Personal Note From Patrick, The Editor

Hi Reader, ever thought about reusing your tips or tubes?

To do so, many laboratories autoclave them to ensure they are sterile.

However, autoclaving takes time and energy - it’s at least 121 °C for 30 minutes, after all.

So, does reusing items actually make sense? Let's answer a question no one else addressed yet:

Today's Lesson: Reuse Or Incineration

Exploring which option is more sustainable

Number Of The Day

Approximately 400 000 000 tons of plastic are produced every year. While this number is predicted to grow and accumulate >4725 Mt of plastics in 2050, how we treat our waste seems to change too. Incineration, i.e., burning waste is becoming more common than landfilling. Energy recovery seems promising to gain some energy from an otherwise emission-rich process, but is it effective enough to be more sensible than autoclaving items for reuse?

400 000 000

Autoclave or Discard?

PS This is an interesting but, at times, very technical topic.

I have put together a slightly longer, full version here, below is a digest that leaves out some nuances. Ok let's go:

I write these lines before actually doing my research into the topic.

I have previously uncovered shortcomings in allegedly sustainable practices by conducting analyses nobody else had done.

Whether it is about the nuances of take-back programs, marketing tricks and carbon negative products or the fact that closed-loop recycling doesn’t exist, I am again and again surprised by how many nuances are simply cut out. However, only what is truly sustainable will help us in the long term. Therefore, let’s keep going!

Some loved me for it; some hated me for it.

Still, no matter the outcome I arrive at, there might be mistakes on my side or assumptions that don’t fit your case.

I really don’t know what the outcome will be - therefore, let’s dive in.

The Main Question

The main question here is whether it is more sustainable to autoclave and reuse plastic items or to discard them.

Autoclaving typically happens between 121 and 134 °C at 106 kPa for at least 30 minutes.

Sterilizers/autoclaves come in various forms and sizes. The model on the left is a medium-sized unit common in many laboratories, while the benchtop solution on the right is somewhat less common. However, in clinical or industrial settings, much larger models are also available.

This, of course, requires a significant amount of energy.

On the other hand, when incinerating plastics, the heat produced through energy recovery can be used to generate electricity and, to some extent, provide heat for buildings.

So, which option makes more sense?

Energy Consumption of Autoclaves

First, let’s look at how energy-intensive autoclaving really is.

Here, we are talking about autoclaving, or steam sterilization - in other words, using hot water vapor to sterilize items.

However, pinning down exact numbers is not easy.

Priorclave has written an overview of sterilizer design, whereas Ogugua et al. have put together a paper on theoretical models for energy consumption and heat dissipation in autoclaves.

There is substantial variation due to:

Model differences: size (larger sterilizers are often more energy-efficient but consume more energy overall)
Efficiency: newer models generally perform better
Set-up: jacketed vs. non-jacketed units, with the former requiring more energy
Steam generation: electric heating, in-built steam generators, or direct steam supply

I have not heard a single sustainability expert discuss this topic in depth - probably because there is little reliable data available.

Even the two experts in the field referred in their paper to a single number estimated by a company to approximate autoclave energy use.

These data show how much energy steam generation and autoclaving can consume, taken from an S-Lab analysis in the Edinburgh Cancer Research Centre. However, these data are too broad to tell you how much energy sterilizers really use.

Naturally, I tried to dig deeper and compiled peer-reviewed studies as well as information from different manufacturers.

My Summary: Autoclave Use

Numbers from manufacturers and studies range from 5–78 kWh per cycle. I would argue that 15 kWh per cycle is a reasonable median estimate.

About five studies estimated energy consumption to range between 0.2–3.6 kWh per kilogram. Based on the literature, 2 kWh/kg seems like a sensible estimate.

However, remember that laboratories generally use smaller autoclaves than hospitals or industrial facilities.

(For comparison, newer ultra-low-temperature freezer models use 5–15 kWh per day to maintain −70 or −80 °C.)

Additional Energy Sinks

Typically, plastic items need to be rinsed beforehand, and some labs use dishwashers for this purpose.

Again, energy consumption varies widely, but a reasonable estimate is 0.8–5 kWh per run.

