy products and not all the whey is absorbed”. Although Brazil is one of the largest cheese producers in the world, Almeida was unable to obtain figures on whey disposal when he contacted the Brazilian Cheese Industry Association (Abiq). The cheese producers contacted did not provide this data either.

“We have legislation and oversight, but we lack incentives and research and development [R&D] programs to facilitate and encourage the management of whey. We need to connect production areas throughout the country, reduce the cost of transporting waste to the cooperative, and develop technologies for processing whey in the case of small and medium-sized producers,” says Almeida. In the European Union (EU), government incentive programs for the reuse of whey are common.

With funding from the Coordination for the Improvement of Higher Education Personnel (CAPES), the biologist developed part of her research at Delft University of Technology (Netherlands), with co-advisor David G. Weissbrodt. “It took me a month to get enough serum to do my experiment, because they reuse all of their production and also import it. But I did the entire microalgae reactor stage in Holland,” recalls the biologist. The next step in the research is to scale up the process.

Almeida has already published two articles on her research and plans to publish at least three more resulting from her thesis, which is already available in the Unicamp research repository. “I have always found microalgae fascinating. We often say that trees are the lungs of the universe, but in reality it is microalgae,” says the biologist, who developed her doctorate within a comprehensive bioenergy program involving Unicamp, the University of São Paulo (USP) and the São Paulo State University (Unesp).

For Mockaitis, coordinator of the Laboratory of Biotechnology Applied to Bioenergy and the Environment at Feagri, the project aims to meet an energy demand and, at the same time, provide an option for mitigating an environmental problem. “This is much more than a doctoral thesis. This is the work of a lifetime.”