Preferential treatment: choosing between recycling and incineration

Which poses the greatest threat to our future: climate change resulting in global warming due to CO₂ emissions; or a shortage of resources resulting in possible economic instability, as the demands of an ever-increasing global population outstrip diminishing primary supply?

This bleak question is difficult to answer. Climate scholars will point to the serious implications of climate change, the difficulty of controlling CO₂ emissions and the slow penetration of renewables into energy markets. However, those concerned with resources can highlight the threat of a shortage of raw materials in the short or long-term to the lifestyles of a general population increasingly dependent on a wide range of products, the inevitability of declining production as we exhaust easily accessible sources of raw materials, and the frequently realised threat of political instability in mineral producing. Furthermore, as currently underprivileged nations catch up to the living standards enjoyed by richer ones, and as new technologies continue to make use of rare elements, the need for raw materials can only increase.

The question may, however, not in fact be as pertinent as it at first seems. Fossil fuels are also, after all, a raw material for the production of plastics, while material production often requires a lot of energy. In reality, savings in raw materials and energy interlink, with the same problems and solutions bridging both climate and materials policy. Avoiding both threats will involve building this bridge, and in its construction we should look to recycling as supplying the main pillar.

Energy inside and out

The relationship between waste and energy is undeniable. On the one hand there is the internal component: that is, the energy contained within all waste, which can either be largely retained through recycling or released through combustion. On the other hand there is the external component: all the energy that is needed to get the waste moving in the right direction — both literally and figuratively — throughout the collection, transportation and treatment processes. Waste management works because in most cases the possible savings of internal energy outweigh the accompanying expenditures in external energy — even when transporting waste over long distances. If our focus is on maximising the internal energy benefit of waste management, conserving it through the reuse of products or secondary raw materials (recycling) is more effective than recovering it as heat and electricity through incineration.

Incineration: not always a grate idea. Photo by Ole Poulsen, via Wikimedia Commons.

Yet the choice between incineration and recycling is not always easy. An economic approach requires a careful assessment of the costs and benefits, in which occasional or cyclical factors may temporarily affect the outcome — such as prices in the markets for primary and secondary materials. Climate change concerns are, however, ever present, as is the demand for ‘green’ power. In this context, when commodity markets are weak the opportunity to obtain energy from waste can make it tempting, at least temporarily, to deprioritise recycling.

Recycling energy

If recycling is viewed against a background of strong climate policy then our ambitions of avoiding materials shortages and achieving a substantial reduction of CO₂ emissions can be seen to be parallel objectives. Industry must then take on the challenge, even if the economic value of recycling is not spectacular. A clear example is found in the alternative processing of currently combusted residual waste. Increased recycling of sortable dry waste and other household waste, combined with savings through thermal treatment with high energy efficiency constitutes a deliverable green project with the potential to make a substantial contribution to CO₂ reduction. It has been estimated that this could amount to 4.53Mt, or 7–10% of the total reductions required from the industrial sector in the Netherlands. Increased recycling supplies a significant majority of this benefit.

The increased pressure on business and society as a whole to avoid or limit greenhouse gas emissions renders the assessment of global CO₂ footprints as the key decision-making tool. This is particularly so because CO₂ emissions per capita in the western world — especially the United States, Australia and Europe ­— are significantly higher than in emerging countries such as China and India.

All emitters, great and small. Source: David JC MacKay, Sustainable Energy – without the hot air

Furthermore, these emerging countries produce many of the products consumed by the more developed nations. The socio-economic catch up of the Third World will be accompanied by an increase in their CO₂ emissions, and — as learnt from Copenhagen 2009 — this makes for a difficult basis on which to form global climate policy. Because the heat and electricity recovered through energy from waste is badged as ‘renewable’, it can appear attractive to encourage. Energy from waste piggybacks on the positive valuation of biomass as a link in a short cycle energy chain: the CO_2­ emitted by burning biomass is balanced by that captured as crops grow, ready to be burned again. The organic fraction of waste can be viewed in the same way; while the fact that waste is continually produced by societies can make it seem like as inexhaustible source of energy as solar power.

Choosing and proving

It is not hard for the recycling sector to demonstrate that recycling waste into secondary raw materials uses less energy and generates less carbon emissions than the production of primary raw materials. To take one of the clearest examples, the conversion of metal ores into pure metals takes immense energy, which remains embedded in materials and products and can be saved by the proper separation and processing of metal waste. By using secondary raw metal materials in place of primary resources, savings of more than 90% can be achieved for metal types such as aluminium, lead, tin and nickel. Although zinc (75%) and copper and iron (60%) score somewhat lower, the savings to be made are still significant.

The manufacture of glass also involves a lot of energy, which is largely preserved in recycling. The recycling of paper, cardboard and plastics presents a more nuanced picture, although weighing up the costs and benefits still shows that recycling is again more than worth the effort. But the alternative of energy from waste incineration remains useful in some cases, especially when there is oversupply of certain materials. Choosing a preferred approach must rely on a detailed life cycle analysis (LCA) to establish whether the environmental benefits achievable through recycling outweigh those of energy generation; the comparative CO₂ footprints of each option will certainly form part of this assessment.

LCA considerations are also important in deciding on the best recycling or incineration method. It can help us choose between recycling collection and processing systems, so that the most beneficial option can be selected. When opting for incineration, we can use LCA to help choose between different combustion techniques, while also taking account of factors having to do with distribution of heat and electricity — for example, the opportunity to sell heat is more dependent on the place and time of its production than is the sale of electricity. Energy from waste is likely to deliver the greatest benefits when it is carried out on a small to medium scale, at facilities designed to fit in with region-specific energy needs.

But it is the choice of overall approach that was our original concern, and here the results of LCA are clear, and should impress both climate scientists and waste managers. Although the scale of the benefit might vary depending on the value of the materials available for separation and the treatment technologies involved, for the vast majority of waste streams recycling is preferable to combustion. Our challenge is to ensure that policy makers understand why recycling is more beneficial than energy from waste, and that they reflect this in setting our future waste strategy.

We are grateful to Ad Lansink for the opportunity to publish this article. It is based upon a chapter of De Kracht van de Kringloop, by Ad Lansink and Hannet de Vriers-in ‘t Veld, a book on the history and future of Lansink’s Ladder. It appears here for the first time in English.