Sue Ellen Taelman

The environmental sustainability of microalgae as feed for aquaculture: a life cycle perspective

The environmental sustainability of microalgae production for aquaculture purposes was analyzed using exergy analysis (EA) and life cycle assessment (LCA). A production process (pilot 2012, 240 m(2)) was assessed and compared with two upscaling scenarios (pilot 2013, 1320 m(2) and first production scale 2015, 2.5 ha). The EA at process level revealed that drying and cultivation had the lowest efficiencies. The LCA showed an improvement in resource efficiency after upscaling: 55.5 MJ(ex,CEENE)/MJ(ex) DW biomass was extracted from nature in 2012, which was reduced to 21.6 and 2.46 MJ(ex,CEENE)/MJ(ex) DW in the hypothetical 2013 and 2015 scenarios, respectively. Upscaling caused the carbon footprint to decline by factor 20 (0.09 kg CO2,eq/MJ(ex) DW in 2015). In the upscaling scenarios, microalgae production for aquaculture purposes appeared to be more sustainable in resource use than a reference fish feed (7.70 MJ(ex,CEENE) and 0.05 kg CO2,eq per MJ(ex) DW).

Accounting for land use in life cycle assessment: The value of NPP as a proxy indicator to assess land use impacts on ecosystems.

Terrestrial land and its resources are finite, though, for economic and socio-cultural needs of humans, these natural resources are further exploited. It highlights the need to quantify the impact humans possibly have on the environment due to occupation and transformation of land. As a starting point of this paper (1(st) objective), the land use activities, which may be mainly socio-culturally or economically oriented, are identified in addition to the natural land-based processes and stocks and funds that can be altered due to land use. To quantify the possible impact anthropogenic land use can have on the natural environment, linked to a certain product or service, life cycle assessment (LCA) is a tool commonly used. During the last decades, many indicators are developed within the LCA framework in an attempt to evaluate certain environmental impacts of land use. A second objective of this study is to briefly review these indicators and to categorize them according to whether they assess a change in the asset of natural resources for production and consumption or a disturbance of certain ecosystem processes, i.e. ecosystem health. Based on these findings, two enhanced proxy indicators are proposed (3(rd) objective). Both indicators use net primary production (NPP) loss (potential NPP in the absence of humans minus remaining NPP after land use) as a relevant proxy to primarily assess the impact of land use on ecosystem health. As there are two approaches to account for the natural and productive value of the NPP remaining after land use, namely the Human Appropriation of NPP (HANPP) and hemeroby (or naturalness) concepts, two indicators are introduced and the advantages and limitations compared to state-of-the-art NPP-based land use indicators are discussed. Exergy-based spatially differentiated characterization factors (CFs) are calculated for several types of land use (e.g., pasture land, urban land).

Environmental sustainability assessment of a microalgae raceway pond treating aquaculture wastewater: From up-scaling to system integration.

The environmental sustainability of aquaculture wastewater treatment by microalgal bacterial flocs (MaB-flocs) in an outdoor raceway pond was analyzed using life cycle assessment. Pikeperch aquaculture wastewater treated at pilot scale (Belgium; 28m(2)) and industrial scale (hypothetical up-scaling; 41 ponds of 245m(2)) were compared. The integration of the MaB-floc raceway pond in a broader aquaculture waste treatment system was studied, comparing the valorisation of MaB-flocs as shrimp feed and as biogas. Up-scaling improves the resource footprint of the plant (848MJex,CEENEkg(-1) MaB-floc TSS at pilot scale and 277MJex,CEENEkg(-1) MaB-floc TSS at industrial scale) as well as its carbon footprint and eutrophication potential. At industrial scale, the valorisation of MaB-flocs as shrimp feed is overall more sustainable than as biogas but improvements should be made to reduce the energy use of the MaB-floc raceway pond, especially by improving the energy-efficiency of the pond stirring system.