What is anaerobic digestion?

3 May 2023

Anaerobic digestion is a natural biological process that breaks down organic matter in the absence of oxygen. It is a type of microbial fermentation that occurs in anaerobic (oxygen-free) conditions and produces biogas, a mixture of methane and carbon dioxide.

During anaerobic digestion, microorganisms, such as bacteria and archaea, consume organic matter and convert it into simpler compounds such as methane, carbon dioxide, and water.

There are several benefits of using anaerobic digestion in dairy farming:

  1. Reduced greenhouse gas emissions: Anaerobic digestion reduces the amount of methane and carbon dioxide released into the atmosphere from storing and handling manure.
  2. Renewable energy: Biogas produced during anaerobic digestion can be used as a source of renewable energy for the farm, reducing the need for fossil fuels.
  3. Improved manure management: Anaerobic digestion can reduce the volume of manure and make it easier to handle and transport. The resulting digestate can be used as a soil amendment or fertiliser.
  4. Cost savings: Using biogas as a source of energy can reduce energy costs for the farm, and the digestate can be used as a replacement for bought-in fertilisers.

In 2014 the Lake district Biogas AD plant was set up at First Milk’s Lake District Creamery to process effluent and whey permeate from the creamery. Initially set up and run by an independent company, First Milk bought the operation in-house in 2020.

The anaerobic digester processes the whey permeate and residues produced at the creamery into bio-methane that is used by the creamery, as well as fed to the national grid and supplied to local users. The site produces 1,000m³/day of biogas, water, and organic material. Part of the biogas is used by the creamery for steam generation, replacing the use of fossil fuels.

Transportation costs are reduced as the shipping of whey permeates from the site would otherwise require 3,000 truck movements a year. Residual sludge management costs are also lowered as the residues are being fed to the AD plant, and the creamery’s energy requirement has been reduced by 25% as a result of eliminating drying of the whey permeates.

It makes our Lake District creamery Europe’s first dairy processing site to supply bio-methane to the national grid.

Overall, anaerobic digestion can be a sustainable solution for dairy farming, reducing greenhouse gas emissions, providing renewable energy, and improving manure management. However, the installation and operation of anaerobic digesters require careful planning and management to ensure efficient and safe operation.