Deshai Botheju

Oxygen Effects in Anaerobic Digestion – A Review

This article reviews the experimental and theoretical studies conducted on the possible effects of oxygen in biogas generating anaerobic digesters. The interactions of oxygen with various biochemical processes associated with anaerobic digestion are discussed together with other relevant aspects. The conventional perception of oxygen being merely toxic in anaerobic digestion (AD) is refuted. Digesters can withstand significant levels of oxygenation without drastic negative impacts. Limited quantities of oxygen can even lead to improved AD reactor performance under certain operating conditions. Co-existence of anaerobic and aerobic cultures in a single bioreactor environment has been demonstrated. It is shown that the partial aeration assisted AD can serve as a beneficial treatment strategy for simultaneous waste treatment and energy generation, for a multitude of organic waste categories.

Biogasification of Waste Monoethanolamine Generated in Post Combustion CO2 Capture

Publisher Summary This chapter intends to investigate the suitable operating conditions for converting waste Monoethanolamine (MEA) into a CH4 rich biogas through anaerobic biogasification. MEA contaminated liquid waste generated in post combustion CO2 captures poses a disposal issue. Anaerobic biogasification potential of waste MEA is evaluated in a series of laboratory experiments conducted under different operating conditions. Provision of a limited amount of oxygen may enhance the methane potential of waste MEA. Codigestion of MEA together with a readily biodegradable substrate is found to be a solution to overcome ammonia and pH inhibition caused by low C/N ratio and high alkalinity. Substrate inhibition caused by waste MEA can be overcome by acclimatization. MEA degradation pathways via acetic and ammonium, with and without oxygen, are included in an anaerobic digestion model (ADM 1-Ox). MEA degradation to methane by anaerobic digestion with no or small quantities of free oxygen is adequately predicted by model simulations. Micro-aeration has a favorable effect on the methane generation potential. A cosubstrate approach is required to obtain stable biogasification of waste MEA in a continuous flow reactor, in order to increase the low C/N ratios typical for amine wastes and hence to avoid the ammonia and pH inhibition.

Monoethanolamine biodegradation processes

Publisher Summary Monoethanolamine (MEA) is often used as the solvent of choice in CO2 scrubbing processes. Such scrubbing systems are increasingly being built during recent times due to the increased attention on carbon dioxide capture and sequestration (CCS) concept associated with CO2 free power generation initiatives. Technical maturity of this solvent absorption system together with its unique features like high loading capacity for CO2 at low partial pressures, fast reaction kinetics and high removal efficiencies may ensure high use of this chemical. A significant amount of MEA containing liquid wastes is generated due to degradation of the solvent in gas scrubbing. Land filling and incineration has been used for the disposal of such wastes in small quantities but such disposal methods may be neither economical nor environmentally sustainable for handling large quantities of such liquid wastes. Release of untreated or poorly treated amine wastes into the environment can harm the local ecosystems and public health. Ecotoxicity of different amines and health impacts of various chemical components present in waste amines.