She studies: Whey as a potential raw material for the production of renewable biofuels: a review. Image Credit: New Africa / Shutterstock.com
Whey waste: a critical environmental issue
The sectors of the food and agricultural industry are essential to meet the nutritional needs of the growing world population. Dairy products are one of the most consumed types of food globally, with food products such as milk, cheese, yogurt and desserts produced and sold in large quantities every year.
As in any industry, however, the dairy industry produces significant amounts of waste during production. Various agro-industrial residues are produced during dairy production, with whey in particular receiving particular attention in research due to the large quantities of this critical waste material produced. More than 160 million tons of whey are produced each year worldwide.
Disposing of this material is problematic, and due to the environmental damage it can cause, governments in multiple jurisdictions have introduced regulations to control the amount of untreated whey waste entering water bodies or soil.
The ecological damage caused by untreated whey is well recognized by researchers. These agro-industrial wastes cause eutrophication in water bodies and affect the pH of the soil, increasing its acidity, depending on the type of whey discarded. The type of cheese, the curdling processes and the source of the milk affect the acidity of contaminated soils.
Whey biorefinery concept. Image credit: Osorio-González, CS et al., Energies
Production of biofuels from Cheese Whey
Recognizing the extent of cheese production and environmental contamination caused by waste products such as whey, research has in recent years turned to the use of cheese waste products for value-added products in line with the concept. of circular economy.
Biofuels are a cleaner alternative to fossil fuels, and significant research has been conducted to produce them from agro-industrial waste streams. Some studies have explored the use of whey-derived products from cottage cheese production to produce these sustainable fuels. Researchers have identified limitations in the use of this substrate, such as a low solids content, high biological demand and an increase in acidity.
Several processes are used to treat whey for the production of value-added products such as biofuels, each with its own distinct advantages and disadvantages. For this purpose, all physical, chemical, biological and physico-chemical processes are used. Utilizing this important waste stream from the dairy industry can help meet the growing global demand for renewable and sustainable energy production.
Conventional process for the treatment of whey. Image credit: Osorio-González, CS et al., Energies
The card inside Energies provided timely analysis of recent advances in the use of whey cheese waste for value-added production of biofuels such as biodiesel, biomethane, biohydrogen and bioethanol. The document also provides an overview of the technologies and microorganisms currently used for this purpose.
State of production and properties of the whey
In 2020, 183 million tons of whey were produced worldwide. Four types of milk are commonly used for the production of cheese: cow, sheep, goat and buffalo. Two types of whey are produced, acid and sweet, with acid whey resulting from the direct use of organic acids and the production of lactic ferments, while sweet whey is produced by the coagulation of milk proteins with animal and microbial enzymes.
The physicochemical properties of the different types of whey are the direct result of the processes used during production. The chemical composition varies according to the source of the milk, such as moisture, total solids, percentage of lactose, protein content, fat content, ash content and pH values.
The technologies required for the value-added synthesis of products such as biofuels are expensive, which limits their use in small and medium-sized cheese producers. The use of this substrate as a carbon source for microorganisms produces several secondary metabolites such as organic acids, enzymes and biofuel components. Producing biofuels from whey substrates improves producers’ income and reduces environmental impact.
Production of biofuels from whey
To produce value-added biofuels, researchers need to consider several important parameters and factors. For the production of biomethane and biogas, whey can be used in pure powder form or in co-digestion mode in bioreactors, with waste products such as sugar cane pomace, sugar cane stills and slaughter sludge. of poultry explored over the past decade.
Whey represents a sustainable alternative to fossil fuels for biohydrogen, with the dark fermentation producing the highest yields. However, this process is challenging and processes need to be optimized to produce these high yields. Developing new microbial strains will help the process. Bioethanol production can be enhanced through the use of wild ethanogenic microbial strains that can metabolise lactose.
Whey is a low cost, renewable and abundant raw material for the production of bacterial lipids essential for biodiesel synthesis. Substrates such as deproteinized whey, cottage cheese whey, whey permeated and secondary whey wastewater have been explored in recent research. These materials have been used as substrates for strains such as M. circinelloides And W. anomalous.
Main phases of the anaerobic digestion processes. Image credit: Osorio-González, CS et al., Energies
The paper provided an in-depth analysis of current research perspectives on the use of whey for the production of sustainable biofuels. A low-cost, abundant and renewable material, the valorisation of this dairy industry product will help reduce environmental impact and waste generation in the dairy industry and can play a key role in the green economy of the future.
Osorio-González, CS et al. (2022) Whey as a potential raw material for the production of renewable biofuels: a review Energies 15 (18) 6828 [online] mdpi.com. Available at: https://www.mdpi.com/1996-1073/15/18/6828.