Increased milk and dairy product production has contributed to the rapid growth of the cheese industry, leading to the generation of large quantities of acid whey. Acid whey presents an environmental challenge due to its high organic load, but it is also a potential source for the production of renewable energy and other valuable products.The aim of this master's thesis was to investigate the sustainable use of waste acid whey, partially deproteinized acid whey, and permeate obtained through ultrafiltration of partially deproteinized acid whey. Two sets of experiments were carried out. The first set consisted of biochemical methane potential tests in laboratory bottles, while the second set included experiments in laboratory bioreactors. The first bioreactor experiment was conducted without feeding, while in the second experiment feedingof acid whey and permeate was included. During the experiments, no inhibition of the methanogenesis process was observed. The highest biogas and methane production was achieved using acid whey and permeate as substrates. In the first biochemical methane potential test, mixtures with permeate produced 13% more methane than those with acid whey, whereas in the repeated test, methane production from permeate was 3.5% lower than that from acid whey. In laboratory bioreactors, the use of acid whey in the first experiment resulted in 28% higher methane production compared to permeate, while in the second experiment, this difference was 18.7%. Through terminal restriction fragment length polymorphism analysis, we aimed to determine whether different acid whey fractions influence the microbiome profile. Feeding with acid whey and permeate led to changes in the bacterial community of the microbiome but did not affect the composition of the archaeal community. Our findings indicate that acid whey, partially deproteinized acid whey, and permeate can be used for biogas production.
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