Water Journal : Water Journal November 2011
refereed paper water NOVEMBER 2011 79 greenhouse emissions partnership, and by researching publicly available literature (eg, opportunities considered by other Australian and international water utilities). For example, the addition of macerated food waste to anaerobic digesters to increase biogas production had been considered previously by Sydney Water's engineers. Installation of additional co-generation engines fired by biogas at sewage treatment plants, mini-hydro plants, wind and solar power had been assessed in an earlier renewable energy generation study. Opportunities were identified in the areas of energy efficiency, demand management, waste heat recovery, energy capture, greenhouse gas capture and destruction, and alternative low or zero emissions energy sources. Opportunities were first screened at a high level to ensure that they were compatible with Sydney Water's operational limitations (eg, available land and land usage restrictions), and were within project scope. The key screening criteria applied are shown in Table 1. Approximately 20 opportunities failed the preliminary screening step. The remaining 90 opportunities were refined and some were split into multiple opportunities. For example, the 'wind turbine' opportunity was split into separate opportunities according to turbine size, and sites with a very high wind resource were separated from other potential sites. Opportunities that failed screening but which had some merit for Sydney Water were marked for future research. These included microbial fuel cells, sewage treatment plant aeration control improvements and membrane bioreactor technology. The preliminary analysis step assessed the net present value per tonne of carbon dioxide equivalent emissions (NPV/t CO2-e) abated per annum (for each opportunity), which provided a second screening step. The NPV used high-level approximate data for initial capital cost, annual operational expenses and savings from annual avoided energy consumption. Opportunities were then prioritised on the basis of agreed thresholds of cost per tonne of emissions abated and the tonnes of emissions abated per annum. This reduced the number of opportunities to approximately 65, which progressed to a detailed assessment. The detailed analysis step used the Sydney Water CCA Tool. The tool was populated with financial data including detailed capital and operational expense estimates, and installation project management costs. Where appropriate, a lag time was included for each project to account for the time required for project implementation in both expenditure and savings. Where an opportunity would generate electricity (eg, wind, solar, biogas or biomass sources), the opportunity was generally sized in order to meet site demand rather than focus on export of electricity to the grid. The assessment accounted for benefits from the generation of renewable energy certificates, any other green credits (eg, NSW Energy Savings Scheme Certificates) and feed-in-tariffs (where they may exist). CCA Tool Development The CCA Tool is an Excel-based tool that enables an assessment of opportunities to reduce carbon emissions in terms of the volume reduction, associated costs and benefits, and risk. Sydney Water developed the Tool in parallel with the early stages of the opportunity identification and assessment. The 'Option Input Template' in the Tool was essential for the detailed analysis of each opportunity (Step 5 in Figure 1). The major output of the Tool is a Cost of Carbon Abatement Curve, showing the volume of carbon abatement potential for each opportunity in order of increasing cost, along with a flexible data table summarising key information. The Tool has four main sections: Opportunity Input Template, Generic Inputs, Calculations and Results (see Figure 2). The Option Input Template ('O-Template') must be populated for every opportunity that is to be shown on the CCA Curve. It ensures a standard approach to data gathering and input, so that opportunities can be assessed on a consistent basis. Both qualitative and quantitative data is captured in the O-Template. Qualitative data includes information such as location, land requirements, technology type and status, and a basic risk assessment. Quantitative data includes electricity and other energy savings, renewable energy generation, generation of green credits (eg, Renewable Energy Certificates), and all project installation, maintenance and management costs. presented at Table 1. Preliminary screening criteria. Screening criteria Possible values -- Pass Possible values -- Fail Technology status • R&D near term (< 10 years) • Pre-commercial pilot • Commercially available • Technology in use at SWC • R&D long term (≥ 10 years) HSE impacts • No HSE concerns • Adverse visibility, noise, odour, air quality, biodiversity or safety impacts Political/social acceptance • No adverse political/ community impacts • Adverse political/ community impacts Opportunity compatibility • Opportunity compatible with SWC operations • Opportunity not compatible with SWC operations Project scope • All other projects •Scope1&2GHGs Out-of-scope projects: • Offsetting projects • N2O abatement projects Opportunity Input Template Opportunity description Assumptions Risk assessment Savings Costs Generic Inputs Common assumptions applied to all opportunities Scenario assumptions Calculations Common calculation Detailed option outcome viewer Results Scenario variables Interactive data table Graphical results -- cost curve Data quality checking Administration of graphics Figure 2. Basic structure of the CCA Tool.
Water Journal December 2011
Water Journal September 2011