Analysis of cyanobacteria as cosubstrate for anaerobic fermentation of distillery waste
Marisev, Aleksandr (2018)
Tampereen ammattikorkeakoulu
2018
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2018082214616
https://urn.fi/URN:NBN:fi:amk-2018082214616
Tiivistelmä
In this paper, the biogas and methane potentials were analysed by utilizing cyanobacteria as cosubstrate with distillery waste. Cyanobacteria Arthrospira platensis was produced in a tubular airlift photobioreactor and was harvested in weekly basis. As well, the growth rate of Arthrospira platensis was observed during each weekly harvest. For better analysis of substrate, batch tests were performed, where one test was distillery waste monosubstrate and the other test was cyanobacteria-distillery waste mix. As well, for comparison, two bioreactors operating in continuous mode were used, one with distillery waste only and the other one with cyanobacteria-distillery waste mix.
It was identified that Arthrospira platensis can grow in cases when the standard medium concentration was diluted. Also, the growth rate was identified to be higher by 18 % than the other same culture with the same light. From weekly harvested medium, it was possible to recover 10,62 g/l (in average during total experiment time) of cyanobacteria biomass as the highest amount from one loop. However, it was impossible to reproduce the same growth rate of Arthrospira platensis when it was cultivated in digestate medium, by having no cell increase whatsoever, in the end resulting with approximately 25 grams of bio-mass when harvested at the end of experiment.
From batch test results, biogas production was higher from distillery waste substrate (1111 l/kg VS for distillery waste and 845 l/kg VS) for cyanobacteria-distillery waste mix (20% cyanobacteria and 80 % distillery waste proportion)), while the methane production was nearly the same for both substrates, which was 60 % for distillery waste substrate and 61 % for cyanobacteria-distillery waste mix. Hydrogen sulphide concentration was 30 % higher than distillery waste substrate, but at the end of the experiment was not present anymore. During 35 days of continuous fermentation, the results showed the similar biogas production from both substrates (475 l/kg VS for distillery waste and 520 l/kg VS for cyanobacteria-distillery waste mix (same proportion as batch tests), with around 51 % average methane concentration). However, by the end of experiment, the reactor with cyanobacteria-distillery waste mix had a higher methane concentration, with a difference of 5-6 %. Although, the hydrogen sulphide concentration was identified to be high from this reactor with an average difference of 30 % (1180 ppm highest).
It was identified that Arthrospira platensis can grow in cases when the standard medium concentration was diluted. Also, the growth rate was identified to be higher by 18 % than the other same culture with the same light. From weekly harvested medium, it was possible to recover 10,62 g/l (in average during total experiment time) of cyanobacteria biomass as the highest amount from one loop. However, it was impossible to reproduce the same growth rate of Arthrospira platensis when it was cultivated in digestate medium, by having no cell increase whatsoever, in the end resulting with approximately 25 grams of bio-mass when harvested at the end of experiment.
From batch test results, biogas production was higher from distillery waste substrate (1111 l/kg VS for distillery waste and 845 l/kg VS) for cyanobacteria-distillery waste mix (20% cyanobacteria and 80 % distillery waste proportion)), while the methane production was nearly the same for both substrates, which was 60 % for distillery waste substrate and 61 % for cyanobacteria-distillery waste mix. Hydrogen sulphide concentration was 30 % higher than distillery waste substrate, but at the end of the experiment was not present anymore. During 35 days of continuous fermentation, the results showed the similar biogas production from both substrates (475 l/kg VS for distillery waste and 520 l/kg VS for cyanobacteria-distillery waste mix (same proportion as batch tests), with around 51 % average methane concentration). However, by the end of experiment, the reactor with cyanobacteria-distillery waste mix had a higher methane concentration, with a difference of 5-6 %. Although, the hydrogen sulphide concentration was identified to be high from this reactor with an average difference of 30 % (1180 ppm highest).