Renewable energy will help us decarbonize our atmosphere, but all technologies have their limits. In this section, we’ll take a look at some of the most popular renewable solutions to find these limitations – in terms of environmental impacts and energy generation potential. Overall, renewable energy alone won’t help make our societies sustainable. If we want to attain sustainability, renewables will help – but are only one part of the solution. The much, much larger part will be reducing our impacts by consuming less of the world’s resources – by lowering both our energy and material demands.

When evaluating each of these technologies, remember that everything we make requires extracted materials and energy to be manufactured/transported. Green technology is a prime example for showing the importance of life-cycle assessments [which we’ll talk about in a later section]. While most green technologies are still being called ‘clean’ because they don’t pollute while generating electricity, we’ll see that other stages of their life-cycle can have significant impacts.

Solar, Wind, and Batteries

In 2019, solar PV [photovoltaic] accounted for roughly 2.6% of electricity production worldwide. Solar panels convert solar energy into electricity, thanks to engineered materials like semi-conductors.

In 2019, wind turbines accounted for roughly 5.3% of electricity production worldwide. Wind turbines have a gear system connected to a generator, where the mechanical energy is eventually converted electricity. They’re usually very tall since wind speeds increase with elevation.

These technologies don’t emit any pollutants in the atmosphere when producing energy, so what’s the catch?

Well, they pollute tonnes of GHGs and toxic compounds during their production. And that’s mostly because they need very specific materials to function, including high amounts of rare metals [low mineral grade deposits and/or low metallic concentration within the ore].

Solar panels are made from a wide range of metals [depending on the type of panel] including arsenic, copper, gallium, germanium, indium, and/or tellurium to name a few of the critical ones. Solar panels use a bunch of silicon as well, which may be considered abundant – but is rarely found in its pure form.

Wind turbines are giant metallic structures [mostly composed of zinc and copper] that also depend on a few ‘critical‘ commodities, like dysprosium, neodymium, praseodymium [all used for turbine magnets], aluminum and rare earth elements. For reference, the typical onshore wind plant is made with 9 times more mineral resources than a gas-fired plant.

Unfortunately, that’s not all. Both technologies are intermittent, since the Sun doesn’t shine all day, and wind varies too. That’s why energy storage is essential to provide a continuous energy supply throughout the 24-hour day. This is where batteries come in.

Chemical batteries store energy chemically and release it as electricity. Unfortunately, these types of batteries are also metal-intensive and require several critical materials such as cobalt, graphite, nickel, rare earth metals, and of course lithium [for lithium-based batteries]. Battery storage systems will play an important role as we look to decarbonize our societies, as clearly indicated by their increasing metal demand.

The following graph shows the extent to which ‘clean’ energy technologies will increase their specific metal demands from 2020-2040 in the Sustainable Development Scenario [SDS]. For example, the clean-tech sector’s lithium demand is expected to increase 42-fold by 2040 [i.e. clean-tech’s 2040 lithium demand will be 42 times its 2020 demand].

Even if we’re able to extract all the necessary metals to help renewables overtake fossil fuels, there’s still the issue of lifetime. Solar, wind, and batteries use technologies that damage over time, so they need to be replaced every 2-4 decades, at most [e.g. wind]. Consequently, if we choose to complete the ‘green revolution’ and deplete many metal reserves, we better have a plan for how to manage the second/third/next waves of the revolution.

Solar thermal [or concentrated solar power – CSP] is another type of renewable technology that depends on solar power, but focuses on capturing solar heat – which can then be used to generate electricity. This technology currently isn’t making an impact at the global scale, as it faces many practical challenges of its own [e.g. isolated in deserts but requires water] – in addition to some of those listed above. In 2018, solar thermal generated just 13.4 TWh [terawatt hours measure quantities of energy] of electricity – compared to 570 TWh for Solar PV.


Hydrogen has gained so much clout over the past few years that some companies and governments have decided to switch over to this semi-renewable energy ‘source’. It’s already being produced and used by industries for other applications than electricity generation, and that’s expected to ramp up in the next few decades.

Hydrogen isn’t really an energy source – or at least that depends on how it’s retrieved. If it’s made through hydrolysis, then it acts like a battery. If it’s stripped from natural gas, then it’s basically just a fossil fuel. Once hydrogen has been produced/separated by either method, it can store energy [much like a propane tank] until it’s used to generate electricity with a fuel cell. While the electricity generation through a fuel-cell won’t emit any pollutants, we should note that fuel cell manufacturing requires loads of metals as well [e.g. platinum-group metals].

Fuel Cells

Through chemical reactions, a fuel cell provided with hydrogen and oxygen can generate electricity. The beauty of a fuel cell is that their only by-products are clean water and heat. Quality fuel cells are around 50-60% efficient, compared to less than 20% for internal combustion engines [we’ll soon see why that’s not a very fair comparison]. With oxygen abundantly present in air [21%], the fuel cell can simply intake nearby air, use the oxygen, and release the air’s other gases that weren’t needed. So far so good. However, hydrogen is required as well. And no, we can’t take this one from air.

Making Hydrogen Part 1: Hydrolysis

There are essentially 2 ways to produce hydrogen: the way people think of when they say hydrogen is clean, and the way that’s actually being used [yes there are a few more – see below]. Let’s start with the ‘clean’ one, hydrolysis. Hydrolysis is the opposite reaction of what happens inside a fuel cell. This time, it’s the electricity and water that are consumed to create oxygen and hydrogen. There’s an apparent obstacle right from the get-go with this method – we need to supply electricity. The yield for this reaction is around 80%, meaning that 20% of input electricity is wasted. Combining this hydrogen production method with a fuel cell, the overall process only reaches 40-48% efficiency [ein vs. eout]. Compared to ‘normal’ lithium batteries that are 80-95% efficient, fuel cells from hydrolysis would require roughly twice the electricity for the same final energy output.

