Laboratory Algae Cultivation and BMP Tests with Ulva intestinalis from the Gulf of Riga

Abstract

This study aims to quantitatively evaluate the biogas potential of the green alga Ulva intestinalis from the Gulf of Riga, using BMP test with sewage sludge as inoculum. Meantime the nutrients role in biomass growth has been explored.The results from growing rate evaluation show that the growth of macroalgae was observed up to a certain point (typically 6–8 days of exposure) even within samples without any additional nutrients; on the contrary higher concentration has shown no growth effects. This could be explained with too high nutrient concentrations jeopardizing other conditions that are vital for macroalgae growth.The cumulative CH4 yields show an important spectrum of cumulative methane yields, with the highest one observed in 1:3 A/I (algae/inoculum ratio) in which the macroalgae were chopped (92.1 ± 33.5mL CH4/g VS on average), while the lowest one was observed in 1:5 A/I where the macroalgae had no pre-treatment (36.0 ± 10.5mL CH4/g VS). The results do not show a clear impact of the pre-treatments. The scenarios with no pre-treatment exhibited the effectiveness in a range of 9.7–24.6%, while the chopped ones – 14.56–24.8%, pre-treated with pestle – 12.9–24.13%. The results of this study confirm the suitability of U. intestinalis for biogas production, especially in the Baltic region.