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The fossil fuels accomplish almost 80% of the world energy needs. The ever increasing exploitation of fossil fuels has led to environmental pollution, global climate change and health problems to living beings. Hence to meet the needs of the future energy and to mitigate the environmental pollution, it is critical to look for the alternate fuels. Global energy infrastructure in the future is believed to be accomplished by the energy generated from the low-cost renewable resources. Algae biomass has emerged as a promising biofuel source, as microalgae-based biofuels are biodegradable, renewable, and eco-friendly in comparison to fossil driven fuels. This study aims to examine the importance of microalgae as an alternative renewable energy source and evaluate the key challenges in the production of microalgae biofuel. [ABSTRACT FROM AUTHOR]

The utilization of renewable fuel alternatives holds promise for reducing the financial burden of regulatory compliance and the social responsibility associated with greenhouse gas emissions. Hydrothermal liquefaction (HTL) is one of the most versatile technologies for converting renewable biomass feedstocks (especially in the wet state) into biofuel (biocrude oil) in a compact plant. Therefore, this review is devoted to thoroughly reviewing and critically discussing biocrude oil production from biomass feedstocks through the HTL process. This review starts by discussing the principles of biomass HTL processing and product upgrading, aiming to provide a grounded and broad understanding of current developments in this domain. The data reported in the published literature are analyzed and visualized in order to scrutinize the effects of the main process parameters on the quantity, quality, cost, and environmental impacts of resultant biofuels. Higher biocrude oil yields are obtained at temperatures, pressures, and residual times between 300 and 350 °C, 24–27 MPa, and 15–25 min, respectively. Concerning yield and calorific value, biocrude oil derived from homogeneous catalysts demonstrates figures of 23.6 % and 32.1 MJ/kg, whereas that from heterogeneous catalysts exhibits percentages of 66.8 % and 40 MJ/kg, respectively. The challenges and prospects for the future development of biocrude oil are also discussed. HTL has a long way to go before being used for biofuel production on a large scale. Future studies appear to be directed towards the use of HTL technology under the biorefinery framework to maximize the exploitation of biomass into value-added products, while minimizing waste generation. [Display omitted] • Biocrude oil production from biomass by hydrothermal liquefaction is reviewed. • The principles of hydrothermal liquefaction and biocrude oil upgrading are discussed. • The effects of the main parameters on various aspects of biocrude oil are investigated. • The higher biocrude oil yields are obtained at 300–350 °C, 24–27 MPa, and 15–25 min. • Environmental and economic aspects of biocrude oil production are thoroughly discussed. [ABSTRACT FROM AUTHOR]

• An integrated process was developed for gasification and power production. • The impact of parameters on syngas and power production is investigated. • Power generation was in the range of 4 to 5 MW from 1000 kg/h feed. • Energy analysis was carried out using the Aspen Energy Analyzer tool. • 78% of heating utilities are fulfilled within the system using heating integration. Date palm waste (DPW) is an important waste that is abundantly available in the Middle East. However, this DPW is underutilization in the entire Middle East region. DPW could be a useful source of feedstock to generate sustainable and renewable energy via various thermochemical processes. The core objective of current investigation is to convert the DPW into syngas and the electricity generation from the produced syngas. Furthermore, to configure an integrated system to predict the gas composition and power generation under operating variables of temperature, steam/biomass ratio, compression ratio, and air flowrate. The integrated process simulation model of gasification and power generation model was developed using Aspen Plus V10®. The model consisted of two parts; the production of syngas from steam gasification and the second was the combustion-integrated power turbine system for power generation. The syngas composition at a temperature of 850 °C and steam/biomass of 1.0 was obtained as; H 2 37.88 vol%, CO 14.24 vol%, CO 2 11.29 vol%, CH 4 0.001 vol%. The power generation from the gas turbine increased from 3.2 to 3.6 MW with the increase in temperature. Whereas the total power generation was in the range of 3.2 to 5 MW with an increased steam flowrate of 500–2500 kg/h. Energy analysis shows that the process heat integration of the system is able to fulfill the 78 % utilities requirement within the system. This study provides the potential utilization of DPW for renewable fuel gas and electricity generation through a sustainable route and also provides environmentally friendly disposal of DPW in the Middle East and elsewhere in the world. [ABSTRACT FROM AUTHOR]