Energy rationale for the Use of the Thermophilic Mode of Anaerobic Bioconversion of Liquid Organic Waste in the Climatic Conditions of the Russian Federation

The transition of livestock production to industrial processes and the concentration of animals associated with this process on large farms and complexes has caused a sharp increase in the volume of manure that must be disposed of without pollution. One of the ways of processing organic waste (biomass) is its anaerobic digestion in biogas plants through the vital activity of microorganisms (methanogenesis).Biogas obtained using microbiological processing of biomass can be used as a raw material for heat and electric energy. Annually, 0.17% of the total livestock manure produced at Russian agricultural enterprisesis used for biogas production.The main component of a biogas plant is a manure fermentation reactor, the required volume of which is determined by the daily output of manure from the livestock farm, the temperature and the hydraulic retention time of treatment. This research explored thermal energy consumption of biogas plants, using the example of a biogas plant of a modular design that depended on the average annual outdoor temperature. Based on the calculations, the thermophilic mode was found to be more energy-efficient than the mesophilic one; thus, with the thermophilic mode, the specific energy consumption needed for the plant was lower at the average annual outdoor temperatures of all the constituent entities of the Russian Federation. At the same time, the specific biogas yield in the thermophilic regime was 20-50%higher than in the mesophilic regime. Keywords: anaerobic processing, agricultural waste, thermophilicmode, mesophilicmode, energy costs, energy rational

Evolution of chemical composition and gas emissions from aged pig slurry during outdoor storage with and without prior solid separation

Chemical composition and gas emissions from two types of pig slurry were evaluated: the liquid fraction of mechanical solid-liquid separated slurry (SS), and raw slurry (RS). The slurry was obtained at the end of a pig fattening period and was stored in 100 l vessels for 15 weeks simulating outdoor storage conditions. During this period, representative samples were taken and analysed for chemical composition. Methane, carbon dioxide, ammonia, water vapour and nitrous oxide emissions were recorded. The results showed a high biological degradation during the first five weeks of outdoor storage in SS and RS slurries, as a result of an increase in the dissolved chemical oxygen demand, volatile fatty acids and carbon dioxide emission observed in this period. However, methanogenic activity was not evident until week 6 of storage in both slurries, confirmed by the volatile fatty acids accumulation and the negligible methane emissions during the first five weeks of storage. The results showed that differences in the initial slurry organic matter content, influenced by solid separation process affects the evolution pattern of the organic matter degradation. Storage time can considerably affect the biodegradability of organic matter in pig slurry. © 2011 IAgrE.This work was supported by the Agrobiogas project financed by the Agroalimed Foundation of the Conselleria de Agricultura, Pesca, Alimentacion y Agua of Valencia, Spain.Moset, V.; Cambra López, M.; Estellés, F.; Torres Salvador, AG.; Cerisuelo, A. (2012). Evolution of chemical composition and gas emissions from aged pig slurry during outdoor storage with and without prior solid separation. Biosystems Engineering. 111(1):2-10. doi:10.1016/j.biosystemseng.2011.10.001S210111

Evolution of composition of dairy manure supernatant in a controlled dung pit

Anaerobic conversion of dairy manure into biogas is an attractive way of managing this waste. It is well known that the hydrolysis of large molecules into small, directly biodegradable ones is the rate limiting step of the overall anaerobic process. The present work studies the development of the hydrolytic and acidogenic stages of dairy manure with different solid concentrations (40, 60 and 80 g VS/L) at ambient temperature (20 ° C). The purpose was to determine the operational conditions that provide a liquid fraction with a high soluble chemical oxygen demand (COD) and a high volatile fatty acids (VFA) content in manure before the methanogenic stage starts up. At 20 ° C, the evolution of the studied parameters showed that, in a controlled plug-flow dung pit, the hydrolytic and acidogenic stages progressed moderately in a continuous way during the 25 days that the experimentation lasted, whereas no methanization was observed. Supernatant COD and VFA concentrations increased 30% and 107%, respectively, for the 60 g VS/L samples. Manure was also operated at 35 ° C with a similar increase in supernatant COD but a higher increase in VFA, 154%. For both operational temperatures, the predominant VFAs were, in this order, acetic, propionic and butyric acids. During the operation at 35 ° C, the methanogenic stage started between days 20 and 25 for the samples with lower solids content, i.e. 40 and 60 g VS/L

Acidophilic degradation of methanol by a methanogenic enrichment culture.

An acidophilic methanogenic enrichment culture was obtained in a continuous up-flow anaerobic sludge blanket reactor operated at pH 4.2 with methanol as the sole carbon source. The specific methylotrophic methanogenic activity of the enriched reactor sludge at pH 5 was 3.57 g COD g−1 volatile suspended solids day−1 and the apparent doubling time of the biomass was 15.8 h. Acidic conditions were obligatory, since the enrichment culture was not able to produce methane or to grow at pH 7. Based on morphological characteristics, the dominant methanogenic species in the enrichment culture was a Methanosarcina

Acidophilic degradation of methanol by a methanogenic enrichment culture.

An acidophilic methanogenic enrichment culture was obtained in a continuous up-flow anaerobic sludge blanket reactor operated at pH 4.2 with methanol as the sole carbon source. The specific methylotrophic methanogenic activity of the enriched reactor sludge at pH 5 was 3.57 g COD g−1 volatile suspended solids day−1 and the apparent doubling time of the biomass was 15.8 h. Acidic conditions were obligatory, since the enrichment culture was not able to produce methane or to grow at pH 7. Based on morphological characteristics, the dominant methanogenic species in the enrichment culture was a Methanosarcina

Sustainable Treatment and Reuse of Diluted Pig Manure Streams in Russia: From Laboratory Trials to Full-Scale Implementation

This article summarizes the results obtained during the laboratory and pilot development of integrated biologic and physicochemical treatment and reuse of diluted pig manure streams. The application of a straw filter was an effective means to separate the solid and liquid fractions of raw wastewater and resulted in the removal of a significant part of the dry matter, total nitrogen, and phosphorus (65, 27, and 32%, respectively). From the filtrate generated, 60-80% of the total chemical oxygen demand (COD) was removed in an upflow anaerobic sludge bed reactor operating at 15-30°C. Ammonia was efficiently eliminated (>99%) from the anaerobic effluents using Ural laumantite as an ion exchanger. However, the nitrogen-content of the zeolite was too low to consider this method of ammonia removal economically feasible. The phosphate precipitation block, consisting of stripper of CO2 and fluidized-bed crystallizator, was able to decrease the concentration of soluble phosphate in the anaerobic effluents up to 7-15 mg of phosphate/L. The application of aerobic/anoxic biofilter as a sole polishing step was acceptable from an aesthetic point of view (the effluents were transparent and almost colorless and odorless) and elimination of biochemical oxygen demand (the resting COD was hardly biodegradable). However, the effluent nutrient concentrations (especially nitrogen) were far from the current standards for direct discharge of treated wastewater. We discuss the approaches for further improvement of effluent quality. Finally, we provide an outline of a full-scale system that partially implements the laboratory- and pilot-scale results obtaine