• European Marine Science
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• Biomass and Bioenergy close

International audience; Biomass is a promising renewable alternative to decarbonize and to secure energy production on small islands, as most insular power generation systems rely heavily on imported fossil fuels. Feedstock procurement is a key aspect of bioenergy chain sustainability, and local resources as well as imported biomass can be considered if the electricity generated presents environmental benefits. We used Life Cycle Assessment (LCA) to evaluate the environmental impacts of 1 kWh of electricity produced in Guadeloupe from the combustion of locally grown energy cane and imported wood pellets. The energy cane agricultural supply was simulated using a bio-economic model to elaborate and analyze five scenarios involving different biomass mixes and geographical areas of production. Our results show that electricity produced from energy cane reduced the impacts of ABIOTIC DEPLETION, ACIDIFICATION and PHOTOCHEMICAL OXIDATION by 29% compared with pellet-based electricity. The environmental impacts of the energy cane cultivation stage varied by a factor of 1.5-3.7 among regional areas of cultivation because of differences in yields, soil emissions and land conversion for energy crop farming. The substitution of 5% of fossil energy by biomass in the island electricity mix can reduce GLOBAL WARMING and ABIOTIC DEPLETION impact by 4.5%. However, this change requires 3.5 to 5.2 times higher LAND OCCUPATION per unit of energy produced. Given the limited land availability on small islands, this latter point confirms that the combination of locally grown energy crops with imported biomass will be a suitable strategy to develop sustainable bioenergy for small islands.

Abstract Facility siting has traditionally been performed using economic metrics alone to determine suitable locations for a new facility. In this era of climate change concerns and political discord, a more holistic approach to biorefinery siting may yield alternative locations that meet stakeholder goals for community acceptance and reduced environmental impacts. A multi-criteria decision support tool (DST) that incorporates economic, environmental, and social metrics concurrently is introduced to assess the repurpose potential of existing facilities as a wood-based biorefinery. Economic siting criteria are represented by biorefinery operational cost components that vary geospatially. The environmental criterion is the Global Warming Potential of the supply chain, as measured through greenhouse gases emitted from the feedstock procurement, preprocessing, and transport equipment. Social criteria are represented by 1) the number of regional jobs created through the installation of a biofuel supply chain, and 2) county-level social assets that may influence biorefinery project success. Weights and scale values are derived for each set of metrics. An overall facility score is produced by summing the three metric scores. Additionally, overall user-defined metric weights are used to adjust the importance of the three metrics, thus altering the overall facility scores. The DST is applied to a case study in Western Oregon and Western Washington to refine a list of candidate pulp mills down to a select few for further investigation. It was found that the mills scored differently when overall metric weights were adjusted. Therefore, different stakeholder preferences may yield a different priority list of facilities.

Abstract The harvesting of microalgae is currently one of the bottlenecks hindering the commercial production of microalgae-based biofuels and products. The objective of this study was to determine the best flocculant and its optimum concentration in order to harvest the marine microalga Conticribra weissflogii (previously Thalassiosira weissflogii ) for further use in the production of biofuels or bioelements. Experiments were conducted with cultures in the logarithmic and stationary growth phases. The low-charge FLOPAM ® FO 4240 SH was the most effective at concentrations of 2 and 4 mg m −3 in the LOG phase cultures, with flocculation efficiencies >90%. Smaller flocculation efficiencies were observed for cells in the stationary growth phase, most likely due to the production of dissolved organic carbon by the microalga. The highest microalgae density generated higher flocculation rates, whereas the pH and salinity negatively impacted flocculant efficiency.

Flocculation is a promising approach for reducing the cost of harvesting microalgae. Flocculation of microalgae can be induced by precipitation of calcium phosphate (Ca-phosphate) when pH increases above 8.5, a pH level that can be achieved by simple photosynthetic CO2 depletion. Using the freshwater microalgae Chlorella vulgaris as a model, we identified the combinations of minimum pH and Ca and PO4 concentrations to induce flocculation. Predicted concentrations of amorphous Ca3(PO4)2 precipitation (chemical modelling) explained flocculation in these solutions. The efficiency of flocculation decreased with increasing microalgal biomass concentration. Solution renewal experiments suggest that flocculation is inhibited by algal organic matter in the medium, even when present at relatively low concentrations relative to concentrations in stationary phase medium. Addition of dissolved organic compounds showed that organic acids with a high molecular weight (e.g. humic acids, alginate) have a strong inhibitory effect on flocculation whereas glucose or acetate had no such effect. These effects may be related to complexation of Ca2+ or effects of organic matter on growth of the Ca-phosphate crystals. Precipitation of Ca-phosphate in media with high organic matter content requires a high water hardness (500 μmol L-1 Ca) and high PO4 concentrations (350 μmol L-1 P). Flocculation can be facilitated by addition of surplus PO4 to the medium. This surplus PO4 may be recovered after flocculation by re-dissolution of the Ca-phosphate through mild acidification. © 2013 Elsevier Ltd. publisher: Elsevier articletitle: Influence of organic matter on flocculation of Chlorella vulgaris by calcium phosphate precipitation journaltitle: Biomass and Bioenergy articlelink: http://dx.doi.org/10.1016/j.biombioe.2013.03.027 content_type: article copyright: Copyright © 2013 Elsevier Ltd. All rights reserved. ispartof: BIOMASS & BIOENERGY vol:54 pages:107-114 status: published