2023 CCEA A-Level Environmental Technology 3930 Practice Paper with Answers

The bacterium is Thiobacillus ferrooxidans. One advantage of biohydrometallurgy over traditional metal smelting is that it requires much less energy, since it operates at ambient temperature and pressure rather than the very high temperatures needed for smelting, making it both cheaper to run and less polluting (traditional smelting is energy-intensive and highly polluting).

[1] for correctly naming Thiobacillus ferrooxidans; [1] for a valid advantage (e.g. lower energy use, lower pollution/emissions, suitable for low-grade ore that smelting cannot economically process).

Any two of the following metal ions may be removed from contaminated soil using alpine pennygrass or Indian mustard: cadmium, zinc, copper, lead, gold, uranium.

(2 x [1]) [2]: one mark for each correctly named metal ion, up to a maximum of two, from: cadmium, zinc, copper, lead, gold, uranium.

One method used for the bulk production of hydrogen gas is steam reforming of fossil gases (alternatively: electrolysis of water, or photocatalytic water splitting).

[1] for any one of: steam reforming of fossil gases; electrolysis of water; photocatalytic water splitting.

The waste management hierarchy is a framework that ranks waste management options in order of environmental preference, from most to least preferred: prevention, reduce, reuse, recycle, energy recovery, and disposal (e.g. landfill) as the last resort.

[1] for a basic reference to a ranked order of waste options; [2] for a full definition naming at least four of the stages (prevention, reduce, reuse, recycle, energy recovery, disposal) in broadly the correct order.

Embodied energy is the total amount of energy required to extract raw materials and to process, manufacture and transport a material or product, from its source to the point of use.

[1] for a basic reference to energy used in production; [2] for a fuller definition referencing extraction/processing/manufacture and transport.

P represents population, A represents affluence, and T represents the damage caused by technology (I itself represents the total environmental impact).

[1] for correctly stating all three of P = population, A = affluence, T = damage caused by technology (must give all three for the mark).

The two major generating methods for tidal power are: tidal stream generators, for example SeaGen at Strangford Lough; and tidal barrages, for example the Rance Estuary barrage in France.

[1] for tidal stream generator with a correct named example (e.g. SeaGen/Strangford Lough); [1] for tidal barrage with a correct named example (e.g. Rance Estuary, France).

Temperature difference \( = 20 - 4 = 16\text{°C} \).
Rate of heat flow \( = U \times A \times \Delta T = 1.4 \times 2.5 \times 16 \).
\( 1.4 \times 2.5 = 3.5 \); \( 3.5 \times 16 = 56 \).
Rate of heat flow = 56 W.

[1] for correctly calculating the temperature difference as 16°C; [1] for correct substitution into the formula; [1] for correct multiplication/transposition; [1] for the final answer 56 W with correct unit.

(i) Heat energy transferred to the water, \( Q = mc\Delta T \).
Temperature change \( \Delta T = 65-20 = 45\text{°C} \).
\( Q = 100 \times 4.18 \times 45 = 18\,810 \) J (18.81 kJ).
(ii) Heat energy released per gram of ethanol \( = \dfrac{18\,810}{0.92} = 20\,446 \) J/g, which is 20 400 J/g (20.4 kJ/g) to 3 significant figures.

(i) [1] for correct formula Q=mcΔT with ΔT=45; [1] for correct substitution; [1] for final answer 18 810 J (accept 18.8 kJ).
(ii) [1] for correct method (dividing heat energy by mass of ethanol); [1] for final answer 20 400 J/g or 20.4 kJ/g (3 s.f.), ft from part (i).

(a) In phytoextraction, plants are grown directly on metal-contaminated mine tailings. The plant roots take up metal ions from the soil, which then accumulate in the plant's above-ground tissue (stems and leaves) as it grows. The plants are then harvested, and the metal-rich biomass is processed (for example by incineration) to recover the metal in a concentrated form. For example, white mustard can be used to extract copper from mine tailings, or sunflower can be used to extract gold.
(b) One limitation of phytoextraction is that it is a very slow process compared with conventional metal extraction, since it depends on the natural growth rate of the plants over one or more growing seasons and the relatively low concentration of metal that plants can accumulate; this means phytoextraction is generally only suitable for treating low-value, low-grade contamination over a long timescale, rather than providing a fast, high-yield alternative to conventional mining and extraction methods.

(a) [1] for describing uptake of metal by plant roots/accumulation in tissue; [1] for describing harvesting and processing to recover the metal; [1] for a correct named plant/metal pairing (e.g. white mustard/copper, sunflower/gold).
(b) [1] for identifying a valid limitation (e.g. slow process, low yield, large land area required); [1] for a developed explanation of why this limits commercial use.

