Most sustainability claims in food production are statements of intent. Targets, commitments, a page on a website. The harder question, and increasingly the one procurement teams ask, is mechanical: what physically happens to the waste, the oil and the energy, and what was the cost of the building itself?

The food waste problem

A production kitchen generates organic waste at volume: trim, peelings, offcuts, plate waste, product that fails spec. Conventionally it goes into bins, gets collected by lorry, and travels somewhere else to be dealt with.

Two separate emissions costs follow. The first is the journey, repeated multiple times a week. The second, and much larger, is what happens at the destination. Food waste sent to landfill breaks down without oxygen, and anaerobic decomposition produces methane, a greenhouse gas far more potent than carbon dioxide over the near term. In 2022, 31% of total UK methane emissions arose from the waste sector (mostly from organic waste in landfill sites).

If you can deal with it where it is produced, you skip both.

How the biodigester works

Our sites run Power Knot LFC biodigesters, and they are aerobic, which is the opposite of what most people picture when they hear "biodigester."

Anaerobic digestion, the process used in large industrial facilities, breaks material down without oxygen and captures the resulting biogas for energy. Aerobic digestion, which is what happens on our sites, uses oxygen instead. It is the same process that breaks down leaf litter on a forest floor, just much faster.

Mechanically:

Food waste is loaded into a sealed stainless steel chamber. It can be added at any point in the day, so there is no batching and no waiting.
Inside, a medium called Powerchips houses colonies of micro-organisms, working with an enzyme blend that accelerates the process.
Paddles turn slowly and intermittently, mixing waste with oxygen. The movement is deliberately gentle rather than macerating, because the microbes are doing the work, not the machine.
The process is exothermic, holding the chamber at roughly 42°C, which speeds decomposition further.
Within 24 hours, most food waste is reduced to grey water, which discharges safely to the sewer.

It handles what a production kitchen actually throws away: fruit and vegetables, raw and cooked meat, fish, cheese, bread, rice. Because the chamber is fully enclosed and the machine will not run with the door open, there is no exposed waste, which is what eliminates the odour and pest problems that come with waiting bins.

For a chef, the change is simple: waste goes into the machine rather than into a bin that someone then has to bag, wheel out and store until collection.

Aerobic vs Anaerobic

Aerobic digestion does not recover energy. Send food waste to an industrial anaerobic digestion facility and the biogas can be captured to generate electricity, with the leftover digestate used as fertiliser. That is genuine resource recovery, and on that measure anaerobic digestion is the stronger technology.

What on-site aerobic digestion does instead is eliminate the waste stream entirely at source: no storage, no collection journeys, no landfill, and no methane. The carbon dioxide released is biogenic, meaning the carbon came out of the atmosphere when the food was grown rather than out of the ground.

So the fair way to put it is this: for a kitchen with reliable access to a well-run anaerobic digestion route, that route recovers more value. For a production site in London, where the realistic alternative is bins, lorries and whatever the contractor actually does with it, processing on site is materially better than the status quo. Neither is a reason to make less waste in the first place, which remains the only intervention that beats both.

The part that matters commercially

Every LFC unit connects to the LFC Cloud, which records how much waste has been digested by hour, day, week, month and year, and converts that into the CO2 equivalent diverted from landfill. That data is retained for five years.

Which means the waste processing on our sites is measured, not estimated. And we can extract those figures per site and per tenant, and supply them to a partner for their own carbon reporting.

Used cooking oil

A production kitchen at volume gets through a lot of cooking oil, and poorly handled oil is one of the more common causes of drainage failures in commercial kitchens.

Used cooking oil is collected by Quatra and processed into used cooking oil feedstock, which becomes low-carbon biofuel: HVO (hydrotreated vegetable oil, a direct diesel substitute) and SAF (sustainable aviation fuel). Quatra reports that these fuels cut CO2 emissions by up to 87% compared with the fossil fuels they replace.

Grease trap waste is collected separately by Can Drainage and processed into paraffin.

A disposal cost becomes a feedstock. This is what distinguishes a circular process from a linear one, and it is why the oil is worth talking about at all. Sending it away to be dealt with is not a sustainability measure. Sending it somewhere it displaces fossil fuel is.

Energy: the decision to remove gas entirely

The single biggest energy decision we made was to build all-electric. Every piece of kitchen equipment across every site runs on electricity rather than gas. Water heating and temperature control run on air source heat pumps rather than gas boilers. There is no gas supply to design around.

A gas-fired kitchen burns fossil fuel on site. Its emissions are fixed by the fuel, and they will be the same in 2035 as they are today. An electric kitchen's emissions are determined by the grid it draws from, and the UK grid has been decarbonising steadily for over a decade and will continue to do so.

The practical consequence for an operator is that your production emissions fall over time without you doing anything. No capital project, no equipment replacement, no change to how you work. As the grid gets cleaner, the same kitchen produces a smaller footprint. A gas kitchen cannot do that. Decarbonising it means ripping out and replacing the equipment.

Grid decarbonisation is not our achievement; it is the country's. What we did was make the decision that lets our partners benefit from it, which is a design and capital choice most operators have not made, because electrifying a kitchen is harder and more expensive up front than installing gas.

Two further things sit alongside it:

Cost, not just carbon. DESNZ puts average non-domestic electricity at 23.61p per kWh for the first quarter of 2026. While average electricity rate across the Karma Kitchen portfolio is 19.85p per kWh, negotiated in bulk across all six sites. This saving passes directly to our partners.
EV charging is provided at all six sites, which matters for operators running their own distribution vehicles.

The part almost nobody counts: the building

Every commercial kitchen built from scratch carries embodied carbon: emissions locked into concrete, steel, ductwork, refrigerant and fit-out materials, all released before a single meal is produced. It is a substantial one-off cost, and it is almost never included when a food business calculates its footprint.

Two things reduce it.

The first is not building at all. An operator moving into an existing, already fitted production unit does not incur that fit-out carbon a second time. The infrastructure exists; using it does not double its emissions.

The second is sharing. Extraction, refrigeration, drainage and power serving several operators spreads that embodied carbon across all of them rather than loading it onto one. Per tenant, the building's footprint is a fraction of a dedicated facility's.

This is where our own position is most deliberate: we are strict about using existing buildings and structures. Sites are taken on and adapted rather than built from the ground up.

The most sustainable production kitchen is usually not the newest or best specified. It is the one that already exists and is being used properly.

What this means if you're the operator

Most food businesses reading this are not asking an environmental question. They are asking a procurement question, because their own clients are asking them.

Corporate catering contracts, retail supply agreements and public sector tenders increasingly require carbon and waste data. For a food business, most of that footprint sits in Scope 3: emissions produced across your supply chain rather than directly by you, including the facility you produce in.

The practical consequence is that your production site forms part of your reported footprint whether you have thought about it or not. Producing somewhere with on-site waste processing, oil recovery and measured diversion data means those numbers arrive with the space, rather than being a programme you have to fund, build and evidence yourself.

What this doesn't solve

None of this touches the largest part of a food business's footprint, which is almost always the ingredients. What you buy, how it was farmed, and how much of it is animal protein will make up around 49% of total emissions, with transport contributing an additional 9-10%.

Although outweighed by a wide margin, infrastructure is the part of the footprint an operator can change quickly by choosing where to produce. It is not the whole footprint, and anyone implying otherwise is selling something.

The short version

Sustainability in food production is mostly reported as intent. The parts that can be verified are mechanical: where the waste goes, what happens to the oil, where the electricity comes from, and whether the building needed to be built at all.

Producing at volume and being asked for carbon data by your clients? Talk to us about your production requirements.