Landfill mining waste to energy means digging up waste that has already stabilised in a landfill, screening it into a solid refuse fuel (SRF), and converting that fuel into electricity by pyrolysis. In a three-phase proposal for a city landfill in South-East Asia, about 140 tonnes a day of mined waste would feed a 2.5 MW first phase, and 275 tonnes a day would feed each of two 5 MW phases after that.
The challenge: a growing dump and no easy way out
The city’s landfill was receiving roughly 500 to 600 tonnes of fresh household waste a day, and the waste already in place was estimated at around 140,000 tonnes. Rubbish was dumped without structure, space was running out, and the site produced fugitive methane. Waste in warm, wet regions is also high in organic matter and moisture, which makes it a poor fuel as received.
The project had three goals: reduce the waste going into landfill, reduce the waste already there, and create a useful asset from what is currently a liability. Construction also had to proceed without stopping the daily tipping.
The approach: let the landfill do the pre-treatment
Why not mass-burn incineration?
The proposal argues against burning raw mixed waste. Without sorting and drying, high-moisture waste can consume more energy than it yields. Source separation by households would help, but it takes many years to put in place, so the plan assumed it would not be available. The route chosen instead was a sorted, dried fuel feeding a pyrolysis plant.
Aerobic stabilisation in the landfill
The central idea is to structure the landfill so that fresh waste can stabilise in the presence of air. Over time the moisture and biodegradable content fall, and plastics begin to break down. That makes the mined material easier to sort than fresh waste:
- No first-stage trommel is needed on the mined material, and no large reception hall.
- Moisture content is already lower, so drying costs less.
- Less biodegradable matter means a higher calorific value.
After stabilisation, the 140,000 tonnes in place were expected to leave around 100,000 tonnes to be mined.
From landfill to SRF
- Mining: an excavator removes stabilised waste from the older areas, ideally one excavator to keep diesel use down.
- Primary separation: a trommel sited in the middle of the landfill removes fines and rejects. Because rejects go straight back into the landfill, haulage is minimal. This stage is outdoors and runs for around ten hours a day.
- Covered conveyors and SRF storage: separated material moves to a covered hall next to the shredder, where it acts as a buffer.
- Shredding and drying: the SRF is reduced in size and dried, then conveyed to the pyrolysis feed hopper. This second stage is under cover and operates 24 hours a day.
In the Phase 1 design basis, 140 tonnes a day of landfilled waste at about 38% moisture produces roughly 105 tonnes a day of wet SRF, which is about 82 tonnes a day dry. Around 35 tonnes a day of rejects and moisture are removed. The SRF was assumed to have a dry lower calorific value near 15 MJ/kg and a moisture content of about 20%.
Pyrolysis, steam and power
The SRF is fed into a pyrolysis unit, where it is heated without oxygen to produce a syngas and a carbon-rich char. The char is gasified, and the gases pass to a thermal oxidiser. The hot gas then raises steam in a boiler, and the steam drives a turbine generator. The flue gas passes through a dry scrubber and bag filter before the stack, with continuous emissions monitoring.
| Phase | Output | Mined waste | Pyrolysis units |
|---|---|---|---|
| I | 2.5 MW | about 140 t/day | 1 |
| II | 5 MW | about 275 t/day | 2 |
| III | 5 MW | about 275 t/day | 2 |
Together the three phases would give 12.5 MW and mine about 215,000 tonnes a year, assuming roughly 85% availability. The output depends on a detailed waste analysis.
Why it works: no new landfill space needed
Rejects returned to the landfill are small, about 40 tonnes a day after Phase II, and they go into the void created by the mining itself. The proposal therefore needs no new landfill space. The same logic reduces the site area over time, cuts the uncontrolled methane from old waste, and replaces some fossil-fuelled electricity.
On emissions, the proposal compared expected stack concentrations against EU directive limits for waste incineration and found the project figures to be below them, for example for dioxins. The current rules sit in the Industrial Emissions Directive, which you can read on EUR-Lex. Pyrolysis and gasification take place in an oxygen-deficient atmosphere, so the conditions that create dioxins and furans are limited, and a thermal oxidiser at 1,000°C or above finishes the job.
The trade-offs are honest ones:
- Landfill mining uses heavy diesel plant and the separation equipment needs significant power.
- Waste quantity and quality are estimates until a waste analysis is done. If waste is insufficient for all phases, the later ones would be reduced.
- Compost from mixed waste carries heavy-metal and reputation concerns, so it is better treated as a windfall than as a core revenue stream.
What to consider for your own project
- Test the waste first. Moisture, organic content and calorific value decide whether SRF is viable. Sample at depth, not just at the surface.
- Phase the build. A 2.5 MW first phase proves the process before larger units are committed.
- Keep tipping going. Plan construction and mining so the site never has to refuse waste.
- Locate the separation plant close to the mining face. Haulage by diesel truck is a cost and an emission, and rejects should return to the landfill with minimal movement.
- Verify the data. A due diligence step with independent professionals should check all waste and design data before financial close.
FAQ
What is landfill mining?
It is the excavation and processing of waste that is already buried, to recover fuel, materials and landfill space.
What is solid refuse fuel?
SRF is a sorted, shredded and dried fraction of waste with a controlled moisture and calorific value, used as fuel in place of raw waste.
How is pyrolysis different from incineration?
Pyrolysis heats waste without oxygen, turning it into gases and char which are then burnt in a controlled thermal oxidiser. Incineration burns the raw waste directly.
Does the landfill have to close during construction?
No. The proposal states that construction would not hinder ongoing tipping.
Considering energy from an existing landfill?
Tell us about your site and waste records and we will assess whether mining and SRF production make sense.