(a) In the manufacture of biodiesel, vegetable oil is reacted with methanol in the presence of sodium hydroxide as a catalyst, in a process called transesterification. This reaction converts the triglycerides in the vegetable oil into biodiesel (fatty acid methyl esters) and glycerol as a by-product, which is separated out, leaving the biodiesel to be purified for use as fuel. One advantage of biodiesel is that it is produced from renewable crops rather than fossil fuels, so its use can reduce net carbon dioxide emissions and dependence on finite oil reserves. One disadvantage is that growing the vegetable oil crops needed (such as rapeseed or palm oil) can compete with land needed for food production and can drive deforestation or habitat destruction if energy crops are grown intensively.
(b) Strategy 1: Improving and investing in public transport (for example more frequent, reliable bus and rail services) can encourage people to switch from private car journeys to public transport, reducing the total number of vehicles on the road and therefore reducing overall emissions and congestion.
Strategy 2: Introducing congestion charging in city centres makes driving into busy areas more expensive, which discourages unnecessary car journeys and encourages people to use alternatives such as walking, cycling or public transport, thereby reducing traffic volume and associated emissions in the charged area.

(a) [1] for describing the transesterification reaction (vegetable oil + methanol, sodium hydroxide catalyst); [1] for a correct advantage; [1] for a correct disadvantage; [1] for overall clarity/accuracy of the process description.
(b) [1] for identifying a first valid strategy; [1] for identifying a second, different valid strategy; [1] for a developed explanation linking at least one strategy to reduced environmental impact.

(a) Insulation (e.g. in walls, loft and floors) reduces the rate of heat flow out of a building by reducing conduction of heat through the building fabric, keeping heat inside for longer and reducing the energy needed for heating. Air tightness refers to how well a building prevents uncontrolled air leakage through gaps, cracks and poorly sealed joints; a more air-tight building loses less heat through draughts, improving energy efficiency, though it must be balanced with adequate ventilation for air quality. Glazing (for example double or triple glazing, with a low U value) reduces heat loss through windows, which are otherwise one of the least thermally efficient parts of a building's fabric.
(b) BREEAM is the principal environmental building performance measurement system used to assess and certify the sustainability of non-domestic and some domestic buildings, rating them against criteria such as energy use, water use, materials, pollution and ecology to award a certified rating (e.g. Pass, Good, Very Good, Excellent, Outstanding). The Code for Sustainable Homes (CSH) is a related national standard specifically for rating the sustainability of new homes, assessing categories such as energy and CO2 emissions, water, materials, and waste, to encourage the construction of more environmentally efficient housing.
One significant challenge in using the CSH-style approach to improve the UK's existing housing stock is that most existing homes were built before such standards existed and are therefore expensive and disruptive to retrofit to a high sustainability standard, for example by adding cavity wall or solid wall insulation, replacing windows, or improving air tightness; this makes it far harder and more costly to significantly improve environmental performance of existing housing compared with designing sustainability into new-build homes from the outset.

(a) [1] for insulation reducing conductive heat loss; [1] for air tightness reducing draught/heat loss; [1] for glazing reducing heat loss through windows; [1] for overall accuracy/clarity across all three factors.
Level 1 ([1]-[2]) for part (b): Basic knowledge of BREEAM/CSH; limited explanation of the challenge; basic QWC.
Level 2 ([3]-[4]): Sound knowledge of both BREEAM and CSH; clear explanation of the retrofit challenge; satisfactory QWC.
Level 3 ([5]-[6]): Detailed, accurate knowledge of both systems and their assessment criteria; thorough, well-developed discussion of the challenge of upgrading existing housing stock; confident specialist vocabulary; high standard of QWC.

In a PEM fuel cell, hydrogen gas is supplied to the anode, where it is oxidised, splitting into hydrogen ions (protons) and electrons: \( \text{H}_2 \rightarrow 2\text{H}^+ + 2e^- \). The polymer electrolyte membrane allows the hydrogen ions to pass through it towards the cathode, but does not allow electrons through; the electrons are instead forced to travel around an external circuit, generating an electric current that can do useful work. At the cathode, oxygen gas (usually from the air) is reduced, combining with the hydrogen ions that have crossed the membrane and the electrons that have completed the external circuit to form water: \( \tfrac12\text{O}_2 + 2\text{H}^+ + 2e^- \rightarrow \text{H}_2\text{O} \). The overall reaction is therefore the direct electrochemical combination of hydrogen and oxygen to produce water and electrical energy, with water and heat as the only by-products.

