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Alternatives to Burning Plastics in Waste to Energy Plants
Bruce Barbour - November 2025
This residual waste currently goes to landfill. My local council is proposing, urged on by State Government, that instead this waste be burnt in a waste to energy (WtE) plant being built locally.
The company building this waste to energy plant say that burning this waste is preferable to putting it in landfill, claiming a large decrease in CO2-e release from WtE compared to landfill. Unfortunately they are not telling us what they are comparing the WtE plant with. Is it an:
- Old style landfill (and practices):
- hole in the ground;
- fill with unseparated household waste – full of organic waste;
- cover with soil and forget.
OR is it a
- Modern landfill (and practices):
- hole in ground lined with plastic;
- waste that has had most of the organics removed is then placed;
- when filled cover with plastic and soil, and a greenhouse gas extraction system implemented.
As all the old style landfills are either closed or should be closing down shortly the comparison of the WtE plants must be to the modern landfill.
The plastics in the landfill do not breakdown to release CO2 or methane (at least not for a very long time). Microplastics perhaps but again also a very long time frame.
The waste to energy plant burns the organics which convert to CO2 (instead of methane) - which is good. What is not good is that it burns the plastic waste (70% of the waste stream) the energy from which is used to generate electricity. However in so doing releases a lot of CO2 into the atmosphere. For every tonne of plastic burnt approximately 3 tonnes of CO2 will be released. For my proposed local plant it would be over a million tonnes of CO2 per annum.
My calculation concluded that the amount of CO2-e produced by the WtE plant far exceeded the CO2-e from a modern landfill (and landfill practices).
The life of the plant is at least 30 years - and possibly up to 40 years, and it wouldn't commence operations until early 2030s. This will mean that it will run well past 2050 when Australia has committed to be at Net Zero. This means that at least a million carbon credits would have to be purchased each year to cover the plant. Carbon credit are over $40 a tonne and by 2050, when a lot of companies may be in the market the price could have skyrocketed. And anyway as I have discussed on other pages some carbon credits are dodgy, that is they don't mean a tonne of carbon sequestered. So Net Zero might be achieved on paper but not in reality. And the first option should always be to not release the carbon into the atmosphere. Carbon credit offsets were only meant to be for where there was no way (technology or practice) to prevent the CO2-e emissions that were to be offset. Burning plastic "waste" in a waste to energy plant does not meet that criteria.
My Proposal
Landfilling the plastic is preferable to burning. So we could continue current practice and dump residual waste in a modern landfill. But there are problems with this approach.We are told that we are running out of landfill. I find this difficult to accept (for Melbourne Australia) in that we are going to have huge holes in the ground to fill in the Latrobe Valley from the discontinued open cut coal mines. Dedicated trains could be used to transfer the waste to the pits. However I do accept that even modern landfills are not desirable environmentally and are expensive to build, operate and then to close and rehabilitate. Change is warranted.
I am just going to concentrate on the municipal waste stream (as I have in the rest of this article).
With our current recycling system a lot of the issues have been dealt with. The two remaining problems are 1. The thin film plastics which constitute 70% of the waste stream, and 2. the residual organics which constitute 10% of the waste stream but virtually all of the problems with methane release and some of the problem with leachate production.
What I would do
1. Collect separately via the suburban recycling bins all of the thin film plastics - so out of the Red Bin and into one of the other recycling bins. (This will require a complete rethink of which waste goes into which bin to have easiest and cheapest waste collection and separation, with least contamination and maximum recycling.)2. This thin film plastic will be baled. It will then be landfilled! But the big difference is that it will remain in the bales and not mixed and compacted with other waste. There will be dedicated landfill sites taking only baled plastic. The baled plastic will be stacked and when the site filled the bales covered with plastic which will then be covered with soil (say up to a metre?).
So what are the benefits of this system? There are many:
- A baled plastic landfill will be cheaper to set up.
- It will be cheaper to run - just stacking bales instead of running over them multiple times with large compactors. (Those large compactors are a million dollars ($A) plus each and burn huge volumes of diesel daily.) Staffing would be a fraction of a typical landfill.
- May not need a leachate system - to be determined.
- Probably need a small gas collection system as some of the plastic may have been dirty with food waste which could break down. Wouldn't anticipate this to be much of a problem. Any residual food waste amongst the plastic is probably more likely to breakdown to CO2 than methane as there would be quite a bit of air available in the plastic bales, relative to the amount of food waste. If it is mainly CO2 it would just be a matter of releasing it into the atmosphere from under the plastic cover. The amount of methane produced may also be insignificant. This would need to be assessed.
