Fire detection for green waste and composting sites

Last updated 30 October 2026. A composting site is built around heat. Green waste is shredded, laid out in long windrows and left to warm up as microbes break it down. Most of the time that heat is exactly what you want. When it cannot escape, or when a hot load arrives in the green waste, a pile can smoulder for hours before anyone sees smoke. This page explains what the Environment Agency (EA) and the WISH Forum ask of open windrow and in-vessel composting sites and green waste transfer sites, and how camera smoke and fire detection fits into your fire prevention plan (FPP).

Which composting sites need a fire prevention plan?

The EA’s fire prevention plans guidance lists “compost and plant material” as a combustible waste. It applies in part to biowaste treatment: open windrow composting, in-vessel composting and dry anaerobic digestion. Operators in those sectors may not have to include every activity in their plan, and the guidance asks them to contact the EA for more information. It does not apply to wet anaerobic digestion or to land spreading.

The EA’s appropriate measures for biological waste treatment are firmer. Permitted composting and anaerobic digestion facilities must have an FPP that meets the EA guidance, including how they will prevent uncontrolled decomposition and self-heating by managing temperature and moisture. So whether you run a large open windrow pad, an in-vessel plant, or a smaller site that bulks up garden waste before it moves on, you should expect your plan to cover the green waste you store as well as the compost you make.

Green waste turns up at several kinds of site:

• Open windrow composting sites, which shred garden and parks waste and compost it outdoors in long rows.
• In-vessel composting plants, which compost food and garden waste in enclosed tunnels or halls before it matures outside.
• Green waste transfer sites, which take garden waste from councils and the public and bulk it up for a composter.
• Biomass and wood fuel yards that also handle woody green waste. Our page on wood recycling yards covers the wood side.

Why do compost and green waste piles catch fire?

Your FPP needs a control for each likely cause of fire. At a green waste site, these are the ones the guidance comes back to:

• Self-heating that gets out of hand. Composting makes heat on purpose. The appropriate measures ask you to size windrows so that passive heat convection is not held back, and to avoid persistent high temperatures. A pile that is too big, too dry or too tightly packed holds its heat, and a hot spot can start to smoulder deep inside.
• Heat from shredding. The EA FPP guidance says heat from treatment such as shredding or chipping must be released so that waste is cool before you form it into piles for storage.
• Hot loads. WISH Forum guidance warns of hot ashes and other wastes from garden burners after the first warm, dry weekends of spring, and of bonfire ashes and firework residue in early November. Both arrive mixed into garden waste.
• Plant and hot works. Shredders, screens and loading shovels work hard in dusty, dry conditions. The appropriate measures ask for a permit to work for hot works and for loose combustible material not to build up around plant.
• Arson and fly-tipping. Rural sites with long boundaries are easy to get into. The appropriate measures name arson, fly-tipping, theft and vandalism among the things your security must prevent.

Self-heating

None of these causes needs anyone to be on site. A windrow that was fine at five o’clock can be smoking by midnight, and the first person to notice may be a neighbour. Our waste site fire risk assessment guide shows how to work through each area of your site.

What happens when a composting site catches fire?

At 8.51pm on 5 January 2026, Devon and Somerset Fire and Rescue Service sent crews to a fire in a compost heap near Brixton in the South Hams. When they found further seats of fire they asked for five more fire engines and an aerial ladder platform, and crews from 13 stations were listed as attending. Through the night, specialists on site used a thermal probe to track temperatures while crews damped down. In the morning the compost was turned over by machinery on site, and the service reported at 09:09 that the fire was out, more than 12 hours after the first call.

In September 2026, Oxfordshire Fire and Rescue Service and the EA issued a joint statement about a fire of green waste at a composting site in Oxfordshire, attended during the week starting 14 September. Responders agreed that a controlled burn, with the smouldering material regularly doused with water, was the safest way to manage a fire of that size and type. The statement of 25 September said the fire was out, the operator had been told to clear the burnt material, and the EA would investigate the cause and whether any permit conditions had been breached.

Both fires were deep-seated, slow to put out and needed plant to pull piles apart. That is typical of compost. Once a fire is inside a large pile, it is hard to reach. Finding it early, while it is still at the surface of one row, is what keeps it small.

Reception at dusk

Which piles do the EA limits apply to?

This is where composting differs from other waste sites. Section 10.3 of the EA FPP guidance says that for composting activities, the maximum pile sizes do not apply when the waste is actively managed and monitored during the composting process. Section 11 says the same for separation distances. But waste stored before and after active composting must follow the maximum pile sizes.