[1] for correctly describing oxidation of hydrogen at the anode (splitting into H+ ions and electrons); [1] for the correct anode half-equation or equivalent description; [1] for describing electrons travelling via the external circuit to generate current; [1] for describing H+ ions passing through the membrane; [1] for correctly describing reduction of oxygen at the cathode combining with H+ and electrons; [1] for the correct cathode half-equation (or correctly identifying water as the only product).

One challenge is production cost and source: most hydrogen produced in bulk today is made by steam reforming of fossil gases, which itself uses fossil fuels and releases carbon dioxide, undermining hydrogen's potential environmental benefit unless it is instead produced by low-carbon methods such as electrolysis powered by renewable electricity, which is currently more expensive; this means widespread 'green' hydrogen production remains costly and is not yet available at the scale needed to fully replace fossil fuels in transport.
A second challenge is safe storage and transport: hydrogen has a very low density as a gas, so it must be stored either at very high pressure or as a cryogenic liquid at extremely low temperature to hold a useful amount of energy in a reasonably sized tank; both approaches require heavy, expensive, specialist storage tanks and infrastructure, and hydrogen is also highly flammable and prone to leaking through very small gaps due to its small molecular size, raising safety concerns that must be carefully managed in vehicle design and refuelling infrastructure.

Level 1 ([1]-[2]): Basic knowledge; challenges identified with little development; basic QWC.
Level 2 ([3]-[5]): Sound knowledge and understanding of at least one challenge with clear, developed explanation; satisfactory use of specialist vocabulary; satisfactory QWC.
Level 3 ([6]-[7]): Detailed knowledge and thorough discussion of two distinct, well-developed challenges (e.g. production source/cost and storage/safety), with confident use of specialist vocabulary and a high standard of QWC.

In anaerobic digestion, organic waste first undergoes mechanical pretreatment, where it is shredded or pulped to increase its surface area and remove contaminants, making it easier for micro-organisms to break down. In hydrolysis, complex organic material such as carbohydrates, fats and proteins is broken down by bacteria into simpler, soluble molecules such as sugars, fatty acids and amino acids. In acidogenesis, these simpler molecules are further broken down into volatile fatty acids, along with smaller amounts of ammonia, carbon dioxide and hydrogen sulphide. In acetogenesis, the volatile fatty acids are converted into acetate, hydrogen and carbon dioxide. Finally, in methanogenesis, methanogenic bacteria convert these products into biogas, which is mainly methane and carbon dioxide.
The biogas produced is collected and burned in a combined heat and power (CHP) engine or generator: the combustion drives a generator to produce electricity, while the heat produced as a by-product of combustion (and from the engine itself) is captured and used, for example to heat buildings or the digester itself, meaning the overall process delivers both usable heat and power from a single fuel source, improving overall energy efficiency compared with generating electricity alone.

[1] for correctly outlining mechanical pretreatment; [1] for correctly outlining hydrolysis; [1] for correctly outlining acidogenesis and/or acetogenesis; [1] for correctly outlining methanogenesis producing biogas; [1] for correctly explaining how the biogas is used to generate both heat and power (CHP).

Tidal stream generators, such as SeaGen at Strangford Lough, work like underwater wind turbines, using rotating blades placed in areas of fast-flowing tidal current to generate electricity; they are generally cheaper to install, cause less disruption to the surrounding estuary or coastline, and can be installed in more locations than a barrage, but generate relatively small amounts of electricity per device. Tidal barrages, such as the Rance Estuary barrage in France, instead involve building a dam across an estuary, allowing water to flow through turbines built into the barrage as the tide rises and falls; barrages can generate much larger, more predictable amounts of electricity from a single site, but are very expensive to construct and can significantly alter the estuary's tidal flow and ecosystem over its whole width.
One environmental impact common to both wave and tidal energy devices is their effect on marine life and habitat: the physical presence of the devices, together with noise and the movement of turbine blades, can disturb or injure marine animals such as fish, seals and diving birds, and can alter local sediment patterns and habitats within the surrounding marine environment.

[1] for a correct description of how tidal stream generators work; [1] for a correct description of how tidal barrages work; [1] for a valid comparative point (e.g. cost, scale of output, environmental disruption); [1] for a second valid comparative point; [1] for identifying a valid common environmental impact (e.g. marine life/habitat, noise, visual impact, conflict with other sea users); [1] for a developed explanation of that impact.

