Biofuels and their sources of production: A review on cleaner sustainable alternative against conventional fuel, in the framework of the food and energy nexus

Modern times are facing a massive crisis with rising global energy demand and carbon dioxide emission due to the consumption of fossil fuels. The depletion of petroleum-derived fuel has created a demand for an alternative fuel source. Fossil fuels are also regarded as conventional fuels, are the prime sources of non-renewable energy, whose loss cannot be sustained in years. According to the 2019 global statistical review of world energy, there is a 0.5% increased carbon dioxide emission rate and 1.3% primary energy consumption worldwide. These increased rates are a triggered alarm to humankind and the environment. Meanwhile, renewable sources such as biofuel show a potential usage with low carbon dioxide emission, less polluting and can be created from biomass in the forms of organic waste. Moreover, they are effective against greenhouse gases (GHGs) emission and the impact of changing climate from transports and vehicles. Today the biofuel research is performed globally because of the two fundamental properties, sustainability and renewability. There are many effective biomass production sources and fall into three categories, including the First generation, Second generation and Third generation biofuel. The first generation comprises food crop-related biomass, whereas the second generation includes lignocellulosic biomass, and the third generation features potential renewable sources in the form of algal biomass. The paper aims to review the various sources of biofuels and the methods used in the production, and discuss its advantages and sustainability.