Waste and Environmental Impact

What is the difference between municipal waste, industrial waste and hazardous waste? Give an example of each type.

The pyramid represents the waste management hierarchy, from the most desirable option (1, top) to the last option (5, bottom). Assign each level its strategy: landfill, prevention, recycling, reuse and energy recovery.

What is recycling and which three materials of mineral origin are recycled with great savings (glass, aluminium, steel)? Which geological resource is conserved in each case?

What is a household recycling centre and which types of waste does it accept that must not go into the general bin?

What is composting and which fraction of urban waste does it make use of? Which product is obtained and what use does it have?

What is energy recovery from waste and how does it differ from materials recycling? Which position does it occupy in the management hierarchy?

What are construction and demolition waste and which part of it (aggregate, metals, timber) can be reused or recycled?

Batteries, used oil and tyres require specific management. Explain what makes them hazardous or problematic and which collection system exists for each one.

What geological conditions must the site for a landfill meet? Consider rock permeability, water table depth and slope gradients.

An unlined landfill generates leachate that ends up polluting the aquifer. Explain what leachate is and describe the barrier system (clay layer, geomembrane, geotextile, drainage) of a modern landfill.

Landfills generate biogas as organic matter decomposes. Explain its main composition, how it is captured and which two fates it has (flaring or energy recovery), and why it must not be released into the atmosphere.

Describe the sealing and closure of a landfill (impermeable cover, topsoil layer, biogas and leachate capture) and explain which controls are maintained during the post-closure stage.

A consortium plans to install a solar photovoltaic plant on the 15 hectares of a municipal solid waste landfill sealed just four years ago. The project envisages founding the panel rows using conventional ramming of steel profiles to a depth of two meters and routing the cabling in standard trenches.

1. a) Explain the two biogeochemical and mechanical processes that cause differential settlement in a landfill mass and predict their consequences on the rigid supporting structure of the photovoltaic panels.
2. b) Justify technically why driving metal profiles and digging trenches pose a serious hazard to the integrity of the containment barrier (high-density polyethylene geomembrane) and to the passive degassing systems for accumulated biogas.
3. c) Design two technical modifications (one concerning the foundation system and another concerning the design of conduits and supporting structures) that make the solar photovoltaic installation viable and safe without compromising the landfill sealing or creating a risk of methane deflagration.

An island association of municipalities annually generates 150.000 t of municipal solid waste with an average composition by weight of 44% wet organic matter, 16% non-recyclable plastics, 14% paper and cardboard, and 26% other materials. The current landfill will reach capacity in 18 months and available island space is minimal. The urgent construction of a waste-to-energy (WTE) incineration plant is proposed.

1. a) Analyze the composition of the waste and predict what thermodynamic (lower heating value) and combustion problems will arise if the bulk waste is fed into the furnaces without prior and efficient separate collection of organic matter.
2. b) Compare the most critical pollution vector of incineration (emission of dioxins, furans, and management of fly ash) against that of the landfill (leachate generation and fugitive methane emissions with high global warming potential). Explain what technological gas-cleaning barriers are required by law for the incinerator to be environmentally acceptable.
3. c) In accordance with the European waste hierarchy, justify for which specific fraction of the waste stream waste-to-energy incineration is justified, and refute the statement that "burning trash discourages recycling".

An autonomous community must urgently locate a waste-to-energy and sewage sludge treatment plant that will process 200.000 t annually. After initial technical studies, two candidate municipalities remain on the table:

• Municipality A: Mountainous rural area, with low population density, below-average per capita income, an economy based on extensive livestock farming, and a highly permeable karst aquifer that supplies downstream regions.

• Municipality B: Peri-urban area of a major city, with high population density, medium-high per capita income, consolidated industrial parks, a good highway network, and a virtually impermeable marly geological substrate.

1. a) Analyze how the NIMBY syndrome ("not in my backyard") and the LULU phenomenon ("locally unwanted land uses") will operate in both municipalities, distinguishing each population's capacity for sociopolitical mobilization compared to the real techno-environmental risk deduced from the terrain's geology.
2. b) Justify how decision-making based exclusively on minimizing immediate social conflict can lead to a case of "environmental injustice" (sacrificing vulnerable communities), whereas one based purely on geotechnics will generate judicial and social deadlock.
3. c) Design a mediation and public consensus protocol that moves beyond the traditional DAD model ("Decide, Announce, Defend") by integrating early public participation, non-monetary territorial compensation (public services, regional ecological transition), and local environmental monitoring committees.

Two geological sites have been proposed to host a Deep Geological Repository (DGR) for high-level nuclear waste:

• Site A: Granitic massif at a depth of 600 m, in an area of low historical seismicity, but crossed by a dense network of Late Hercynian joints and with active mining concessions nearby for tungsten and lithium exploration.

• Site B: Formation of plastic clays and shales 200 m thick located at a depth of 450 m, tectonically stable and with no evidence of mineral resources, but immediately overlying a regional carbonate aquifer under exploitation for irrigation.

