Beyond composting: What happens when you turn food scraps into energy?

Most of us throw away food from time to time, whether it's leftovers, peelings or produce that has gone past its best. One study suggests that around 25-30% of food produced is lost or wasted along the way.

While composting is a popular solution, there is another technology attracting attention around the world: home biogas systems.

What is biogas and how does it work?

Biogas is fuel that can be made from recycling organic matter like food waste and loss, animal manure, agricultural residues and crops. The process takes these waste products and turns them into renewable energy and fertiliser.

When we talk about food waste, this includes any food that was originally intended for human consumption but is discarded, lost or uneaten. Whereas food loss refers to food that never reaches consumers due to problems during farming, being removed according to supermarket cosmetic standards, oversupply, storage issues, contamination or spoiled during transport.

The extreme temperatures and prolonged heatwaves this year have led to an increase in food loss and waste, as fridges and freezers have struggled to keep up with the warmer weather. As a result, biogas is attracting more attention as a way to reduce food waste while turning it into something useful.

The process of making biogas works a bit like our digestive system but uses Anaerobic Digestion. It creates a farming loop by returning nutrients back to the land in several steps:

1.      The waste is first collected and prepared so that any contaminants like plastic packaging, metal, bones and other non-organic matter are removed, and what's left becomes organic slurry.

2.     The slurry is then stirred around in warm oxygen-deprived (anaerobic) tanks to be ‘digested’.

3.     Under these conditions, bacteria will grow and break down the slurry further, producing biogas as a by-product of anaerobic digestion.

4.     The biogas will then bubble up to the top of the slurry and be piped away to be cleaned and used as renewable energy, creating the natural gas more commonly known as biomethane. Alternatively, the raw form can be used to power engines, machines or turbines onsite.

5.     What is left in the tanks is called digestate and is a valuable fertiliser rich in nutrients and replacing expensive chemical fertiliser. Digestate can be split further into liquid and fibrous fertilisers, making it a versatile by-product.  

These sites, called Anaerobic Digestion plants (AD plants), are a promising and effective way of reducing CO₂ emissions and creating essential renewable energy sources. The Anaerobic Digestion and Bioresources Association claims that:
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“Instead of burning it [organic waste], or sending it to landfill, AD plants could potentially turn that waste…into 10% of the UK’s domestic gas, which means less landfill, stable energy prices, fewer carbon dioxide emissions and even a financial saving for homes, businesses, farms and councils across the country.”

While the UK is still developing its AD plants, the potential they hold is a promising glimpse into the future.

How is it already used?

Around the world, biogas technology is already being used on a large scale to turn organic waste into renewable energy. As the technology develops, smaller systems designed for individual households are becoming increasingly available.

The type of AD plant can vary depending on what is required, from wastewater treatment to agricultural waste or mixed bio-waste, to name a few. Biomethane produced at these commercial plants is currently used in the gas grid for cooking, lighting, refrigeration, heat generation, fuel for vehicles or machines and generating electricity. It is already being used on a commercial level, and there is a lot of promising technical progress and innovation trickling the technology down to individual consumers.

Can homeowners use biogas?

The simple answer is yes, there are options for at-home biogas producers. However, as with anything, there are positives, and there are challenges. Before investing in one, we’ve suggested some recommendations below:

Positives:

• They are less smelly than landfill or compost piles and will therefore not attract rodents or insects as much.
• Reduces food waste output for households.
• Produces fertiliser from existing waste, saving purchasing your own.
• It’s a green and renewable option for producing gas for cooking or heating water.
• Can be hooked up to a specific gas cooker to heat water and cook food or used for heating.

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Challenges:

• There is an upfront cost which can vary depending on what size you get or if you get one ready built.
• Space requirements should be thought out. Although they come in lots of different sizes, they do take up more space than a traditional composter, for example.
• There is lower gas production during the colder months or in low-input houses not producing a lot of organic waste.
• Requires regular maintenance and upkeep to work efficiently.
• Gas or fertiliser can be difficult to store, and currently in the UK residential biomethane cannot be added to our gas grid.

Is it practical in the UK?

At-home biogas plants are absolutely a viable option for UK homes, but it’s important to do some research beforehand, measure your food scraps to figure out your output and set expectations for what you want out of one. There are plenty of resources available on home biogas systems, and it's worth reading tips from existing users before getting started. It is also essential to check the Government guidance on at home anaerobic digestion.

Depending on the space and resources you have available, there are a few simpler alternatives that still focus on recycling food scraps, these include:

• Compost bins.
• Hot composters.
• Food waste recycling collections provided by the council.
• Learning how to make food using scraps, reducing food waste in the first place.

With food waste creating around 8-10% of greenhouse gases globally, home biogas plants could reduce this impact significantly. As homeowners continue looking for ways to reduce waste, save money and lower their environmental impact, technologies like home biogas are attracting increasing attention.

Seeing as UK households contribute around 58% of the food waste nationally, why not invest in a solution that reduces waste, recyclesyour food scraps and helps the environment? Home biogas systems won't be right for every household, but they offer an interesting glimpse into how future homes could make better use of everyday waste.

Find our more about Recycle Week 2026 and for homeowners looking to reduce food waste and live more sustainably, they are a technology worth keeping an eye on.