Biogas, Biodiesel and Bioethanol as Multifunctional Renewable Fuels and Raw Materials

Nowadays the world economy is based mainly on petrol as an energy source and raw material for chemical products. The global economic growth in the past century has led to high energy consumption, mainly from fossil fuels, such as coal, oil, and natural gas. The extensive use of fossil fuels formed and stored underground for millions of years has made impossible for the present vegetation on Earth to treat the emitted carbon dioxide by photosynthesis, leading to strong emissions of carbon dioxide and greenhouse effect with the consequent climate changes. One of the ways to cope with this global problem is to close the carbon cycle in nature by the use of renewable biofuels enabling recycling the sources of biological origin by energy production and consumption of the resulting carbon by photosynthesis. Some of these biofuels are biogas (a mixture of methane and carbon dioxide) generated from organic waste; ethanol, produced by fermentation of carbohydrates; and biodiesel, produced by transesterification of lipids. Another feature of this approach is the utilization of organic waste as energy, thus leading to multiple benefits for the environment: waste treatment with energy production, closing the natural carbon cycle, and saving of fossil fuels. Biofuels with their feedstock also serve as raw materials for new technologies for chemicals being now produced from petrol, natural gas, and coal.