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Gasification of waste – is it clean; and is it green?

Gasification, along with ‘pyrolysis’ and ‘plasma technologies’, is one of the exciting new buzzwords in the world of energy-from-waste. These “advanced thermal treatments” (ATTs) certainly sound futuristic, the stuff of science-fiction even, but do the claims their proponents make stack up, and how different are they from old-fashioned incineration?

The key difference is that rather than directly burning the waste they super-heat it in the absence of oxygen so that a combustible gas is released. This may make them more efficient, and allows them to be more ‘modular’ and flexible to varying amounts of waste than hungry mass-burn incinerators, but if the gas is then just burned to generate electricity they lose much of that increased efficiency. The best use of these sorts of syngas are as transport fuel or home heating through injection into domestic gas grids.

Incineration has gained itself a bad name over the years, not just on health grounds but also because even where waste incinerators recover energy in the form of either or both electricity and heat, they remain extremely inefficient and carbon intensive facilities.

Indeed, the UK Government’s own figures recently stated that the emissions associated with current British incinerators are responsible for 540g CO2e/kWhr – more than the grid average of 500g CO2e/kWhr and over ten times the limit of 50cCO2/kWh the Committee on Climate Change has recommended for the grid average come 2030.

So gassifiers – and any ‘energy-from-waste’ technology – needs to demonstrate that they are genuinely low carbon, unlike incinerators. At Friends of the Earth we’ve yet to see the evidence of this, so we remain open-minded, but sceptical.

Part of the reason for our scepticism has to do with what would make up the feedstock of the facility. Much of what currently goes either to landfill or to incineration is in fact recyclable, and as recycling rates rise, and separate food and other organic waste collections become more prevalent, what you find is that it tends to be just the hardest to recycle materials that are left behind. These, it turns out, tend to be mixed plastics and other fossil-derived materials. In other words, the energy-from-waste facility would be ‘burning’, however indirectly, a fossil fuel, and chances are that it would be doing so less efficiently than those that burn said fossil fuel directly, such as gas fired power stations.

So far we’ve only considered the emissions coming directly from the combustion of the waste, or waste-derived ‘syngas’, directly. We shouldn’t forget, though, that everything we use and consume also has a ‘footprint’, or ‘footprints’, which is the amount of energy, or carbon, or materials, or land and so on that went into making it.

Burn a piece of paper and you’ll release some energy, but that will only be a tiny fraction of the energy that went into making that paper. You save all that energy by avoiding making and using the paper in the first place, and save much of it by reusing and recycling the paper.

This means that we need to be constantly reducing how much ‘residual’ waste  – waste that isn’t reused or recycled and is therefore sent to landfill or ‘energy-from-waste’ plants – we create. Recycling is already at around 70% in Flanders, Belgium, and at similar levels in other cities and countries around the world. Some areas are aiming far higher, and what we can’t recycle we should be phasing out.

So what does that mean for energy-from-waste plants such as plasma-arc gasifiers? Put simply, it means we should be aiming to reduce and ultimately phase out the very thing they depend on for fuel – residual waste. And this isn’t just an environmentalist’s wish list: since the revised Waste Framework Directive (rWFD) this ‘waste hierarchy’ for treating waste is now enshrined in EU member states’ law.

There will always be some waste that is difficult to prevent, reuse or recycle, so whatever technology we choose to treat that waste must be genuinely low carbon and must not, as says the waste hierarchy, conflict with efforts to prevent, reuse or recycle it. If new technologies fulfil those criteria then they may have a space, but that space will be small and should be ever-reducing.

About Julian Kirby

Julian Kirby
Julian Kirby is a campaigner at Friends of the Earth UK.

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