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3 Anaerobic Digestion Process Feedstock Materials Including Chocolate

Many people who take an interest in Anaerobic Digestion and Biogas are fascinated by the idea that so many waste materials can be used to make green power. There is always a comparatively large postbag for me in emails asking about novel feed materials, and my usual reply is that as long as these are organic materials, are capable of bring broken down by bacteria fairly easily, and don't also contain substances which may be toxic, they will usually be suitable as a biogas making digester feedstock.
Yes, including chocolate! (Scroll down to see more about that!)
That's why I have put together today's article as a combination of some article available on the web which go into real-life cases of feed stock use, in AD Plants, as follows:

Anaerobic Digestion Turns Dung Into Renewable Energy

Anaerobic digestion is turning cow – well you know – dung – into environmentally-friendly energy to heat and power your home. Actually, anaerobic digestion is turning your dung into renewable power too.

dung as anaerobic digestion feedstock
Public Domain from pixabay

Anaerobic digestion uses micro-organisms to break down organic materials – such as farm manure – in an air-tight, oxygen-free tank (called a digester). The hungry micro-organisms munch on the organic matter, and as they digest it, they produce methane and carbon dioxide gas. That’s why it is called the “anaerobic digestion process.” As the whole process uses natural organic matter to generate gas, anaerobic digestion systems are commonly also called “biogas systems.” …

A pleasant side effect of tossing their animal manure into the anaerobic digester is a reduction of the smell of manure on the farm – as it is being collected and broken down in an air-tight system.

Oh, and your waste is being used to generate renewable green energy too. Municipal water treatment plants use anaerobic digesters to break down sewage sludge and eliminate pathogens in our wastewater.

Anaerobic digesters capture methane from our solid waste too. Municipalities sort organic solid waste into different streams, such as food waste, yard waste and soiled paper, to prevent clogging of the pumps due to the large volume of these waste streams. Each separated waste stream is diverted into its own anaerobic digester, which breaks down the organic matter, while generating biogas which may be used for electricity and heat.

Food and drink processing plants use anaerobic digestion to turn the waste left-over from producing what we consume, into renewable energy and heat, which often is enough to run the food processing plant. The biogas generated by the anaerobic digestion process can also be collected and used to power natural gas vehicles, and piped into municipal natural gas systems to heat homes and businesses…. via Anaerobic Digestion Turns Dung Into Renewable Energy

Anaerobic Digestion of Tannery Wastes

The conventional leather tanning technology is highly polluting as it produces large amounts of organic and chemical pollutants. Wastes generated by the leather processing industries pose a major challenge to the environment. According to conservative estimates, more than 600,000 tons per year of solid waste are generated worldwide by leather industry and approximately 40–50% of the hides are lost to shavings and trimmings.

dung as anaerobic digestion feedstockImage: Public Domain from pixabay

Everyday a huge quantity of solid waste, including trimmings of finished leather, shaving dusts, hair, fleshing, trimming of raw hides and skins, are being produced from the industries. Chromium, sulphur, oils and noxious gas (methane, ammonia, and hydrogen sulphide) are the elements of liquid, gas and solid waste of tannery industries.

Biogas from Tannery Wastes

Anaerobic digestion (or biomethanation) systems are mature and proven processes that have the potential to convert tannery wastes into energy efficiently, and achieve the goals of pollution prevention/reduction, elimination of uncontrolled methane emissions and odour, recovery of bio-energy potential as biogas, production of stabilized residue for use as low grade fertilizer.

dung as anaerobic digestion feedstockImage: Public Domain from pixabay

Anaerobic digestion of tannery wastes is an attractive method to recover energy from tannery wastes. This method degrades a substantial part of the organic matter contained in the sludge and tannery solid wastes, generating valuable biogas, contributing to alleviate the environmental problem, giving time to set-up more sustainable treatment and disposal routes. Digested solid waste is biologically stabilized and can be reused in agriculture, after going through the anaerobic digestion process.

Until now, biogas generation from tannery wastewater was considered that the complexity of the waste water stream originating from tanneries in combination with the presence of chroming would result in the poisoning of the process in a high loaded anaerobic reactor.

When the locally available industrial wastewater treatment plant is not provided by anaerobic digester, a large scale digestion can be planned in regions accommodating a big cluster of tanneries, if there is enough waste to make the facility economically attractive. In this circumstance, an anaerobic co-digestion plant based on sludge and tanneries may be a recommendable option, which reduces the quantity of landfilled waste and recovers its energy potential. It can also incorporate any other domestic, industrial or agricultural wastes. Chrome-free digested tannery sludge also has a definite value as a fertilizer based on its nutrient content…

AD Plant at ECCO’s Tannery (Netherlands)

A highly advanced wastewater treatment plant and biogas system became fully operational in 2012 at ECCO’s tannery in the Netherlands. A large percentage of the waste is piped directly into the wastewater plant to be converted into biogas. This biogas digester provides a source of renewable fuel and also helps to dispose of waste materials by converting waste from both the leather-making processes, and the wastewater treatment plant, into biogas using the anaerobic digestion process. All excess organic material from the hides is also converted into biogas.

This project enables ECCO Tannery to reduce waste and to substitute virtually all of its consumption of non-renewable natural gas with renewable biogas. The aim is to use more than 40% of the total tannery waste and replace up to 60% of the total natural gas consumption with biogas. via Anaerobic Digestion of Tannery Wastes

Anaerobic digestion process turns chocolate into renewable energy

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.

chocolate as a anaerobic digestion process and biogas plant feedstock material

Image by cacaobug via Flickr

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 the process of 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.

chocolate as an anaerobic digestion process feedstock material
Public Domain from pixabay

“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.”

Biogas created during anaerobic digestion now provides 10% of Fawdon’s energy

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.

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.”

The anaerobic digestion process system at Fawdon cost around £3.3 million to set up. The expense of such systems is 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 Fawdon’s anaerobic digestion processing 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.

Nestlé 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. via Anaerobic digestion turns chocolate into renewable energy

Well, who would have thought that there was such a thing as “rejected chocolate“!

All I can say is that any chocolate that ever enters our house gets eaten (and quickly too!) so, the concept for me (and I guess for most people!) is a new one! However, it would be sad if it was being wasted, so making renewable energy from it, by using the anaerobic digestion process, must surely be a very good idea.

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