In practice that splits your site into two kinds of pile:

• Windrows in active composting, which you turn, water and check for temperature as part of the process. The pile size table does not cover these, but the appropriate measures still set rules for how you build and manage them.
• Everything else: green waste waiting to be shredded, shredded material waiting to go into a windrow, oversize from screening, and finished compost waiting to be sold. These are stored waste, and the standard limits apply.

Where limits apply

What are the pile size limits for compost and green waste?

Section 9.2 of the EA FPP guidance has a row for “compost and green waste (excluding during the active composting process)”. The limits are:

• Loose and larger than 150mm: 750 cubic metres.
• 30 to 150mm, or baled: 450 cubic metres.
• Smaller than 30mm: 450 cubic metres.

Maximum volumes

The general limits apply to stored piles as well. No pile may be more than 4 metres high or more than 20 metres long or wide. Piles must be at least 6 metres apart and 6 metres from the site boundary, buildings and other combustible material, unless you use a suitable fire wall with at least 120 minutes of fire resistance. You must also keep a quarantine area that can hold at least 50% of your largest pile, with 6 metres of clear space around it. Our guide to EA fire prevention plan detection requirements covers the detection side of the same guidance.

The EA also asks you to store waste in its largest form for as long as you can, because smaller pieces are more prone to self-combustion. At a green waste site that means shredding close to when material goes into a windrow, rather than shredding a large stockpile and leaving it.

How long can compost and green waste be stored?

Section 8 of the EA guidance says combustible waste must be stored for less than 6 months, unless the material is compost and the EA has agreed that you can store it for longer. Compost is the only waste with that exception written in. You must still follow the first in, first out principle and show how you record what is stored and for how long.

If you keep any combustible waste at the maximum pile size for more than 3 months, you must show what extra measures you will take to prevent self-combustion, such as temperature monitoring. The guidance also asks you to plan for seasonal changes in supply and demand. For a composter that cuts both ways. Garden waste floods in from spring to autumn, and compost sales slow in winter, so piles of both raw material and finished product can grow at the times of year when they are hardest to move.

Screening outputs

What temperature monitoring does the EA expect?

Temperature is the main way composters control fire risk, and the appropriate measures for composting plants are specific. You should:

• monitor windrow temperatures daily during the sanitisation and stabilisation stages;
• monitor the temperature of all stored waste weekly, including oversize and screened material;
• take a representative core temperature, using probes that are long enough to reach it;
• optimise moisture, and avoid persistent high temperatures;
• leave enough space between windrows for turning and for safe access in a fire;
• keep enough water, leachate or process liquor available to fight a fire.

The FPP guidance adds that your plan must set out the triggers you will use, such as a temperature, a rate of temperature change or visual signs of heating, and the actions you will take when one is reached. Staff must be trained to find and manage hot spots. It also notes that surface temperature readings are unlikely to give an accurate core temperature, though they can help to spot localised heating and unusual trends.

Daily and weekly checks

Why can’t temperature probes catch every fire?

WISH’s WASTE 28 guidance (issue 3, March 2020) says thermal probes have been used at green waste composting and similar operations for many years. Most windrows are narrow enough for a 1 to 2 metre probe to reach towards the centre. But WISH is also clear about the limits. Research shows that hot spots inside a pile tend to move around as oxygen and fuel are used up, so it can be a matter of chance whether a probe is pushed in at the right place. Readings are also taken once a day or once a week, not every minute.

WASTE 28 does not apply specifically to composting sites, but WISH says its principles do apply to areas such as oversize storage and bunkers, and those are often the piles that are checked least often. It also warns that fires in loose waste can re-ignite many hours after the visible fire has been put out.

Two jobs

That is why the two methods work together. Probes and turning manage the heat you can measure. A camera that watches the surface of every windrow and stockpile, all night, catches the smoke that breaks out between readings.

What fire detection does a composting site need?

Section 13 of the EA FPP guidance says you must have procedures to detect a fire in its early stages, and your plan must show how the detection system raises the alarm both during working hours and when the site is closed. It must be proportionate to your activities and risks, and it can be automated or manual. The examples of suitable automated systems are smoke and heat detectors including temperature probes, CCTV visual flame detection systems, and spark, infrared and ultraviolet detection. Design, installation and maintenance must be covered by an appropriate third-party certification scheme or meet a recognised standard; if neither applies, you must show you can still meet the three objectives of the plan.

