What Is Renewable Energy?

Renewable energy is clean or sustainable energy which comes from natural sources that are constantly replenished. Unlike fossil fuels, renewables typically emit very small amounts of CO2 and no toxic pollution. They are therefore much better for human health and the environment, including the oceans and the atmosphere.
Wind Power Project, Fujian, China
Fujian China, has become one of the country’s key provinces for wind power development. © Fujian Energy Group

Renewables are Climate Friendly

Renewable energy is obtained from resources that are naturally regenerated on a human timescale. The main renewables are (a) solar power (b) wind (c) hydropower (d) geothermal energy (e) biomass. Other sources of renewable energy include wave and tidal power, hydrogen power and ocean thermal-energy conversion. All these types of energy come from clean, non-exhaustible sources. Another renewable is bioenergy, from biofuels and biomass, which is typically replaced within the span of a human life.

The main advantage of renewable energy is its climate-friendly nature – it doesn’t harm Earth’s climate system the way that fossil fuels do. Renewables emit almost no greenhouse gases and therefore have no impact on the man-made greenhouse effect which is the main cause of global warming and its huge ecological footprint.

In addition, renewable energies cause very low levels of pollution – nothing like the smog or other environmental effects of fossil fuels – and they have a relatively small impact on local ecosystems.

All active climate scientists agree that any climate action plan must make renewables our main source of energy.

Almost all types of renewable energy can be used to generate electricity, although effective energy storage technologies are still being developed. At present, renewables account for roughly 27 percent of electricity generation and 11 percent of primary energy consumption. 1 See also: Climate Change for Students.

Solar Power Tower, Andalusia Spain. One of the earlier renewable energy power plants.
One of the world’s first commercial concentrating solar power towers operating in Andalusia, Spain. The 11 megawatt (MW) complex produces electricity using 624 large movable mirrors called heliostats. Photo: Koza1983 (CC BY 3.0)

Is Renewable Energy Sustainable?

Not necessarily. Renewable energy is not by definition sustainable, even though in practice most renewables are sustainable. After all, a fuel may renew itself, but we may use too much of it, too quickly.

Sustainability refers to wider issues involved in the creation, distribution and use of the energy concerned. For example, wind power is renewable, but if wind turbines were found to cause serious health or environmental effects, it would not be regarded as sustainable. For more details on renewability versus sustainability, see: Sustainable Energy Explained.

Is Renewable Energy More Expensive Than Fossil Fuel Energy?

Over the past five years, the price of solar energy and other green energies has fallen significantly. For instance, since 2010, the benchmark price for wind power has dropped by 50 percent; solar power by 84 percent; while the price of lithium-ion battery storage has fallen by more than 75 percent since 2012. The increasing cost effectiveness of clean technologies is now threatening the balancing role that the natural gas industry assumed was theirs. The cost of generating electricity using renewables is dropping steadily. In some areas it is now cheaper than using gas or coal. In terms of global averages, hydroelectric power is now the cheapest source of renewable energy, coming in around $0.05 per kilowatt hour (kWh). Meantime, the cost of developing new power plants using onshore wind power, biomass, solar photovoltaic (PV), or geothermal energy, is now typically under $0.07/kWh, while offshore wind costs around $0.12/kWh. [IRENA (2020), Renewable Power Generation Costs in 2019, International Renewable Energy Agency, Abu Dhabi. ] Of course, cost effectiveness can’t make the sun shine or the wind blow, but it’s a definite tipping point.

“Looking back over this decade, there have been staggering improvements in the cost-competitiveness of these low-carbon options, thanks to technology innovation, economies of scale, stiff price competition and manufacturing experience.”
Elena Giannakopoulou, Head of Energy Economics at Bloomberg New Energy Finance (BNEF).

“The cost of generating renewable energy has fallen – a lot.”
Douglas Broom. World Economic Forum. May 7, 2019.

Why Is Renewable Energy Important?

At present, most of our energy (especially energy for heat and transport) comes from high carbon fossil fuels, such as coal, crude oil, petroleum and natural gas, as well as peat (a younger form of coal). Because they contain carbon, these fuels give off heat-trapping greenhouse gases like carbon dioxide when burned. These gases heat up the planet which leads to rising temperatures and numerous other effects of global warming, including extreme weather events, rapid melting of Arctic sea ice, drying out of forest land, rising sea-level, loss of habitats and biodiversity along with many other environmental effects.

