Wicks, Jaymee (2013) Investigation of factors influencing maximum biogas production of abattoir wastewater. [USQ Project]
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Abstract
Australia has ever increasing pressure to increase its renewable and alternative energy sources from the implementation of environmental protection schemes, legislations and taxes such as the carbon tax, implemented in July 2012. There is an increasing movement globally to reduce greenhouse gas emissions and reduce the reliability upon fossil fuels.
The development of biogasification plants in sectors such as agriculture, which produces the highest volumes of methane per sector, can assist businesses to reduce emissions, reduce sludge volume, lower reliability on the power grid, decrease costs of taxes and policies and increase revenue through excess supply back to the power grid.
Abattoir wastewater, in particular, has considerable volumes of methane and carbon dioxide gases being produced through the use of anaerobic treatment ponds that reduce the organic loading of wastes. These ponds have the potential to be transformed into covered anaerobic ponds or digestion reactor tanks to produce methane in a way that it can be captured. Once obtained the methane gas can be used to produce electricity or flared.
Little research is available on the feasibility of methane capturing through the anaerobic digestion of abattoir wastewater as the wastes are hard to characterise due to their varying composition between different abattoirs. Abattoir wastewater is typically hard to digest and therefore co-digestion has been investigated to evaluate the methane potential when combined with other easily biodegradable, carbon rich sources.
This dissertation reports on the findings made from two experimental processes. The first of which looked into the feasibility of co-digestion with nutrient rich vegetable wastewater and the second looked into the impacts of inoculum to substrate ratio and temperature on the biogas production of the abattoir wastewaters alone.
The results from the feasibility test showed that co-digestion was not compatible with the abattoir wastewater. It was evident that the abattoir wastewater produced higher volumes of biogas when anaerobically digested alone, than in comparison to the volume of biogas produced through co-digestion. The blood water alone produced the highest volumes of biogas with 736.9 mL/200 mg/L DTOC closely followed by the saveall wastewater with 724.9 mL/200 mg/L DTOC. The mixture of 80% vegetable waste, and 10% of each abattoir wastewater stream gave 588.6 mL/200 mg/L DTOC followed by the glucose substrate with 308.4 mL/200 mg/L DTOC. The lowest biogas production was by the vegetable wastewater with 69.1 mL/200 mg/L DTOC.
From the second experimental process it was found that low inoculum to substrate ratios and higher temperatures produced the highest volumes of biogas. The optimum was found at an ISR of 5 and a temperature of 40 °C but further research needs to be completed for a true conformation of these results.
This research will give further insight into the potential volumes of methane and biogas that can be obtained through the optimisation of a number of variables.
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