Dmitri Exam Qs

Question 1

• Briefly describe the human causes of loss of biodiversity. What are the causes that impose the most significant risk in terms of the global loss of biodiversity today?

Answer 1

Species extinction over time is a naturally occurring process that takes place without influence from humans. However, human activity has the potential to lead to loss of biodiversity, and its impacts have led to extinction rates much higher than reasonable predictions of naturally occurring rates.

Human causes included over exploitation of biological resources, for example fishing rates much higher than reproduction rates in fish leads to declines in their populations. Most tuna stocks are already fully exploited – meaning there is no room for fishery expansion, and some are already over-exploited – meaning there is a risk of stock collapse.

In addition, destruction of species’ habitats through human modifications, development and agriculture leads to a loss of biodiversity. For example, palm oil production from rainforests in Southeast Asia had led to the endangerment of orangutans as well as other species.

Pollution from industrial process can lead to excessive levels of nitrogen and phosphorus containing compounds in water. Nutrient over-loading results in eutrophication, which in turn means organisms within the body of water will not have sufficient oxygen for survival.

Anthropogenic climate change also has significant impacts on loss of biodiversity. For example, the melting of ice caps has to led to a loss of habitat for a number of species including polar bears, and coral reefs have declined due to heat stress.

Most significant: Climate change
IPCC report published in October 2018 highlighted the importance of ensuring climate changes is kept below 2 degrees.
At 2 degrees, the Arctic would have ice free summers, all of the world’s reefs would be lost, and there would be significantly increased risks of heatwaves, draughts and flooding which would of course lead to loss biodiversity.

Question 2

• Define the term ‘Pollution’ in accord with the 1996 EU Directive on Integrated Pollution Prevention and Control. Using this definition, specify the pollution and major pollutants associated with the work of power plants, which use natural gas as a fuel, and motor vehicles, which use gasoline as a fuel. Explain the origins of the chemical pollutants generated by power plants and motor vehicles and briefly comment on the adverse effects of these pollutants on humans and the environment.

Answer 2

The direct or indirect introduction of substances, vibration, heat or noise, into air, water or land, due to human activity. This introduction may be harmful to human health, or the quality of the environment, result in damage to material property, or impair or interfere with amenities and other legitimate uses of the environment.
Power plant:
Chemical pollutants include carbon dioxide and NOx (particulates such as sulphates produced when coal or heavy oil factions used as fuel).
Other pollution is heat pollution that occurs during the combustion.
Origin of the chemical pollutants:
Carbon dioxide produced from the complete combustion of hydrocarbons:
2HC + 2.5O2 -> 2CO2 + H2O
Due to the high temperatures, nitrogen reacts with oxygen producing NOx:
N2 + O2 -> 2NO
Adverse effects of these pollutants:
Carbon dioxide contributes to global warming and ocean acidification.
NOx contributes to acid rain, photochemical smog, is a lung irritant and causes respiratory issues, and eutrophication through delivery to water bodies through rain.

Motor vehicles:
Chemical pollutants: CO2, CO, NOx, HC, fine particulates such as SO2
Other pollutants: noise, heat, sometimes vibration
Origin of the chemical pollutants:
CO produced as a by-product of incomplete combustion, in which CO2 is the main product:
HC + O2 -> CO2 + CO + H2O
Due to the high temperatures, nitrogen reacts with oxygen producing NOx:
N2 + O2 -> 2NO
Sulfur in the fuel reacts with oxygen to produce sulfur dioxide.
Adverse effects of these pollutants:
Carbon dioxide contributes to global warming and ocean acidification.
NOx contributes to acid rain, photochemical smog, is a lung irritant and causes respiratory issues, and eutrophication through delivery to water bodies through rain.
CO is toxic to human health, sulfur dioxide is in acidificant which contributes to acid rain, as well as a human irritant.

Question 3

• Define the terms for ‘clean-up’ and ‘cleaner’ technologies illustrating your definition by ‘Financial cost vs Environmental load curves’. With the reference to vehicles employing conventional internal combustion engines, name two technologies that could be considered as clean-up and cleaner technologies.

Answer 3

Clean up technology reduces the environmental damage of an established plant or process though the addition of modifications or end of pipe pollution abatement measures, whilst increasing the financial cost, therefore moves up the curve.

Cleaner technology is the implementation of technology that manufactures the same product/provides the same service at the same financial cost, but with lower environmental load, therefore the curve moves to the left.

Clean up tech example is the three-way-catalyst (TWC) used in car exhausts to reduce CO, HC and NO emission.
Cleaner tech example is hybrid cars which use twice less fuel as conventional combustion engines, or using lean burn engines as they use less fuel due to the higher air/fuel ratio and consequently emit less CO2.

Question 4

• Describe the technology, including major chemical reactions, that is currently used worldwide for abatement of the chemical pollutants generated by conventional internal combustion engines
Comment on the possibilities of the use of this technology in conjunction with the work of lean-burn engines
Does the abatement technology described belong to ‘clean up’ or ‘cleaner’ technology?

Answer 4

Three-way-catalysts (TWC)
A typical TWC is based on a Pt/Rh/CeO2/Al2O3 formulation. Able to operate because of the stoichiometric air/fuel ratio in conventional internal combustion engines.
Reduction reactions:
2CO + 2NO -> 2CO2 + N2
HC + NO -> CO2 + H2O + N2
Oxidation reactions:
2CO + O2 -> 2CO2
HC + O2 -> CO2 + H2O 
At the A/F ratio of 14.5%, there is almost 100% conversion of CO, NOx, and HC

Lean burn engines operate at A/F ratio of 20 or above, resulting in a large excess of oxygen present in the exhaust. NOx cannot be removed using TWC in an oxygen rich exhaust as there would be no HC and CO coming in.

TWC is a clean-up technology, as it is an end of pipe measure that increases the financial cost in order to reduce the environmental load.