AMMONOX: Ammonia for Enhancing Biogas Yield and Reducing NO_x-Analysis of Effects of Aqueous Ammonia Soaking on Manure Fibers

摘要

Laboratory experiments have shown that aqueous ammonia soaking (AAS) is a promising treatment for increasing the methane yield of the solid fraction of manure (fibers). AMMONOX is a new concept based on the sustainable use of ammonia for enhancing biogas production at biogas plants digesting manure. The proposed process is based on an optimized AAS treatment of manure fibers in combination with an efficient ammonia recovery step. The enhancement of biogas production is achieved by enriching manure with AAS-treated fibers, or other ligno-cellulosic residues, while the ammonia recovered can be used for fulfilling the needs of the treatment itself. Excess of ammonia could be produced when ammonia is recovered from both the treated fibers and the digester effluent, which could be used for the reduction of NO_x in biogas-based electricity generation by gas turbines. In this survey study, the importance of different factors affecting the performance of AAS of digested manure fibers was investigated in order to conclude on which variables to optimize. Principal component analysis of the present data was used for a preliminary analysis of effects. The temperature and the ammonia concentration during AAS were the most influencing variables in terms of methane yield under the conditions tested. Further experiments should be conducted in order to investigate the effect of shorter AAS duration than the ones tested (lower than 24 h) and for assessing the importance of the solid-to-liquid ratio in the treatment mixture; the follow-up campaign should be optimized with respect to possible interactions/correlated experimental factor effects.