Among the following fuels, which one causes the minimum environmental pollution at the point of use when it is burned as a fuel?

Introduction / Context:
Different fuels release different combustion products when burned, and these products can affect air quality and the environment. Fossil fuels such as coal, diesel and kerosene emit gases and particulates that contribute to air pollution and climate change. Hydrogen, on the other hand, behaves differently when used in a clean system. This question checks whether you can identify the fuel that produces the least pollution at the point of use when burned.

Given Data / Assumptions:

• Complete combustion of carbon containing fuels produces carbon dioxide and sometimes harmful pollutants.
• Incomplete combustion can produce carbon monoxide, unburned hydrocarbons and particulates.
• Hydrogen combustion in pure oxygen or air mainly produces water vapour.
• We focus on emissions at the point of use, not on production related emissions upstream.

Concept / Approach:
Coal, diesel and kerosene are hydrocarbon or carbon rich fuels. When they burn, they produce carbon dioxide, nitrogen oxides, sulphur oxides (depending on sulphur content) and particulate matter. These emissions contribute to smog, acid rain and greenhouse effects. Hydrogen, when burned in air, reacts with oxygen to form water vapour and relatively small amounts of nitrogen oxides due to high temperatures, but no carbon based pollutants. Therefore, hydrogen as a fuel at the point of use causes minimal environmental pollution compared with traditional fossil fuels in the options.

Step-by-Step Solution:
Step 1: Examine each fuel and recall its main combustion products. Step 2: Recognise that coal combustion releases carbon dioxide, sulphur dioxide, ash and soot, all significant pollutants. Step 3: Note that diesel and kerosene combustion also releases carbon dioxide, nitrogen oxides and particulates from vehicle exhaust. Step 4: Recall that hydrogen combustion primarily produces water vapour and minimal carbon emissions because hydrogen does not contain carbon atoms. Step 5: Conclude that hydrogen causes the minimum environmental pollution at the point of use among the listed fuels.

Verification / Alternative check:
Engineering and environmental science literature often promotes hydrogen as a clean fuel for fuel cells and combustion engines, emphasising that water is the main emission. While there can be challenges related to hydrogen production and storage, the local emissions during use are much cleaner compared with fossil fuels. Reports on air quality and vehicle emissions consistently show that coal and petroleum based fuels contribute heavily to particulate pollution and greenhouse gas emissions, whereas hydrogen powered systems do not emit carbon dioxide directly at the tailpipe.

Why Other Options Are Wrong:
Option a, diesel, is a petroleum fuel that produces exhaust containing particulate matter, carbon dioxide and nitrogen oxides, all of which harm air quality.

Option b, kerosene, is also a hydrocarbon fuel that releases carbon dioxide and other pollutants when used in lamps or engines.

Option d, coal, is among the dirtiest fuels, producing ash, soot, sulphur dioxide and heavy carbon dioxide emissions.

Common Pitfalls:
Some learners may think that a fuel used in household stoves or lamps, such as kerosene, is cleaner simply because they have seen it used in daily life. Others may not consider the fact that hydrogen lacks carbon and therefore cannot produce carbon dioxide when burned. It is important to differentiate between local exhaust emissions and the broader environmental impact of producing each fuel when judging pollution levels.

Final Answer:
Among the listed fuels, Hydrogen causes the minimum environmental pollution at the point of use when it is burned.