Delivering Low Carbon Anaerobic Wastewater Treatment and Renewable Energy Production

The water industry is the fourth most energy intensive secotr in the UK and uses approximately 2 -3 % of net UK electricity releasing approximately four million tonnes of green house gas emissions (carbon dioxide equivalent) every year. The industry is making progress to produce more renewable energy from its waste biomass sources. However, only 493 GWh was generated by water utilities in the UK in 2005/06 about 6.4 % of its actual requirements. The government has called for research into potentially more efficient energy generation technologies from biomass which would contribute significantly to the UK's policy objectives of 10% of electricity supply from renewable energy by 2010 and for the reduction of greenhouse gas emissions. Innovative research into low carbon treatment and production and storage and use of biogas in the water sector has the potential to offer step-change benefits to the UK's energy system. This project seeks to secure a paradigm shift in wastewater treatment and biogas application. A pilot scale feasibility study is proposed to examine: (1) the fundamental operation of an anaerobic bioreactor using fortified influent wastewater; and (2) increasing the energy-production capacity of the generated renewable biogas. This approach significantly alters the wastewater treatment flow-sheet by reducing dependence on the energy intensive activated sludge process. The project has the potential for UK energy savings of 0.12 kWh per cubic metre of wastewater treated. Over 1 million cubic metres of wastewater are treated every day which potentially corresponds to savings of 438GWh per year and 188,469 tonnes of carbon dioxide per year. This is approximately equivalent to off setting 122,000 people flying London to New York return. Potentially fortified anaerobic treatment will also yield >10 % more biogas than is currently available from anaerobic digesters. Therefore, it is important to increase its energy production capacity in line with government developments for local energy and increased energy security. Currently biogas is used in combined heat and power in the UK water sector but biogas use in fuel cells, as a transport gas and for gas supply could provide greater flexibility and efficiency with more storage opportunities. However, these applications require biogas to be upgraded. This project seeks to examine in-situ methane enrichment to provide a better economy of scale for upgrading biogas and thereby maximising the overall energy production capacity of wastewater carbon. This project will therefore help to provide the 'scientific advance and industrial innovation to utilise biomass to meet the increasing demands for sustainable products from renewable sources' called for by the government.