What to ask before you buy a pyrolysis plant

Most pyrolysis equipment is bought on purchase price and a headline throughput figure. Those are the two numbers least correlated with whether the plant will make money.

These are the questions we would ask on your behalf. None of them are hostile. A good vendor will have the answers ready, and a vendor who does not have them has told you something useful anyway. Get them in writing, and get the ones that matter into the acceptance clause.

1. Yield and output

• What char yield, on what basis? Dry mass or wet? With or without ash? A yield quoted on wet feedstock at unstated moisture is not a number.
• On which feedstock, at what moisture and particle size? A figure achieved on kiln-dried hardwood chips tells you nothing about maize cob at 25% moisture.
• Measured where, and by whom? Manufacturer's test rig, or an operating installation? Ask to speak to the site.
• What is the fixed-carbon content and the H/C_org ratio of the output? If you intend to certify carbon, this determines whether you can. Ask for lab reports, not a datasheet.
• How consistent is it, batch to batch? Ask for the spread, not the best run. Variability is what breaks downstream product specifications.

2. Feedstock envelope

• What is the accepted moisture range, and what happens at the top of it? Every plant has a moisture level above which it quietly stops performing.
• What particle size range, and what pre-processing is assumed? Chipping and screening equipment is often absent from the quote and substantial in the budget.
• Which feedstocks have been run through it, as opposed to being listed as compatible? Ask for the materials, not the categories.
• What happens with high-ash or high-silica material such as rice husk or straw? Ash behaviour causes slagging, abrasion and discharge problems that woody trials never reveal.
• What is the tolerance for contamination — stones, soil, metal, plastic? Real feedstock in a rural setting arrives with all four.

3. Throughput and availability

• Is the throughput figure instantaneous or annual? One tonne an hour on the nameplate at 40% availability is about 3,500 tonnes a year; 600 kg an hour at 85% is about 4,500. The smaller machine is the better asset.
• What availability has been achieved on an operating installation, over at least a year? This is the number that determines revenue, and it is almost never in the brochure.
• What is the planned downtime for scheduled maintenance and refractory work?
• How long from cold start to steady state, and how much feedstock is consumed getting there? For a plant that stops each night, this can dominate the energy balance.

4. Commissioning

• How long has commissioning taken on comparable sites? Not how long it is planned to take.
• Who commissions it, and where do they travel from? Establishes both cost and how long a future problem will take to resolve.
• What must be ready before they arrive? Vendors routinely assume a level of civil work, power and feedstock preparation that is not in the quotation.
• What are the acceptance criteria, and what happens if they are not met? If there is no measurable acceptance test, you have no leverage after the crates arrive.

5. Maintenance and spares

• Which parts wear, and how often? Ask specifically about augers, seals, refractory, grates and discharge components.
• Which of those can be fabricated locally, and which must be imported? This question predicts more future downtime than any other on the list.
• What lead time on imported parts, and what does the vendor hold in stock?
• What tools and skills does routine maintenance need? If it requires specialist equipment your team does not have, budget for it now.
• Can a competent local workshop repair it, or does every fault require the OEM? Ask what the realistic response time is, then cost that wait at your own production rate.

6. Logistics and installation

• What are the module dimensions and weights? Check them against the actual road, not the map — and against the bridges on it.
• What lifting capacity is needed? Then check what crane capacity exists within reach of the site, not within reach of the capital.
• What civil works and foundations? Can they be built by an ordinary local contractor, or do they need specialist work?
• What power supply, and what happens during an outage or a voltage dip? A controls system that needs a clean supply will need conditioning equipment.
• What is the footprint including feedstock storage, drying and char handling? The reactor is usually the smallest part of the yard.

7. Operating labour

• How many operators per shift, and at what skill level?
• How long does training take, and is retraining included when staff turn over? They will turn over.
• Are there written operating procedures in a language your operators read?
• What can an operator diagnose alone? If every fault needs a remote engineer, your availability is capped by someone else's response time.

8. Instrumentation and data

• What is measured and logged as standard? Temperature at which points, feed rate, output mass?
• Can you export the data, in what format, and do you own it?
• Is the instrumentation sufficient for your carbon methodology? Establish this before purchase — retrofitting monitoring to satisfy an auditor is expensive and sometimes impossible.
• What happens to logging when connectivity drops? Rural sites lose connectivity; gaps in the record become gaps in issuance.

9. Safety and emissions

• How does it fail? On loss of power, loss of feed, or an operator error — does it fail safe?
• How are tars and condensates handled and disposed of?
• What are the flue emissions, and against which standard were they measured?
• What permits does this require in your jurisdiction, and who is responsible for obtaining them?
• What is the fire risk during char discharge and cooling, and how is it managed? Freshly made char can self-heat.

10. The number that matters

Purchase price is the smallest part of what a plant costs. Build the comparison on five-year total cost of ownership, and insist that each vendor price the same scope:

• Equipment, freight, duties and insurance
• Civil works, foundations and lifting
• Installation and commissioning, including travel and accommodation
• Feedstock pre-processing equipment — chipping, screening, drying
• Operator training, and retraining
• Spares holding, and consumables
• Expected maintenance labour and refractory replacement
• Realistic downtime, costed as lost production
• Decommissioning or major overhaul at end of life

The cheapest machine on the quotation is very often the most expensive installation, and the difference shows up in year two rather than year one.

Put it in the contract

Answers in a meeting are worth little. The ones that determine whether the plant earns money belong in the acceptance criteria, with a defined test, a defined feedstock, and a defined consequence if they are not met:

• Char yield, on a stated feedstock at stated moisture and particle size
• Output specification, including fixed carbon and H/C_org
• Sustained throughput over a defined continuous run, not a peak reading
• Availability over a defined test period
• Commissioning completion date, with remedies for overrun
• Spares list, lead times, and price protection
• Training delivered and demonstrably understood

We do not sell pyrolysis equipment and have no commercial interest in which vendor you choose. For disclosure: we are developing a machine of our own with engineering partners, but it is not available and this list is not a way of steering you towards it. We publish it because a badly specified plant becomes somebody's problem for a decade, and often ours, two years in, working out why it never ran properly.