Exercises: Waste, recycling and circular economy

Explain the 3 Rs rule — reduce, reuse, recycle — with an everyday example of each applied to water bottles: what would you do to reduce, how would you reuse, and what does recycling the bottle mean? Which of the three avoids waste completely?

The order of the 3 Rs matters: reducing is better than reusing, and reusing is better than recycling. Explain why recycling is the last option and not the first (recycling also uses energy and transport, and does not recover $100\ \%$ of the material) using the example of printing sheets of paper.

Match each type of waste with its bin: plastic packaging and cans, paper and cardboard, glass, food waste and general waste, with the yellow, blue, green, brown and grey bins. Add two examples of waste that do NOT go into any of these five and state where they should be taken.

WEEE refers to waste electrical and electronic equipment: mobile phones, computers, household appliances, batteries. Explain what the acronym stands for and why this waste is special: what hazardous materials it contains (heavy metals) and what valuable materials can be recovered.

The household waste recycling centre is the local site for waste that does not go in street bins. Make a list of six types of waste taken to the recycling centre (cooking oil, batteries, electronics, light bulbs, furniture, paint) and explain the risk of throwing each of them into normal household waste.

An old mobile phone should never go in the rubbish bin. Give two reasons: what hazardous substances it can release into landfill (battery, heavy metals) and what valuable materials are lost forever if it is not recycled (copper, gold, rare earth elements). Where should its journey end?

Buying second-hand is reusing on a large scale. Name three things that you or your family could buy second-hand without any problem (books, clothes, furniture, games) and explain the benefits: for your wallet, for the planet, and for the seller.

The linear economy is "extract, manufacture, use and dispose"; the circular economy tries to close the loop like nature, where the waste of one process is food for another. Explain the difference using a drawing or a diagram described in words and give an example of a "closed loop" in nature (fallen leaves from a tree).

The figure shows two ways of organising production and consumption, labelled a and b.

State which diagram represents the linear economy and which represents the circular economy, justifying your answer by what happens at the end of the chain, and explain which two processes in diagram b close the loop (repairing what breaks and recycling what no longer works).

The figure shows the journey of a properly managed old mobile phone, but one of the steps is covered up.

Explain what happens in the covered step (the recycling plant, where the mobile phone is dismantled and its materials are separated) and compare the two destinations in the figure: what is recovered in the good pathway and what is lost forever in the bad pathway.

Reusing is not just using something again for the same purpose: it is also giving it a new life (upcycling), such as an old ladder converted into a bookshelf or T-shirts converted into bags. Explain the difference between reusing, upcycling and recycling, with an example of each using the same object: a worn tyre.

Many secondary schools have a textbook scheme: books are passed from year to year. Analyse which "R" applies, how many years a well-cared-for book can remain in circulation, and what conditions are needed for the system to work (taking care of the book, loan organisation). What happens to the book when it is no longer usable?

A mobile phone contains copper, some gold and silver, aluminium and rare earth elements, as well as plastic and glass. Explain why it is worthwhile to recover these materials (they prevent new mining and are valuable) and what technical problem exists in separating them (they are closely combined and attached to a tiny circuit board). Relate this to the price sometimes paid for old mobile phones.

The coffee maker at home stops heating up. Analyse the decision to repair or discard as an engineer: what would you check first (fuse, heating element, cable), how much the repair costs compared to a new coffee maker, what happens to the old one if you throw it away, and where you would seek help (technical support service, repair cafés, tutorials). This is a theoretical analysis: do not open or handle the appliance while it is plugged in; any internal check must be done by an adult or a technician with the coffee maker unplugged from the mains.

The neighbourhood organises a swap market: games, clothes and books you no longer use in exchange for other people's. Explain which "R" this practices, what benefits it has compared to buying new and compared to throwing things away, and what rules would be needed to make the swap fair and safe (condition of items, hygiene, organisation).

Propose a "reduce" plan for the classroom with three specific and measurable measures: one for paper, one for single-use plastic, and one for energy. For each one, state what is done, who is in charge, and how you will check at the end of the term if it has worked (which figure you will compare).

A soft drink company launches an advertising campaign with the slogan: "Consume as many containers as you want guilt-free: our plastic bottles are 100% recyclable and turn into new bottles forever."

1. a) Refute this claim technically by analyzing the three real limits of recycling: the progressive degradation of plastic properties in each cycle (downcycling), the difficulty of separating packaging with polymer blends or inks, and the energy consumption required by the recycling process compared to using virgin raw material.
2. b) Based on these limits, justify why the circular economy hierarchy always places reduction and reuse ahead of recycling, and propose a technical distribution alternative for this drink that complies with the first two "R's".

A city council is debating two proposals to manage waste electrical and electronic equipment (WEEE):

• Proposal 1: Reward anyone who turns in their mobile phone at the recycling center with 15,000 € so it can be shredded and its materials recycled directly.

• Proposal 2: Provide a 15,000 € subsidy to local repair shops to replace screens or batteries and put the devices on the second-hand market with a warranty.

1. a) Evaluate both proposals for two real-world cases: a three-year-old mobile phone with a degraded battery but otherwise in perfect condition, and an old mobile phone with a burnt-out and irreparable motherboard.
2. b) Justify which of the two proposals better complies with the principles of the circular economy and the conservation of critical raw materials (such as lithium and cobalt).
3. c) Explain what environmental impact and resource depletion is generated by the habit of keeping useless devices in a drawer for years instead of introducing them into these circuits.

