A systematic review on biofuel production and utilization from algae and waste feedstocks– a circular economy approach

Abstract

Energy demand on a global measure grows continuously due to increased population, industrialization and economic growth. Fossil fuel resources that are currently available are definitely not sufficient to meet the growing demand. In addition, the continuous emissions from automobiles and industrial sectors should be attended to so that a complete remedial and sustainable alternative for fossil fuels is obtained. The appropriate replacement for fossil fuel is biofuel, as they are renewable and eco-friendly. First generation and second generation biodiesel derived from various sources are extensively researched and experimented practically by the past researchers. This article summarizes a continuous and comprehensive assessment of different feedstocks needed for third and fourth generations of biodiesel. Various sources of feedstock, steps for biodiesel production, yield of biodiesel obtained through different methods, properties of biodiesel like fatty acid profile, density, viscosity, cetane number, flash point, cloud point, economic feasibility and considerations are also discussed. Third generation biodiesel like microalgae can be widely used in CI engines. It is observed that their performance and combustion analysis in a CI engine is determined by the physico chemical properties of obtained biodiesel and nature of feedstock. Species selection and cultivation methods of microalgae, future perspectives of cultivating techniques and lipid production are summarized in detail. Fourth generation biodiesel like solar fuels and synthetic biomass production are covered, though their application in various energy fields is still not revealed. The type of transesterification that best suits the free fatty acid profile of fuel is selected and other reaction parameters like reaction time, reaction temperature, catalyst quantity and oil methanol molar ratio are explained individually for third generation feedstocks. Proper adoption of suitable methods would help in yielding the maximum biodiesel. Future energy demand can be dealt with by the combination of various third and fourth generation oil feedstocks.