A Feasibility Study on an Anaerobic Digester (AD) Plant Installation in Orkney

Strathendrick Biogas Ltd have established the feasibility of an Anaerobic Digestor plant on Orkney to process local waste and deliver heat, power and gas to residents.

Introduction

Anaerobic digestion is a process through which bacteria break down organic matter such as animal manure, wastewater biosolids, and food wastes without oxygen. Organic materials such as food waste, slurry, sewage and manure, known as ‘biomass’ can be broken down until it emits biogas (gas produced from biological sources). In a domestic environment, anaerobic digestion is what happens in home composting bins and industrially is used to process waste and also in the fermentation processes used to make many food and drinks.

Challenge

All waste produced on Orkney is currently shipped off the island, which increases the island’s carbon emissions. If an AD plant could be situated on Orkney, it could reduce the carbon emissions created by shipping waste off-island, as well as providing heat, power, and gas to residents. The challenge was therefore to establish whether an AD plant was feasible through analysis of waste quantities and composition, available technology, community buy-in, environmental impacts and economics.

Solution

IBioIC awarded funding under its Feasibility Fund programme to support investigations by Strathendrick Biogas Ltd and Robert Gordon University into the feasibility of an AD plant.

Strathendrick Biogas Ltd undertook screening and analysis reporting, and investigated infrastructure requirement and economic analysis, while the team at RGU produced a waste mapping report and environmental impact report.

Five scenarios for AD plant operation were modelled and all showed at least 19 years for investment pay back, demonstrating that significant investment would be required to make the project economically viable for the business.

Outcome

A survey of waste revealed 76,000 tonnes/annum of waste on Orkney over a variety of organic, textile and plastic categories, which could generate 5M m3 biogas and 11M kWh electricity per year. The project found that AD produces the greatest environmental benefits for processing waste compared to landfill or producing animal feed.

The project therefore demonstrated that waste streams are sufficient and an AD plant on Orkney is feasible. Five scenarios were taken forward to economic analysis where all were viable, with investment.

Thanks to this project, Strathendrick Biogas Ltd are now in a position to seek additional funding.

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