Ivan Wood and Sons, a market leader in the preparation and supply of quality fresh and pre-prepared fruit and vegetables to the catering trade, approached the Scottish Biofuel Programme to explore the potential of utilising their business waste products to feed an on-site Micro Anaerobic Digestion plant (Micro AD). The project looked at the bio-gas potential from the various waste produced by the business, from its vegetable preparation process. By extracting the maximum potential from this material they hope to turn waste into an asset.
Ivan Wood and Sons have a custom build, modern, fresh preparation unit where the company produce high quality fruit and vegetable daily to bespoke customer orders. As well as their pre-prepared hand cut and turned fruit and vegetables they are looking to produce vegetable stock.
The feedstock analysis looked at potato peelings, starch product and cooked vegetables used to make stock. The analysis concluded that feedstock that had been used in the stock making process were not suitable for use in the Micro-AD plant as it produced a gas yield which was well below the threshold required for a viable plant.
Using the potato peelings and starch products, however, created a positive business case for the build of a Micro-AD plant. The proposed plant needs to be considered as fixed asset investment, where RHI is treated as revenue and off- set electricity and gas costs as savings.
The site which Ivan Wood and sons propose seems well suited to utilise a Micro AD plant. The best scenario for the implementation of Micro-AD plant would be to use the produced biogas in a combined heat and power engine (subject to FIT’s review) to provide renewable electricity and heat contributing to cost savings on heating process waters and office space. It was estimated that if such a plant could be built for £5,111/m3 it would have a payment payback of 9 years
At a Glance: Ivan Wood and Son
Site Assessment- site constrains could be resolve by clever design of the proposed installation.
Feedstock type – Vegetable peelings, starch from companiess processing activities.
Feedstock biogas potential- The feedstock represents a strong opportunity with theoretical biogas yield for potato peelings of 83.4 m3/tonne and starch product 199 m3/tonne.
Projected volume of feedstock – 312 tonnes/ annum
Biogas use- Proposed biogas to CHP engine to produce electricity and heat. Viability of this option depends on the outcome of the Feed in Tariff scheme review. If FiT’s rates for small scale AD are reduced significantly the biogas to boiler option (heat only production) will benefit the business more.
• With recent FiT changes the biogas to boiler option will be investigated to provide
CHP - gross electrical output of 85 MWhe and 85 MWhth
Biogas to Boiler system - gross heat output of 233MWhth
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) of £181 562 needs to be achieved
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.
Next Steps- technical specification to be send out to AD plants suppliers.