Recycling Food Waste into Renewable Electricity and Bio-Gas
By: Recycling Centre
Tags: Recycle, Recycling

Recycling Food Waste into Renewable Electricity and Bio-Gas

Food Recycling in particular, waste food recycling is big business. Across the UK thousands of tonnes of food waste mounts up from supermarkets, food production plants and even our homes and was until quite recently often dumped in landfill sites. Landfilling food waste is not only costly to do but it’s not good for the environment to just bury it and let it rot away over time. Besides waste food is now considered a valuable resource and there are a few companies here in the UK that are putting waste food to good use by using it to generate renewable electricity and bio-gas energy. The generated energy is then used locally to heat up homes and businesses or is fed into the gas and electric supply network.

From waste food to bio-gas and renewable electricity.

So how do these companies take what was once considered a waste food problem and turn it into a useful, clean and environmentally friendly bio-gas and renewable electricity solution?

The process used is called Anaerobic Digestion, it’s a very complex system of nature and science that work together described by the experts as “Anaerobic digestion is a complex biological process involving the breakdown of organic matter in the absence of air in large, sealed and insulated vessels with controlled heating and mixing.”

Food waste is collected from various places like food manufacturing plants, bakeries, supermarkets and local council collection programs. Once it arrives at the waste food processing plant it goes through the following process to generate bio-gas and high-grade fertilizers.

Step 1: Food & animal waste arrives on site

Waste food arrives on site to be processed; all packaging is removed using specialised equipment. Once stripped of packaging the waste food enters a sealed building where both liquid and solid wastes are processed together to form a type of slurry liquid.

Step 2: Hydrolysis Tank

The slurry is pumped into the hydrolysis area for the Anaerobic Digestion Process (ADP) to begin.

Step 3: Pasteurisation

The food waste arrives at the pasteurisation plant and the Combined Heat and Power Unit (CHP) heats up the materials to 70 degrees for a minimum of one hour to eradicate all harmful bacteria and dangerous pathogens.

Step 4: Digestion Process

By this point the slurry is in a pasteurised state and is passed to digestion tanks to ferment and break down into gas. It’s this part of the process where the natural bio gas is generated from rotting slurry. The gas rises to the top of the tank and passes into a gas holding tank to be stored and the flow is regulated then piped to the CHP.

Step 5: Electricity

The Combined Heat and Power unit or CHP uses the flow regulated bio gas as fuel to power the CHP which in turn feeds excess or electricity and gas back into the national grid providing renewable energy to local homes and businesses.

Step 6: Carbon Capture

The Bio plant generates renewable energy but it also has three interesting ways in which the process carries out its own carbon capture from the plant.

A) Heat: The CHP generates heat to pasteurise the slurry, the heat is generated using the bio gas made on site.

B) Gas to Grid: Unused Gas from the CHP is sent to a polishing plant to clean it and then its fed into the national gas network to be sold.

C) Land: Once all available Bio-Gas has been harvested the remaining slurry is spread onto agricultural land as it makes a perfect fertiliser, its rich in nutrients that food crops and plants love such as nitrogen.

This entire process is innovative in the way it combines naturally occurring biological processes with modern science to harvest gas and produce green energy. It provides an answer to the problem of waste food and how its dealt with.

Any type of innovation that solves an environmental problem is good news, but this type of recycling to provide energy that’s not only used within the process that generates it but is also sold on for profit is simply a environmental master stroke and seems like a low carbon viable source of energy for the future.

The video below shows the entire process from when the waste food arrives on site to the point its spread as fertilizer. (video is for illustration purposes only and is owned by Biotech)

Illustrating the process of Anaerobic Digestion Process