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A choice of evils:  Landfill vs Burning Refuse

November 26, 2018 8:50 PM
By Julian Hawkins

Long term commitment on refuse collections is neededA few months back, the BBC produced a rather depressing programme - The Secret Life of Landfill. I gave up watching it after a while, as it was just making me angry.

The site operators were clearly putting a lot of effort into storing refuse in high technology landfill, as if that made the refuse go away permanently. But it doesn't - unless the site is steadily covered up with sediment, buried and converted into rock over the next hundred million years, the contents will, in time, be released into the environment.

Out of sight, out of mind - but only for a limited period.

This is an important problem and will come back to bite us, or our descendants. Some old tips near the sea are now being exposed by rising sea levels. This hazard compares to that posed by the dumping of plastics, but is not quite so serious as global warming.

The obvious answer is the well-known mantra: reduce, reuse, recycle.

There's no dispute about the benefit of recycling where it can be done at reasonable cost, but if you take a mass of mixed plastics and melt them together, you just get a sticky mess. Proper recycling needs well sorted materials, and sometimes even that won't work. Think of thin plastic film from the top of a food container, smeared with food residue. That sort of mixture takes a lot of effort to recycle, if it can be done at all.

One "solution" is to burn refuse to generate electricity. Some proponents claim it is a great way to generate power. The contrary position is that we should recycle everything in a totally circular economy. So which is correct?

Refuse to power just is not a great way to generate electricity. I don't have a figures for the total energy available/recovered, but efficiencies are quoted as about 18 to 28%. Coal can be burned at about 40 % efficiency, natural gas around 50%. You can raise total efficiency by using the waste heat, e.g. for district heating, but that also works for fossil fuels.

But landfill is terrible. In addition to the difficulty in permanent disposal mentioned above, the organic waste releases greenhouse gases: Carbon Dioxide and also but Methane, which is far worse in the short term. And people sometimes build on old landfill sites.

I think the right question is not which is better, but which is worse?

There isn't one good answer, because there isn't one type of rubbish - it's a mix of many products and materials. But we can simplify by splitting it into two groups:
· Organic (contains carbon), including food, dead plant and animal matter, a lot of plastic, paper, and many natural and unnatural chemicals.
· Inorganic, including glass, metals, salts, concrete, and many more chemicals.

There's an easy answer for inorganic waste - don't burn it. Most of isn't flammable. Most metals are, but you end up with oxides, like rust if you burn iron. This doesn't make the situation better, and it could lead to poisonous materials being released into the environment.

The best thing you can do with most inorganic waste is to reuse/recycle it. The next best option is to store it safely somewhere that it can be retrieved once you have worked out how to reuse/recycle it. Traditional landfill won't cut it.

Organic wastes are different. These can generally be burned safely if you have the right equipment. They should produce a bit more power than you put into the burning process - you may need something like natural gas to help the process along, but you can use the combined heat to generate electricity.

However, you may not get very much power out - depending on the exact setup - whereas you put a lot of energy into creating the plastic in the first place. It is obviously better to reuse or recycle where you can do so efficiently.

So my view is that burning refuse for power is, sometimes, a lot better than landfill, because that is terrible, but only where the good options aren't practical.

A few more points.

First, this argument assumes that waste is sorted into organic and inorganic. That can be easier said than done. In practice, I think we need both people to sort waste when they dump, and paid workers to sort refuse which machines can't easily distinguish. Re-designing manufacturing and packaging to facilitate recycling could make this a lot easier.

Second, paying somebody to take it abroad is a bad idea, for several reasons:
· Moral Hazard - they have a motivation to take our money and dump the stuff
· Economic impact - we have to pay for this, which could be harder to afford if Brexit happens
· Loss of useful materials which we could recycle

Third, there is an opportunity to increase dispatchable demand for electricity in the near future. In about ten years' time, we should have excess electricity on sunny summer days and windy nights. We need processes to use this that can be switched on and off at short notice without reducing efficiency, such as electrolytic generation of hydrogen in order to reduce mixed organic waste to high quality liquid fuels. Processes like this are being developed now, but they need a lot of cheap energy to be viable. We haven't got that yet, but enough solar panels and wind turbines will get us there.

So this problem can be solved in ways that are advantageous to environment and the UK, rather than yet another expense, provided we deploy the right solutions in the right way. It may well be possible to dispense with burning rubbish in the future, but I don't think we are there yet.

Explanatory references:

https://en.wikipedia.org/wiki/Waste-to-energy - figures for thermal efficiency
https://en.wikipedia.org/wiki/Plastic_recycling - general information on the subject

Also, I am sceptical about claims that plastic or food waste are good sources of energy, for this line of reasoning.

Plastic is generally derived from fossil fuels, which could also be burned as power. If you burn fossil fuels directly for electricity, you can get about 30 to 50% efficiency. Turning them into plastic and then burning at end of life goes through a lot of steps, each of which reduces efficiency:
· fabricating the material and product,
· collecting them at end of life,
· sorting and filtering the refuse stream,
· burning a product which was note designed as a fuel.
Each step will involve substantial loss in efficiency, so the end to end efficiency will be poor at best. Of course, this could still be a lot better than landfill.