Ali Heidarzadeh Vazifehkhoran

Co-ensiling of straw with sugar beet leaves increases the methane yield from straw

This study examined the effect of co-ensiling of wheat straw and sugar beet leaves on the biochemical methane potential (BMP) by both lab-scale and pilot-scale co-ensiling. BMP was increased by co-ensiling, and the increase ranged from 19 to 34% after 9months of co-ensiling in lab-scale and from 18 to 32% after 6months of co-ensiling in pilot-scale. No effluent run-off was found through pilot-scale co-ensiling and there was a mass loss of only 0.1%. The study demonstrates that co-ensiling of straw and green biomass has potential as biological pretreatment and for avoiding effluent run-off from pure beet leave silage.

Use of tannery wastewater as an alternative substrate and a pre-treatment medium for biogas production

This study investigated biogas production as an alternative treatment of tannery wastewater (TWW) and its use as a pre-treatment medium to increase CH4 yield from anaerobic digestion (AD) of wheat straw. The TWW had high levels of sulfate and chloride, so biochemical CH4 potential could be estimated only when the TWW was diluted. Untreated straw yielded 255 NL CH4 (kg VS)-1, whereas straw that had been pre-treated with TWW yielded 314 NL CH4 (kg VS)-1 (35% increase). Treatment of TWW by AD with a co-substrate might be possible using a controlled feedstock mixing ratio. Use of TWW as a pre-treatment medium by simple co-storage before AD would be beneficial as an inexpensive treatment of lignocellulosic biomass.

Biogas Digester Hydraulic Retention Time Affects Oxygen Consumption Patterns and Greenhouse Gas Emissions after Application of Digestate to Soil

Knowledge about environmental impacts associated with the application of anaerobic digestion residue to agricultural land is of interest owing to the rapid proliferation of biogas plants worldwide. However, virtually no information exists concerning how soil-emitted NO is affected by the feedstock hydraulic retention time (HRT) in the biogas digester. Here, the O planar optode technique was used to visualize soil O dynamics following the surface application of digestates of the codigestion of pig slurry and agro-industrial waste. We also used NO isotopomer analysis of soil-emitted NO to determine the NO production pathways, i.e., nitrification or denitrification. Two-dimensional images of soil O indicated that anoxic and hypoxic conditions developed at 2.0- and 1.5-cm soil depth for soil amended with the digestate produced with 15-d (PO15) and 30-d (PO30) retention time, respectively. Total NO emissions were significantly lower for PO15 than PO30 due to the greater expansion of the anoxic zone, which enhanced NO reduction via complete denitrification. However, cumulative CO emissions were not significantly different between PO15 and PO30 for the entire incubation period. During incubation, NO emissions came from both nitrification and denitrification in amended soils. Increasing the HRT of the biogas digester appears to induce significant NO emissions, but it is unlikely to affect the NO production pathways after application to soil.