Click to enlarge. This graphic stems from Parker et al., assessing different models of household dishwashers. It should give you a sense of variation we see in various models.

Then there is drying: can items air-dry, or are they dried in an oven?

Drying ovens are often very energy-intensive, and given the wide variation in models, sizes, and settings, we probably must assume values between 5–20 kWh just for drying.

Energy Recovery – How Sustainable Is It?

First, some technical clarification: we are talking about incineration, not pyrolysis or gasification.

This is an incineration plant – Germany has approximately 68 municipal waste incineration facilities with an aggregate annual capacity of around 19.6 million tons.

Pyrolysis occurs without oxygen; gasification with limited oxygen; neither fully burns the waste and instead produces oils or syngas.

Both are generally less energy-efficient than incineration but offer other advantages.

We also have to acknowledge that burning plastics is not clean.

Some plastics, such as PVC, contain chloride, and plastics in general contain additives (e.g., plasticizers, PFAS) that enhance stability and performance.

As a result, ash, acids, and toxic gases are inevitably generated during incineration.

Here, you see a schematic of an incineration plant’s inner workings. If you’d like to learn more about the topic, this is an excellent source.

Again, it is difficult to identify a single representative number.

Ideally, one would burn a clean, homogeneous waste stream, but sorting is labor-intensive and energy-demanding. Therefore, plastics are often incinerated as mixed waste, reducing overall efficiency.

> Based on various sources, we can assume that for common lab plastics suitable for reuse (predominantly PP, with PE and PS), 30–46 MJ/kg (8–13 kWh/kg) can theoretically be recovered.

> Electric conversion efficiency is roughly 20–30% for older facilities and up to 85% totally energy conversion for combined heat and power (CHP) plants that export steam for district heating or industrial use.

That means in practice, 4–10 kWh per kilogram of plastic are likely to be recovered.

Now, the relevant question is: how energy-intensive is plastic production?

Energy Consumption of Plastic Production

Here, we have to consider the entire process - from extracting crude oil to synthesizing plastics.

Once again, energy requirements vary by plastic type and synthesis route. However, to cut a long story short:

For PP, PE, and PS, energy consumption lies between 70–85 MJ/kg, or 19–24 kWh/kg.

Life cycle assessment data that mostly convert energy consumption in emissions (we can reverse this process) support this estimate.

Other Factors to Consider

An important factor to keep in mind is that autoclaves are extremely water-intensive.

Modern systems use 2–20 L per cycle, but older sterilizers left idle could waste over 200 L per day.

McGain and colleagues have published two fantastic articles on the consumption of electricity and water in idle sterilizers—and the numbers are mind-boggling, with savings of over $8000 annually simply by turning them off. However, please note that many newer models are less wasteful by design.

Similarly, leaving older systems idle can also account for up to 40% of total energy consumption, using up to 5kWh per hour - comparable to the daily energy use of a freezer.

Theoretically, transport distance also matters, given that both newly purchased items have to reach the lab and waste has to be transported to the plant.

Still, not all plastic waste is incinerated. Landfilling remains common in many regions and can lead to methane emissions and microplastic pollution. Recycling is still rare; at best, most plastics are downcycled.

All in all, these considerations change little about our analysis, as both incineration and autoclaving come with challenges of their own.

Therefore, let's move on:

The Final Verdict

Let’s do the math:

Autoclaving: ~2 kWh/kg (range: 0.2–5 kWh)

Washing: 0.8–5 kWh

Drying: 5–20 kWh

= ~2 kWh if rinsed and air-dried

= ~9.5 kWh on average with washing and drying (range: 0.2–30 kWh)

Plastic production: 19–24 kWh/kg

Minus energy recovery: 4–10 kWh

= 9–20 kWh net consumption

Taking all of this into account, is it more sustainable to autoclave plastic items?

Probably yes.

Under favorable conditions, the savings can be substantial; under unfavorable conditions, autoclaving may not be worthwhile.

Applying The Knowledge

You don’t always need to autoclave items before reusing them. If sterility isn’t required, they can be reused directly or after a wash.

If necessary, if autoclaving is even slightly more sustainable than incineration, this effect will compound the more often we reuse our items.

