There are many ‘food waste’ processing units offered on the market.  However, few can claim to process and transform food waste into valuable renewable resources, including renewable energy and a nutrient rich fertiliser.

Anaerobic digestion (AD) is a biological process that breaks down organic materials, such as food waste, in the absence of air.  It is an environmentally friendly and sustainable method of recycling food waste.

By utilising anaerobic digestion plants, we can convert organic material into biogas, a versatile fuel that can power vehicles, generate heat and electricity, and be fed into the national grids.  We can also use food waste and directly retain all the carbon and nutrient values, returning them to the soil as a fertiliser.  This is especially important as, at the current rate, reports indicate that a significant portion of the world’s soil is already degraded or at risk of degradation, with some projections suggesting that we will lose 50% of all fertile soils by 2050 due to the continued use of chemical fertilisation (harmful both in production and application), which is stripping our soil of its natural goodness.

Anaerobic digestion plants
Footprint Recycling collaborates with waste collectors who divert food waste to a network of anaerobic digestion (AD) plants across the UK.  This network enables us to transport food waste to nearby plants, thereby minimising its carbon footprint.

Anaerobic digestion is a process where bacteria break down organic matter, such as food waste, in the absence of oxygen.  As the bacteria consume the food waste, they produce biogas, which rises to the top of the digester.  This biogas consists mainly of methane, the primary component of natural gas.  The solid content of the food waste falls to the bottom of the digestion chamber and is extracted to create a nutrient-rich organic fertiliser.

How it works
In simple terms, the anaerobic digestion system functions much like a huge stomach.  Like all stomachs, it requires regular feeding and a balanced diet to operate efficiently.  To ensure the bacteria have the right recipe, the food waste must be prepared and any packaging removed.  The process involves several steps:

• Collection of food waste
• Transport to AD plants
• Removal of packaging and preparation of food waste
• Feeding the digester with the prepared food waste
• Production of biogas and organic fertiliser.

The process and outcomes
Digesters come in various shapes and sizes, each with its unique characteristics.  Getting the precise mix of nutrients to keep the micro bacteria well-nourished and efficient is an art.  This can involve adding ingredients such as manure or other specific trace elements to the feedstock.  Achieving the proper nutrient balance is essential for maximising the energy recovered from food waste.

Process:

• Hydrolysis: Food waste is mixed into a slurry and broken down into smaller molecules.
• Pasteurisation: The slurry is heated to 70°C to sterilise it.
• Acidogenesis: Compounds are transformed into volatile fatty acids in an oxygen-free environment.
• Acetogenesis: Fatty acids are broken down into acetates and hydrogen.
• Methanogenesis: Acetates and hydrogen are converted into methane and carbon dioxide.

Outcomes:

• Biogas: Methane is purified and injected into the national gas grid.
• Electricity: Methane is converted into electricity through combined heat and power units.
• Biofertiliser: The remaining digestate is used as a nutrient-rich biofertiliser.

Benefits of anaerobic digestion
Anaerobic digestion offers numerous environmental and economic benefits, making it a key player in sustainable waste management.  Some of the key benefits include:

• Reduction of greenhouse gas emissions
• Minimise waste sent to landfills
• Generates renewable energy
• Supports sustainable agriculture
• Generation of nutrient-rich organic fertiliser supporting sustainable argriculture
• Contribution to the circular economy
• Improves waste management, reduces costs, ensures regulatory compliance and enhances sustainability.

And finally…
Anaerobic digestion is a powerful tool for transforming food waste into valuable renewable resources.  By using a network of AD plants, we can efficiently convert organic material into biogas and organic fertiliser, reducing our carbon footprint and contributing to a sustainable future.  Understanding the process and benefits of anaerobic digestion is crucial for advancing waste management practices and maximising the potential of food waste.

Footprint Recycling collaborates with waste collectors who divert food waste to a network of anaerobic digestion plants across the UK