Energy production and development have impacts on non-energy sector concerns including food security, water security, and sustainable land-use. Biofuel pathways differ in the tradeoffs they present within this “energy-water-food nexus” (EWFN). In this study, we focus on algal systems in the context of these interrelated challenges. We present areas of key consideration within the EWFN for large-scale algal system planning and commercialization, consider key resource inputs and outputs in the context of traditional biofuels compared with algal biofuels, provide examples of current global practices and EWFN impacts pertaining to liquid biofuels, and discuss potential opportunities and tradeoffs in applications of algal systems to EWFN challenges. The work described here could be used as a guide for future analysis that could quantitatively evaluate algal system feasibility in terms of economic viability, spatially and temporally explicit environmental impacts and production levels, and cross-sectorial impacts.

Energy crisis is a worldwide problem; Pakistan is facing severe shortage of this, especially in summer. To overcome these crises, huge amount of fossil fuels is being utilized which ultimately resulting in their exhaustion. In order to cope up the increasing energy requirements, alternative energy sources are required that should be cost-effective, environment friendly and technically feasible. In this scenario biodiesel production from algae has attracted scientist's attention worldwide. At present, the major constraint in biodiesel production from algae is nutritional cost for algal growth. Present research work was planned to minimize nutritional requirements of algae by using food industry waste water as a medium for algal growth towards economical biodiesel production. For this purpose four algal strains (A1, A2, A3 and A4) collected from different fresh water sources were evaluated for their potential use in biodiesel production. The waste water was pre-analyzed to determine the concentrations of different nutrients. All algal strains were grown in Bristol media and different dilutions (10, 20, 40, 80 and 100%) of food industry waste water. Growth data was recorded for one week. The results showed that algal biomass gradually decreased with increasing dilution of food industry waste water and was found higher in 100% waste water concentration than other dilutions. Cultivated algae were harvested for biodiesel production with n-Hexane as oil extractant and NaOH as a catalyst in different combinations through a chemical process ca\led transesterification. The FFA (free fatty acid) profile of algae 1 (A1) by using 75% hexane and 0.5% NaOH combination was found to be higher than other combinations. Higher concentration of NaOH (1%) resulted in soap formation. The aforesaid situations, plus owing to the best biomass production using 100% waste water concentration, deemed algae 1 (A1) as the best candidate among all four strains evaluated for biodiesel production.

The gasification of biomass in supercritical water is a promising technology for hydrogen production and the paper reports a thermodynamic analysis, based on minimization of Gibbs free energy, of the gasification with supercritical water of different biomass and agro-food residues: almond shells, digestate from wastewater treatment, algae and manure sludge. Numerical simulations were performed in order to assess the effect of temperature, pressure and biomass-to-water ratio on gas-phase yield and composition.A partial energy integration was also discussed, by considering the energy recovery from a turbine expansion of the gas-phase stream leaving the gasifier. The proposed thermodynamic approach allows predicting not only gasification efficiency of gasifier but also energy balance on the entire gasification process. Results showed that the dry substrates (almond shells and algae more than digestate and sludge) tend to form more carbon monoxide. Besides, data comparison revealed that the produced hydrogen comes from biomass and water for high process temperature, while when temperature decreases, the thermodynamic path tends to promote water formation from the hydrogen of the dry biomass.

Urban areas are considered net consumers of materials and energy, attracting these from the surrounding hinterland and other parts of the planet. The way these flows are transformed and returned to the environment by the city is important for addressing questions of sustainability and the effect of human behavior on the metabolism of the city. The present work explores these questions with the use of systems analysis, specifically in the form of a Multi-sectoral Systems Analysis (MSA), a tool for research and for supporting decision-making for policy and investment. The application of MSA is illustrated in the context of Greater London, with these three objectives: (a) estimating resource fluxes (nutrients, water and energy) entering, leaving and circulating within the city-watershed system; (b) revealing the synergies and antagonisms resulting from various combinations of water-sector innovations; and (c) estimating the economic benefits associated with implementing these technologies, from the point of view of production of fertilizer and energy, and the reduction of greenhouse gases. Results show that the selection of the best technological innovation depends on which resource is the focus for improvement. Urine separation can potentially recover 47% of the nitrogen in the food consumed in London, with revenue of $33 M per annum from fertilizer production. Collecting food waste in sewers together with growing algae in wastewater treatment plants could beneficially increase the amount of carbon release from renewable energy by 66%, with potential annual revenues of $58 M from fuel production.

