Raw materials as the source for products are exhaustible. How to deal with this in the best way? You can look at this from different angles. Materials saving, for example, is an option: use less material for a product than you originally intended, so take a look at the design. If you have a material with better properties at your disposal – for example, high strength steel instead of ‘ordinary’ steel – then you can make a thinner product with less material that is just as strong. In addition to this ‘saving in space’, you can also ‘save in time’ by using a product for a longer period of time, i.e. ‘sustainable’ in a certain sense. Rather a product with better (e.g. corrosion resistant) or stronger materials and therefore a longer life span, than using a product for a short time and having to replace it. This also includes self-healing materials.
You can also assemble a product from components (modular), so that only failed or broken parts need to be replaced, and the remaining good parts can still function. This also allows you to introduce new revenue models for materials and products that respond to the trend that people increasingly prefer to use products rather than wanting to own them. Just think, for example, of a consumer who does not buy a lamp or a car in this approach, but purchases ‘light’ or ‘transport’ as a service. The ‘leasing company’ of the products – in fact a service provider – has an interest in ensuring that these products (the leased lamps or cars) last as long as possible.
Materials can also get a second life by not disposing of used materials, but by recycling: processing them in a way that allows them to be reused. This takes less material anyway – ‘buy one, get one for free‘ – but also reprocessing costs less energy than manufacturing them out of raw materials. For example, metal melting costs much less energy than the energy required to
extract the metal from the metal ore. In a sense, renewable materials such as paper, wood or bioplastics work in a similar way. These raw materials can grow over and over again.
Biodegradable packaging
Packaging protects products during transport and storage, and ensures a longer shelf life of food products. Packaging is also useful to provide attractive information about the product. The most important packaging materials of today are plastic (bags and bottles), paper/cardboard (boxes), glass (bottles and jars), metal (especially tinplate) and wood (crates). Only wood as a raw material for cardboard and wooden packaging materials is renewable.
Many plastic packaging items are used for only a short period of time, after which they are disposed of in the dustbin. Would it be possible to make this packaging from a biodegradable material, so that it is decomposed into natural compounds that can form bioplastics again at a later stage? Fortunately, biodegradable packaging materials already exist. A short tour of the supermarket results, among other things, in biodegradable garbage bags that can be disposed of in the compost bin, and packaging of potatoes and carrots.
Materials are biodegradable if they are quickly decomposed by bacteria into natural com- pounds: water, carbon dioxide and sometimes minerals. Biological degradation, biodegradation in short, takes place in the water or in the soil, but also in composting plants to which we send our vegetable, fruit and garden waste. Biological degradation is therefore closely related to composting.
In the soil we refer to biodegradation if 90 % of the material is decomposed within two years. A plastic bag that decomposes completely in nature after decades or hundreds of years is certainly not biodegradable.
The biological degradation process is carried out by enzymes produced by bacteria. The enzymes – which are in fact proteins with special functions – break down the packaging material to carbon dioxide and water in the end. The energy released during this process and the degradation products are used for the reproduction of the bacteria. The entire degradation process itself is therefore maintained by sufficient supply of material.
The time required for the complete degradation of the packaging material depends on the particle size: the smaller the particles, the more surface area there is, the more bacteria can attack at the same time and the faster the degradation process proceeds. A first step in the breakdown is often a process in which water causes degradation: large molecules are broken down by moisture into smaller molecules. This means that the speed at which the material is able to let water (vapour) pass through is also a measure of the rate of degradation. In a wet environment, on a compost heap for example, bacteria break down a starch-based plastic in a few days. In a dry environment, this can take several months. In subsequent steps in the degradation process, bacteria break down the smaller molecules. In technical composting plants with processing temperatures between 50 and 65 °C, bioplastics are degraded for 90 % to carbon dioxide and water within a few months. These degradation products are returned to the green plants in a cycle, which can form, for example, bioplastics. And so the circle is round again.
To avoid any confusion: bioplastics are not necessarily the same as biodegradable plastics. Bioplastics are polymers made from materials of biological origin, which can be found, for example, as renewable raw materials on farmland. Bioplastics are the counterparts of ‘normal’ plastics that usually have oil as raw material. The term ‘bioplastics’ refers to the raw materials, i.e. at the beginning of the product, while ‘biodegradable’ refers to the end of a product’s life cycle.
Recycling of aluminium and magnesium
A strong aluminium or magnesium housing contributes to the long service life – and therefore to the sustainability – of a notebook computer. But one day such a housing comes to an end, and then you can process the light metal in such a way that the material can be reused. Recycling aluminium and magnesium is desirable in order to handle the natural raw materials with care. And although aluminium and magnesium are abundantly present in the earth’s crust as part of chemical compounds – especially oxides – it takes a lot of energy to obtain the pure metals from these compounds. Recycling of an aluminium or magnesium component is usually done by melting the ‘waste’, which consumes 90 % less energy than production from raw materials.
Glass in the glass container
People in the Netherlands throw more than 80 % of the onetime packaging glass – jars and bottles without a deposit – into the glass container. That is about 22 kg of glass per person per year. Reuse of this glass saves raw materials and energy, and prevents more than 400,000 tons of waste per year. Indeed, 1.2 kilograms of used glass can be used to make 1 kilogram ‘new’ glass, and every 10 % of glass shards provides 2.5 % energy savings. Depending on the availability and quality of these shards, glassworks use between 50 and 80 % of used glass.
Not all glass can be disposed of in the glass container. For many people, glass ceramics or ‘oven-proof glass’ look like ordinary glass. But the fragments of this heat-resistant glass – such as in baking dishes, ceramic hobs and coffee pots – do not melt at the temperature that is customary in glass production. The only solution to this problem is to dispose of it via the waste processing company.
In addition to ‘normal’ glass, PET bottles and other plastics are increasingly being recycled. PET is brief for polyethylene terephthalate, a thermoplastic polyester.