Renewable energy is the main pathway out of this climate crisis to a low carbon and more sustainable energy system. For more about its climate change mitigation benefits as well as its health and economic advantages, see: Benefits of Renewable Energy.

How Much Renewable Energy Do We Use?

Renewables currently supply about just over 11 percent of total global energy, and 27 percent of electrical power. Includes hydroelectric.

Primary Energy by Fuel Type 2020
Global primary energy consumption by fuel source in 2019. Source: BP Statistical Review of World Energy 2020
Electricity Generation by Fuel Type
Global electricity generation by fuel source in 2019. Source: Electricity – BP Statistical Review of World Energy 2020

What Is Renewable Energy Used For?

Renewable energy provides power for the three main areas of electricity generation (solar, wind and hydropower), transportation (biofuels) and heating (solar, biomass, geothermal). In addition, it is an important source for rural (off-grid) energy services. Of these, electricity generation is by far the most productive application for renewables, since solar, wind and hydropower are converted to electricity much more efficiently than oil or coal. To get electricity from oil or coal requires putting it through steam turbines at a power plant, a process in which more than 62 percent of the energy is wasted. 2 However, no real breakthrough by renewables or any other clean energy source is likely unless it proves to be a feasible substitute for fossil fuels in the areas of transportation and heating.

Is The Use Of Renewable Power On The Increase?

Yes. Renewable energy is becoming cheaper and more efficient. Lower prices in particular have been a driving factor behind higher sales of solar photovoltaics (solar panels that produce electricity), and wind power. In 2017, non-subsidized renewables were the cheapest form of electricity in 30 countries, and renewable energy is forecast to become significantly cheaper than energy from fossil fuels after 2020. 3

Furthermore, as of 2019, more than two-thirds of all new global electricity capacity installed was renewable. 4

A continence of this trend would make renewables the world’s largest power source in 2025. However, until economies are back on a more ‘normal’ footing after Covid-19, it is difficult to forecast with complete accuracy. 5

Note, however, that “capacity” is not the same as actual “electricity generation”. Wind and solar will always account for a higher proportion of capacity than generation, because they cannot produce power when the wind does not blow and the sun does not shine. 6

The electricity sector may be the most likely growth area for renewables with the double-digit growth of solar photovoltaics and wind in recent years, as well as the solid contribution of hydropower generation. But, electricity accounts for only 20 percent of global energy consumption, so the performance of renewable power in the heating and transportation sectors remains a critical factor in the transition from fossil fuels to clean energy. 7

Electric vehicles recharging.
Electric vehicles (EVs) shown (left to right) include: Nissan Leaf, Smart ED, and Mitsubishi i MiEV electric vehicles at Plug’n Drive’s EV Show in Toronto, Canada. Photo: © Plug’n Drive/ (CC BY-SA 2.0)

So far renewable energy has made no great impact in either of these two sectors. That said, a moderate increase in its share of heating is forecast, by 2023, as strong growth in heat demand is anticipated due to continuous economic and population growth.

The share of renewables in the transportation sector will be the least impressive of all three areas. Analysts expect it to grow 0.4 percent by 2023, due to ongoing and robust oil consumption. 7

Other analysts detect more positive trends, indicating that the increased uptake of electric cars (EVs) and solar power, in conjunction with natural gas, may put a stop to the growth of coal and oil as early as 2020. 8

Where Is Renewable Energy Used?

All over the world. More than 100 cities around the globe, for example, obtain at least 70 percent of their electricity from renewable sources. Which is good news because – according to the International Renewable Energy Agency – cities account for 70 percent of man-made carbon dioxide emissions. These 100 cities are sourcing a growing share of the energy they need from renewables, in order to become more sustainable and combat climate change. In fact, 40 of them already possess a 100-percent renewable electric power supply.

Of course, electricity isn’t everything – cities also need a lot of power for their public transport systems and their heating, most of which is still powered by fossil fuels. (Although many other European cities are also switching to renewables for heating and transport, says Eric Woods, director of Navigant Research, a green energy consultancy.) But it’s an important start for a vital network of the global community. After all, half the world’s population lives in cities, so city authorities have a crucial role to play in helping the planet to become more self-sustaining. The Global Covenant of Mayors for Climate and Energy has been an important influence in the effort to achieve local urban transitions from fossil fuels to renewables, helping more than 7,000 cities and regional authorities around the world to act on climate change.

