51. Energy performance and greenhouse gas emissions of kelp cultivation for biogas and fertilizer recovery in Sweden
- Author
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Emma Risén, Mauricio Sodré Ribeiro, Fredrik Gröndahl, Ulrika Welander, Joseph Santhi Pechsiri, Göran M. Nylund, Anette T. Jansson, Jean-Baptiste E. Thomas, Maria Malmström, and Henrik Pavia
- Subjects
Engineering ,Environmental Engineering ,020209 energy ,Kelp ,02 engineering and technology ,010501 environmental sciences ,Raw material ,engineering.material ,01 natural sciences ,Biogas ,0202 electrical engineering, electronic engineering, information engineering ,Environmental Chemistry ,Waste Management and Disposal ,0105 earth and related environmental sciences ,Waste management ,biology ,business.industry ,Energy performance ,biology.organism_classification ,Pollution ,Third generation ,ALGAS MARINHAS ,Biofuel ,Greenhouse gas ,Fertilizer ,business - Abstract
The cultivation of seaweed as a feedstock for third generation biofuels is gathering interest in Europe, however, many questions remain unanswered in practise, notably regarding scales of operation, energy returns on investment (EROI) and greenhouse gas (GHG) emissions, all of which are crucial to determine commercial viability. This study performed an energy and GHG emissions analysis, using EROI and GHG savings potential respectively, as indicators of commercial viability for two systems: the Swedish Seafarm project's seaweed cultivation (0.5ha), biogas and fertilizer biorefinery, and an estimation of the same system scaled up and adjusted to a cultivation of 10ha. Based on a conservative estimate of biogas yield, neither the 0.5ha case nor the up-scaled 10ha estimates met the (commercial viability) target EROI of 3, nor the European Union Renewable Energy Directive GHG savings target of 60% for biofuels, however the potential for commercial viability was substantially improved by scaling up operations: GHG emissions and energy demand, per unit of biogas, was almost halved by scaling operations up by a factor of twenty, thereby approaching the EROI and GHG savings targets set, under beneficial biogas production conditions. Further analysis identified processes whose optimisations would have a large impact on energy use and emissions (such as anaerobic digestion) as well as others embodying potential for further economies of scale (such as harvesting), both of which would be of interest for future developments of kelp to biogas and fertilizer biorefineries.
- Published
- 2016