A smart system is a system that uses sensors, data collection and automated control (often linked by digital communication networks) to monitor and optimise its own performance in real time, rather than operating on a fixed, pre-set basis. In waste management, for example, smart bins fitted with fill-level sensors can automatically signal when they need to be emptied, allowing collection routes to be optimised so that lorries only visit bins that are actually full, reducing unnecessary journeys, fuel use and emissions.
The carbon capture and storage (CCS) process used to reduce carbon dioxide emissions from fossil fuel power plants involves three main phases. First, trapping and separating: carbon dioxide is captured from the power plant's exhaust gases before it is released into the atmosphere, using chemical or physical separation processes. Second, transport: the captured, compressed carbon dioxide is transported, typically by pipeline, from the power plant to a suitable storage site. Third, storage: the carbon dioxide is injected and permanently stored, either underground (for example in depleted oil and gas reservoirs or deep saline rock formations) or underwater beneath the seabed, preventing it from being released into the atmosphere.

[1] for a correct definition of a smart system (sensors/data/automated optimisation); [1] for a correct, relevant application in waste management or transportation with sufficient detail; [1] for correctly naming 'trapping and separating' as the first CCS phase with a valid description; [1] for correctly naming 'transport' as the second phase with a valid description; [1] for correctly naming 'storage' as the third phase; [1] for correctly distinguishing underground and underwater storage; [1] for overall clarity and technical accuracy across the whole answer.

Fig. 5 shows a clear and sustained fall in the percentage of Northern Ireland's municipal waste sent to landfill, from 65% in 2010 to just 19% in 2023, a reduction of 46 percentage points over 13 years. Historically, Northern Ireland was heavily over-reliant on landfill as its main method of waste disposal, which created significant difficulties: suitable sites able to satisfy geological and environmental requirements (for example low permeability to reduce the risk of leachate contaminating groundwater) are limited, and identifying new sites is made harder by public opposition to landfill developments being located near communities (often referred to as a 'not in my back yard' response), as well as the loss of land that could otherwise be used productively.
The steep decline shown in Fig. 5 reflects the impact of policy measures introduced to move waste management up the waste hierarchy, away from landfill. The landfill tax, which increases the cost of disposing of waste in landfill sites, has provided councils and businesses with a strong financial incentive to reduce, reuse and recycle waste instead, since these alternatives avoid the tax. At the same time, the Northern Ireland Waste Management Strategy has set out priority waste streams and targets, informed by EU strategies and directives, that have driven investment in recycling infrastructure such as Materials Recovery Facilities, and in alternative waste treatment such as composting and anaerobic digestion, giving councils practical alternatives to landfill. Together, these financial and strategic policy drivers explain why landfill's share of municipal waste disposal has fallen so consistently over the period shown in Fig. 5.

Level 1 ([1]-[2]): Basic description of the trend in Fig. 5; limited reference to landfill difficulties or policy; basic QWC.
Level 2 ([3]-[4]): Sound description of the trend with correct use of figures; adequate explanation of siting difficulties and at least one policy driver (e.g. landfill tax OR Waste Management Strategy); satisfactory QWC.
Level 3 ([5]-[6]): Detailed, accurate use of the data in Fig. 5 (including correct calculation/comparison of values); thorough discussion of siting difficulties AND both the landfill tax and the Waste Management Strategy as drivers of the trend; confident use of specialist vocabulary; high standard of QWC.

In urban areas, sustainable community development focuses on making the best use of existing high-density infrastructure. Energy supply can be improved through microgeneration integrated with smart grid technology, allowing buildings to generate and share renewable electricity locally and balance supply and demand efficiently across a densely connected network. Waste management in urban areas typically relies on planned, centralised systems, such as kerbside recycling collections and Materials Recovery Facilities, which are viable because the high density of housing makes collection routes efficient. Transport challenges in urban areas centre on integrating and expanding flexible public transport networks (buses, trams, cycle infrastructure) to reduce reliance on private cars, which is feasible because of the high concentration of potential users along fixed routes.
In isolated rural communities, by contrast, the low density and dispersed nature of dwellings makes it very costly and environmentally damaging to extend mains energy, water, waste water and communication networks to every property, so sustainable solutions instead focus on independent, small-scale, indigenous energy sources, such as biomass boilers, small-scale wind turbines, agricultural waste treatment, or small district heating schemes serving a small cluster of buildings, rather than reliance on a centralised national grid connection. Waste management in rural areas similarly relies on small-scale, on-site solutions, particularly septic tanks for waste water treatment, since it is not economically justifiable to build and maintain sewer networks to every isolated dwelling. For transport and communication, rather than building new physical transport infrastructure to improve accessibility (which would be very costly and environmentally damaging for a small number of users), rural sustainability strategies instead emphasise the use of communication technologies, such as high-speed broadband enabling remote working and online services, to improve accessibility to rural areas without generating additional travel demand.
Overall, while both urban and rural strategies share the same underlying goals of reducing environmental impact and improving resource efficiency, urban solutions exploit high density and existing infrastructure through smart, centralised technology, whereas rural solutions must instead prioritise independent, small-scale, decentralised technology suited to dispersed, low-density communities.

