Читать книгу Liquid Biofuels - Группа авторов - Страница 36

Biomass energy has a great potential among alternative energy sources and it is a resource that can provide continuous energy, not discrete like wind and sun. The fact that biomass energy is easily stored provides an advantage over other renewable energy sources. Biomass does not cause an increase of CO₂ in the atmosphere [113]. Biomass is a fuel that does not contribute to the greenhouse effect theoretically in case of renewal of forest and plant existence; therefore it released as much carbon as takes carbon dioxide from the atmosphere if it burns. Biomass energy is divided into biodiesel, bioethanol and biogas, and each has its own advantages and disadvantages [114].

Advantages of biodiesel are being safer, easily biodegradable and non-toxic. It is a renewable resource and can be produced with local facilities. It contributes economically and strategically because it reduces dependence on oil. It contributes to agriculture and industry with by-products such as fertilizer, pulp and glycerin [115, 116]. On the other hand, disadvantage of biodiesel is having heat value slightly lower than petrodiesel. This situation causes a low power drop due to combustion in the engine. It is affected by cold weather conditions more quickly than petrodiesel. Especially clouding is seen earlier. This is a limiting factor for the use of biodiesel in cold climates. NO_x emissions are somewhat higher than petrodiesel [115-117].

The advantage of bioethanol is that it can be shown to decrease the emission values of the gases harmful to the environment; this is caused by a more efficient and cleaner combustion due to the oxygen it contains. It contributes to the reduction of air pollution. The value of plants used as raw materials will increase with the increasing demand for bioethanol, which will improve the economy and create wider market opportunities in the agricultural field. It will contribute to the economy as it can be replaced with gasoline as much as its usage rate. The octane of bioethanol is higher than gasoline. High octane creates more pressure and increases the thermal efficiency of the engine [117, 118]. On the other hand problems can occur in long-term storage of bioethanol. Bioethanol and water in the tank, which remain immobile, can decompose from gasoline and settle to the bottom of the tank. To prevent this, the fuel system must be completely emptied and cleaned before storage. Also, a gasoline stabilizer can be placed in the fuel tank after draining. In vehicles using bioethanol, while it is difficult to work in cold weather, there is also the possibility of steam plug formation in hot weather [119].

Biogas technology allows both energy recovery and waste to be obtained from organic waste/residual substances. It is a cheap, environmentally friendly source of energy and fertilizers; it provides waste recovery. It ensures that the disease factors that threaten human health and groundwater caused by animal fertilizers largely lose their effectiveness [120]. Considering the drawbacks of biogas, the nitrogen in the feed material might turn into an organic form of ammonium. Ammonium turns into ammonia or nitrate. If the storage conditions of the fermented fertilizer are not suitable, nitrogen and ammonia emissions occur. This causes health problems arising from waste, biogas risk of poisoning, explosion and fire. Pathogens and parasites cannot be completely removed in mesophilic and thermophilic reactors. For removal, energy pasteurization is required. Investment costs of biogas plants are high [121, 122].