Biogas production: evaluation of the influence of K2FeO4 pretreatment of maple leaves (Acer platanoides) on microbial consortia composition.

The potential of K2FeO4 as a pretreatment agent of a lignocellulosic material was examined on leaves of Acer platanodides as the sole substrate for biogas production by anaerobic digestion carried out through modelling laboratory-scaled semi-continuous reactors differing in loading rates and substrate (pretreated and untreated leaves). The quality of bioagas produced by K2FeO4-pretreated leaves was significantly better in terms of higher methane content and lower content of H2S. K2FeO4 had no crucial influence on growth inhibition of biogas-producing bacteria, which were analysed by comprehensive culture-independent methods utilising high-throughput sequencing of specific genes [bacterial and archaeal 16S rRNA, formyltetrahydrofolate synthetase gene (fhs), methyl-coenzyme M reductase α subunit gene (mcrA) and fungal internal transcribed spacers (ITS)]. The higher amount of CH4 in biogas utilising pretreated leaves as substrate could be caused by a shift to acetoclastic methanogenesis pathway, which was indicated by the higher amount of homoacetogenic bacteria and acetotrophic methanogens detected in those reactors.

Anaerobic digestion of waste biomass from the production of L-cystine in suspended-growth bioreactors.

Waste biomass from the industrial production of the amino acid L-cystine contains above-average concentrations of organic pollutants and significant concentrations of nitrogen and sulfur. The specific biogas production (SBP) of waste biomass was monitored in parallel suspended-growth laboratory anaerobic bioreactors. After severe inhibition was observed, three different procedures were applied to inhibited reactor sludge to counter-attack the inhibitory effects of sulfides, respectively hydrogen sulfide: micro-aeration, dilution with water and precipitation by ferrous iron cations. The performance of bioreactors was weekly monitored. Organic loading rates (as chemical oxygen demand, COD) ranged from 1.07 to 1.97 g L(-1) d(-1). At the end of the experimentation, SBP averaged 217, 300 and 320 l kg(-1) COD with a methane content of 21%, 52% and 54%; specific sludge production averaged 133, 111 and 400 g total solids kg(-1) COD, and inhibition was 49%, 27% and 25%; for the applied procedures of micro-aeration, dilution and precipitation respectively.

Long-term monodigestion of crude glycerol in a UASB reactor.

The aim of this study was to discuss the experience from long-term operation of a laboratory UASB reactor inoculated with suspended or granulated biomass for the treatment of different kinds of crude glycerol in undiluted or diluted state. The UASB reactor was operated under mesophilic conditions. It was demonstrated that the anaerobic treatment of crude glycerol as the only substrate in the UASB reactor is feasible, although the specific inhibition effects and requirements resulting from the nature and composition of the g-phase have to be considered. Deficient concentrations of nutrients had to be compensated by their supplementation into the digester. Long-term microbiological treatment of undiluted crude glycerol led to the process inhibition due to the accumulation of dissolved inorganic salts. When dosing diluted g-phase previously treated by acidulation, very good removal efficiency of COD, stable biogas production and high share of methane in the biogas were observed at the organic loading rates of up to 12kg/(m(3)d).