Composting brings one problem that most waste sites do not have: steam. Active windrows steam, especially on cold mornings and when they are turned. A detection system that cannot tell steam from smoke will either raise false alarms all winter or be switched off. So the questions to ask of any camera system are how it handles the normal look of your site, and whether each alert comes with a clip so the keyholder can check it before they set off.

Zones on a site plan

How do you protect a composting site at night?

Most composting sites are staffed in the day and empty at night and over the weekend, often in open countryside. The appropriate measures say you must prevent entry by intruders and protect against arson, fly-tipping, theft and vandalism, using one or a combination of security guards, fencing, controlled entry, adequate lighting, warning signs and 24-hour surveillance such as CCTV.

Perimeter after dark

With camera detection, each windrow, bay and stockpile can be its own detection zone. When smoke or flame appears in a zone, the alert goes to the duty keyholder’s phone with a short clip, so they can see what is happening before they drive out. Email alerts go to the wider duty list, and an alarm receiving centre (ARC) or call alerts can be added for sites where nobody is on call overnight. Fence and gate alerts after closing give you a chance to act before anything is lit. Our out-of-hours site security checklist covers the security side of a closed site.

How quickly do you need to respond?

The EA guidance says you must be able to move waste into the quarantine area as soon as possible or, at most, within 1 hour of a fire starting. At a composting site the usual first response is mechanical: a loading shovel or excavator pulls the burning part of a row away and breaks the pile open so it can be damped down. That needs a driver, a machine and water, and it all starts with somebody knowing there is a fire.

Write the response into the plan with names, roles and travel times. Say who receives the alert, who goes to site and how they get in. Name the plant they will use, say where the water comes from (the appropriate measures expect enough water, leachate or process liquor for firefighting) and explain how firewater run-off will be contained. Keep watching a pile for many hours after a fire appears to be out. Our FPP detection template and fire prevention plan checklist help you set this out.

Where does Woodcock AI fit at a composting site?

Woodcock AI turns the CCTV you already have into AI smoke and fire detection. It connects to your existing cameras or recorder over ONVIF or RTSP, so cameras that already overlook your windrow pad, bays and gates can start watching for smoke and flame without being replaced.

• Polygon detection areas. Draw a shape that follows the edge of each windrow, bay or stockpile, so every alert names the area on your FPP site plan. See polygon detection zones.
• Self-learning, fitted to each scene. Each camera’s model is fitted to its own view and learns from that site’s normal footage, including the steam that rises from windrows when they are turned or on a cold morning. Read about our self-learning AI.
• Years of development, in use today. Woodcock AI has been developed over several years and runs on real UK waste and industrial sites.
• Alerts that reach a keyholder. App alerts with a clip and email come as standard, with an alarm receiving centre (ARC) and call alerts as optional add-ons. Per-camera schedules keep smoke and fire detection on around the clock, with intrusion or line-crossing alerts on the fence and gate once the site is closed.
• Records for your plan. Each alert keeps its time, area and clip. We run smoke tests on site at commissioning, so you have evidence that the system works on your cameras.

Camera detection does not replace temperature probes, turning, moisture control or a life-safety fire alarm. It adds a layer that watches the surface of every row and pile, all night, and tells someone straight away. For how it works in detail, see our AI smoke and fire detection camera page, our guide to thermal cameras and AI CCTV for an FPP, and video smoke detection on existing CCTV. For other waste sites, see AI CCTV for waste and recycling, waste transfer stations and plastics recycling sites.

Which sources is this page based on?

• GOV.UK, Environment Agency, Fire prevention plans: environmental permits (last updated 11 January 2021; checked 30 October 2026).
• GOV.UK, Environment Agency, Biological waste treatment: appropriate measures for permitted facilities, section 5: general management (first published 21 September 2022; checked 30 October 2026).
• WISH Forum, WASTE 28: Reducing fire risk at waste management sites (issue 3, March 2020).
• Devon and Somerset Fire and Rescue Service, Outdoor fire, Brixton (5 and 6 January 2026).
• Environment Agency and Oxfordshire County Council Fire and Rescue Service, joint statement on a green waste fire at a composting site (25 September 2026).

We have summarised these documents in our own words. Always read the current versions and follow your permit. This page is general guidance, not legal or regulatory advice; your regulator decides what is acceptable for your site.

Frequently asked questions

Last reviewed 30 October 2026