In the United States cities are becoming even more committed to sustainable, clean energy. Across the country, 170 cities have pledged to become 100-percent renewable.

Renewables are also gaining traction in rural areas, including those in developing countries. One particularly empowering factor for this growth, is the fact that renewable energy resources are far more widespread than fossil fuels, much of which are concentrated in a limited number of countries. Solar power, for instance, is available to large areas that up to now have had no indigenous energy sources. In such cases, renewable energy development goes hand in hand with new electrification projects.

Are All Types of Renewable Energy Equally Effective?

No. Solar power is the cleanest, most efficient and most abundant type of renewable energy. Wind is clean but limited, since most of it is inaccessible – being either found at high altitudes or else far out to sea. Hydroelectric power is more reliable but also limited in capacity as it is already not far from its maximum output; plus, it has environmental costs. Bioenergy competes for land with food-growing, so this too is limited in scope until new technologies are found.

Geothermal power has a higher load factor than solar or wind (its energy source is continuous rather than intermittent), so it produces significantly more electricity per MW of capacity. Unfortunately, the geological sources of geothermal energy are limited, so its development has been concentrated in a small number of countries.

Will Energy Consumption Keep Rising?

Yes. At least until 2100. The world’s population in 2018 was 7.616 billion. It is set to hit 8 billion sometime in 2023, and 11 billion sometime in 2088. 9 This constitutes a 44 percent increase in energy-consuming humans in 70 years – one reason why some climatologists are predicting that our climate plan can’t cope.

Look at it another way. In 2018, global energy consumption grew by about 2.3 percent. If this were to continue, then by 2100 we would be using more than 6 times as much energy as we are today. See also: Root Cause of Climate Change.

Therefore, it seems that the global need for energy will require the continued use of a significant amount of fossil fuel for much longer than expected. And it will require renewable energy capacity to surge and keep surging for several decades. And it will require a massive amount of carbon capture and storage at the point of combustion (of fossil fuels), as well as the extraction of carbon from ambient air.

Spencer Dale, group chief economist at B.P., put it like this: “…strong growth in renewables is essential to the decarbonisation process, but is unlikely to be sufficient… a range of other fuels and technologies are likely to be required, including widespread coal-to-gas switching, and also an increasing use of carbon capture use and storage – CCUS.” 10

Is Nuclear Power The Solution To Our Energy Problem?

Yes and No. Yes, nuclear fuel can help because it’s a reliable and proven low carbon fuel. No, it probably can’t help because it is not seen as safe, and because we have yet to solve the security and containment issues concerning nuclear waste. Also, few people – in the developed world at least – trust the nuclear industry so its advice would not be believed. Any decision one way or another needs to be taken by an institution of trust, without any vested interest. For an in-depth article on this issue, see: Is Nuclear Power a Replacement for Fossil Fuels?

Another application of nuclear theory is Nuclear Fusion (as opposed to nuclear fission) which seeks to create limitless supplies of renewable power by fusing two isotopes of hydrogen. Development is under way although scientists won’t know if the theory is workable for decades.

What Are The Main Types Of Renewable Energy?

There are five major types of renewable power: solar, wind, hydropower, geothermal and biomass/biofuels. Next generation renewables include hydrogen energy, as well as marine energies like wave power and tidal power, all of which are still in development.

Except for certain categories of biomass, none of these energy sources emit greenhouse gases and thus have no effect on climate change, except insofar as they reduce the need for fossil fuels. Even so, one should take into account the production, transportation and associated activities performed during the life cycle of any renewable fuel. 11 12

Solar Energy

Solar power renewable energy is captured and turned into electricity with numerous evolving technologies, the most effective being concentrated solar power (CSP), and solar photovoltaics (PV). 13

Concentrated solar power (CSP) technology harnesses focused sunlight. CSP plants use mirrors and lenses to concentrate (focus) sunlight, turning it into high-temperature heat. This heat is then channelled through a conventional generator and converted into electricity. The CSP plant typically has two sections: one that collects solar energy and converts it to heat; and another that turns the heat energy into electricity.