1. a) Evaluate the hydrogeological and geomechanical suitability of both rock formations against the risk of soluble radionuclide migration in the event of engineering barrier failure. Justify which one you would rule out first.
2. b) Discuss why the concept of "absence of exploitable resources" is a critical geological safety criterion on a 100.000-year scale, taking into account accidental human intrusion in future civilizational scenarios.
3. c) Design a governance proposal for the selection process that addresses the common social conflict (NIMBY syndrome) without relying solely on economic transfers or compensations to the affected municipalities.

Spent nuclear fuel discharged from a nuclear reactor has two distinct radiological components: short/medium-lived fission products ($^{137}\text{Cs}$, $t_{1/2} = 30,1$ years; $^{90}\text{Sr}$, $t_{1/2} = 28,8$ years), responsible for the high initial thermal emission rate, and long-lived minor actinides and transuranics ($^{239}\text{Pu}$, $t_{1/2} = 24.100$ years; $^{241}\text{Am}$, $t_{1/2} = 432$ years; $^{237}\text{Np}$, $t_{1/2} = 2,14 \times 10^6$ years).

1. a) Calculate approximately how many years must elapse for the activity of the fission products $^{137}\text{Cs}$ and $^{90}\text{Sr}$ to decay to less than 0,1% of their initial value (approximately ten half-lives) and interpret why, during this time interval, the waste cannot be directly confined in a DGR without prior cooling in pools or interim storage facilities (ISF/CISF).
2. b) Based on the time required for the radiotoxicity of transuranics to drop to the levels of the original natural uranium ore (over 100.000 years), demonstrate the conceptual unfeasibility of managing these wastes through surface storage under continuous human surveillance (El Cabril model) and justify the imperative need for a Deep Geological Repository (DGR).
3. c) Assess the reliability of the "multiple barriers" principle of a DGR in a hypothetical scenario of tectonic reactivation that fractures the host rock 10.000 years after closure: predict the behavior that the glass/ceramic matrix of the waste, the metallic copper or steel canister, and the bentonite buffer would exhibit against infiltrating water.

The circular economy proposes that waste should become raw material for other processes. Give two real-world examples and explain which geological resources are saved in each case.

Public works projects must include mitigation measures and, when damage cannot be avoided, compensatory measures. Distinguish between both types of measures with an example related to dam construction.

Recycling aluminium saves around $95\ \%$ of the energy needed to produce it from bauxite. Explain where that saving comes from (electrolysis versus remelting) and which resources and emissions are avoided.

A new motorway crosses an agricultural valley. Summarise the phases of the environmental impact study (alternatives, inventory, identification of impacts, measures, monitoring) and what is decided in each one.

To obtain 1 kg of gold, a conventional open-pit mining operation exploits an ore with a grade of 2,5 g/t of rock, with a stripping ratio (waste/ore) of 3:1. Meanwhile, printed circuit boards from discarded mobile phones exhibit an average concentration of 250 g/t of gold.

1. a) Calculate the total mass of geological material (ore plus waste rock) that must be removed in the open-pit mine compared to the mass of electronic waste required to obtain that same kilogram of precious metal.
2. b) Evaluate the comparative environmental impact of both extraction pathways considering: land take, the risk of acid mine drainage associated with host sulfides, and the generation of toxic waste or leachates.
3. c) If the grade of "urban mining" of mobile phones is one hundred times higher than that of natural ore, deduce and justify two reasons (one logistical and one metallurgical or economic) that explain why most marketed gold continues to be extracted through traditional extractive mining.

A tech multinational markets wireless earbuds whose lithium-ion battery is embedded in epoxy resin inside a heat-sealed polycarbonate casing. When the battery reaches the end of its useful life (around 2 years), the device stops working and 90 % of users discard it in the residual municipal waste stream.

1. a) Analyze, based on the Extended Producer Responsibility (EPR) principle, what economic, environmental, and occupational safety costs the manufacturer is externalizing onto municipalities and MSW treatment plants.
2. b) Design three mandatory ecodesign measures for this product directly targeting prevention, component separability, and repairability, justifying the environmental benefit of each.
3. c) Evaluate a technical trade-off arising from your redesign: how does replacing heat sealing with detachable mechanical joints affect the product's sweat/water resistance (IPX rating)? Justify how you would resolve this conflict without negating recyclability.

An open-pit mining project aims to exploit a polymetallic sulfide deposit (pyrite, chalcopyrite, and sphalerite). The open pit will reach a depth of 160 m, cutting through two piezometric levels, and the tailings pond and waste rock dumps will be located at the headwaters of a river basin that feeds an urban water supply reservoir.

1. a) Model the chain of hydrogeochemical transformations that will be triggered by lowering the water table through pumping and exposing the sulfide minerals of the slopes and waste rock dumps to atmospheric oxygen and rainwater. Predict the pH variations and the mobility of heavy metals in runoff waters.
2. b) Design a set of preventive and corrective measures structured along two fronts: geotechnical stability control of the waste rock dumps to prevent liquefaction phenomena, and passive treatment of acid drainage waters using constructed wetlands and permeable reactive barriers.
3. c) The operating company proposes abandoning the pit at the end of its useful life so that it fills with water and forms a "recreational lake". Justify why this approach can lead to a meromixis catastrophe with limnic overturn, and explain the role of financial bonds and guarantees required in the Environmental Impact Assessment to prevent the State from assuming the remediation costs.