Integrated Approach for Development of Environmental Biotechnologies for Treatment of Solid Organic Waste and Obtaining of Biohydrogen and Lignocellulosic Substrate

Abstract

Solid food waste is a significant threat to the environment. Thermodynamic calculations allow determining theoretically possible metabolic pathways for degradation of organic compounds by microorganisms, and to select the optimal one to increase efficiency of food waste recycling. The purpose of our work was application of thermodynamic calculations to find out suitable fermentation parameters for regulation of microbial metabolism Environmental Research, Engineering and Management 2018/74/4 32 to ensure a high rate of waste decomposition and formation of valuable products. The following methods were used: colorimetric and potentiometric for pH and oxidation-reduction potential (ORP) measurement, volumetric and chromatographic for the study of volume and composition of synthesised gas, and mathematical for fermentation parameters calculation. Fermentation of multicomponent kitchen food waste under theoretically calculated optimal parameters pH = 7.0 and Eh in the range form-250 to-350 mV provided extremely high metabolic activity of a hydrogen-producing microbial community, which resulted in a decrease in duration of batch fermentation to three days and an increase in hydrogen yield from 16 to 80-115 L/kg of dry waste. The coefficient of waste destruction (Kd), i.e., the ratio of initial and final weight of waste, reached 91. Obtained after fermentation, an unfermented lignocellulosic substrate was shown to be applied as plant probiotics and to supply mineral nitrogen for plant nutrition in an arid condition. Thus, high efficiency of application of a thermodynamic prognosis method of microbial interaction with organic compounds was shown to become the base for biotechnology of destruction of environmentally hazardous solid food waste with simultaneous obtainment of valuable products: environmentally friendly energy carrier-molecular hydrogen, as well as a lignocellulosic substrate to increase crop yields.

A Noxious Weed Ambrosia artemisiifolia L. (Ragweed) as Sustainable Feedstock for Methane Production and Metals Immobilization

“…In the agroindustry, they are used to suppress the growth of phytopathogenic bacteria and fungi and preserve crops [40,41]. Moreover, they are employed in environmental protection biotechnologies to degrade toxic organic [42] and inorganic waste [43]. The use of microorganisms for the biological purification of soil and wastewater from toxic metals is one of the most in-demand fields [44].…”

Універсальна Біотехнологія Знешкодження Токсичних Органічних Відходів І Металів З Отриманням Цінних Продуктів

“…В основу нашої розробки покладено термодинамічний прогноз для оптимізації зброджування відходів. Він зводиться до таких положень [4]: усі шляхи мікробного метаболізму допустимі лише в зоні термодинамічної стабільності Н 2 О, у діапазоні Е о  = -414…+814 мВ; оптимальними умовами для водневого та метанового бродіння є рН = 7,0 за анаеробних умов, тобто за потенціалу -414 мВ.…”

Hydrogen Dark Fermentation for Degradation of Solid and Liquid Food Waste

“…The efficiency of the hydrogen synthesis and waste degradation can be optimized by controlling several key parameters, including the pH and redox potential of the culture medium, the concentration of organic compounds or the ratio of solid waste and liquid phase in the bioreactor, the waste mixing mode, the process temperature, and the type of microbial community used in the fermentation [29,33,34]. The microbial growth during fermentation results in the acidification of the medium, which decreases to pH of 4.0-5.0 [35,36].…”

“…The microbial growth during fermentation results in the acidification of the medium, which decreases to pH of 4.0-5.0 [35,36]. The adjustment and maintenance of pH during the fermentation within neutral range (pH = 6.0-7.0) accompanied by waste mixing were theoretically and experimentally prove to speed up the degradation of waste and increase the hydrogen yield [33,37]. In addition, the pH adjustment at the start of the process can significantly shorten the lag phase of the fermentation [38].…”