The largest CSP projects in the world include the 950 MW Noor Energy 1 CSP-PV project in Dubai, Ivanpah Solar Power Facility (392 MW) in the United States (which uses solar power tower technology), the Noor/Ouarzazate Solar Power Station (360 MW) in Morocco. 14 15

Solar photovoltaic systems (PV) consist of solar panels each containing many, smaller units known as photovoltaic cells. These PV cells (little sandwiches made up of two slices of silicon) convert sunlight into electricity by exploiting the photovoltaic effect – put simply, a process in which two dissimilar materials in close contact produce an electrical current when hit by light or other form of radiant energy. (Photovoltaic simply means “sunlight to electricity.”) 16 17

The largest PV power plants in the world, in terms of capacity include: the 1,547 MW Tengger Desert Solar Park (China); the 1,000 MW Kurnool Ultra Mega Solar Park (India), the 1,000 MW Datong Solar Power Top Runner Base (China) and the 850 MW Longyangxia Dam Solar Park (China).

Who Uses The Most Solar Energy?

As of 2019, the top 10 countries using the most solar power include: (1) China (2) USA (3) Japan (4) Germany (5) India (6) Italy (7) UK (8) Australia (9) France (10) South Korea. 18

How Successful Is Solar Energy?

Electricity generated from solar increased by 22 percent in 2019, with China accounting for over half the growth.

Although solar power has significant advantages over fossil fuels, it still only accounts for around 1 percent of the world’s energy consumption, and 2 percent of the share of global electricity (2019). But that share has tripled between 2000 to 2019. 

Solar is rated as the most promising of all renewable sources of sustainable energy.

Wind Power

Wind power renewable energy also comes from the sun. Sunlight strikes the Earth unevenly, causing areas of warmer and less warm air. This leads the Earth’s climate system to even things out by moving air about as global wind. The energy that travels in the wind can be harnessed to provide electricity. The standard wind power machine is called a wind turbine. Turbines vary in size and when grouped are known as wind farms.

Mojave Wind Farm, California. A major renewable energy power source.
Alta Wind Energy Center (AWEC), also known as Mojave Wind Farm in California is one of the biggest wind farms in the world. Photo: © CC BY-SA 3.0

Most wind turbines (also called aerogenerators) are designed along the lines of the traditional wind-driven propeller blades, with the propeller shaft connected to an electrical generator. The blades can rotate around an axis in either the vertical or horizontal plane.

Wind farms are most productive in areas where winds are stronger and more constant, notably in offshore and high-altitude locations. Average productivity of wind turbines varies between 16 and 57 percent annually, with capacity of modern utility-scale wind turbines ranging from about 600 KW up to 9 MW of electrical power.

What Are The Land Use Conflicts Of Wind Power?

Ecological Effects arise when turbines encroach onto bird migration routes or sensitive animal habitats. Bogs and other wetlands may suffer if turbine construction and access tracks affect the hydrology of the area. Also, wind farms need a large area of land over which the turbines can be spread. To reduce the ‘wind shadow’ effect, turbines typically have a gap between them of about three to five times the diameter of their blades. However, the land between the aerogenerators can still be used for agricultural or similar purposes.

What Is The Potential Of Wind Power?

The amount of wind power that can be captured and converted into electricity is immense. According to the American Wind Association, wind farms positioned throughout the Midwest could satisfy the energy needs of the entire country; meanwhile, the land beneath the turbines could still be farmed. 19 Other analysts believe that wind has nowhere near the potential of solar power but it still has an important contribution to make. 20 The actual contribution of wind power to U.S. electricity generation is 7.3 percent. 21 Its contribution to global electric power is 4.7 percent. 22

Who Generates The Most Wind Power?

According to the Global Wind Energy Council (2020), the following countries account for more than 80 percent of global wind energy: China (36.3 percent), USA (16.2 percent), Germany (9.4 percent), India (5.8 percent), Spain (4.0 percent), UK (3.6 percent), France (2.6 percent), Brazil (2.4 percent) and Canada (1.1 percent).


Probably the most traditional and successful form of renewable energy, hydropower involves the capture of gravitational energy from a flow of falling water.

