After the Department of Agriculture launched a €40m action plan to kickstart the anaerobic digestion industry on Irish farms late last year, a West Cork community school launched their own investigation into the technology which is hoped will provide farmers with an option to turn waste into renewable energy, as well as provide an alternative income stream.
‘ANAEROBIC Digester – Gadget or Gimmick?’ – that’s the title of an ambitious study undertaken by three fourth-year students of Skibbereen Community School.
The Government announced plans for the construction of 200 anaerobic digestion plants by 2030 last year. Anaerobic Digestion (AD) refers to a process that converts organic materials, including agricultural waste, into biogas which can be upgraded to biomethane. This in turn can be injected into the gas grid, or used as a renewable fuel.
AD, which is already established in many other European countries, presents many opportunities for farmers from leasing land for the construction of plants, to helping with their own slurry management. Also, a digestate is a by-product of the process and can be used as an organic fertiliser.
Skibbereen CS students Anna McCarthy, Orla McCarthy, and Shauna Hourihane undertook a ‘study of the practical, financial, and environmental benefits of using an anaerobic digester in our school’ for this year’s BT Young Scientist & Technology Exhibition.
The 16-year-old students were motivated to undertake the project firstly because of their interest in the environment and use of sustainable practices.
‘Also when we arrived back to school last September, we discovered that a new anaerobic digester, manufactured and installed by a local company MyGug was being used by our home economics department to power a cooker. We originally didn’t know much about it and wanted to research a way to get the maximum benefit from it,’ said Orla.
After further research, they realised that a lack of brown bins for food disposal in the school was an obstacle.
‘With a school population of over 900 students and 100 staff members this was definitely not a sustainable way to dispose of our food waste daily. We decided that this would definitely be a topic that we would be interested in doing a project on,’ said Lauren.
They launched an AD awareness campaign and also conducted a survey among the school population and introduced a brown bin system to increase the amount of food waste available to the anaerobic digester.
Impressively, they calculated the food waste collected daily, monitored the biogas and fertiliser produced and investigated which food group exports the most energy per kg. ‘The food that produces the most biogas from an anaerobic digester is typically high in organic matter and carbohydrates,’ said Anna.
Some of the best food sources for biogas production in anaerobic digesters they found are fruits and vegetables (potatoes, bananas, apples, and other overripe or discarded produce); fats, oils, and greases; dairy waste, such as spoiled milk and cheese whey, and bread and grains.
‘The overall yield of biogas from these materials depends on several factors, including the specific composition of the food waste, temperature, and the operational conditions of the anaerobic digester. For instance, materials like fruit peels and potato waste can generate more biogas per unit of weight than some other types of food waste, while high-fat foods typically produce the highest methane yields due to their lipid content,’ explained Orla.
Judges at the BTYSE described the study as an ‘innovative project which was thoroughly researched’.
Having completed the project, the students feel that more education is still needed in the area, particularly as the importance of anaerobic digesters is growing due to global concerns about waste management, renewable energy and environmental sustainability increase.
‘For example, in our school the majority of students were unaware of anaerobic digestors and their use. They have huge potential by converting food waste into valuable energy and fertiliser, and they offer a practical and efficient and sustainable solution to managing food waste problems. However, to get the maximum potential, more education is definitely needed around their use and potential,’ said Anna.
‘Moving forward, we hope to continue to monitor students’ behaviour in relation to disposing of their food waste in our brown bins, allowing us to collect a sufficient amount of organic waste to feed our AD, creating more biogas to power cookers in our home economics room,’ concluded Shauna.
