A waste tyre pyrolysis plant processing 100 tonnes a day can generate roughly 8 MW of electricity gross, or about 7 MW net after the plant’s own demand. That is the outline from a proposal for a tyre-to-energy scheme in West Africa. The figures depend heavily on tyre quality, cooling water and what the owner supplies, so they are best treated as a worked example rather than a rule of thumb.
The challenge: tyres as a fuel
Waste tyres are a bulky disposal problem and also a dense fuel. The design assumed a calorific value of about 33 MJ/kg and effectively no moisture, since tyres do not hold water the way household waste does. That is roughly twice the energy per kilogram of mixed municipal waste, which the same proposal used as a comparison at around 16 MJ/kg.
The client was a waste company looking to treat tyres and export power to the local grid. The question was how much power a given tonnage could support, and what the owner would have to provide around the main plant.
The approach: pyrolysis, gasification and a steam cycle
The design assumed 100 tonnes a day with 85% plant availability, which works out at about 4.2 tonnes an hour while running. At 33 MJ/kg, that feed carries a little under 40 MW of energy (our arithmetic from the proposal’s figures). Roughly 85% of the thermal energy in the feedstock was expected to be captured in high-pressure superheated steam boilers, and the steam drives a turbine.
How the plant works
- Feed: a hopper and compactor screw meter the tyres into the process and seal it from the air.
- Pyrolysis: the feed is heated without oxygen, driving off a fuel gas.
- Gasification: the carbon char left behind is converted to more gas, leaving a small ash residue.
- Thermal oxidation: the combined gas is burned in an oxidiser, which has a pre-heater burner for start-up.
- Heat recovery: a waste-heat boiler produces the high-pressure steam.
- Power: a steam turbine drives the alternator, with controls for exporting to the local network.
Equipment is delivered as modular packages and assembled on site, which shortens time on the ground.
What the numbers mean
- 8 MW gross, 7 MW net. The plant’s own electrical load was estimated at about 1 MW. Gross output is about 20% of the fuel energy, which is typical of a small steam cycle.
- The cooling choice moves the net figure. If clean water from a river or large lake is available, the parasitic load is lower. A closed-circuit air-blast cooler needs fans of around 0.5 MW. An intermediate option sits between the two.
- Moisture is the sensitive variable. The design allowed up to about 20% moisture on a dry basis. Above that, throughput is held but net energy for power falls.
What the owner has to provide
The scope covered the pyrolysis plant, boiler and turbine, installation supervision and commissioning. It did not include tyre reception, storage or size reduction, which the proposal said it could add if required. Also excluded were:
- Foundations, buildings and civil works
- Utilities, site access and the grid connection, including substation and protection
- Permits and third-party approvals
- Operating staff for commissioning and routine running
- Connection to a back-up fuel supply for start-up
These exclusions often cost as much as the interface equipment itself, so they belong in the early budget.
Programme: about 18 months
The delivery programme added up to 74 weeks:
| Stage | Weeks |
|---|---|
| Front-end engineering design (FEED) | 4 |
| Client approval | 2 |
| Detailed design | 12 |
| Client approval | 2 |
| Manufacture and procurement | 30 |
| Installation on site | 12 |
| Commissioning and performance testing | 12 |
That does not allow for third-party approvals or holiday shutdowns. The FEED package fixes the heat and mass balance, process flow and piping and instrument diagrams, general arrangement drawing and equipment data sheets before any metal is ordered.
Why a steam cycle, and what to check first
Pyrolysis and gasification followed by a boiler decouples the thermal process from the power plant. The gas does not go through an engine, so contaminants that would foul an engine matter less. The cost is the efficiency of a small steam turbine and the cooling demand that comes with it. For general context on how energy from waste is regulated and compared, see Defra’s guide to energy from waste.
What to consider for your own project
- Secure the tyre supply. A plant that runs at 85% availability needs a steady, long-term feedstock contract.
- Decide who handles size reduction. It is a separate package with its own power demand and maintenance.
- Settle the cooling method early. It changes net output and site water demand.
- Check the grid. Export needs a connection agreement, a substation and protection, none of which were in scope here.
- Plan for permits. They run in parallel with design but can set the real programme.
FAQ
How much electricity can a tyre pyrolysis plant generate?
In this design, about 8 MW gross from 100 tonnes of tyres a day, and around 7 MW net after the plant’s own load.
Do tyres need shredding first?
Yes. The proposal assumed the owner would handle reception and size reduction, though the supplier offered to quote for it.
How long does a plant like this take?
The programme was 74 weeks from the start of FEED to the end of commissioning, excluding approvals.
What affects the net output most?
The cooling method, the moisture in the feed and the plant’s availability.
Looking at tyre or waste-to-energy options?
Tell us your feedstock tonnage and site constraints and we will talk through what a plant could deliver.