Waste and Environmental Impact

What is the difference between municipal solid 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, aluminum, steel)? Which geological resource is conserved in each case?

What is a household recycling center and which types of waste does it accept that must not go into the regular trash can?

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 waste management hierarchy?

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

Batteries, used oil and tires 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 the 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".

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.

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 aluminum 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 highway crosses an agricultural valley. Summarize 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 cell 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 use, 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 cell 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 state 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: Suburban 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, statewide ecological transition), and local environmental monitoring committees.

Unit challenge. Is your household's "metabolism" sustainable? Design an integrative geo-environmental audit using real data from your home environment.

1. Real data collection: Check a recent bill from your home or consult the hourly energy mix on your regional grid operator's website (for example, the U.S. Energy Information Administration's Hourly Electric Grid Monitor at eia.gov). Record the energy consumption in $kWh$ and estimate the water consumption in $m^3$ (use the national standard of $0.13\text{ m}^3$/person·day if you do not have a meter).

2. Geological and impact diagnosis: Identify the energy sources and raw materials (such as $Cu$ or $Li$ in your devices), scientifically distinguishing between resource, deposit, and reserve. Analyze the pressure on local water basins, the impact on soil (urban sealing, erosion), and quantify the household waste generated in $kg$/week.

3. Report and circular proposal: Prepare a brief report with a graph or balance diagram (water/energy inputs and waste/impact outputs) and propose two realistic circular economy measures to mitigate edaphic degradation and resource depletion.

Evaluation criteria:

• Rigorous distinction and correct application of the concepts of resource, reserve, and deposit.

• Precision in the processing and graphical representation of the quantitative data obtained.

• Environmental justification and feasibility of the proposed solutions for soil, water, and waste.

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 government from assuming the remediation costs.