Chief Joseph Dam, Washington, USA. Hydroelectric power is the most reliable type of renewable energy.
Chief Joseph Dam, Washington State, USA. Opened 1979. Photo: © U.S. Army Corps of Engineers

To convert the gravitational energy of falling water, it is necessary to use a natural waterfall, or else build a dam and reservoir to produce a constant flow. In either case, the falling water is used to drive turbines which convert the energy into electricity. Large dams can have a capacity in excess of 10 GW.

Smaller run-of-the-river hydro schemes typically generate up to 50 MW of power. These schemes are often used on smaller rivers or as environmentally low-impact developments on larger rivers. Instead of depending on stored water from a reservoir, they channel part of the river water along the edge of the river valley (using pipes and tunnels) until it is a suitable height above the valley floor. It then falls earthwards through a sluice to drive a turbine. 23

In China, there are more than 45,000 small hydro installations 24 . In the United States, a good example of a run-of-the-river dam is Chief Joseph Dam on the Columbia river. Its 27 main generators in the powerhouse, give it an installed capacity of 2,620 MW and an annual generation of 9,780 GWh (2009).

What Are The Environmental Impacts Of Hydropower?

Although hydropower is considered to be a clean source of energy because it gives off no damaging greenhouse gas emissions, and sustainable because it is continually replenished by rain and snow, large hydroelectric installations have a number of negative environmental side-effects. 25

Large dams can interfere with river ecosystems, harming wildlife and displacing communities. Turning a fast-flowing river into a large body of standing water not only creates breeding grounds for mosquitoes and the like, but also starves downstream river plain areas of sediments and minerals.

Spawning fish like salmon and sturgeon are typically unable to navigate their way upstream, while other aquatic populations can become cut-off and isolated.

Dams typically require vast amounts of rock, sand, gravel and cement – all of which need access roads to get to the site – as well as other infrastructure.

What Is The Potential Of Hydropower?

Hydropower is the biggest source of renewable energy in the world, accounting for about 7 percent of global energy 26 and 18 percent of global electricity. 27 In the United States, hydropower provides 7 percent of the country’s electrical power.

However, annual net capacity growth has slowed over the past few years, due to fewer large hydro projects being developed in China and Brazil. 7

Who Generates The Most Hydroelectric Power?

China is the world’s largest producer of hydroelectricity. Brazil, Canada, the U.S. and Russia are also major producers. The largest hydroelectric installations include: The Three Gorges Dam (Hubei, China): capacity 22,500 MW; the Itaipu Power Plant (Brazil/Paraguay border): capacity 14,000 MW; the Xiluodu Dam (Yunnan, China) on the Jinsha River, the upper course of the Yangtze River: capacity 13,860 MW.

The largest hydroelectric installation in America is the Grand Coulee Dam on the Columbia River: capacity 6,800 MW.

What Are The Other Forms Of Water Energy?

In addition to hydroelectric energy, water also contributes to Wave power, which harnesses the energy of ocean surface waves, and Tidal power, which captures the energy of tides. These two forms of hydropower have significant future potential but are not yet widely employed commercially.

Geothermal Energy

How Geothermal Plants Work: Diagram
How a Geothermal Power Plant Works. Photo: © EPA.gov

Earth’s geothermal energy stems from the radioactive decay of isotopes of uranium, thorium and potassium in the Earth’s mantle. The “geothermal gradient” – the difference in temperature between the core of the planet and its surface – causes a flow of heat from the core to the surface. This geothermal heat is used for electricity generation, space heating or hot water.

  • Low temperature geothermal schemes utilize hot groundwater (heated by hot rocks) to power district heating systems. 
  • High temperature geothermal schemes harness high temperature steam (from very hot groundwater) to generate electricity.
  • Enhanced geothermal systems (EGS) involves drilling holes several miles deep into granite rock measured at 400 degrees Fahrenheit or higher, after which water at high pressure is pumped into one of the holes. As it comes into contact with the hot rock formation it turns into steam and returns to via another shaft where it is converted into electricity.
  • New geothermal technologies include new types of turbines that utilize “low temperature fluids”. This allows areas with lower temperature rocks to be used for the generation of electric power.

What Are The Environmental Impacts Of Geothermal Heat?

