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Electricity from cheese via biogas

Posted by Alex Barrett on 13 May 2016 at 10:05 am

A new power plant has recently opened in the Lake District, which will generate electricity from cheese. The installation has been built at the Lake District creamery, it will take waste material from cheese production, and use it to generate biogas through the process of anaerobic digestion. The plant will generate 5 MW of thermal energy, this is enough to supply 25% of the creamery’s energy requirements. It will also supply 1,600 homes in the local area with biogas. [1, 2]

Anaerobic digestion is a very useful process for turning organic waste into usable fuel. The Lake District plant has been developed to capitalise on the waste produced by the cheese making process, but anaerobic plants can be a benefit to any industry where organic waste has to be disposed of. Large volumes of waste are generated at each stage of food and drink production, and it is estimated that “a third of all food grown for human consumption in the UK is thrown away.” [3]

Biomass that goes into landfill will be broken down by bacteria, releasing methane into the atm0sphere. The Biogen website reports that “Every tonne of food waste recycled by anaerobic digestion as an alternative to landfill prevents between 0.5 and 1.0 tonne of CO2 entering the atmosphere.” [4] The government estimates that 9.2 million tonnes of biodegradable waste went to landfill in 2013. [5] This proportion is dropping as more and more waste is recycled, but nonetheless landfill remains a significant contributor of greenhouse gas emissions. [6]

Anaerobic digestion works on the same principle, but instead of burying organic waste and letting it leak methane into the atmosphere, the gas is trapped and used as fuel. Organic material is placed in a sealed tank, anaerobic bacteria break down carbohydrates to produce methane. Anaerobic means “in the absence of air”, as these species of bacteria thrive in oxygen poor environments. Unlike a landfill site this reaction occurs under controlled conditions and the methane is captured in the form of biogas. [7]

Anaerobic digestion doesn’t completely reduce greenhouse gas emissions, since the biogas will still be used as fuel, releasing greenhouse gasses into the atmosphere. However it does provide some advantages. Methane is far more damaging to the environment than carbon dioxide, so releasing CO2 by burning biogas results in less overall emissions than releasing it as methane would have done. It also lets us get some use out of this methane, before it becomes a pollutant. This reduces the amount of natural gas we burn, as it is replaced with the more sustainably generated biogas.

Small scale anaerobic digestion systems are already quite popular, especially for farms, which generate a lot of agricultural waste. Many rural communities have set up biogas production facilities to make use of plant and animal waste. This is particularly useful in areas which are not connected to the gas grid.

Larger, industrial scale plants are becoming increasingly popular. There is a growing recognition in the food industry that waste can be used, rather than thrown away. The Biomass Energy Centre state that: “It has been estimated that up to 92% of ingredients used in brewing ultimately become waste, principally spent grains, and the dairy industry uses around 40 million m3 annually, mainly for cleaning, which produces effluent containing high levels of organic residues.” [3]

Recycling waste material to provide energy can reduce the costs of the manufacturing process, so there is a clear financial benefit for large corporations to invest in this process. The Lake District plant is the first time anaerobic digestion has been used by the dairy industry in Europe, but it is likely that it won’t be the last.

References

  1. Clearfleau
  2. The Telegraph
  3. Biomass Energy Centre
  4. Biogen
  5. DEFRA: UK statistics on waste (Links to pdf)
  6. DEFRA: Impact of Energy from Waste and Recycling Policy on UK GHG Emissions
  7. Sustainable sanitation and water management

Image credit: Alex Barrett 2016

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