2016 - Past Paper Questions Flashcards
Explain the following terms: Low Solids High Solids Residence Time Single - Stage Multi - Stage
Low solids:
Low solid digestion is where the feedstock is around 15% solid material [1]
High solids:
High solid digestion is where the feedstock is around 55% solid material. [1]
Residence Time:
The time taken for the full degradation of the material in an anaerobic digestion system. [1]
Single Stage:
The biological reactions occur in one holding tank and the biogas comes from this tank. [1]
Multistage:
Hydrolysis, acetogenesis and acidogenesis occurs in one tank whilst the methanogenesis which produces the biogas occurs in a separate tank. [1]
Outline how anaerobic digestion can be used to provide heat and power (CHP)
Biogas from an AD plant can be burnt in a CHP plant to generate power (electricity) and heat [1];
Instead of losing the heat, as in traditional power plants, it is diverted into local heating systems. [1]
Name three types of waste product which can be composted in a domestic situation
Any three from: • Lawn clippings. [1] • Shredded stalks. [1] • Vegetable peelings. [1] • Hedge clippings. [1] • Cut flowers. [1] • Tea bags. [1] • Leaves. [1] • Eggshells. [1]
Explain briefly why composting is unsuitable for treating any form of catering waste
Cooked food must never be used in composting because it will attract vermin
Describe one efficiency measure which can be implemented on the window and explain why this measure would improve the energy efficiency
Any one measure and explanation from:
• Sealing around the edges of the window [1]; this will improve airtightness and reduce heat loss caused by draughts. [1];
• Installing double (or triple) glazed windows [1]; These will have improved U-values and will reduce heat loss through window. [1];
State one economic and one environmental benefit of energy conservation to be gained by putting in cavity insulation
Economic benefits: Any one from: • reduced heating costs. • improving the value of your home. • grant assistance available for the work.
Environmental benefits: Any one from: • reduced carbon emissions. • increased levels of home comfort. • reducing likelihood of condensation and mildew.
Explain how a tidal barrage generates energy from the tides
A barrage is built across an estuary with gates and turbines built into the wall of the dam [1];
As the tide flows in the gates are open and the turbines are operated producing electricity [1];
At high tide the gates are closed trapping the water inside [1];
When water level outside has fallen sufficiently(e.g. 5 m) the gates are opened [1];
The released water turns the turbines again producing electricity. [1]
Outline two advantages of a Tidal stream generator over a tidal barrage installation
Any two advantages from:
• They are cheaper to construct. [1]
• They are smaller and have less environmental impact. [1]
• The turbine blades turn slowly and have less effect on sea life. [1]
Give one Example of a ‘Geo - Engineering’ technique and explain how it can be applied
- Cloud seeding [1] where clouds are injected with crystals to produce ‘rain on demand’. [1]
- Space reflectors [1] which block a proportion of the sun’s rays from entering the earth’s atmosphere thereby reducing global warming. [1]
- Afforestation [1] whereby global scale planting of trees absorbs CO2 from the atmosphere. [1]
- Biochar [1], the process of ‘charring’ biomass so that the carbon it contains is locked up in the soil. [1]
Describe the operation of Bio-Photovoltaic devices
Bio-Photovoltaic (BPV) devices generate electricity from light energy [1] by exploiting the photosynthesis of living organisms such as moss, algae, cyanobacteria and vascular plants. [1]
Describe the process of Bioremediation
Adding micro-organisms to soil [1] to remove contaminants.
Discuss the economic and environmental benefits of using bioremediation techniques compared to traditional treatment methods
Bioremediation:
• Bioremediation can be carried out under atmospheric conditions.
• Bioremediation can be carried out in situ so soil is not removed from the site.
• The contaminants are reduced to (almost) zero.
• The by-products are non-toxic so water and air pollution is minimised.
• Bioremediation uses bacteria that occur naturally in the soil so the ecosystem is maintained.
• Bioremediation is economical because it does not require large energy inputs.
Traditional treatment:
• Traditional treatment is expensive because of the high energy costs (heating).
• Greenhouse gases such as carbon dioxide are produced.
• Soil may need to be treated ex situ/off site which requires heavy machinery.
• Traditional treatment can produce toxic by-products which require further treatment.
• Soil may need to be disposed of after treatment which leads to increased landfill.
Outline the role of genetic engineering in modifying micro organisms for bioremediation
Any two points from below:
Micro-organisms can be genetically engineered to:
• decontaminate a site more rapidly than unmodified micro-organisms;
• tolerate harsher conditions;
• remove toxic materials (such as heavy metals).
Identify two issues of concern arising from the use of genetic engineering of micro organisms for bioremediation
Any two from:
• Genetically engineered micro-organisms may wipe out existing bacteria.
• They may affect the existing soil ecology with unknown consequences.
• They may not behave the same way in the field as they do under laboratory conditions.
Describe two difficulties with locating a new landfill site
Any two points from:
• Planning permission is required which can delay the landfill becoming operational by several years. [1]
• A permit is required for operation which requires that full surveys have been carried out. This process is time consuming and adds to the up-front costs for the operator. [1]
• There may be objections from local residents due to noise/odour issues. This will delay planning permission being granted and subsequent award of a permit. [1]
• Suitable transport links are required so that waste can be brought to the site in heavy goods vehicles. [1]
