Interest to harvest wild cyanobacteria exists due to the environmental and socioeconomic risks during cyanobacteria blooms coupled with demands for nonterrestrial-based alternatives for biofuel sources. This research, therefore, sought to estimate the wild cyanobacteria harvesting potential using Nodularia spumigena, and using the Baltic Sea as the case study. Data from literature provided during years 2003-2009 were used to perform estimations. Additional benefits of harvesting were also assessed by estimating the nutrient removal and biogas production potentials from the harvested biomass. Results indicate that one boom unit has the potential to harvest approximately 3 to 700 kg dry weight of N. spumigena per hour depending on the algae concentration of the bloom. Results also suggest that nutrient removal and biogas production potentials provide substantial additional incentives to the harvesting operation during years of extensive and highly concentrated blooms. However, during nonextensive or nonconcentrated blooms such potentials are low.

The interest in harvesting biomass from the Baltic Sea has increased in recent years. However, there is a lack of available data on macroalgae biomass and of cost-effective methods for site-specific quantification of macroalgae. In this study, macroalgae biomass has been quantified in Trelleborg and thus the nutrient reduction that could be achieved by harvesting on a regional scale. The biomass was estimated on the basis of existing inventories of macroalgae, photic zone distribution and bottom substrata. An independent model for estimating the potential of macroalgae growth was applied where factors affecting the growth of macroalgae, for example nutrients, light and temperature, were considered. The estimated summer stock of macroalgae biomass along the 58 km coastal stretch in Trelleborg amounts to 19 000 tonnes dry weight (dwt) red filamentous algae. If 10-30% of this summer stock were to be harvested, a nutrient reduction of 50-150 t of nitrogen could be achieved. The model for estimating biomass proved promising and worthy of further investigation.

Interest in industrial-scale cultivation of microalgae biomass has increased in recent years, due to its potential in phytochemicals, wastewater treatment, and aquaculture feed. Previous studies have focused on freshwater systems and phototrophic microalgae growth. In this study, preliminary observations were performed on mixotrophic growth of Tetraselmis tetrathele in crude unaltered saline wastewater and its nutrient removal and aquaculture feed potential. The wastewater was obtained directly from a Pacific white shrimp farm. The results showed successful phototrophic and mixotrophic growth of Tetraselmis tetrathele in saline wastewater, with maximum specific growth rate of approximately 0.2 day-1. Some nutrient removal was achieved (phosphate), and use of biomass as feed for shrimp aquaculture are further discussed.

Energy systems analysis and greenhouse gas (GHG) emissions of open pond microalgae cultivation systems is attracting considerable interest in the past decade due to their potentials for the production of biofuels and phytochemicals. However, there has been little discussion on energy systems analysis of microalgae produced from power plant flue gas and its use as an alternative protein source. This study aims to analyze edible protein energy return on investment (ep-EROI) and the overall GHG emissions for a medium-to-large scale Nannochloropsis oceanica cultivation system using power plant flue gas in northern China. Besides, additional benefits of the microalgae cultivation system were assessed on the overall nutrient recovery potential of the harvested biomass. Results of the study indicated that cumulative energy demand and GHG emissions for production of Nannochloropsis oceanica products were intermediate to other conventional protein sources in the literature, such as fish. Results of the EROI-based analysis showed that the Nannochloropsis oceanica cultivation system achieved a moderate ep-EROI of 0.11.

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 (0.5 ha), biogas and fertilizer biorefinery, and an estimation of the same system scaled up and adjusted to a cultivation of 10 ha. Based on a conservative estimate of biogas yield, neither the 0.5 ha case nor the up-scaled 10 ha 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.