Green energy is a rapidly growing global market due to the large impact energy generation has historically had on climate change and other aspects of the environment. Fossil fuel consumption is considered a key driver of the climate emergency we now face. Many nations have responded to this by beginning to divest their energy sources away from fossil fuels and towards renewable energy.
Discussions concerning green energy often tend to focus on generating renewable electricity. Electricity might be considered one of the most heavily relied-upon resources we are capable of harnessing, but the global energy mix is split across many other mediums too.
For this reason, there should be far more to the conversation of green energy than simply means of generating renewable electricity.
Energy sources versus energy carriers – what’s the difference?
Many countries develop and grow based upon their ability to harness energy, as energy can greatly influence the standard of life. A country must be able to both acquire energy from a source, as well as transport it to use in applications which require energy. This means before we can actually consume energy, we must first acquire it from an energy source, and transport it in the form of energy carriers.
Energy sources are derived from the natural environment and may be finite or replenishable. Fossil fuels and fossil-derived substances like oil sands or uranium are a finite (non-renewable) energy sources. Wind energy, tidal energy, geothermal energy and solar energy are examples of renewable energy sources, because they replenish naturally on a human timescale. Biomass energy sources such as wood are relatively renewable, subject to whether the growth rate of the biomass exceeds the rate of use.
Energy carriers are convenient forms of stored energy which are not available in the natural environment. The energy carrier discussed most frequently is electricity, but other examples include gasoline, hydrogen and water. Energy carriers are usually the means by which we can use energy for processes like manufacturing, transport, food and day-to-day activities. Water is an example of a raw material which is also an energy carrier.
It is important to understand the distinction between energy sources and energy carriers because it requires very different actions to pursue sustainable energy sources and sustainable energy as a whole. Out of the entire global energy mix, only a small fraction is processed into electricity – the majority is embodied in transportation, products, food and water.
The Big Secret – Embodied Energy!
Embodied energy describes all of the energy used directly or indirectly in each process step of a product or system. To contextualise, 391 billion litres of bottled water was consumed in 2017. The energy needed to make one 0.5 litre bottle of water can be up to 10.2 million joules – do the maths on the impact of those billions of litres of water on energy consumption! The graphic below shows you why – each input and process requires energy, embodies energy, and may be an energy carrier too.
It is a common assumption that the environmental impacts of a plastic bottle are all related to making the plastic and disposing the plastic – particularly now that we know how much ends up in the ocean. However, a significant impact is also created behind the scenes: it is only when we look at the entire life cycle or system of the water bottle that we can see the true amount of energy which goes into the it.
For example, water embodies the energy used to power the machinery used to extract water, the energy used to run desalination plants and the energy used to process and treat water and water treatment plants. Energy is also demanded in almost every stage of this plastic water bottle. Essentially, energy is consumed both directly and indirectly by most of the products that we make, and it is important to account for all of these inputs to accurately represent the total energy consumed.
Embodied energy is also of great interest in the construction sector, because the impacts that occur upstream of a building from manufacturing concrete, bricks and other materials are largely invisible to the builder or architect. The New Zealand Green Building Council found that they could reduce the carbon emissions of a standard home by 29% and save enough carbon by 2050 that is equivalent to taking 460,000 cars off the road, simply by improving the way building materials are manufactured. This shows the importance of identifying embodied energy, and unlocks even greater potential for decarbonization in products, buildings and systems.
What does this mean for sustainability?
There is an incredibly strong connection between energy and raw materials which also couple as energy carriers, such as water. By looking at the life cycle of a product or system, we can identify which aspects have the highest demand and contribute the most to total embodied energy. By understanding these relationships, we can target and streamline our efforts to improve the sustainability of our products, buildings and services.
There must be a push to decouple traditional, non-renewable energy sources from raw materials like water, which are in high demand on individual, local and global scales. One company, Zero Mass Water, has achieved this by creating hydropanels, which could provide ‘renewable water’ in the same way solar panels can provide renewable electricity.
Ultimately, there is a lot more to ‘green energy’ than just looking at renewable energy sources, although these are incredibly important. What we have yet to pursue is for green energy sources to be used in the processes which produce our materials (e.g. water or crops), our products (e.g. plastic or concrete) and wider infrastructure (e.g. transportation or buildings). This is yet another opportunity to pursue a more sustainable and resilient planet – it only requires that we use life cycle thinking to design and develop, and it could take us much closer towards achieving zero carbon by 2050.