There are few effects on the environment from geothermal heat. Very small amounts of hydrogen sulfide and carbon dioxide may be emitted from hot water brought up from underground. Waste water from geothermal installations can contain salts and traces of heavy metals.

Geothermal Energy Is Continuous Not Intermittent

Geothermal power generation is a well-established form of renewable energy. It is noted in particular for having a high load factor (its heat energy is continuous rather than intermittent), which means that each megawatt (MW) of capacity generates significantly more electricity during a year than a megawatt of wind or solar capacity.

Is Geothermal Energy An Important Power Source?

Yes. Geological conditions needed for geothermal power are concentrated in a relatively small number of areas, so it is not as widespread as other renewables. But in those areas, it plays a major role, e.g. in Kenya (51 percent of power), Iceland (30 percent) and Philippines (27 percent).

Geothermal electricity generation around the world increased by 3 percent in 2019 reaching 13.93 gigawatts installed capacity. This still accounts for less than 1 percent of global energy output.


Diagram showing the Bioenergy Cycle: How Biomass is Converted to Fuel.
Bioenergy Cycle: How Biomass is Converted to Fuel. Image: Oak Ridge National Laboratory, U.S. Department of Energy.

Bioenergy is energy obtained from the conversion of solid, liquid or gaseous products derived from biomass. The production of bioenergy has become a massive billion-dollar industry with huge subsidies, because it is seen as a renewable form of clean energy and a major alternative to fossil fuels. But see our article: What is the Effect of Wood Burning on Climate Change?

What Is Biomass?

Biomass includes a wide array of plant or animal material used for energy production. It includes: wood or forest residues, waste from food crops (corn stover, wheat straw, bagasse), cultivated energy crops (e.g. miscanthus, sorghum, switchgrass, hemp, poplar, willow, sugarcane), horticulture (garden waste), food processing residues (corn cobs, used cooking oil, animal fata), animal waste (manure, rich in nitrogen and phosphorus), or human waste from sewage plants. 28

What Are Biofuels?

Biofuels are renewable transport fuels that are made from biomass. The main types of biofuels presently available include: biodiesel, bioethanol, hydrotreated vegetable oil (HVO) and biomethane. 29 30


Biodiesel is an oil produced from plants or animals and deployed as an alternative to or blended with petroleum diesel and used in diesel-powered vehicles. Biomass sources for biodiesel include: vegetable oils and animal fats, palm oil, soybean oil, sunflower oil and tallow. 


Bioethanol is an alcohol made from sorghum, corn, wheat, potatoes, sugar cane, even cornstalks or vegetable waste. It is usually blended with gasoline and used in petrol vehicles. 

Hydrotreated Vegetable Oil

HVO is a type of renewable diesel which can be employed as a replacement for or combined with diesel.


Biomethane is made by removing impurities from biogas and can be employed in natural gas vehicles. It is also integrated into the gas grid in order to provide heat and electricity.

What Is Biogas?

Biogas acts like a biofuel or a regular type of bioenergy. It’s a by-product of plant and animal waste that decomposes in the absence of oxygen. Typical low-oxygen environments include landfills and sewage waste treatment facilities. Biogas primarily consists of methane and carbon dioxide – both powerful greenhouse gases – thus care is needed to prevent biogas from entering the atmosphere. Biogas is used in cooking or for electricity generation, or as a renewable transport fuel. Examples of usage include: city bus systems in both Norway and Finland powered by biogas from sewage. Freshkills landfill biogas facility in New York City, which produces sufficient methane to power 30,000 homes a year while generating $3-5 million annual revenue for the city.

What Are The Environmental Impacts Of Bioenergy?

There are three areas of concern: wood-burning; competition with food; and deforestation.

  • Wood-Burning – Not Environmentally Friendly

It is important to understand the ongoing controversy about biomass, more commonly known in Europe as bioenergy. The use of biomass for energy has attracted criticism, not least because the most common source of biomass is wood. Wood is not a fossil fuel, but it has some of the characteristics of fossil fuels.

It includes forest residues (dead trees, branches and tree stumps), as well as yard clippings and wood chips. When burned, wood biomass releases CO2, but it has still been classified as a renewable energy source in the EU and UN legal frameworks. The reason given is that during its life-cycle the tree will have absorbed a significant amount of CO2. When the wood is burned the absorbed carbon is released back into the atmosphere. The absorbed CO2 is balanced by the CO2 released when the wood is burned, making the process carbon-neutral.

