Michel Béland

Buffer requirements for enhanced hydrogen production in acidogenic digestion of food wastes

The requirements for pH buffer addition for hydrogen production and acidogenesis in batch acidogenic digestion of a food waste (FW) feedstock with limited alkalinity was studied at various initial pH conditions (6.0-8.0). The results showed that, without buffer addition, hydrogen production from this feedstock was insignificant regardless of the initial pH. With buffer addition, hydrogen production improved significantly if the initial pH was greater than 6.0. Substantial hydrogen production occurred when the pH at the end of the batch digestion was higher than 5.5. The maximum hydrogen production was found to be 120 mL/g VS added when the initial pH was 6.5 and buffer addition was in the range of 15-20 mmol/g VS. The effect of pH buffering on the formation of volatile fatty acids (acetic acid, propionic acid and butyric acid) was similar to its effect on hydrogen production. The results of this study clearly indicated shifts in the metabolic pathways with the pH of fermentation. The changes in metabolic pathways impacted upon the dosage of buffer that was required to achieve maximum hydrogen generation.

AN EARTH-SYSTEM PREDICTION INITIATIVE FOR THE TWENTY-FIRST CENTURY

Some scientists have proposed the Earth-System Prediction Initiative (EPI) at the 2007 GEO Summit in Cape Town, South Africa. EPI will draw upon coordination between international programs for Earth system observations, prediction, and warning, such as the WCRP, WWRP, GCOS, and hence contribute to GEO and the GEOSS. It will link with international organizations, such as the International Council for Science (ICSU), Intergovernmental Oceanographic Commission (IOC), UNEP, WMO, and World Health Organization (WHO). The proposed initiative will provide high-resolution climate models that capture the properties of regional high-impact weather events, such as tropical cyclones, heat wave, and sand and dust storms associated within multi-decadal climate projections of climate variability and change. Unprecedented international collaboration and goodwill are necessary for the success of EPI.

Laboratory pilot scale study for H2S removal from biogas in an anoxic biotrickling filter.

The purpose of this laboratory pilot scale study at the Wastewater Technology Centre (WTC), Environment Canada, Burlington, ON was to investigate the anaerobic biological removal of H2S from biogas under real-time operating conditions. Biogas produced in a 538 litre pilot anaerobic digester was continuously fed into a 12 litre biotrickling filter containing plastic fibres as packing bed media. The process was monitored for several months. The biogas flowrate and H2S concentration ranged between 10 to 70 L/h and 1,000 to 4,000 ppmv respectively over the course of the test period. Nitrate-rich wastewater from a pilot scale sequencing batch reactor effluent was used as the nutritive solution for the biotrickling filter. The paper presents the influence of several operational parameters such as biogas flowrate, hydrogen sulphide concentration and composition of nutrient solution on process performance. To date, our results show H2S removal rates up to 100% without adverse effects on the methane concentration of the biogas. No system deterioration was observed over long term operation. This non-conventional technology is very promising and could be considered for full scale applications.

Investigation on the use of nitrified wastewater for the steady-state operation of a biotrickling filter for the removal of hydrogen sulphide in biogas.

A biological process for the removal of hydrogen sulphide (H2S) in digester biogas was investigated using nitrified municipal wastewater as a nutrient solution under anoxic conditions. Biogas was c...

Evaluation of different packing media for anoxic H2S control in biogas.

This paper presents the experimental results obtained during the operation of two biotrickling filters packed with 6.7 L of commercially available plastic fibres and lava rocks, respectively. The biotrickling filters were tested under similar operating conditions for hydrogen sulphide (H2S) removal from biogas under anoxic conditions, in order to determine the influence of biogas flow rate and H2S concentration on the process performance and to facilitate process modelling. The biogas flow rate was adjusted to between 25 and 75 L/h, while the input H2S concentration was varied between 500 and 1500 ppmv. The process performance was evaluated by two simultaneous system responses, namely the H2S removal efficiency and H2S loading rate, which were subsequently described by a second‐order empirical model and an interaction model, respectively. Good agreement between the experimental results, model prediction and simultaneous dual‐response simulation was obtained.

Empirical modelling and dual-performance optimisation of a hydrogen sulphide removal process for biogas treatment

This study was conducted in order to investigate the use of a simple, low-cost technology for the removal of hydrogen sulphide (H(2)S) from biogas, consisting of an anoxic biotrickling filter. Modelling and optimisation of the process was achieved by studying two independent variables (H(2)S concentration and biogas flowrate) and two simultaneous performance criteria (H(2)S removal efficiency (%) and H(2)S loading rate (g/(m(3) bed day)), which were inversely related. The experiments were carried out on a bioreactor with a 12 L packing volume. H(2)S concentration and biogas flowrate were varied in the range of 2000-4000 ppm(v) and 10-70 L/h, respectively. A model sensitivity analysis indicated the influence of the process variables on the bioreactor performance. Process optimisation was undertaken on a H(2)S removal efficiency basis, while maintaining a target H(2)S loading rate, depending on the desired quality for the biogas use and the technological requirements.

The scope of science for the International Polar Year, 2007-2008

Produced by the ICSU/WMO Joint Committee for IPY 2007–2008 By: Ian Allison and Michel Beland (Co-Chairs), Keith Alverson, Robin Bell, David Carlson, Kjell Danell, Cynan Ellis-Evans, Eberhard Fahrbach, Edith Fanta, Yoshiyuki Fujii, Gisbert Gilbertson, Leah Goldfarb, Grete Hovelsrud-Broda, Johannes Huber, Vladimir Kotlyakov, Igor Krupnik, Jeronimo Lopez-Martinez, Tillmann Mohr, Dahe Qin, Volker Rachold, Chris Rapley, Odd Rogne, Eduard Sarukhanian, Colin Summerhayes, Cunde Xiao

Status and Progress of the International Polar Year

The International Polar Year 2007–2008 (IPY), which was launched on 1 March 2007 with an observing and fieldwork period between then and 1 March 2009, is now more than halfway through its official period. In this brief report we review the progress and achievements of IPY to date, and we provide a view to the eventual outcome of the program. In doing this, we assess IPY progress against criteria similar to those that were used to endorse IPY projects [Rapley et al., 2004]. We particularly try to establish the extent to which IPY has catalyzed a level of research and advance that would not have otherwise occurred.