- The plastic is even less likely to breakdown to CO2, methane or even micro-plastics compared to typical landfill, as it won't be in contact with water or soil or UV light or chemicals from other waste.
- Burning risk in the landfill would be reduced once covered. The burning risk in the other residual waste landfill would also be reduced due to the huge reduction in flammable material.
- A baled plastics landfill is essentially a method of carbon sequestering - it captures and stores the carbon before it is even released to the atmosphere. Which is better than releasing the CO2 to the atmosphere and then trying to recapture it later, which is problematic and would be very expensive, if it could be done. And the carbon storage would be in a much more dense form than CO2. 1 tonne of plastic contains as much carbon as between 2.2 and 3 tonne of CO2 (depending on the type of plastic) and is much denser than the CO2 gas and comparable to or greater than the mass density of carbon storage in wood. Sequestering through baled plastic landfill of used but not yet recyclable plastic would mean that our electricity would need to be fully supplied from renewable sources, as it should be in a World that is (or should be) tackling climate change. Even if the baled plastic is eventually removed for re-use - see next dot point - the removed plastic would need to be recycled in such a way that most, if not all, of its carbon is retained in the new (plastic) product produced, which itself would be recycled at the end of its life.
- The plastic is not mixed with other waste. So in the future when a good method of plastics recycling is found the bales will be easy and cheap to access for processing. It is not wasted or burnt. It is stored. In the future it will be a resource to be mined. If it is not needed it will stay buried and inert, sequestering its carbon content. Plastics mixed with other waste in a standard landfill would be very costly to recover for recycling.
In terms of the last point we are going to need plastics for a long time in the future. Plastic is a very useful and flexible material. Hard wearing and inert - which is part of the reason it is so hard to recycle. And it is light-weight which is useful for the energy efficiency of many products. While we can envision a future without fossil fuels for energy (though it sometimes seems far away and there are some other uses such as aviation that are still a big issue) a future without plastic is less clear. We can certainly have less but not nil, at least not for a long time. So unless we want to have to keep drilling for oil for new plastic production we are going to have to figure out ways of recycling all types of plastic. Or to find organic alternatives to plastics with all of plastic's useful properties. Both options should be a high priority for ongoing research.
The system I am proposing effectively warehouses the plastic waste. But without the cost of the warehouses (a landfill solution would be much cheaper than building warehouses) and without the risk of the plastic catching fire in the warehouse, releasing noxious fumes close to housing.
The costs of disposal / storage should be borne by the manufacturers of new plastic (thin film or all plastics) as a levy per tonne on new product. (This should be implemented regardless.)
It should also be made clear that used thin film plastics are available at no cost to anyone that have shown they can and will recycle them. We could even pay them to take the product (at least initially) because it costs to get rid of it otherwise. However rorting would have to be guarded against.
If bales are bound with wire it probably should be stainless steel wires to ensure long life.
The bales would be less dense than compacted landfill. The landfill would fill quicker but would be cheaper to build and run. But bales are only made this way because bales are seen as a temporary storage solution rather than for a longer term. It would be worthwhile from a number of perspectives to investigate methods of increasing the density of the bales. Perhaps the plastic could be cut into strips and then heated prior to being compacted in a high pressure and hot baler. Hopefully high enough pressure and temperature so the plastics bond together in a fashion (perhaps even adding a small proportion of plastics based glue) so they don't want to spring apart, and have a higher baled density. Plastics mechanical recycling processes may have already, at least in part, addressed this issue. Whatever process is adopted it still needs to be relatively cheap and low energy - it does not need to be as good a quality as normal mechanical recycling would require. If higher density "bales" were viable it might be preferable, for manufacture and packing, to make them flatter, maybe 200 mm thick with larger other dimensions. Higher density would mean more waste per cubic metre of landfill and also would be able to take higher loading in the landfill.
In terms of new landfill for plastic bales, if there is indeed a lack of suitable sites, could consider burying on farmland. The process would be to buy a suitable farm. Plan layout. Scrape out large areas of land removing topsoil and then other soil down say 2 meters. Place bales say 3 metres high. Cover with plastic. Cover plastic with dirt. Sow to pasture. Lease the farm out for grazing production. (It shouldn't be resold as post-bale placement usage needs to be controlled and it needs to be available to be able to recover the plastic bales for recycling.) Numerous issues with this in terms of planning, environment and opinions of surrounding farms and others. Just a suggestion as a possible option. Not critical to the system. As I said Victoria (Australia) in the near future will have a large number of very large unused coal mines in the Latrobe Valley to be filled.
