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

An old cell phone should never go in the trash can. Give two reasons: what hazardous substances it can release into a 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 cell phone, but one of the steps is covered up.

Explain what happens in the covered step (the recycling plant, where the cell 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 cell phone contains copper, some gold and silver, aluminum 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 cell 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".

Your old cell phone has three possible destinations: a drawer at home, the recycling center, or selling it second-hand after replacing its battery. Compare the three in terms of environmental impact, financial benefit, and what happens to its materials in the end, and decide which you would choose in each situation: a cell phone that works well and an unusable cell phone.

A cell phone battery arrives at the recycling center. Research and describe its ideal traceability: what treatment it receives, what materials are recovered (lithium, cobalt), what risks are involved in handling it (fires), and what the law should require from manufacturers to keep batteries in the loop (taking responsibility for collecting them: extended producer responsibility).

Design a realistic local circular economy business: tool rental instead of sales, refurbished cell phones with a warranty, or restored furniture. Explain how it closes the loop, where the income comes from, what advantage it offers the customer, and what main obstacle it would have to overcome to work.

Your class has been tasked with organizing the end-of-year party for 150 attendees with a budget limit of 200.00 pesos. 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 product is advertised as "eco-friendly and 100% natural", with green packaging and drawings of leaves, but provides no data. Explain what greenwashing is, what three checks you would make before believing it (official certifications, concrete data, full life cycle), and why the green color of the packaging is not evidence.

In several European countries, the DRS (Deposit Return Scheme) is in place, where consumers pay a deposit of 0.10 pesos 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 grade extends the lifespan of $2$ cell phones by one extra year, and manufacturing a cell phone generates about $60\ \text{kg}$ of CO₂, calculate how many new cell 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 kilometers driven by car that produce the same emissions, knowing that a car emits about $0.2\ \text{kg}$ of CO₂ per kilometer) and reflect on the power of small habits multiplied.