Labcon has published a white paper in which they show that their tubes can be reused even after being autoclaved or freeze-thawed. Read the post here.

Generally, it seems feasible to autoclave lab items several times.

Also monetary savings are imaginable, though they vary widely depending on the item reused, electricity prices and waste disposal fees.

However, much depends on user behavior:

Try to keep washing and rinsing efficient.

Moreover, if you use drying ovens, make sure they don’t run overnight.

Autoclaves scale poorly at low loads, so per-kilogram energy use can explode if labs autoclave small batches.

Therefore, always fill autoclaves properly before running them.

This graphic comes from McGain et al., with 1,314 data points indicating that autoclaves become more efficient with larger loads because the load-dependent energy (heating the plastic) does not compare to the fixed overhead (warming the chamber, steam generation, standby losses).

Finally, this discussion also highlights the importance of proper waste separation: contaminated items must be autoclaved before incineration, creating a major energy sink.

Discarding uncontaminated items in regular waste is therefore crucial.

Key Takeaways

Energy recovery is not a solution - it is an improvement. Burning fossil-based plastics is not sustainable.
Autoclaving consumes significant energy and water; it is not the sustainable solution, but a more sustainable practice.

On average, autoclaving and reusing plastics appears more sustainable and helps build a greener culture.

Reducing plastic use remains the most effective strategy.

How We Feel Today

References

Houssini, K., et al., 2025. Complexities of the global plastics supply chain revealed in a trade-linked material flow analysis. Communications Earth & Environment, 6, 257. doi:10.1038/s43247-025-02169-5.

Dokl, M., et al., 2024. Global projections of plastic use, end-of-life fate and potential changes in consumption, reduction, recycling and replacement with bioplastics to 2050. Sustainable Production and Consumption, 51, pp. 498–518. doi:10.1016/j.spc.2024.09.025.

Ogugua, C.J., et al., 2023. Energy analysis of autoclave CFRP manufacturing using thermodynamics based models. Composites Part A: Applied Science and Manufacturing, 166, 107365. doi:10.1016/j.compositesa.2022.107365.

McGain, F., et al., 2016. Hospital steam sterilizer usage: could we switch off to save electricity and water? Journal of Health Services Research & Policy, 21(3), pp. 166–171. doi:10.1177/1355819615625698.

McGain, F., et al., 2017. Steam sterilisation’s energy and water footprint. Australian Health Review, 41(1), pp. 26–32. doi:10.1071/AH15142.

McGain, F., et al., 2012. A life cycle assessment of reusable and single-use central venous catheter insertion kits. Anesthesia & Analgesia, 114(5), pp. 1073–1080. doi:10.1213/ANE.0b013e31824e9b69.

Overcash, M., 2012. A comparison of reusable and disposable perioperative textiles: sustainability state-of-the-art 2012. Anesthesia & Analgesia, 114(5), pp. 1055–1066. doi:10.1213/ANE.0b013e31824d9cc3.

Marczak, H., 2022. Energy inputs on the production of plastic products. Journal of Ecological Engineering, 23(9), pp. 146–156. doi:10.12911/22998993/151815.

Eboh, F.C., et al., 2019. Economic evaluation of improvements in a waste-to-energy combined heat and power plant. Waste Management, 100, pp. 75–83. doi:10.1016/j.wasman.2019.09.008.

Javed, M.H., et al., 2025. Advancing sustainable energy: environmental and economic assessment of plastic waste gasification for syngas and electricity generation using life cycle modeling. Sustainability, 17, 1277. doi:10.3390/su17031277.

Boumanchar, I., et al., 2018. Municipal solid waste higher heating value prediction from ultimate analysis using multiple regression and genetic programming techniques. Waste Management & Research, 37(6), pp. 578–589. doi:10.1177/0734242X18816797.

Soni, A., et al., 2025. Waste-to-energy technologies: a sustainable pathway for resource recovery and materials management. Materials Advances, 6, pp. 4598–4622. doi:10.1039/D5MA00321A.

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Edited by Patrick Penndorf
Connection@ReAdvance.com
Lutherstraße 159, 07743, Jena, Thuringia, Germany
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Green Education – Is Autoclaving Sustainable Or Should You Discard?