Domestication Of Crop Stalks Anaerobic Fermentation Inoculum Characteristics Of Study

Agricultural organic wastes can be converted into clean fuels,e.g.,biogas, through anaerobic digestion,and can be made full use with the result of solving the problem of biomass and energy conversion.The objectives of this study were:(1) to investigate the feasibility of direct anaerobic digestion of rice straw;(2) to determine the effects of nutritional salts addition on biogas and methane production;(3) to disclose its kinetic characteristics in anaerobic digestion and to make the complicated mechanisms clearer.Anaerobic digestions of straw were carried out for about 100 days at room temperature(22±2℃) without other pretreatment.It was confirmed that the reactors could run stably and an average biogas yield of 204.3-373.3 ml-g^-1 TS loaded could be achieved with average methane content being 60-80%.Two obvious biogas production peaks could be observed for all the reactors during anaerobic digestion. The initial hydrolysis process could accelerate the following methanogenesis,which might result in the appearance of second biogas production peak during mid-later period.The effects of different nutritional salts addition on inoculum were discovered as early arrival of biogas production peaks,shortening of digestion period and increase of biogas production to a certain extent.The effect of phosphate addition was found to balance the nutritional needs in anaerobic digestion of rice straw and to make the digestion process more effective.The additions of Ca²⁺ and Mg²⁺ could accelerate biogas production,resulting in earlier appearances of biogas production peaks by 5-10 days as they improved the permeability of microbial cells and increased nutrient absorption.The biogas production for Mg²⁺ addition scenario increased by 10%with comparison to control experiments.The first-order kinetic model was applied in this study and it well fit the anaerobic digestion process of rice straw as only substrate,in which two obvious biogas production peaks were firstly and repeatedly discovered.The relative rate constants of the first digestion period were smaller than those of the second period for all the experiments.The kinetic studies were agreed with the experiment results of anaerobic digestion of rice straw.