Demand-oriented energy supply by the anaerobic digestion of organic waste

Abstract

The share of renewable energy is steadily increasing globally. Nevertheless, power generation from renewable energy sources, such as solar and wind energy, is highly dependent on suitable weather conditions and therefore highly fluctuating. Thus, alternatives to compensate fluctuations in the energy production are necessary. Biogas plants have the potential to balance energy generation fluctuations and work independently from unstable weather. Experiments on laboratory scale showed that the storage of food waste had only a marginal impact on its energy content. A rapid acidification due to a lactic acid fermentation leads to a pH decrease and concomitant organic acids increase, preserving the stored organic waste. The pH dropped from initially 4.8 to 4 within the first 2 days of storage. It declined until day 10 to 3.6 and stayed at this level until the end of the experiment. Due to a low pH and a high VFA concentration, only minor amounts of gas were produced during storage. No formation of explosive gas mixtures was detected during the storage. Therefore, no safety precautions are necessary to avoid danger from explosion. The results obtained in laboratory were confirmed by experiments on real scale. Thus, pre-condition of organic waste for a flexible feeding and demand-oriented energy supply is feasible to balance energy generation fluctuations.