Level 1 ([1]-[3]): Basic knowledge of urban and/or rural sustainability issues; limited comparison; may address only one setting in any depth; basic QWC.
Level 2 ([4]-[6]): Sound knowledge and understanding of both urban and rural sustainability challenges; a clear comparison covering at least two of energy, waste and transport/communication; satisfactory use of specialist vocabulary; satisfactory QWC.
Level 3 ([7]-[8]): Detailed, accurate knowledge of both urban and rural contexts; thorough, well-developed comparison across all three of energy supply, waste management and transport/communication, explicitly contrasting the two settings and the reasons for the difference; confident specialist vocabulary; high standard of QWC.

An ecological footprint is a measure of the demand that an individual, community or nation places on the Earth's natural resources, usually expressed as the area of biologically productive land and water required to provide the resources consumed and to absorb the resulting waste (including carbon dioxide emissions, which links directly to the concept of a carbon footprint, itself often the largest single component of an overall ecological footprint). Comparing a population's ecological footprint with the biologically productive area actually available shows whether its lifestyle is sustainable within the Earth's carrying capacity.
The I = PAT relationship helps explain why ecological footprints continue to rise globally: total environmental impact (I) is the product of population (P), affluence (A, broadly consumption per person) and the damage caused by technology (T, the environmental impact per unit of consumption). This shows that even if technology becomes cleaner (reducing T), rising population and rising affluence (increasing consumption per person, particularly as developing economies grow) can still cause total impact to increase; sustainable development therefore cannot rely on technological improvement in isolation; all three factors need to be addressed together.
One Planet Living (OPL) is a framework and set of principles that aims to help individuals, organisations and communities to live within the fair share of the Earth's resources that would be available if everyone on the planet consumed at the same rate, i.e. living as though only 'one planet's' worth of resources existed. OPL directly targets reducing ecological footprint by promoting lower-carbon, more resource-efficient ways of living, encompassing energy, transport, food, waste and materials, rather than depending solely on new technology to offset ever-increasing consumption.
Several technologies studied in this course do make a genuine contribution to reducing environmental impact (the T term in I=PAT). Renewable and low-carbon energy generation, and efficient buildings incorporating high-performance insulation, air tightness and glazing assessed under BREEAM/CSH standards, both reduce the fossil fuel energy, and therefore emissions, associated with a given level of comfort or activity. Waste-to-energy technologies such as anaerobic digestion recover useful heat and power from material that would otherwise be disposed of, reducing both landfill use and the need for additional fossil fuel generation. Hydrogen fuel cells offer a route to decarbonising transport and stationary power where direct electrification is difficult, producing only water as a by-product at the point of use, although (as discussed elsewhere) hydrogen production and storage still present significant technical challenges.
However, none of these technologies alone is sufficient to guarantee sustainability if population and affluence continue to rise unchecked, since improvements in T can be outpaced by growth in P and A; for example, more efficient vehicles or buildings can still lead to higher total emissions if the number of vehicles or the size and number of buildings increases faster than efficiency improves (a phenomenon related to the 'rebound effect'). This supports the statement that behavioural change, such as reducing unnecessary consumption, energy use and travel, and adopting OPL-style lower-impact lifestyles, is equally as important as technological development in achieving a genuinely sustainable future, since technology addresses only one of the three factors in the I=PAT relationship, while population and affluence-driven consumption must also be actively managed.

Level 1 ([1]-[5]): Basic knowledge of ecological footprint, I=PAT and/or OPL; limited or no reference to specific technologies; answer largely descriptive/list-based; limited engagement with the given statement; basic QWC.
Level 2 ([6]-[10]): Sound knowledge and understanding of ecological footprint, I=PAT and OPL; adequate discussion of at least two relevant technologies with some evaluation of their contribution; some engagement with the statement (behaviour vs technology); satisfactory use of specialist vocabulary; satisfactory QWC.
Level 3 ([11]-[15]): Detailed, accurate knowledge and understanding of ecological footprint, the I=PAT relationship and One Planet Living; thorough, well-evaluated discussion of at least three technologies studied across the course, explicitly weighed against the need for behavioural change; a clear, well-reasoned overall judgement on the given statement; confident, wide-ranging use of specialist vocabulary drawn from across the specification; high standard of QWC with a coherent, well-structured extended response.