What Planet Are You On?'s Dr Brian Kelleher, the Chair of the degree in Environmental Science and Technology, School of Chemical Science, Dublin City University, explains why we shouldn't call the items we dispose of at home or in work or school "waste".

"If you judge a fish by its ability to climb a tree, it shall live its whole life assuming that it is a waste," said Albert Einstein. There is no waste in nature, everything is used in one form or the other in the natural world.

The generation of "waste" is a human peculiarity that makes no sense. In nature, everything is re-used, recycled and recovered. We are beginning to realise this through our pursuance of the circular economy where everything can get a second chance, at least.

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How we consider waste or rubbish needs to change. For a start, it would be useful to substitute the word "waste" with "resource". Waste collectors and operators would then be called "resource collectors and operators". This may seem superficial but the fact is that the materials that we so crudely dump or combust all have a use but if we treat this material as "waste" it can extremely harmful to us and our environment in the form of greenhouse gases and pollution.

A good example of this is "organic waste", anything that was recently living, e.g. food, garden clippings, remains of organisms (including us!). This is a very rich resource. Our aim, without doubt, should be to waste as little as possible but sometimes waste is unavoidable.

For food that we cannot consume it is imperative to dispose of it in a considered manner. When we place our unused food in the compost bin, if we are lucky enough to live in an area that supplies them, the food is composted at a commercial facility where it is eventually added back to soil as compost. If we can do this, we are partially replacing the nutrients that were extracted from soil to grow the food in the first place.

Yes, we will waste much of the energy (e.g. transportation and refrigeration) that went into the provision of food but at least we replace some of the organic matter that was originally extracted from soil. There is an old Chinese proverb that says that "Man – despite his artistic pretensions, his sophistication, and his many accomplishments – owes his existence to a 15cm layer of topsoil and the fact that it rains".

Quite simply, what we take from soil we should seek to replace. We have been getting away with the use of synthetic fertilisers for decades but we now understand that this is causing great harm to soil health and biodiversity.

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A major problem with the way we dispose of our "resources" in Ireland is misplacement in the wrong bin. If we stay with the organic component of waste as an example, the EPA report that the contents of our brown bins include 19% plastics, 10% textiles, 9% metals, glass and wood and 2% hazardous materials.

This is a resource disaster and means that it is extremely difficult to extract the organic material from the other contents and has a large energy and carbon cost. Because of this, the mixed material is either landfilled, where the organic materials will degrade to form methane, a major greenhouse gas, or it is incinerated, where it is emitted as carbon dioxide, another gas that contributes to our warming climate crisis.

In other words we turn a material that could be used to sustainably protect soil health into gases that contribute to global warming!

There are many other recovery options for organic waste, although recycling as compost to return to soil is without doubt the best (other than minimal generation of waste in the first place). These include biological treatments that are based on microbial mediated reactions that transform organic molecules such as proteins, carbohydrates and fats, into compost like output or methane, the main products of composting and anaerobic digestion (AD) processes respectively.

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Fermentation can produce bioethanol from the sugar, starch and lignocellulose fraction of organic materials. Major drawbacks are the cost of enzymes and intensive energy required. Biodiesel, in theory at least, could be produced by extracting the fatty material although the fat/oil content of organic waste may be too low.

Thermal processing involves converting organic materials into energy, heat and fuel (gas, liquid or solid). It can comprise incineration (waste to energy), gasification and pyrolysis. Incineration is a widely known thermal process commonly used to convert waste to energy but is undesirable due to the generation of greenhouse gases. It is a quick fix that allows us to ignore our wasteful ways.

Gasification and pyrolysis are thermal processes that convert carbon-based material into combustible gases (e.g. syngas), hydrocarbons/tar (oil) and char/ash, at high temperatures. Gasification occurs under a limited oxygen environment whereas pyrolysis occurs in the absence of oxygen.

Pyrolysis and gasification have advantages over traditional incineration, related to higher energy efficiency, high value products and improved pollution control.

The bottom line, however, is that we need to reduce the waste that we produce and where this is not possible, we re-use and recycle the material. When we need to dispose of materials that we cannot use (resources), we really need to place them in the correct bin where they can be re-used, recycled or added as a much needed component of soil organic matter.

Watch the brand-new series of What Planet Are You On? with presenter Maia Dunphy on RTÉ One this Tuesday to Thursday at 7pm.