Algal Research-Biomass Biofuels and Bioproducts 

About: Algal Research-Biomass Biofuels and Bioproducts is an academic journal published by Elsevier BV. The journal publishes majorly in the area(s): Biology & Chemistry. It has an ISSN identifier of 2211-9264. Over the lifetime, 3101 publications have been published receiving 78393 citations.

Anaerobic digestion of algae biomass: A review

Abstract: The anaerobic digestion of microalgae is a prospective environmentally feasible option for creating a renewable source of energy for industrial and domestic needs. Microalgae anaerobic digestion is a key unit process that integrates efficiency and beneficially into the production of microalgae derived biofuels. Anaerobic digestion culminating in methane fermentation improves the economic viability of microalgae liquid biofuel production and presents an opportunity for power generation from wastewater derived microalgae. However the anaerobic digestion of microalgae biomass is not straight forward due to several technical restraints including low concentration of digestible biodegradable substrate, recalcitrant substrate constituents, cell wall degradability, low carbon to nitrogen ratio, ammonia toxicity and effects from salinity and associated metal ions. Current production methods for liquid biofuel production from microalgae produce approximately 60–70% residual biomass that is currently a byproduct. Anaerobic digestion provides biogas, but it can also provide essential nutrient recovery from lipid extracted microalgae biomass. The biogas produced from the anaerobic digestion process can be used to generate onsite electrical power or thermal heat to offset biomass processing and extraction processes. When both of these processes are integrated and operated simultaneously, the benefits to microalgae biofuel production and wastewater treatment derived energy production are increased significantly. To consider the integration of anaerobic digestion into a commercial-scale integrated microalgae production and biofuel refinery facility or wastewater treatment plant we present a review of the literature, the current state of the art and future directions for research.

Microalgae as versatile cellular factories for valued products

Abstract: As major part of the phytoplankton, microalgae are pivotal for the global food chain. Their exceptional capacity for CO2-fixation illustrates their indispensable significance to sustain earth's ecosystems. Further, they play a still underestimated role in eliminating contaminants from various environments. In addition to ecological benefit, many microalgal species exhibit high nutritional value and, at the same time, generate valued bio-products: Pigments, lipids, bioactive compounds, certain polysaccharides, bio-hydrogen and even biopolyesters with plastic-like properties have the potential for successful market penetration. Three substantial pigment groups, namely chlorophylls, carotenoids, and phycobilins, are essential for light harvesting and CO2 fixation. Those pigments will most likely undergo quick commercial success in “functional food”, cosmetics, aquaculture, pharmaceuticals, or food technology. Due to often high contents of polyunsaturated fatty acids essential for human metabolism, microalgal oils can be commercialized as health food and in the pharmaceutical and therapeutic field, creating much higher value than by converting them to biofuel. Finally, algal biomass remaining as residue after product recovery can be used as forage, biogas feedstock or biofertilizer. This utilization is needed for balancing the material- and energy cycles of the entire process. Thus, technology platforms following the principles of bio-refineries shall be established to enable the design of sustainable and economically feasible production of marketable microalgal products.

A review on the use of microalgal consortia for wastewater treatment

Abstract: The development of anthropogenic activities has led to an excessive disposal of wastes into water bodies, thus reducing water quality and damaging aquatic ecosystems. To avoid the negative impacts associated to the discharge of wastes into water courses, effective remediation processes are required to reduce nitrogen and phosphorus concentrations in discharged effluents. Current methodologies applied for nutrients removal tend to be complex, expensive and energy demanding. Therefore, cultivation of microalgae has appeared as an emerging alternative for nutrients removal from wastewaters. These photosynthetic microorganisms require large amounts of nitrogen and phosphorus for their growth. However, since it is very difficult to maintain pure cultures of these microorganisms in wastewater treatment processes, several studies have reported the use of natural and artificial microalgal consortia composed exclusively by microalgae or by microalgae and bacteria. The use of these consortia in the remediation of wastewaters can be very advantageous because: (i) cooperative interactions between the co-cultivated microorganisms can occur, enhancing the overall uptake of nutrients; and (ii) these systems tend to be more resistant to environmental conditions oscillations. This study provides an updated review of the literature regarding the application of microalgal consortia in the remediation of wastewaters from different sources, focusing on the mechanisms involved in nutrients removal by microalgae and the main interactions established between the microorganisms integrating the consortia and how they can influence nutrients removal efficiencies.

Nutrient recycling of aqueous phase for microalgae cultivation from the hydrothermal liquefaction process

Abstract: Two major considerations of the emerging algae biofuel industry are the energy intensive dewatering of the algae slurry and nutrient management. The proposed closed loop process which involves nutrient recycling of the aqueous phase from the hydrothermal liquefaction of microalgae offers a solution to both aspects. Hydrothermal liquefaction has been shown to be a low energy process for bio-crude production from microalgae. For the purpose of this research, microalgae strains of Chlorella vulgaris , Scenedesmus dimorphus and the cyanobacteria Spirulina platensis and Chlorogloeopsis fritschii were processed in batch reactors at 300 °C and 350 °C. Following liquefaction the product phases were separated and the water phase recovered. The bio-crude yields ranged from 27 to 47 wt.%. The bio-crudes were of low O and N content and high heating value making them suitable for further processing. The water phase was analysed for all major nutrients, TOC and TN to determine the suitability of the recycled aqueous phase for algae cultivation. Growth trials were performed for each algae strain in a standard growth medium and compared to the growth rates in a series of dilutions of the recycled process water phase. Growth was determined by cell count and chlorophyll a absorbance. Growth occurred in heavy dilutions where the amount of growth inhibitors was not too high. The results show that the closed loop system using the recovered aqueous phase offers a promising route for sustainable oil production and nutrient management for microalgae.

Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor

Abstract: Wet algae slurries can be converted into an upgradeable biocrude by hydrothermal liquefaction (HTL). High levels of carbon conversion to gravity separable biocrude product were accomplished at relatively low temperature (350 °C) in a continuous-flow, pressurized (sub-critical liquid water) environment (20 MPa). As opposed to earlier work in batch reactors reported by others, direct oil recovery was achieved without the use of a solvent and biomass trace components were removed by processing steps so that they did not cause process difficulties. High conversions were obtained even with high slurry concentrations of up to 35 wt.% of dry solids. Catalytic hydrotreating was effectively applied for hydrodeoxygenation, hydrodenitrogenation, and hydrodesulfurization of the biocrude to form liquid hydrocarbon fuel. Catalytic hydrothermal gasification was effectively applied for HTL byproduct water cleanup and fuel gas production from water soluble organics, allowing the water to be considered for recycle of nutrients to the algae growth ponds. As a result, high conversion of algae to liquid hydrocarbon and gas products was found with low levels of organic contamination in the byproduct water. All three process steps were accomplished in bench-scale, continuous-flow reactor systems such that design data for process scale-up was generated.