Abstract This study utilized a renewable energy source, agricultural waste, in anaerobic digestion (AD) at appropriate conditions to obtain biogas and biomethane as an energy carrier. Maize stalks underwent ultrasound (US) pre-treatment for better accessibility for microorganisms, as lignocelluloses have a stable structure, insoluble in water and resist both mechanical and enzymatic attack. The digestate after an anaerobic digestion process was used for cultivation of algae after adsorption with activated carbon for clarification. Photosynthetic microalgae have industrial and economic perspectives, so their low-cost cultivation has a great potential for many applications. The results showed the impact of US pre-treatment of maize stalks as a sole substrate and co-digested with algal biomass. The total yields were 1116 cm3/L, 1350.5 cm3/L and 1293.25 cm3/L for the untreated, ultrasonically pre-treated and microwaved maize stalks. The possibility of accumulating algal biomass using anaerobic digestate as a medium was demonstrated. US pre-treatment (400 W) showed high efficiency with respect to the extractives obtained per unit of energy input. Addition of 4 g/L of microalgal biomass as a co-substrate led to an increase in the biogas yield compared to native stalks. A small closed circle system, starting from anaerobic digestion of lignocellulosic substrates followed by microalgae cultivation in the digestate and subsequent return of microalgal biomass back in the bioreactor as a co-substrate was realized, encouraging circular economy. The suggested scheme is a simple and low-cost technology, as the substrate used is freely available and renewable, and algae proved to grow in a waste effluent as medium.

中文翻译：

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使用超声波预处理的玉米秸秆和随后的微藻培养生产生物甲烷

摘要 本研究利用可再生能源农业废弃物，在适当条件下进行厌氧消化（AD），以获得沼气和生物甲烷作为能源载体。玉米秸秆经过超声波 (US) 预处理以更好地接触微生物，因为木质纤维素具有稳定的结构，不溶于水并能抵抗机械和酶的攻击。厌氧消化后的消化液经活性炭吸附澄清后用于藻类培养。光合微藻具有工业和经济前景，因此它们的低成本栽培具有很大的应用潜力。结果显示了美国预处理作为唯一底物并与藻类生物质共同消化的玉米秸秆的影响。总产量分别为 1116 cm3/L、1350.5 cm3/L 和 1293。未经处理、超声波预处理和微波处理的玉米秸秆为 25 cm3/L。证明了使用厌氧消化物作为培养基积累藻类生物质的可能性。US 预处理 (400 W) 显示出每单位能量输入获得的提取物的高效率。与天然秸秆相比，添加 4 g/L 的微藻生物质作为共底物导致沼气产量增加。实现了一个小的封闭循环系统，从木质纤维素底物的厌氧消化开始，然后在消化物中培养微藻，然后将微藻生物质作为共底物返回生物反应器，促进循环经济。建议的方案是一种简单且低成本的技术，因为所使用的基材是免费可用且可再生的，