A comparative life cycle assessment of anaerobic mono- and co-digestion of livestock manure in Bangladesh.

Proper management of biogenic residues, particularly livestock manure and food waste, is a major challenge for Bangladesh. While mono-digestion has traditionally been used on farms for treating manure, inadequate energetic output limits its applicability. Food waste, however, is typically landfilled in current practice. Co-digestion of biowaste emerged as an alternative due to synergistic yield and capacity to handle multiple waste streams. However, its environmental performance is underreported, particularly in developing countries. This study aimed to compare the environmental implications of co-digestion and mono-digestion of livestock manure (poultry and cow manure) with food waste from a life cycle assessment perspective for the regional context of Bangladesh. Two inventory cases were considered, accounting for mechanistically calculated (case M) and experimentally reported synergistic biogas yield (case E). Co-digestion scenarios showed net benefits by reducing three of the five impact categories-considerably reducing climate change (up to 117%), eutrophication potential, and terrestrial ecotoxicity in both cases (54.5 % and 55.7 %, respectively). The highest decrease occurred for climate change by diverting food waste landfilling. However, when synergistic biogas yield was considered, acidification potential and malodor air emissions increased by co-digestion owing to a higher amount of hydrogen sulfide and ammonia in the produced gas, thus entailing significant environmental burdens. The key hotspot in most categories was open storage of digestate, necessitating appropriate post-treatment.

Techno-economic assessment of catalytic gasification of biomass powders for methanol production.

This study evaluated the techno-economic performance and potential benefits of methanol production through catalytic gasification of forest residues and lignin. The results showed that while catalytic gasification enables increased cold gas efficiencies and methanol yields compared to non-catalytic gasification, the additional pre-treatment energy and loss of electricity production result in small or no system efficiency improvements. The resulting required methanol selling prices (90-130€/MWh) are comparable with production costs for other biofuels. It is concluded that catalytic gasification of forest residues can be an attractive option as it provides operational advantages at production costs comparable to non-catalytic gasification. The addition of lignin would require lignin costs below 25€/MWh to be economically beneficial.

In situ synchrotron IR study relating temperature and heating rate to surface functional group changes in biomass.

Three types of woody biomass were investigated under pyrolysis condition to observe the change in the surface functional groups by Fourier transform infrared (FTIR) technique with increasing temperature under two different (5 and 150°C/min) heating rates. The experiments were carried out in situ in the infrared microscopy beamline (IRM) of the Australian Synchrotron. The capability of the beamline made it possible to focus on single particles to obtain low noise measurements without mixing with KBr. At lower heating rate, the surface functional groups were completely removed by 550°C. In case of higher heating rate, a delay was observed in losing the functional groups. Even at a high temperature, significant number of functional groups was retained after the higher heating rate experiments. This implies that at considerably high heating rates typical of industrial reactors, more functional groups will remain on the surface.

Application of the distributed activation energy model to the kinetic study of pyrolysis of the fresh water algae Chlorococcum humicola.

Apart from capturing carbon dioxide, fresh water algae can be used to produce biofuel. To assess the energy potential of Chlorococcum humicola, the alga's pyrolytic behavior was studied at heating rates of 5-20K/min in a thermobalance. To model the weight loss characteristics, an algorithm was developed based on the distributed activation energy model and applied to experimental data to extract the kinetics of the decomposition process. When the kinetic parameters estimated by this method were applied to another set of experimental data which were not used to estimate the parameters, the model was capable of predicting the pyrolysis behavior, in the new set of data with a R(2) value of 0.999479. The slow weight loss, that took place at the end of the pyrolysis process, was also accounted for by the proposed algorithm which is capable of predicting the pyrolysis kinetics of C. humicola at different heating rates.