An overview of production sources, advantages and disadvantages of biofuels as a renewable energy source

Today, the world is facing a huge crisis due to the increase in global energy demand and the greenhouse gases (GHGs) emissions caused by the use of fossil fuels. The consumption of energy carriers produces large amounts of carbon dioxide and other pollutants that pollute the environment. According to the reports of the World Energy Organization in 2019, the amount of carbon dioxide emissions has increased by 0.5% and primary energy consumption by 1.3% worldwide, which can be a warning for humans and the environment. On the other hand, most of the world's energy needs are provided by oil, coal and natural gas resources, all of which are limited and will be exhausted in a short time with the current consumption. The severe decrease in fossil fuel resources, the industrialization of most countries, their dependence on energy, and as a result the increase in the global price of fuel, on the one hand, has caused an energy crisis, and on the other hand, the increase in fuel consumption and inaccuracy in the way it is used has caused It has become a global environmental crisis. Therefore, the energy crisis, pollution and environmental effects caused by the use of fossil fuels have caused humankind to look for new sources of renewable energy, which is a type of renewable energy, biofuels. Biofuels are classified into four categories of first, second, third and fourth generation biofuels based on the raw materials used in their production. The first generation biofuels include biomass related to food products, while the second generation includes lignocellulosic biomass. The third generation has potentially renewable resources in the form of algal biomass, while the fourth generation includes genetically modified (GM) algal biomass. The main purpose of the article is to review the various sources of biofuels, compare different generations of biofuels and discuss the advantages and disadvantages of different types of biofuels.