A new anaerobic digestion system at Nestlé’s factory in Fawdon is turning chocolate and sugar confectionery waste from the site’s manufacturing processes into renewable energy and clean water.
Here’s how it works: Rejected chocolates and sweets which are not suitable for sale or reprocessing, along with waste residues such as starch and sugar are broken down in to small pieces. This mixture is then partially dissolved using the waste liquids from the site’s cleaning processes to create a ‘chocolate soup’.
This ‘chocolate soup’ is then fed into an airtight tank where anaerobic digestion occurs. Anaerobic digestion is the natural process of bacteria breaking down biodegradable material, such as food, without oxygen, and converting it into useful by-products. These by-products are used to meet part of the site’s energy needs.
While the technique itself has been used in agriculture and industry for centuries, what makes the system at Fawdon unusual is that it has been designed to handle a high volume of solid and liquid waste within a short time.
“The system allows us to add tougher residues like starch-based compounds to the process, along with reject product and other materials,” says Inder Poonaji, Nestlé UK and Ireland’s Head of Sustainability.
“As long as the material is biodegradable, the anaerobic conversion process can take place. The waste we are converting here would otherwise be disposed of externally.”
The primary by-product of anaerobic digestion is biogas, a renewable gas comprised largely of methane and carbon dioxide.
The biogas produced at Fawdon is burnt to produce enough heat and power to meet about 10% of the site’s overall energy needs. As a result of the heat and power generated from the biogas, Fawdon’s greenhouse gas emissions are expected to fall by about 10%.
As well as generating cleaner energy, the anaerobic digester has also improved the quality of water discharged from the factory, an amount equivalent to 41 Olympic-size swimming pools annually. This water is now virtually clean on release from the site.
Trial and error
Although the factory is now reaping the benefits of the initiative, it took money and time to get right.
The site piloted the project for three months, using a smaller version of the anaerobic digester.
“There were a lot of elements to consider,” says Inder. “Determining which bacteria to use required significant investigation and trialling. We had to begin small-scale before moving forward.”
Set up at a cost of CHF 4.7 million, the anaerobic digestion system at Fawdon isn’t cheap; a factor that has often held back adoption of similar techniques elsewhere.
But due to the cost savings it has generated, the investment is expected to take around four years to pay off.
Today, the factory’s anaerobic digestion process takes place inside a huge tank, laden with naturally occurring bacteria.
It converts about four tonnes of solid waste and 200,000 litres of liquid waste a day, making the site one of Nestlé’s 72 factories globally that have now achieved zero waste for disposal status.
The company set itself the objective of achieving zero waste for disposal in 10% of its factories by 2015, achieving this two years early in 2013, with 56 of its factories, or 11%, meeting the target.
The Fawdon initiative is just one example of the efforts Nestlé is making worldwide to harness waste for useful purposes in and around its manufacturing facilities.
Last year, the company provided livestock farmers in Panama with small-scale anaerobic digesters to turn animal waste into biogas for cooking and liquid fertiliser. As a result, the farmers no longer rely on wood for fuel, reducing deforestation in the surrounding areas.
The work in Panama follows on similar projects Nestlé has implemented with farmers it works with in places like China, Mexico and Pakistan.
Nestlé also has anaerobic digestion technology installed at its coffee factory in Orbe, Switzerland and is in the process of installing the technology at the company’s Henniez water factory in the La Broye region of Switzerland, with start-up expected in 2016. These efforts support the company’s aim to have zero waste in all its roughly 150 European factories by 2020.