Hi there, 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?
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, newer innovations in plastic waste treatment, namely energy recovery, are widely praised as strong contributors to sustainability.
In short, when incinerating plastics, the heat produced can be used to generate electricity and, to some extent, 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.
This is one of the most efficient ways to sterilize plastic items (e.g., compared to chemical sterilization).
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.
Moreover, there is variation depending on whether one counts only the sterilization phase or the entire use cycle. I chose to focus on the latter to be pragmatic.
Converging Autoclave Numbers
How much plastic can we clean per cycle? I want to be cautious here, as autoclaves should not be overpacked to ensure proper steam distribution, and size differences are substantial.
In a small to medium-sized lab autoclave, one might fit around 20–25 tip boxes, and more than 100 in a large unit.
Assuming a weight of about 90 g per box and 80 g for 96 tips, each box weighs roughly 170 g.
For tubes, we might stack 100 or more in a small to medium-sized model, with each weighing about 13 g.
This means that between 0.5 and 1.5 kg of plastic items can be autoclaved per cycle.
> Assuming an energy consumption of 5–15 kWh per cycle, this places us somewhat above the average energy use per kilogram reported in other studies.
This gives us a general idea of autoclave energy consumption.
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.
Given current electricity and heating demands, this energy is very likely to be used.
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.
Again, variation exists depending on whether molding and processing are included or only raw material conversion.
Of note, the generation of bioplastics such as PLA do not need to be considered here, as they cannot be autoclaved.
For biobased plastics from second-generation feedstocks that yield conventional plastics, energy savings of 5–30% compared to fossil-based plastics are possible.
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.
Then we could think about the impact of the needed equipment itself:
Incineration facilities are resource- and labor-intensive to build, but they are required regardless, given the volume of plastic waste produced.
Autoclaves also must be manufactured, transported, and eventually discarded - but laboratories require them regardless of reuse practices.
PS: Estimating the environmental impact of manufacturing a steam sterilizer is difficult due to limited life cycle data.
Transport distance also matters, given that both newly purchased items have to reach the lab and waste has to be transported to the plant.
Emissions for transport are roughly 15–100 g CO₂e per ton-kilometer, comparable to emissions from generating one kilowatt hour of electricity, depending on the energy mix.
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.
Given that there should be sufficient plastics in municipal waste, this is not an argument against autoclaving.
Moreover, how “sustainable” 1 kWh is depends on how energy is produced in your region (hydro, nuclear, coal, etc.).
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
Of course, if autoclaving is even slightly more sustainable, 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.
However, labor input is often a crucial factor: autoclaving and washing require time, but reuse reduces dependence on supply chains.
Also monetary savings are possible, though they vary widely depending on the item reused, electricity prices and waste disposal fees.
However, much depends on user behavior:
Autoclaves scale poorly at low loads, so per-kilogram energy use can explode if labs autoclave small batches.
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).
Therefore, always fill autoclaves properly before running them.
Moreover, if you use drying ovens, make sure they don’t run overnight.
Both plastic production and autoclaving consume significant energy - therefore, reduction remains king.
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.
So, should you start reusing items? Yes—whenever feasible.
If autoclaving is required, try it if you have the capacity, especially when rinsing and air-drying are sufficient.
Even when energy use approaches that of incineration, these practices help foster a culture of sustainability that can drive broader behavioral change.
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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