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While microalgae oil was perceived as the preferred feedstock to supply the inelastic global demand for biofuel, industry and academia attempts to create viable microalgae-oil production processes has not reach the desired goal yet. UniVerve Ltd. has developed an innovative technological process that provides a scalable, cost effective and sustainable solution for the production of microalgae-biomass. The oil, which can be extracted with off-the-shelf wet-extraction technologies and used as an excellent feedstock for all kinds of biofuel, is expected to be produced at up to US$50 per barrel. As the biomass also contains omega-3, proteins and other valuable biomaterials that can be commercialized in the food and feed markets, a microalgae farm can serve the biofuel, food and feed industries, which currently face an increasing lack of quality feedstock at an affordable price.

The sun is the only source of renewable energy available to us, if geothermal energy is not taken into account. In the form of radiation (UV light, visible light, infrared light, Section 1.1) it sends us annually 178,000 terawatts (1 TW = 10¹² W; unit of power 1 W = 1 J s^–1 = 859.85 calories per hour), that is to say 15,000 times the energy consumed annually by humanity. Only 0.1% of the solar energy received by planet Earth is converted into plant biomass, i.e. 100 × 10⁹ tons per year which corresponds to ca. 180 × 10⁹ tons per year of CO₂ captured from the atmosphere. This CO₂ returns to the biosphere after the death of the plants. Consumption of fossil carbon emits ca. 35 × 10⁹ tons of CO₂ yearly. Biomass is the material produced by all living organisms (plants, animals, microorganisms, fungi)…

Recently, there has been an increase in public awareness on the health, environmental and safety hazards associated with the use of toxic organic solvents in food processing. The high cost of organic solvents, the increasingly stringent environmental regulations and the new requirements from the medical and food industries for ultrapure and high-added-value products have pointed out the need for the development of new and clean technologies for the processing of food products. On the other hand, the 12 principles of green chemistry emphasize the importance of sustainable processes, which minimize waste generation and energy consumption. The compliance of these concepts will lead to a cleaner environment and a more cost-effective use of resources. Thus, the solution passes by the development of more sustainable technologies that significantly increase the efficiency of chemical processes and reduce the operation time of such technologies. Conventional extraction techniques for solid vegetable matrices include Soxhlet, hydrodistillation, shake-flash methods, maceration and pressing. These methods present many disadvantages since they use toxic solvents, with the associated risks for human health and the environment, are time consuming, labor-intensive, present low yield and selectivity, and have high energy consumption. Therefore, the design of green, efficient and sustainable extraction techniques is mandatory. Thus, the green extraction processes should consider the minimization of the use of toxic solvents, reduce waste production, avoid the presence of toxic solvents in the final product and lower the energy consumption of the processes. Among the several techniques complying with these requirements, supercritical fluid extraction (SFE) is considered one of the most suitable for the extraction of compounds from vegetable matrices. Supercritical CO₂ extraction has provided an excellent alternative to the extraction and isolation of valuable compounds from natural products. In this section, SFE studies of compounds from microalgae and aromatic plants are described in more detail. Some of the most interesting experimental results obtained at the Experimental Thermodynamic Laboratory at the Technical University of Lisbon are presented and discussed.

Nannochloropsis oculata, a unicellular green microalgae has become a new prospective for biofuel feedstock which offers a long term of sustainability and energy security. N. oculata accumulate high oil content which is about 28.7-29% oil by biomass weight with the daily oil production of 25.8 mg/day. To enhance the economic feasibility of microalgal-based biofuel production, it is necessary to improve both biomass productivity and lipid content. This paper reviews previous works on microalgae undergo mixotrophic conditions and nitrogen deficient conditions in order to observe the biomass productivity and lipid content for biofuel production. Many microalgae are capable of using many types of metabolism, such as photoautotrophic, heterotrophic, and mixotrophic. In heterotrophic condition, microalgae growth in the absence of sunlight derives energy completely from outsource organic carbon. While in mixotrophic condition, microalgae obtain energy from both photosynthesis reaction in the presence of sunlight and outsource organic carbon. Two stage culture system, is proposed where N. oculata will be grown in various carbon sources such as glucose, glycerol and starch in the first stage and nitrogen deficient condition in the second stage for lipid accumulation.

The pyrolysis characteristics of Chlorella vulgaris (C. Vulgaris) (one kind of microalgae) by microwave oven are studied. The microwave pyrolysis of C. Vulgaris is carried out under different dosages of C. Vulgaris and different contents of activated carbon. The products and pyrolysis temperature are analyzed in order to obtain the optimal conditions. The results indicate that with increasing the dosage of C. Vulgaris, pyrolysis temperature drops and pyrolysis time increases, the average heating rate has the decreasing tendency. The maximum bio-oil yield and gas yield are achieved under 30g of C. Vulgaris and 25g of C. Vulgaris, respectively. The optimal content of activated carbon is 5% with the maximum gas yield of 60.25% and the largest weight loss of 87.47%.