Written by Concha Caina Updated on 12 October 2023 In the face of climate change, it is more important than ever to find sustainable energy sources. But what is the difference between renewable and sustainable energy? And which sources are best for our future?Often used interchangeably, there is a subtle, although very important, difference between the terms ‘renewable’ and ‘sustainable’. What's on this page? 01 What’s the difference between renewable and sustainable? 02 Which green energy is renewable and which is sustainable? 03 Why is nuclear power not renewable but possibly sustainable? 04 The pros and cons of nuclear power 05 How clean is nuclear power? What's the difference between renewable and sustainable?Generally speaking, renewable energy comes from sources that are naturally replenished over time such as solar, wind or geothermal. Meanwhile, sustainable energy is energy that can be produced and used in a way that does not damage or deplete the environment, or at least minimises its environmental impact.If this is the case, are biomass and nuclear actually either renewable or sustainable? Which green energy is renewable and which is sustainable?Let’s start by making an early distinction between the main types of energy and their green credentials.Type of energyRenewable?Sustainable?ExamplesSolarYesYesSolar panelsWindYesYesWind turbinesHydropowerYesNot alwaysHydroelectric damsGeothermalYesYesGeothermal power plantsBiomassYesNot alwaysWood pelletsNuclearNoDebatableNuclear power plantsIt's crystal clear from looking at the above table which ones are the renewables and sustainables ones, and which ones are clearly not. However, biomass and nuclear sources of power are in doubt when it comes to their green credentials – for different reasons.Let’s explore those causes. Why is biomass controversial?The first and more powerful reason why biomass can be controversial is because it can have a negative impact on the environment if it is not managed properly. And that last part of the sentences is the clue; biomass is a renewable energy, but it is not always sustainable.For example, burning biomass usually releases greenhouse gases into the atmosphere, and clearing forests to plant energy crops can contribute to deforestation if it is not properly managed. What are the main sources of biomass fuel?There are four main sources of biomass fuel:Forestry residues: this includes wood chips, sawdust, and bark from logging and milling operationsAgricultural residues: this includes corn stover, wheat straw, and rice husksWaste materials: this includes food scraps, manure, and sewage sludgeEnergy crops: these are plants that are grown specifically for their energy content, such as corn, sugarcane, and switchgrassThe pros and cons of biomass energy Pros Renewable Carbon neutral Widely available Can help reduce waste Can create jobs Cons Can lead to deforestation Can release pollutants into the air Can be expensive Can require a lot of land Can be inefficient For more information, check out our full article about the pros and cons of biomass energy. What are the environmental impacts of biomass power?Biomass can have a number of environmental impacts, both positive and negative. The positive environmental impacts of biomassReduced greenhouse gas emissions: When biomass is burned, the carbon dioxide that is released was originally taken out of the atmosphere by the plants that are now being burned. This means that biomass can be a carbon-neutral energy source. However, that statement has been disputed by the scientific community.Renewable: Biomass is a renewable energy source, meaning that it can be replenished over time. This could make it a sustainable option to meet our energy needs – if properly managed.Locally produced: Biomass can be produced locally, which can help to reduce our reliance on imported energy sources. This can also help to create jobs and boost the economy.The negative environmental impacts of biomassDeforestation: Clearing forests to plant energy crops can contribute to deforestation, which can release carbon dioxide into the atmosphere and harm biodiversity.Air pollution: Burning biomass can release pollutants into the air, such as particulate matter and nitrogen oxides. These pollutants can contribute to respiratory issues and other health problems.Water pollution: Biomass production can also pollute water resources, as fertilisers and pesticides used to grow energy crops can run off into streams and rivers.Land use change: The production of biomass fuel can lead to land use change, as land is converted from forests, grasslands, or other natural ecosystems to grow energy crops. This can have a negative impact on biodiversity and ecosystem services.However, biomass can also be a sustainable energy source if it is used in a way that minimises its environmental impact. For example, biomass can be used to generate heat and electricity in combined heat and power (CHP) plants, which can help to reduce emissions. Biomass can also be used to produce transportation fuels, such as biodiesel and ethanol, which can help to reduce reliance on fossil fuels.Ultimately, the sustainability of biomass depends on how it is produced and used. If biomass is managed properly, it can be a valuable