Even assuming that this is true – and some scientists dispute that the figures balance – wood burning also gives off one of the most potent greenhouse gases, nitrous oxide (N2O). The actual amount emitted is fairly small, (200g of CO2 equivalent per kilo/2.2 pounds of wood burnt), but N2O is 300 times more powerful at heat-trapping than carbon dioxide and lasts 120 years in the atmosphere. Another greenhouse gas, methane is also emitted. Methane (CH4) is roughly 30 times more powerful than CO2. Lastly, wood combustion also produces significant amounts of the toxic gas carbon monoxide.

In addition, burning wood gives off a large amount of microscopic particles, or aerosols, known as particulate matter (PM). These particles – of which the most common is black carbon – are small enough to penetrate human lungs and even enter arteries to the brain. In the United States, numerous bioenergy plants have received fines for their excessive emissions. 31

In a nutshell, although it is possible for some wood to have captured a certain amount of CO2 before it was burned, which would reduce its overall CO2 emissions, it is not exactly environmentally friendly. 32

The World Health Organisation (WHO) estimates that outdoor air pollution accounts for roughly 4.2 million premature deaths each year, while indoor air pollution causes around 3.8 million deaths annually. Most of these fatalities occur in developing countries, where wood/charcoal burning is still widespread. 33 34 The burning of other biomass in these countries, in the form of crop stubble also contributes to urban smog as well as the strange toxic haze known as the Asian Brown Cloud, that materializes over parts of India, Pakistan and China during the dry winter season.

  • Bioenergy Competition With Food Production

Second, there are worries that the production of bioenergy may lead to a competition for land with food producers. In addition, some studies suggest that the greenhouse gas emissions of certain crops used for ethanol and biodiesel are no better or worse than fossil fuels (Fargione et al., 2008; Searchinger et al., 2008).

  • Biomass Cultivation May Lead To Deforestation

Third, some experts worry that, under certain circumstances (like rising prices), the demand for land space to grow energy crops may lead to further deforestation, which would seriously undermine their value as a clean fuel.

How Successful Is Bioenergy?

Precise global statistics on the contribution of bioenergy and biofuels to global energy consumption are hard to come by. Some prestigious reports say bioenergy accounts for 25 percent of the energy needs in some less developed countries, but less than 1 percent in developed countries. Others give it a 10 percent share of global energy, but with insufficient details.

Studies into bioenergy production have also shown a bewildering range of life-cycle greenhouse gas savings – ranging from an 86 percent reduction, to a 93 percent increase compared with fossil fuels. 35 36 37

Renewable Energy: Conclusion

The climate science is unequivocal: renewable energies are better for Planet Earth in a whole variety of ways. They will stop the loss of biodiversity and mitigate the effects of global warming on humans, which generally hurt the poorest the most.

The continuing global reliance on hydrocarbon fuels and the resulting emissions gap clearly indicate the scale of the challenge we face in devising climate action policies that replace fossil fuels with renewables. But, there’s no reason in principle why this can’t happen within the course of this century, as long as governments around the world cooperate and provide proper leadership.


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  29. See for instance: DCCAE. Ireland. []
  30. Biofuels made from waste are the business, says UK’s Royal Academy (2017). []
  31. “Wood-Fired Plants Generate Violations.” Wall Street Journal. July 23, 2012. (28) []
  32.  “Carbon emissions from burning biomass for renewable energy.” Partnership for Policy Integrity (PFPI) PDF. (30) []
  33. Ambient (outdoor) air pollution.” WHO. []
  34. Household air pollution and health.” WHO. []
  35. Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change.” Timothy Searchinger et al. Science 29 Feb 2008: Vol. 319 []
  36. Life-cycle analysis and the ecology of biofuels.” Davis SC, Anderson-Teixeira KJ, DeLucia EH (2009) Trends in Plant Science, 14, 140–146. []
  37. Improvements in Life Cycle Energy Efficiency and Greenhouse Gas Emissions of Corn-Ethanol” (2009). Liska, Adam J. et al. NCESR Publications and Research. 1. []
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