Abstract
Anaerobic digestion to produce biogas is generally considered as one of the most sustainable technologies for the production of renewable energy. During this microbial process, organically bound nitrogen is released as ammonium that ends up in the digestate and finally may inhibit the process. In this study, it is investigated if ammonium can be removed and recovered out of the liquid fraction of a thermophilic digestate from a potato processor. This is achieved at laboratory scale through an easy and self-designed stripping and scrubbing process using Vigreux and Dufton columns, which are commonly used laboratory fractionating columns. The stripping is performed at pH 8.5 and at 323.15 K (50 °C), which results in the volatilization of the ammonium present in ammonia. Subsequently, the stripping gas charged with ammonia is put into contact with a sulphuric acid solution, resulting in (NH4)2SO4, which can be used as an N–S fertilizer. In addition, the digestion experiments have demonstrated that the biogas yield is 36% higher after removal of the ammonium from the digestate compared to the untreated digestate.
Highlights
The anaerobic digestion of organic waste is generally considered as one of the most sustainable technologies to produce renewable energy
The ammonium removed from the supernatant is recovered as (NH4)2SO4, Anaerobic digestion is generally considered as one of the most sustainable technologies for the production of renewable energy
The main bottleneck of the digestion process is the rather low conversion efficiency of organic material which is partly due to the accumulation of ammonia/ ammonium
Summary
The anaerobic digestion of organic waste is generally considered as one of the most sustainable technologies to produce renewable energy. Anaerobic digestion is a natural microbial process in which microorganisms break down complex organic matter in the absence of oxygen. It is generally considered a two-phase process, it can be subdivided into various metabolic steps with the participation of several microbial groups, namely. Intervention in the digestion process leading to a higher biogas production efficiency is one of the primary measures to reduce costs, to further expand the sector and to stimulate green energy production by means of biogas. There are two main technical reasons for the limited conversion efficiency that needs to be addressed: (1) the limited conversion of organic material into biogas due to the presence of hardly biodegradable
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