**8. Advantages and limitations of biogas technologies**

Biofuels are produced from biomass for a wide range of applications, such as cooking, heating, cooling, and transport. Biofuels can be solid (e.g., fuel-wood), liquid (e.g., bioethanol, biodiesel) or gaseous (e.g., biogas) [208, 209]. Biogas technology utilizes organic wastes for energy production, followed by recycling of the digested substrate as fertilizer [189]. Biogas can be used to generate heat or electricity, or as fuel for manufacturing or transport [210]. Electrical energy and heat generation from biogas is a source of green, environmentally friendly energy. At the same time, there is a reduction in methane emission from the decomposition of unmanaged biomass (especially animal droppings) [211–213]. Main benefits of biogas technology are to transform waste material into a valuable resource thus reducing waste, and providing valuable green energy [86, 189].
