Modular AC coupled hybrid power systems for the emerging GHG mitigation products market

Bioenergy systems particularly waste to energy (WTE) systems are increasingly gaining prominence. Market for modular hybrid energy systems (HES) combining renewable energy sources including WTEs is potentially large. Novel configuration of AC coupling for HES is discussed. Emerging opportunities for market development of hybrid energy systems under green house gas mitigation initiatives particularly Kyoto flexibility mechanisms is analysed

Genotoxic effect induced by hydrogen peroxide in human hepatoma cells using comet assay

Background: Hydrogen peroxide is a common reactive oxygen intermediate generated by variousforms of oxidative stress. Aims: The aim of this study was to investigate the DNA damage capacity ofH2O2 in HepG2 cells. Methods: Cells were treated with H2O2 at concentrations of 25 μM or 50 μM for5 min, 30 min, 40 min, 1 h or 24 h in parallel. The extent of DNA damage was assessed by the cometassay. Results: Compared to the control, DNA damage by 25 μM and 50 μM H2O2 increasedsignificantly with increasing incubation time up to 1 h, but it was not increased at 24 h. Conclusions:Our Findings confirm that H2O2 is a typical DNA damage inducing agent and thus is a good modelsystem to study the effects of oxidative stress. DNA damage in HepG2 cells increased significantlywith H2O2 concentration and time of incubation but later decreased likely due to DNA repairmechanisms and antioxidant enzyme

Value added products from vineyard wastes - a review

Grape pomace is about 10% by weight of the grape input and consists of pressed skins, disrupted cells from grape pulp, seeds and stems. Grape pomace is mainly used as cattle feed or for soil conditioning or dumped in disposal sites. Cell walls of grape pomace are composed of cellulose, hemicelluloses, pectin and lignin arranged in a complex network. Lignin constitutes about 38-40% of the total grape pomace mass. Grape pomace is rich in polyphenols, fibres, tannins, tartaric acid, citric acid, anthocyanin and neutral sugars. Pomace can be separated in to marc (skin and pulp) and seeds in a breaker. Grape marc constituted mainly industrial source of anthocyanin based colorants. Grape seeds are a complex matrix containing approximately 40% fibre, 16% oil, 11 % proteins and 7% complex phenols including tannins in addition to sugars and mineral salts. The seeds of the grapes contain about 8-22% edible oil and the seed oil has been identified as a potential product because of its low saturated fats content and its high concentration (70-75%) of linoleic acid. Grape pomace is rich in phenolic compounds and the interest in phenolic compounds are from their antioxidant properties and their ability to serve as free radical scavengers. Grape seed extracts are reported to possess anticancer, antiulcer, anticataract and antiarteriosclerosis effect. In conclusion grape pomace, the byproduct of wine industry has a huge potential for the isolation of compounds in food preservation as well as for nutraceuticals and therapeutic agents

Comparison of thermophilic and mesophilic one-stage, batch, high-solids anaerobic digestion

Abstract The concept of starting up a batch, high-solids anaerobic digester by simply flooding the bed with a pH-buffer solution was tested using a mixture of vegetable waste and wood chips as feedstock at mesophilic (38 °C) and thermophilic (55 °C) conditions. At both temperatures stable and balanced methanogenesis was rapidly established within four days and was sustained until substrate was exhausted. Methanogenesis was more rapidly initiated in the thermophilic digester than in the mesophilic digester. Acetic, propionic and butyric acids accumulated in the leachate of both digesters during the start-up of digestion of uninoculated batch of waste. Thereafter all acids were degraded; which was quicker in the thermophilic digester. The accumulation and degradation of these acids was slower in the mesophilic digester. These studies showed that inoculum for carrying out thermophilic and mesophilic anaerobic digestion is readily available within the waste and its activity for complete mineralization of organic matter can be enhanced and sustained by providing adequate alkalinity. By employing a process in which anaerobic digestion of subsequent batches of waste was carried out by flooding with leachate drained from the digestion of a previous batch of waste, the volatile organic acid accumulation was maintained low and 95% of the methane yield potential of the waste was produced in 11 days under thermophilic conditions as opposed to 27 days under mesophilic conditions

A review of processes and design methods for organic matter removal in sub-surface flow constructed wetlands treating municipal and industrial wastewaters

The major mechanisms for wastewater treatment in sub-surface flow constructed wetlands (SSF-CW) are physical, chemical, biological and ecological processes. The paper reviews the latest developments in the design methods of SSF-CW system for organic carbon removal. Conventional plug flow exponential decay model, background concentration model and time dependent rate constant models were applied for a typical situation and the land area required for each case is calculated. The limitations of these design methodologies are discussed

Enhanced degradation of waste grass clippings in one and two stage anaerobic systems

The present work investigated the use of a simple rumen-fluid-inoculated anaerobic treatment system for the degradation of organic waste. Fresh rumen fluid collected from a fistulated sheep was used as the inoculum and fresh grass clippings were used as the waste material for treatment. Studies were carried out on both a one-stage system where the ligno-cellulosic fraction breaks down into a mixture of soluble products including volatile fatty acids and a two- stage system where these products are subsequently mineralised to biogas. In the one stage system about 70% of the organic waste was solubilized and in the two stage system about 60% waste material was solubilized in a week. About 50% of the degradation was achieved in a 4 day period, showing that a 4 day solids retention time would be a suitable operating regime. The maximum volatile fatty acid production rate was 327 mg COD 1 -1 h -1. A higher loading rate of 30 g 1 -1 d -1 was achieved in these systems compared to anaerobic digesters. Microbiological studies showed an increase in the number of fungal spores as well as a decrease in the number of protozoa in the treatment system. These numbers attained stable values over the duration of the experiments. The system developed is superior to conventional composting or anaerobic digestion and can be applied for the treatment of ligno-cellulosic agricultural residues