Study the Potential Use of Waste Water Grown Microalgae Biomass as Biofertilizer

Liquid wastewater streams that contain nitrogen must be treated before being discharged into the environment to prevent eutrophication. Already there are several existing conventional treatment technologies that can remove the nitrogen from the wastewater in combination of multiple processes. Depending on the processes involved, a fraction of nitrogen will be released to the atmosphere. On the contrary, there are several types of microalgae have the voracious demand of nitrogen and can assimilate waste bound nitrogen in a single step mostly as intrinsic proteins. Once the microalgae are separated from the water the minerals inside the microalgae cells remain available for plants and it can be used as fertilizer for the plants. Furthermore, removal of microalgal biomass from the wastewater at the end of the process may completely, or at least partially, treat the waste water minimizing the processes and cost of conventional treatment processes. Qatar's climate and non-arable land are ideal combinations for cultivating microalgae. The harvested microalgae can be dried and stored for future growth of fodder plants. On theory, every kg of microalgae biomass will require 1.73 kg of CO2. Some of the microalgae can also utilize specific organic carbon sources that are available in wastewater. However, the concentration of available organic carbon in the wastewater is not sufficient to support complete removal of nitrogen by microalgae. Hence, carbon dioxide must be supplied for complete and faster treatment. As the minerals will be utilized by the fodder plants, a fraction of the organic carbon associated with the microalgae biomass will be locked in the soil and thus increasing the soil's organic content. Therefore, successful application of wastewater grown microalgae biomass as biofertilizer can provide (1) a cost and energy effective wastewater treatment process, (2) nutrients (N, P and other minerals) recycling, (3) sustainable and environmental friendly agricultural application, and (4) carbon sequestration. Algal technology group of Qatar University is growing microalgae biomass in large scale open ponds. Mineral composition of a marine microalgae, Chlorocystis sp., biomass was characterized as 3.45? N, 0.22? P, 2.78? Ca, 0.39? Fe, 0.01? Cu and 0.02? Zn. Currently, this biomass is used to study its application as biofertilizer for the growth of sorghum plants. Soil was mixed with microalgae biomass and 5 kg of the soil mix was added in each pot. Three different microalgal biomass concentrations were applied in peat soil: 1.5 g/l, 3 g/l and 4.5 g/l. In another pot 3 g/kg NPK fertilizer was added while in another pot there was no inclusion of any fertilizer. Currently, each pot is irrigated with freshwater twice a week and the experiment will continue for two months. In parallel, Scenedesmous sp., a local fast growing freshwater microalgae, is currently being grown in wastewater collected from a small wastewater treatment plant, with an aim to be used as biofertilizer. The mineral composition of wastewater-grown Scenedesmous sp. will be determined and used as appropriate ratio for growing sorghum plants. Results obtained for different fertilizers (i.e., 1. NPK, 2. marine microalgae biomass, and 3. Wastewater grown microalgae biomass) will be compared in terms of plant growth, residual minerals in the soil.qscienc

A comparison of bio-crude oil production from five marine microalgae – Using life cycle analysis

Marine microalgae biomass could offer a viable feedstock for sustainably producing biofuel by hydrothermal liquefaction. In this study, five promising marine microalgae (i.e., Tetraselmis, Picochlorum, Synechococcus, Chroococcidiopsis, and Dunaliella), having different characteristics, were studied for biocrude oil production. The overall microalgal biocrude oil production process was divided into six unit operations: water supply, CO2 supply, nutrient supply, cultivation, harvesting, and HTL process. Models were developed for these unit processes such that once the key parameters of any unit process are known, the corresponding energy consumption could be determined. While the selection of the cultivation site influenced the energy requirements for sourcing seawater and CO2, the characteristics of the strain influenced energy requirements for the other four-unit operations. A cradle-to-grave concept was assumed to compare the life cycle assessment of the five strains. Among these strains, Tetraselmis sp. provided the most favorable energy balance with a net energy gain of 1.77 GJ/barrel of biocrude, an energy return on investment value of 2.81, and GHG reduction potential of 129 kg CO2 equivalent/barrel of biocrude. Further investigation with sensitivity analysis confirmed that the net energy yield for Tetraselmis sp. was least affected by a ±10% variation of the parameters of the unit processes.The authors would like to acknowledge the support of the Qatar National Research Fund (QNRF, a member of Qatar Foundation) for providing the funding (under grant NPRP8-646-2-272) for this study

Microalgae biomass production in municipal wastewater and use of the produced biomass as sustainable biofertilizer

Due to the lack of natural water sources, and cost and environmental issues associated with water desalination, Qatar currently emphasizes on the reuse of current wastewater sources, which includes conventional and unconventional approaches to utilize every available water sources, and ultimately promoting the wastewater stream driving from local municipalities. Currently, very few approaches have been taken to utilize this municipal wastewater sources. Moreover, municipal wastewater can also be utilized as growth media for producing microalgae biomass. A well-known approached is to utilize wastewater stream in an integrated farming system such as open pond microalgae cultivation system. In general microalgae, cultivation system requires a large quantity of water supply where additional nutrients and carbon dioxide are needed for microalgae biomass production. Whereas, microalgae grown in municipal wastewater can utilize the available N, P and other trace metals and therefore additional nutrients are not required. The process starts with the integrated treatment of municipal wastewater by selective local microalgae strains which can tolerate the complex stress deriving from the wastewater, consequently producing valuable by-products with zero wastes. In addition, during the cultivation, flue gas can be injected to enhance the biomass productivity. The aims of this study were to screen and optimize native microalgae strains growth in the wastewater stream from Al-Khor municipality. After screening microalgae strains with closed controlled condition, they were tested further with the ambient outdoor conditions in High Rate Algal Pond 200 L open system, using same municipal wastewater. Microalgae biomass were harvested after 10 days of experiments to utilize them as a biofertilizer. Among the microalgae strains two microalgae strain Chlorella sp. and Scenedesmus sp. shown higher biomass yield after the growth period. Overall Chlorella sp. gives a higher nitrogen and phosphorus uptake from the municipal wastewater effluent. Further study also showed a higher plant growth when municipal wastewater grown microalgae biomass was used as biofertilizer as compared to conventional inorganic fertilizer.qscienc