Potential of biomethane from washed ashore algae in Gulf of Riga
2020
Dubrovskis, V., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia);University of Latvia, Riga (Latvia). Inst. of Mathematics and Computer Science | Bisters, V., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Burlakovs, J., Estonian Univ. of Life Sciences, Tartu (Estonia)
There is a strong tourism industry with a high recreational value in the southern Baltic, which is adversely affected by the algae that accumulate along the coast. The project’s concept of transforming the problem into a resource by preventing eutrophication through biogas production has several benefits for the region: removal of phosphorus and nitrogen from the Baltic Sea and their return to arable land (phosphorus is a limited resource to be saved for future food production); improved coastal recreation values and, in the long term, the regional economy; reduction of greenhouse gas (GHG) emissions from algae. Algae can provide bioenergy not only from agricultural land, but from our seas and oceans. Seaweed can be used to purify nutrient enriched water (associated with salmon, for example, on farms). Many species of seaweed can be classified in many ways, for instance, by colour. Genetic difference between green seaweed Ulva lactuca and brown seaweed Fucus is quite large. U. lactuca has a high sulphur content and usually has a carbon to nitrogen (C: N) ratio of less than 10, which makes anaerobic fermentation difficult. To determine the potential of biogas from different seaweeds of the Gulf of Riga, a study was carried out using laboratory equipment. In the study, 16 different bioreactors fermented at 38 ºC three different types of algae most common in the Gulf of Riga, taken from shorewashed seaweed piles. On average, fermentation for 32 days yielded 0.276L•gE−1dom biogas (0.046 L•gE−1dom methane) from brown algae, and 0.248 L•gE−1dom biogas (0.027 L•gE−1dom methane) from red algae. An average of 0.425 L•gE−1dom biogas (0.071L•gE−1dom methane) was obtained from green algae. The study shows that long-lived algae can be obtained in small amounts of methane per unit dry organic matter from land-littered ponds, if no measures are taken to condition them.
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