Pilot-scale conversion of lime-treated wheat straw into bioethanol: quality assessment of bioethanol and valorization of side streams by anaerobic digestion and combustion.

Introduction: The limited availability of fossil fuel sources, worldwide rising energy demands and anticipated climate changes attributed to an increase of greenhouse gasses are important driving forces for finding alternative energy sources. One approach to meeting the increasing energy demands and reduction of greenhouse gas emissions is by large-scale substitution of petrochemically derived transport fuels by the use of carbon dioxide-neutral biofuels, such as ethanol derived from lignocellulosic material.

Results: This paper describes an integrated pilot-scale process where lime-treated wheat straw with a high dry-matter content (around 35% by weight) is converted to ethanol via simultaneous saccharification and fermentation by commercial hydrolytic enzymes and bakers' yeast (Saccharomyces cerevisiae).

The transformation and toxicity of anthraquinone dyes during thermophilic (55 degrees C) and mesophilic (30 degrees C) anaerobic treatments.

We studied in batch assays the transformation and toxicity of anthraquinone dyes during incubations with anaerobic granular sludge under mesophilic (30 degrees C) and thermophilic (55 degrees C) conditions. Additionally, the electron shuttling capacity of the redox mediator anthraquinone-2-sulfonic acid (AQS) and subsequent increase on decolourisation rates was investigated on anthraquinone dyes. Compared with incubations at 30 degrees C, serum bottles at 55 degrees C presented distinctly higher decolourisation rates not only with an industrial wastewater containing anthraquinone dyes, but also with model compounds.

Effect of different redox mediators during thermophilic azo dye reduction by anaerobic granular sludge and comparative study between mesophilic (30 degrees C) and thermophilic (55 degrees C) treatments for decolourisation of textile wastewaters.

The impact of different redox mediators on colour removal of azo dye model compounds and textile wastewater by thermophilic anaerobic granular sludge (55 degrees C) was investigated in batch assays. Additionally, a comparative study between mesophilic (30 degrees C) and thermophilic (55 degrees C) colour removal was performed with textile wastewater, either in the presence or absence of a redox mediator. The present work clearly evidences the advantage of colour removal at 55 degrees C compared with 30 degrees C when dealing with azo coloured wastewaters.

The contribution of biotic and abiotic processes during azo dye reduction in anaerobic sludge.

Azo dye reduction results from a combination of biotic and abiotic processes during the anaerobic treatment of dye containing effluents. Biotic processes are due to enzymatic reactions whereas the chemical reaction is due to sulfide. In this research, the relative impact of the different azo dye reduction mechanisms was determined by investigating the reduction of Acid Orange 7 (AO7) and Reactive Red 2 (RR2) under different conditions.

Activated carbon as an electron acceptor and redox mediator during the anaerobic biotransformation of azo dyes.

Activated carbon (AC) has a long history of applications in environmental technology as an adsorbent of pollutants for the purification of drinking waters and wastewaters. Here we describe novel role of AC as redox mediator in accelerating the reductive transformation of pollutants as well as a terminal electron acceptor in the biological oxidation of an organic substrate. This study explores the use of AC as an immobilized redox mediator for the reduction of a recalcitrant azo dye (hydrolyzed Reactive Red 2) in laboratory-scale anaerobic bioreactors, using volatile fatty acids as electron donor.