Biodigesters can help farms increase profits while also reducing environmental damage. But how do biodigesters work exactly?
This quick guide explains the basics of anaerobic digestion and outlines the key benefits of using biodigesters on farms, in food processing, and beyond.
Table of Contents
How Do Biodigesters Work?
Anaerobic digestion (AD) is a natural process in which bacteria break down biodegradable material in the absence of oxygen. This process occurs inside sealed, oxygen-free vessels known as biodigesters. A variety of organic waste materials (such as animal manure, slurry, and food waste) can be fed into these systems.
Inside the biodigester, microbes work to break down the organic matter. As a result, two valuable byproducts are created: biogas and digestate.
➜ Biogas: This gas mixture is primarily composed of methane (50–75%) and carbon dioxide (25–45%). Biogas can be used much like natural gas for heating, cooking, and electricity generation. When purified by removing the carbon dioxide, biogas becomes biomethane. This is a renewable fuel suitable for injection into the gas grid or for use as vehicle fuel.
➜ Digestate: This is the nutrient-rich material left after the digestion process. It contains essential nutrients such as nitrogen, phosphorus, and potassium, making it an excellent organic fertiliser. It improves soil health and structure, enhances crop yields, and helps reduce the need for chemical fertilisers. The AD process also eliminates pathogens and weed seeds, making the digestate safer and more effective for agricultural use.
Types of Biodigesters & Advantages
Biodigesters come in a range of sizes and configurations to suit different needs. Some are compact units suitable for households or small-scale farms. Others are large industrial plants that can handle thousands of tonnes of waste per year.
They can be designed to operate under different temperature regimes. Mesophilic (35–37 °C) digesters are easier to maintain, more stable, and widely used on farms. Thermophilic (55–60 °C) digesters operate at higher temperatures and produce more biogas, but require more careful management.
Biodigesters are typically installed on flat, sunlit areas and have a lifespan of around 15 to 20 years.
Key advantages include:
- Generation of clean, renewable energy
- Reduced reliance on fossil fuels
- Lower greenhouse gas emissions by capturing methane
- Improved farm nutrient management and soil health
- Enhanced waste management and odour control
Who Can Benefit from Biodigesters?
According to Teagasc, AD through biodigesters offers wide-reaching benefits:
➜ Additional revenue streams
➜ Enhanced nutrient availability
➜ Better compliance with the Nitrates Directive
➜ Diversification opportunities
➜ Improved manure management (pathogen and weed seed kill)
➜ Low-cost waste disposal
➜ Enhanced corporate sustainability image
➜ Cleaner, greener operations
➜ Reduced odours and pollution
➜ Local sources of renewable energy and heat
➜ Job creation and rural development
➜ Reduced nitrate leaching and pollution
➜ Methane capture, reducing GHG emissions
➜ Waste diverted from landfills and incineration
➜ Replacement of synthetic nitrogen fertilisers
➜ Progress toward Climate Action Plan targets
➜ Compliance with EU Landfill and Nitrates Directives
➜ Increased renewable fuel production
➜ Improved energy security through decentralised generation
The Future of Biodigesters in Ireland
Currently, Ireland has only 15 large-scale operational biodigesters, which is far behind many of its European counterparts. However, change is coming. The Irish Government’s Climate Action Plan has set a target to produce 5.7 TWh of biomethane annually by 2030. This will require the development of 150 to 200 new biodigester plants. As a result, biodigesters are expected to become increasingly important in Ireland over the coming decade.
Developing a biodigester project involves navigating a complex planning and regulatory process. At Southern Scientific, we have years of experience supporting clients in the agricultural, industrial, and environmental sectors. We assist in feasibility studies, planning applications, environmental assessments, and regulatory compliance to help you bring your biodigester project from concept to reality.
If you’re considering a biodigester for your farm or facility, reach out to our expert team today.
