Fyne Futures, established in 2004 is based on The Island of Bute and is a subsidiary of Fyne Homes and is committed to environmental sustainability and alleviation of unemployment. The project assessed the feasibly of siting a Micro Anaerobic Digester (Micro AD) in Ardencraig gardens based in Rothesay. The proposed site is set with-in a walled garden which has been developed to create a propagation, education and show garden and tearoom. Ardencraig is owned and maintained by Argyll & Bute Council.
The key objectives of the project the project was to;
• Utilise food waste collected in the area to feed the Micro AD
• Site the digester at Ardencraig
• Offset current gas and electricity use through the energy outputs the digester
• Use the digester outputs at the gardens as a substitute fertiliser
From this project the Scottish Biofuel Programme hoped to prove in practice the technological, operational and commercial models from Micro AD in a variety of settings. Our aim is to demonstrate the commercial viability of deploying models across a number of varying pilot sites which will allow the technology to be replicated throughout Scotland.
It was determined that the best fit for this scenario would be to utilise the biogas from the Micro AD in a hot water boiler, complementing the hot water heating system already being used in the Ardencraig greenhouses. The digestate would be strained with the liquid content be re-fed into the system and the solid content utilised in the gardens as fertiliser.
However, the site assessment raised a number of issues pertaining to the overall suitability of the Ardencraig site. The proximity of receptors and the quality of the ground for hardstanding as well as issues of odour, noise and visual intrusion.
Fyne Future micro AD project at a glance
Site Assessment- The garden is of historical significance and within Rothesay conservation zone. Any designs for an AD digester plant would need careful consideration to the unique setting. Significant engineering works would need to be carried out pushing development costs higher, constraints could be resolved by clever design of the proposed installation.
Feedstock type – Food waste collected from local community and business
Feedstock biogas potential- The feedstock represents an opportunity with theoretical biogas yield 90 to 140 m3/tonne. The higher average volume needs to be achieve to maximise biogas production and revenues and savings.
Projected volume of feedstock – 524 tonnes / annum
Biogas use- Proposed biogas to CHP engine to produce electricity and heat.
• With recent FiT changes the biogas to boiler option will be investigated to provide
Energy Outputs- gross electrical output of 85 MWhe and 85 MWhth
Financial outputs –
CAPEX- If average £5111/m3 capital cost can be guaranteed by suppliers for biogas to micro CHP installation. The estimated total cost of installation (30m3 digester+ site specific development costs) £181 562.
Estimated annual revenue and savings = £31 766
Estimated operational costs = £10 000
The payback period = 9 years
KEY TO SUCCESS- Consistent good quality feedstock, large heat demand, motivated business owner.