Waste characteristics

The whey is a liquid residue generated after the separation of the curd and resulting from the coagulation of milk proteins by acid or proteolytic enzymes. The production of whey comes mainly from cheese manufacturing (Panesar et al., 2007). Whey is classified into sweet whey and sour whey. Sweet whey has a high lactose and protein content, high pH, low fat and acidity, however, acid whey has a higher lactic acid content and lower pH. Whey is also rich in minerals, such as calcium, phosphorus, magnesium, sodium and potassium and in lower concentrations, zinc, iron, copper and manganese (Mazorra y Moreno, 2019).

Table 1

Composition of sweet and acid whey

Components	Sweet whey (g/l)	Acid whey (g/l)
Total solids	63–70	63–70
Lactose	46–52	44–46
Protein	6–10	6–8
Calcium	0.4–0.6	1.2–1.6
Phosphate	1–3	2–4.5
Lactate	2	6.4
Chloride	1.1	1.1

Source: (Panesar et al., 2007).

Table 2

Chemical characterization of whey

Components	Sweet whey (g/l)
Ph	4.6 ± 0.1
COD (g/L)	47.1 ± 2.1
Total Kjeldahl nitrogen (g/L)	0.15 ± 0.02
Total solids (g/L)	55.3 ± 0.5
Volatile solids (g/L)	45.8 ± 0.7
Sulfate (mg/L)	100 ± 5
NO₃ (mg/L)	149 ± 3
PO₄ (mg/L)	665 ± 8
K (g/L)	1.95 ± 0.06
Lactic acid (g/L)	7.5 ± 0.4
Acetic acid (g/L)	0.72 ± 0.08

Source: (Hashemi et al., 2022)

Technology description

Anaerobic digestion

Anaerobic digestion is considered a biotechnology that follows greenhouse gas reduction policies and circular economy development objectives. However, the activity and quality of the inoculum are critical factors to ensure the successful startup and stable operation of an anaerobic digestion reactor (Meng et al., 2023).

Anaerobic digestion is the degradation of organic matter in the absence of oxygen, producing biogas whose main components are methane and carbon dioxide. The formation of methane does not take place in environments where electron acceptors such as oxygen, sulfates or nitrates are present. anaerobic digestion is an effective means of treating liquid and solid waste, effluent treatment by anaerobic digestion has numerous advantages compared to aerobic technology (Arhoun, 2017).

The anaerobic digestion process uses organic matter and converts it by bacterial action into a gas mixture. This reaction occurs in the absence of oxygen and other inorganic electron acceptors, conditions in which the organic matter is used to generate a gas mixture. composed mainly of methane and carbon dioxide (Neumann y Jeison, 2015).

Figure 1

Anaerobic digestion process diagram model (Neumann & Jeison, 2015)

