Transport and Environment

How did you get to college today? Unless you live close enough to walk or cycle, you probably took a bus or train.

Did you know that land-based transportation, like road vehicles and trains, accounts for 85% of transport energy consumption? That statistic may seem surprising when you consider how much energy planes use to stay in the air. However, it's the quantity of vehicles that causes this surprising result. There's an estimated 39,000 active planes in the world today. But there's an astounding 1.4 billion active cars!

Want to know more about transport and energy consumption? Gear up your brain and start reading!

Energy Use for Transportation

Did you know that transportation accounts for 25% of the world's energy use? The movement of passengers and freight around the world is an energy-intensive process, requiring:

• Fuel

• Construction of vehicles

• Construction of roads and railways

It's important to understand the concept of embodied energy: the energy used to build an object.

The Impacts of the Transport Industry on the Environment

Environmental impacts of the transport industry are split into three categories:

• Direct Impacts: the immediate consequence of transport activities on the environment. The cause and effect relationship are clear and understood. For example, Noise Pollution and Carbon Monoxide emissions are direct impacts.

• Indirect Impacts: these secondary or tertiary impacts are often of a higher consequence, but the relationship between cause and effect is harder to understand. For example, particulates generated by incomplete combustion are indirectly linked with respiratory and cardiovascular problems.

• Cumulative Impacts: the synergistic consequences of transport activities. Varied effects of impacts on an ecosystem are often unpredictable. For example, climate change is considered a cumulative impact of many factors, one of which is transportation.

Where is Energy Used in the Transportation Industry?

Land-based transportation (especially roads) accounts for the vast majority of energy consumption.

Fig. 1 – Road transportation accounts for almost four-fifths of transportation energy consumption. Source: StudySmarter Originals

Rail is the most energy-efficient method of transport, whilst aviation is the least.

Sources of Energy Used in the Transportation Industry

The transportation industry is dominated by crude oil and its products, providing 96% of transportation energy. Although it's found as a thick, unrefined liquid, it's converted into useful fuels (such as petrol and diesel) using fractional distillation.

Unfortunately, widespread use of oil has detrimental impacts on the environment.

Indirect Impacts of Transportation on the Environment

How does transport negatively impact the environment?

Extracting Oil

Crude oil is found as a liquid in underground geological formations. Oil extraction takes place on land or offshore. Extraction techniques include drilling and fracking.

Drilling for oil damages the landscape, disrupting wildlife and emitting Pollution. Offshore drilling carries the risk of oil spills, which destroy aquatic communities.

Fracking isn't harmless either. It's been associated with the release of methane, Noise pollution, atmospheric pollution, and seismic tremors.

Carbon Emissions

When oil or its products are burned, they release carbon dioxide as a by-product. Carbon dioxide is a greenhouse gas, so it absorbs incoming solar radiation, Trapping heat in The Atmosphere.

Burning large amounts of fossil fuels like crude oil increases the concentration of Greenhouse Gases, leading to climate change.

Pollutants

When oil or its products are burned, they release harmful atmospheric Pollutants. Some of these Pollutants and their consequences are summarised in this table.

Construction

Manufacturing vehicles and transport networks such as roads and railways negatively impacts the environment:

• Metal resources are extracted from the ground via mining. Mining is a highly destructive, polluting activity that is detrimental to ecosystems and the natural environment.

• The manufacturing process itself requires energy and releases pollutants.

• The landscape is disturbed by the laying of roads and railways.

Maritime Impacts

Large boats, such as container ships or cruise liners, are detrimental to the environment. Fuelling these boats produces large amounts of Greenhouse Gases and pollutants.

Large boats can directly pollute the oceans too, often dumping waste and sewage directly into the sea.

Maritime transport also disturbs marine organisms, especially mammals who rely on echolocation. The sound of boat engines disrupts echolocation; impacting communication, navigation, and the ability to find food.

Aviation Impacts

Planes eject pollution directly into The Atmosphere, releasing carbon dioxide, nitrogen oxides, and contrails.

Fig. 2 – The wispy clouds trailing behind aeroplanes are ice particle clouds called contrails. They may sound harmless, but they act like a greenhouse gas, absorbing solar radiation and warming the atmosphere. Source: unsplash.com

Flying vehicles also affect birds. The majority of bird strikes are fatal for the birds. However, if they are drawn into engines, it can damage the plane, putting the passengers at risk.

Transport and Environment: Methane

Methane (CH₄) is the main component of natural gas. It emits less carbon dioxide, and significantly fewer pollutants than other fossil fuels, gaining a reputation as the ‘cleanest fossil fuel’.

Methane is produced by burning manure, or fermenting it in an anaerobic digester.

Then, it's burned in a vehicle's combustion engine as an alternative to petrol or diesel. It's usually found as a compressed gas, but for some heavy-duty long-haul vehicles, it's found in liquefied form.

Evaluating Methane

Transport and Environment: Electric Vehicles

Instead of using a physical fuel, electric vehicles take in electricity from the National Grid and store it in rechargeable lithium-ion batteries. The batteries power an electric motor, which turns the wheels.

Fig. 3 – Instead of pumping petrol into the fuel tank, electric cars use a plug-in charging cable. Source: unsplash.com

There are three different types of electric vehicle:

• Plug-in electric vehicles run purely on electricity.

• Plug-in hybrid vehicles run mainly on electricity, but use petrol or diesel as a backup if they run out of charge.

• Hybrid-electric vehicles mainly run on petrol or diesel, but also have an electric battery charged through regenerative braking.

Evaluating Electric Vehicles

Electric cars are still in the early stages. However, as they become more popular, the technology will improve. They will be able to travel further, and charging points will become more widespread.

Transport and Environment: Hydrogen

Hydrogen gas is highly flammable. When burned, it only produces water as a by-product. So, scientists have begun incorporating hydrogen into fuel cells to provide a carbon-free alternative to an engine. Hydrogen fuel cells are three times as efficient as a petrol combustion engine, and they don’t release harmful pollutants.

How Do Hydrogen Fuel Cells Work?

Fuel cells use the chemical energy of hydrogen to produce energy.

Two electrodes as placed into an electrolyte, usually a potassium hydroxide solution.

Hydrogen fuel is fed to the anode (negative electrode) and air is fed to the cathode (positive electrode). The hydrogen atoms are split into protons and electrons. The electrons travel through an external circuit, creating a flow of electricity. Meanwhile, the protons travel through the electrolyte to reach the cathode. They unite with oxygen (from the air) and the electrons to produce water and energy in the form of heat.

2H₂ + O₂ → 2H₂O

Evaluating Hydrogen Fuel Cells

I hope that this article has clarified the link between transport and energy usage. Remember that transportation affects the environment; burning crude oil produces carbon emissions and harmful pollutants. To limit the effects of transportation on the environment, scientists have come up with alternative energy sources, such as methane, electricity, and hydrogen.

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^{5. Gwynn Guilford, Cruise ships dump 1 billion gallons of sewage into the ocean every year, Quartz, 2014}

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^{7. U.S. Department of Energy, Hydrogen Basics, Alternative Fuels Data Center, 2022}