part of a renewable energy portfolio. Ways to mitigate the environmental impacts of biomassHere are some solutions to curb the negative impact of biomass on the environment to ensure it becomes a more sustainable source of energy.Use sustainable biomass sources: Biomass should be sourced sustainably, such as from waste materials or residues from agricultural and forestry operations.Use efficient combustion technologies: Burning biomass in efficient combustion technologies can help to reduce emissions.Capture and utilise emissions: Emissions from biomass combustion can be captured and utilised, such as for heat or power generation.Protect forests: Forests should be protected from deforestation, as they play an important role in storing carbon and providing other ecosystem services.Use water wisely: Water should be used wisely in biomass production, and fertilisers and pesticides should be used sparingly. Why is nuclear power not renewable but possibly sustainable?Nuclear energy is not technically renewable, as the uranium used to fuel nuclear reactors is a finite resource. However, it could be considered sustainable if it is produced and used in a way that does not damage the environment.Nuclear power plants do not produce greenhouse gases, which are a major contributor to climate change. They also have a small land footprint compared to other energy sources, such as solar and wind power.However, few phrases inside the energy world have been as controversial as ‘nuclear power’. For many, the combination of the potential for accidents and the disposal of nuclear waste is just too risky. It is radioactive and it can remain hazardous for thousands of years. The pros and cons of nuclear powerThe legacy of the anti-nuclear hardcore 70s movement lives on, despite the growing support for nuclear energy in recent years.These are the main advantages and disadvantages of the most contentious source of energy power. Pros Produces no greenhouse gases Has a small land footprint Reliable and stable Can be used to generate large amounts of electricity Cons Potential for catastrophic loss of life and generational disease Disposal of nuclear waste High upfront costs Requires highly skilled workers How clean is nuclear power?On paper, nuclear power is very clean, as it produces zero carbon emissions during operation. Nuclear energy does not produce any of the greenhouse gases that contribute to climate change – such as carbon dioxide, methane, or nitrous oxide – and nor does it produce any other pollutants, such as sulphur dioxide, nitrogen oxides, or particulate matter.In addition to being clean, nuclear energy is also a reliable and efficient source of electricity and can operate 24 hours a day, 7 days a week, regardless of weather conditions. It can also produce a large amount of electricity from a relatively small amount of fuel.However the concept of being ‘clean’ is debatable for many. There are currently three main problems with nuclear energy – significant enough for the anti-nuclear movement to want to rule out this type of energy for good.Nuclear waste. There is currently no viable solution for the permanent disposal of nuclear waste, and it is a major environmental concern.Risk of accidents. While nuclear power plants are designed to be very safe, there is always the risk of things going majorly wrong. Major accidents, such as Chernobyl and Fukushima, can release large amounts of radiation into the environment and cause widespread damage.Nuclear weapons proliferation. Nuclear power technology can also be used to produce nuclear weapons, which is a major security concern.Ways to mitigate the environmental impacts of nuclear wasteOf all the risks of nuclear power, what to do with the radioactive waste is the most unavoidable one. Whilst there is no single solution that is universally accepted, some of the options being considered include:Deep geological disposal: This involves burying the waste in a deep underground repository where it will be isolated from the environment.Recycling: This involves reprocessing the waste to extract the remaining uranium and plutonium, which can then be used to fuel new nuclear reactors.Transmutation: This involves converting the waste into less radioactive forms, using nuclear reactions.SummaryOne wonders why governments, with public pressure behind them, do not lean 100% towards totally renewable and sustainable energy sources. Governments have dallied, and now they are all rushing – the planet is warming and Putin is cutting off the tap.Going the whole hog is clearly not possible, apparently, because there is still not enough green energy for everything that a society needs – a society like ours that needs a lot of power to function. A lot.This is the key reason why slightly less-than-green sources such as biomass and nuclear energy are very much on the table. Renewable but not sustainable, sustainable but not renewable. Time will tell. Written by: Concha Caina Concha is an experienced writer with a career in communications, having led multiple digital and editorial projects in Spain and the United Kingdom. A champion of the environment, corporate sustainability, and renewable energy, Concha hopes that Europe will become a leader in a greener and more just world.