N°	Title	Journal	Main research focus	Reference
1	A comprehensive evaluation of cheese whey to produce biogas in the Canary Islands.	Biomass and Bioenergy	Dairy industry, Methane Biochemical methane potential, Anaerobic digestion Bioenergy	(Ramos-Suárez et al., 2024)
2	Cheese whey and dairy manure anaerobic co-digestion at psychrophilic conditions: Technical and environmental evaluation.	Environmental Research	Anaerobic digestion, Biogas. Circular economy, Greenhouse gases emissions, Life cycle analysis, Dairy sector	(Casallas-Ojeda et al., 2024)
3	The role of hydrochar on the production of biogas and volatile fatty acids during anaerobic digestion of cheese whey wastewater.	Sustainable Chemistry and Pharmacy	Circular economy, Biogas, Hydrothermal carbonization, Anaerobic digestion, Volatile fatty acids	(Liakos et al., 2023)
4	Enhancing biogas production from cheese whey using Zero-Valent Iron: A comparative analysis of batch and semi-continuous operation modes.	Journal of Environmental Chemical Engineering	Alkalinity, Biogas upgrading, Methanothrix, Microbial pathways, Hydrogenotrophic methanogens	(Charalambous et al., 2023) and its anaerobic treatment presents several challenges. Among these is the production of high levels of volatile fatty acids (VFAs)
5	Integration of anaerobic digestion and chain elongation technologies for biogas and carboxylic acids production from cheese whey.	Journal of Cleaner Production	Biofuel, Biohydrogen (H2), Fatty acids, Chain elongation Fermentation, Clostridium kluyveri, Cheese whey	(Reddy et al., 2022)
6	Feasibility assessment of biogas production from the anaerobic co-digestion of cheese whey, grease interceptor waste and pulped food waste for WRRF.	Energy	Anaerobic digestion, Co-digestion, Energy, Food waste, Volatile-fatty acid, Waste activated sludge	(Bolen et al., 2022)
7	Anaerobic co-digestion of cheese whey and septage: Effect of substrate and inoculum on biogas production.	Journal of Environmental Management	Whey wastewater, Septage, Anaerobic digestion, Methane yield, Inoculum, Modelling	(Bella & Venkateswara Rao, 2022)
8	Anaerobic co-digestion of agro-industrial waste with cheese whey: Impact of centrifuge comminution on biogas release and digestate agrochemical properties.	Biomass and Bioenergy	Organo-mineral fertilizers, Biogas, Particle size, Sewage sludge, Vegetal waste, Anaerobic digestion	(Ivanchenko et al., 2021)
9	Valorization of vinasse and whey to protein and biogas through an environmental fungi-based biorefinery.	Journal of Environmental Management	Wastewater treatment, Fungal biorefinery, Anaerobic digestion, Neurospora intermedia, Amino acids	(Hashemi et al., 2022)
10	In situ biogas upgrading and enhancement of anaerobic digestion of cheese whey by addition of scrap or powder zero-valent iron (ZVI).	Journal of Environmental Management	Acidification, Anaerobic digestion, In-situ biogas upgrading, Cheese whey, Powder zero valent iron, Scrap zero valent iron	(Charalambous & Vyrides, 2021)
11	Effect of co-digestion of milk-whey and potato stem on heat and power generation using biogas as an energy vector: Techno-economic assessment.	Applied Energy	Co-digestion, Potato stem, Milk whey, Heat and electricity, Economic assessment, Biofertilizer	(Martínez-Ruano et al., 2019)
12	Improving biogas production from anaerobic co-digestion of sewage sludge with a thermal dried mixture of food waste, cheese whey and olive mill wastewater.	Waste Management	Anaerobic co-digestion, Food waste, Cheese whey, Olive mill wastewater, Pre-treatment	(Maragkaki et al., 2018)
13	Biogas Production from Poultry Manure and Cheese Whey Wastewater under Mesophilic Conditions in Batch Reactor.	Energy Procedia	Anaerobic co-digestion, cheese wastewater, poultry manure	(Carlini et al., 2015)
14	Biogas production by anaerobic co-digestion of cattle slurry and cheese whey.	Bioresource Technology	Anaerobic digestion, Methane yield, COD reduction, Digestate yield test, Energy production	(Comino et al., 2012)
15	Biogas production from co-digestion of a mixture of cheese whey and dairy manure.	Biomass and Bioenergy	Cheese whey, Co-digestion, Dairy manure, Biogas, Acidifying	(Kavacik & Topaloglu, 2010)

CONCLUSIONS

The efficient management of these raw materials allows us to significantly reduce the environmental impact; contributes to the economic development of society through the construction of plants specialized in the treatment of this liquid waste (biorefineries, industries to produce bioplastics, biofuels, animal food), and promotes scientific research, that is, its use develops the economy circular.

The dairy industry, more specifically the cheese industry, generates waste whose management and final disposal have been widely debated. A promising alternative is to provide adequate treatment using technologies for the use of biomass through anaerobic digestion.

Whey, as an agri-food by-product, can be transformed into new products to generate economic credits, but mainly to avoid environmental impact.

Anaerobic Digestion is a reliable way to process agri-food, industrial and municipal waste; the whey, not having adequate treatment, is causing damage to our land and water reserves. The use of this method could ensure that this cheese effluent can be treated and processed to obtain various benefits, which will not only help the well-being of the planet, but we can also obtain additional monetary income.

Anaerobic codigestion is an option for the use of whey, since through this process it is feasible to obtain alternative energy through the production of fuel biogas. It is recommended to use co-digestion with manure and other agricultural waste.

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Advantages	Disadvantages
High efficiency in the removal of organic load.	Low in the elimination of nutrients and pathogens, the elimination of certain nutrients is not complete or they are partially eliminated.
Simplicity in the construction and operation of the reactors.	Due to the slow growth rate of methanogenic micro- organisms, the initiation period compared to aerobic processes is long, when inoculum is not available.
Anaerobic treatment can be very flexible and easy to apply on a small and large scale.	Possible bad odors, hydrogen sulfide is produced during anaerobic cycles, especially when there are sulfate concentrations.
Low space requirements.	Need for post-treatment, effluent post-treatment is generally required to meet organic matter discharge standards.
Low energy consumption, the energy consumption of the reactor is almost zero.
Low chemical and nutrient requirements, adequate and stable pH can be maintained without the addition of chemical agents and macro- and micronutrients remain stable in the waste, while toxic compounds are absent.

RESUMEN

ABSTRACT

INTRODUCTION

Waste characteristics

Table 1

Table 2

Technology description

Figure 1

Table 3

Technology methods and techniques

Figure 3

Anaerobic codigestion

Figure 4

Figure 5

Recent related research

Table 4

CONCLUSIONS

REFERENCES