Large seasonal water-level fluctuations may influence isotopic signatures of primary producers and the types and amounts of these potential food sources accessible to aquatic fauna of Poyang Lake, the largest freshwater lake in China. In this study, the isotopic signatures of primary producers and consumers were determined, stable carbon and nitrogen isotope analysis and mixing models were combined to investigate the influence of water levels on the diet and isotopic composition of Poyang Lake fish and invertebrates. Five potential food sources (seston, benthic organic matter, aquatic macrophytes, attached algae, and terrestrial plants), 4 species of invertebrates, and 10 species of fish were collected from the lake area during dry and wet seasons between January 2009 and April 2010. The δ 13C values of invertebrates and most fish were within the range of δ 13C values of the potential food sources for both seasons. The δ 13C values of invertebrates and most fish were lower in the dry season than in the wet season, whereas the δ 15N values exhibited different patterns for different species. Mixing models indicated that the most important food sources for common lake fauna were seston in the dry season and aquatic macrophytes and terrestrial plants in the wet season. The fauna were more omnivorous in the wet season than in the dry season. The food web dynamics of Poyang Lake are strongly influenced by changes in the abundance and accessibility of different basal food sources that occur because of seasonal flood pulses. The trophic links within the aquatic communities of Poyang Lake are modified by water-level fluctuations.

Plants and algae are the main sources of natural bioactive compounds used in the food and pharmaceutical industries. It is very important to achieve an efficient and safe technique to recover bioactive compounds while maintaining their quality and properties. Subcritical water extraction is the most promising engineering approach that offers an environmentally friendly technique for extracting various compounds from plants and algae. Application of pressurized water and high temperature in subcritical phase is able to modify the dielectric constant and polarity of the solvent which then contributes to a better extraction process. The technique improves the mass transfer rate and preserves the biological potency of the extracts. This article reviews current studies on the extraction of bioactive compounds from various species of plants and algae using the subcritical water technique and discusses its effects and benefits for the food and pharmaceutical industries.

A novel method was used to estimate assimilation efficiencies (AEs) of dissolved and food associated PCBs (IUPAC 31, 49, and 153) by the Baltic Sea blue mussel (Mytilus edulis). Mussels were exposed to radiolabeled PCBs in a series of short-term toxicokinetic experiments at different algal food concentrations, both at apparent steady-state (ASS) and non-steady-state (NSS) conditions in respect to PCB partitioning between water and algae. The PCB AEs were calculated using a physiologically based bioaccumulation model where experimentally determined uptake and exposure rates at ASS and NSS conditions were combined into linear equation systems, which were solved for PCB AE from water and food. A positive relationship between PCB uptake and algae clearance by the mussels was observed for all three PCBs. The PCB AEs from both water and food increased with congener hydrophobicity (octanol/water partition coefficient [K(ow)]), but AEs decreased with increases in water pumping and filtration rate of the mussels, respectively, The average contribution of food-associated PCB to the total uptake also increased with K(ow) from approximately 30% for PCB 31 and PCB 49 to 50% for PCB 153, mainly as a consequence of increased sorption to the algal food.

Global trends show that habitual omega-3 intakes are short of recommended guidelines, particularly among vegetarians and vegans. The potential health implications of low long chain omega-3 polyunsaturated fatty acid (LCω3PUFA) intakes coupled with concerns about sustainability of fish stocks call for innovative approaches to provide food based solutions to this problem. Nanoemulsions are systems with extremely small droplet sizes that could provide a solution while improving the bioavailability of LCω3PUFA. Oil in water nanoemulsion systems were successfully created using ultrasound with oil loads of up to 50% (w/w) using vegetarian LCω3PUFA oils (flaxseed and algae). Nanoemulsions of 50% (w/w) with mean droplet size measurements of 192 (flaxseed) and 182 nm (algae) using combinations of the emulsifiers Tween 40 and lecithin were prepared.This technique could be applied to create vegetarian LCω3PUFA nanoemulsions suitable for integration into enriched functional food products with the potential to increase LCω3PUFA intake and bioavailability.

Species composition of algae and aquatic plants in Bung Si Phi swamp were investigated during February to July 1985. The samples were collected randomly 3 times in February, April and July respectively. Thirty-five species of algae and seven species of aquatic plants were observed. Closterium sp., Cosmarium sp., Mougeotia sp., Onychonema sp., Pediastrum sp., Tetraedron sp., Anabaena sp., Oscillatoria sp., and diatom were dominant species of algae population while Ceratophyllum demersum, Hydrilla verticillata and Najas minor were dominant species of aquatic plant and occupied major area of the swamp. The proximate analysis of Spirogyra sp. showed 12.81 percent of protein nitrogen content by dry weight. The protein contents of aquatic plants ranged from 10.79 to 13.99 percent by dry weight.