A manufacturer of scooters and mobile devices decides to attach lithium-ion batteries to the chassis using a permanent industrial adhesive to reduce assembly costs, preventing the user or a technician from removing them without breaking them.

1. a) Predict what two serious consequences (one regarding operational safety and another regarding technical feasibility for recovering critical materials like lithium and cobalt) this design will cause when the devices arrive at the recycling plant.
2. b) Apply the principle of Extended Producer Responsibility (EPR): justify what legal and economic obligations European regulations should impose on this manufacturer to prevent the costs of managing that battery from falling on society.
3. c) Propose an ecodesign solution that meets two requirements simultaneously: that the battery is removable for safe reuse or recycling, and that the device maintains its mechanical strength and watertightness.

In your town, it is detected that hundreds of bicycles and small appliances with only minor faults (cut cables, broken switches, or worn parts) end up at the recycling center every month. Design a business model or community initiative based on the circular economy to prevent this waste. Your proposal must detail:

1. Material flow: how disused products are collected, how they are repaired or transformed, and what final destination the parts that are no longer usable have.

2. Economic model: where the income comes from to make it viable in the long term without relying exclusively on subsidies.

3. Value proposition: what real advantage the user gets compared to buying a new, low-cost product.

4. Main obstacle: what technical, legal, or social barrier is the most critical and what solution do you propose to overcome it.

Your class has been tasked with organizing the end-of-year party for 150 attendees with a budget limit of 200,00 €. The previous year, disposable plastic tableware, paper tablecloths, and hundreds of balloons were bought, generating five bins of mixed, non-recyclable waste.

1. a) Design an event management plan strictly applying the 3Rs hierarchy: propose two specific measures for reduction at source, two for reuse, and a selective collection system during the party.
2. b) Justify through an environmental and economic balance why strictly following the order (Reduce -> Reuse -> Recycle) saves more energy, resources, and money for the educational center than simply buying disposable products labeled as "recyclable".

A pair of wireless headphones is marketed with the claim "Bio-Tech Line: 100% ecological and sustainable", packaged in a green box with leaf illustrations. Upon checking the technical fine print, it is found that only 3% of the plastic in the headband comes from corn, while the internal circuits, the soldered battery, and the cable are neither recyclable nor have any official environmental certification.\na) Justify why this product constitutes a clear case of greenwashing, identifying both the visual and technical misleading elements.\nb) Design a protocol of three objective checks that a consumer should apply before buying a device advertised as ecological (regulated eco-labels, life-cycle assessment, and verifiable technical information).\nc) If you were the head of design, what two substantial changes to the product would you implement so that its environmental communication was honest and demonstrable?

In several European countries, the DRS (Deposit Return Scheme) is in place, where consumers pay a deposit of 0,10 € when purchasing a packaged beverage and recover it upon returning the intact can or bottle to a reverse vending machine. In Spain, there is an intense debate on whether to make its implementation mandatory or to maintain only the yellow bin.\na) Develop two technical and environmental arguments in favor of implementing the DRS and two real operational or economic difficulties that this system poses for small neighborhood shops.\nb) Predict what consequences the success of the DRS would have on the current yellow bin system: what waste would continue to be deposited in it and how would it affect municipal management and collection costs?\nc) Take a justified stance: do you consider that the DRS should replace the yellow bin, complement it, or be discarded? Reason your answer using sustainability criteria.

Make a reasoned estimate: if each of the $30$ families in the year group extends the lifespan of $2$ mobile phones by one extra year, and manufacturing a mobile phone generates about $60\ \text{kg}$ of CO₂, calculate how many new mobile phones are avoided per year and how many emissions are saved. Then convert those savings into something easy to understand (compare it with the number of kilometres driven by car that produce the same emissions, knowing that a car emits about $0,2\ \text{kg}$ of CO₂ per kilometre) and reflect on the power of small habits multiplied.

Topic challenge. Did you know that in Spain we generate more than $10,5\text{ kg}$ of electronic waste (WEEE) per inhabitant per year? Become an environmental auditor for your home and design a transition plan toward the circular economy using LibreOffice Calc.

1. Domestic inventory: Locate at least 5 disused or broken electrical or electronic devices in your home (old mobile phones, cables, toys...). Estimate or weigh their combined mass in kilograms (e.g. $1,2\text{ kg}$).

2. Official research: Visit your town hall website or the Ministry for the Ecological Transition (MITECO) website, find the nearest recycling center (clean point), and investigate what critical raw materials or toxic substances these devices contain.

3. Data processing in LibreOffice: Design a spreadsheet with a table classifying each item, its hazardous components, and a solution based on the 7Rs (repair, donate, recycle). Generate a bar chart showing the weight or quantity of each type of waste.

4. Circular plan: Write a short decalog with three family commitments to extend the useful life of your technology and properly manage accumulated waste.

Assessment criteria:

• Rigor in data collection and proficiency in LibreOffice Calc (clear table and chart).

• Understanding of the environmental impact of WEEE and locating the appropriate recycling center.

• Feasibility and originality of the proposed circular economy proposals.