AI (LLM) Review
As I hadn't heard this system being proposed or implemented anywhere I asked AI for an assessment. This time I used GoogleAI instead of ChatGPT because I was using Google search engine at the time. Starting out skeptical (if a machine can be skeptical) it ended up giving a qualified favourable assessment but I am also aware that the AI models have been instructed to give generally positive feedback. Anyway you can read the "conversation" and do your own investigation and make up you own mind as to whether this is worthwhile, at least to do a proper feasibility assessment and small trial.Handling the Rest of the Waste Stream
I have dealt with 70% of the Red Bin waste stream but what about the remaining 30% comprising organics and non combustible waste? It could be put into normal landfill but there would still be the problem with methane generation from the organic waste decomposition (though a lot smaller issue than burning plastics).I suggest that the remaining waste stream goes through a high temperature incinerator or a waste to energy plant - or just an incinerator - to get rid of the organics. OK - so now I am advocating for waste to energy! I was never against waste to energy per se. I was against the greenhouse gases produced in the plant from burning plastics in the plant. But most of the plastic would have been removed (to a baled plastic landfill) - though there would still be some, mainly from synthetic clothing and small hard waste that is made or part made from hard plastics. We can deal with this waste product inclusion at some later time.
To make it more worthwhile for the waste to energy plant operator we could consider putting the food organics and garden organics waste stream (FOGO) through the plant as well. It depends on whether the composted FOGO is of good enough quality to have greater value as compost, perhaps as a fertiliser to replace fossil fuel derived fertiliser, than the value it would have converted to electricity through a waste to energy plant. The WtE plant operator could also consider sourcing crop waste to further augment the organic fuel supply to the plant.
Controversially, I would also consider burning the paper and cardboard from the domestic waste stream. It depends on the carbon balance. Is there less energy use and carbon dioxide other pollution released from making paper and cardboard from new plantation stock or from making "new" paper and cardboard from recycled "waste" paper and cardboard, also taking account of the energy recovered from burning the paper and cardboard waste?
In these scenarios (burning FOGO and/or paper/cardboard waste) what mainly would be burnt would be organics. The organics when burnt would produce mainly CO2 however this CO2 can be seen as part of the natural carbon cycle - the plants sucked up the CO2 from the atmosphere while growing and releases it back to the atmosphere when burnt. There is a zero net gain (discounting at the moment residual synthetics burnt carbon release from production process). The power could be sold at a premium as green electricity.
It is also quite likely that the plant size would be a lot smaller than the proposed plant - designed and sized only to take FOGO and the residual waste stream (excluding most plastics) with an allowance for increases in these wastes over the 30 year life of the plant.*
If the plant was say only a 1/4 to a 1/3 of the proposed size of a plastics burning plant this would also ameliorate some of the other issues with the plant as currently proposed such as the increase in the amount of truck traffic to the site - and its impact on local residential amenity (noise pollution and road damage) - and the height and size of the chimney stack and the amount of CO2 and other pollution out of it. While there would still be potential for noxious gases from the residual waste and fine particles from the organic and residual waste, if the plant is run well at high temperatures and other stack emission scrubbers and appropriately monitored this issue should be manageable and hopefully negligible.
Conclusion
This should basically handle most of the greenhouse gases produced from the waste stream. Please consider this proposal.Any questions or comments please email me.
Notes:
* While it is less desirable than burning no plastic waste it may be acceptable in the short term after operational commencement of the plant to burn some thin film plastic from the waste stream. The logic behind this would be that the electricity produced would create less CO2 than that produced by a generator in the Latrobe Valley burning brown coal for the same amount of electricity (if indeed it does). This assumes the plant produced electricity would be a direct replacement for brown coal generated electricity and does not compete against existing renewables, and not discourage new renewables and batteries. There is no guarantee that I know of that this will be the case. The company is likely to chase the best price they can get for their electricity so may shape their production to suit. I have heard one unverified suggestion that they plan to install batteries to enable them to sell more electricity into the grid at peak periods, to get the best price. In this scenario they may be directly competing with solar and wind, and batteries combinations (i.e. renewables).
The burning thin film and other plastics would have to stop once the Latrobe Valley generators have been taken off line. So by say 2040 and certainly well before 2050, the time Australia has to be at Net Zero. By that time they should cease all production (which is ten or more years before the end of initial production life of the plant) or to have converted to completely organic fuel. As stated previously it is preferable not to burn plastics at all.