Unfortunately, we’re at a time where we can’t afford to increase energy consumption, especially in regions where fossil fuels continue to hold a significant share of the electricity mix. While hydrolysis is considered clean by many, it all depends on where that electricity comes from. And if you’ve been following along, ‘clean’ technologies all have production impacts. Even with renewables, we can’t afford to double our electricity consumption with hydrogen.

We could even go one step further and examine the initial electricity production efficiency at the power plant, and compare the whole process against just burning gasoline in combustion engines – taking transportation as an example. We find that with a standard 33-35% combustion power plant efficiency, the overall efficiency for hydrolysis-hydrogen reaches 13.2-16.8% – similar to the “less than 20%” previously stated for combustion engines.

In 2019, hydrolysis accounted for less 0.1% of hydrogen production worldwide – an insignificant share compared to other production processes that consume gas, coal, or oil.

With hydrolysis, it’s pretty clear that hydrogen acts more like a shitty battery than an actual energy source, since ‘normal’ lithium batteries have 80-95% charge/discharge efficiency – while the hydrolysis/fuel cell combo described above remains below 50% [excluding electricity production]. We should also note that hydrolysis electrolysers have important metal requirements [e.g. zirconium, nickel] – on top of relying on metal-intensive fuel cells later on. That being said, ‘normal’ batteries are metal-intensive as well.

Making Hydrogen Part 2: Steam-Methane Reforming

Since hydrolysis is so inefficient [and currently expensive], the vast majority of industries adopt steam-methane reforming [SMR] instead. Most natural gases are hydrocarbons, meaning they’re composed of hydrogen and carbon atoms. Gases like methane have 4 hydrogen atoms for each carbon atom [i.e. CH4]. SMR plants strip the hydrogen from the carbon in the natural gas to ‘produce’ hydrogen. The carbon ends up as CO2 and eventually finds its way into our atmosphere in the absence of rare carbon control measures.

This type of hydrogen production is far more efficient than hydrolysis, even though it requires high energy input for the reaction to occur – which explains why it accounts for 75% of global hydrogen production. Stripping natural gas essentially saves 2 steps compared to hydrolysis, since there’s no need to burn natural gas to make electricity, which would then allow hydrolysis to produce hydrogen.

Alas, between the carbon emissions and SMR’s high energy requirements, this process is far from clean. And it looks even worse considering that 40-50% of that hydrogen ends up wasted in a fuel cell afterward.

Tying It All Back Together

Once the hydrogen is made, there are still a few challenges left. Notably, hydrogen lacks the infrastructure to be easily transported. While it could certainly be transported in pipelines, other transportation methods are inefficient due to the safety risks associated with driving trucks filled with flammable gas. For example, if hydrogen were to replace gasoline as the fuel of choice, then truckloads of liquid hydrogen would have to supply fueling stations, but liquefying hydrogen requires lots of energy. Same goes for trucks that transport compressed tanks of hydrogen – compressing the gas consumes energy [which adds to the inefficiencies].

Hydrogen research and technology haven’t made any advances that would suggest hydrogen is the fuel of the future. Instead, it has uncovered disappointing truths, which should eliminate it from contention all together. Some exceptions exist – where hydrogen used in the right setting shows some potential to reduce emissions [e.g. smelting]. However, as long as hydrogen production pollutes our atmosphere – what’s the point?


Geothermal [not to be confused with geo-exchange which relies on thermal energy generated from solar radiation], as the name indicates, consists of using the heat present in the Earth. The heat is extracted by heating a fluid to generate steam and rotate turbines. Alas, we’re not able to dig very deep into the Earth, which explains why geothermal energy production is limited to regions of high geothermal activity, like Iceland.

As a result, geothermal energy cannot be produced in enough locations to take on a significant part of the world’s energy mix. In fact, geothermal accounted for less than 0.5% of electricity production worldwide in 2019.

We should note that geothermal is also pretty metal-intensive, mostly due to the special steel alloys required [geothermal has high demands for chromium, nickel, molybdenum, and titanium].


Hydroelectric dams use a very simple principle to produce energy: gravity. Upstream, a dam retains the water elevation much higher than on the other side of the dam. The higher the difference in elevations, the greater the pressure differential. Passing through the dam, the water rotates turbines to generate electricity. Out of all renewable energy systems [excluding biofuels & waste], it holds the greatest share of the world’s energy mix with 2.5% [in 2018] and electricity mix with 16% [in 2019]. Hydroelectricity is a flexible electricity source, since we can vary the amount electricity produced quite well [within design limits]. This helps increase generation for peak demand and avoid waste during off-peak hours [i.e. the dam can act as an energy storage system].

Unfortunately, there are significant drawbacks.

First, dams must be placed along rivers or similar water bodies. There needs to be an upstream and a downstream, so that an accumulation of water can take place. Ecosystems are completely shaken by such installations. Access to a water source is vital for all living species, so modifying the water body seriously endangers many species both upstream and downstream [e.g. water quality and quantity, breeding grounds, etc…]. That includes human populations that depended on the previous water stream’s characteristics to survive. For example, the world’s largest dam in China forced 1.4 million people to relocate between the 13 cities, 140 towns, and 1,350 villages flooded by the reservoir.

The larger the dam, the more energy can be produced. However, this also implies more water accumulation, which results in more damage to the environment.

The rate of installation of new hydroelectric dams is decreasing while removal rates rise, as developing countries are starting to realize that many dams are uneconomical. Hydropower isn’t expected to reach its target of 5,722 TWh of electricity produced per year by 2030, although it was already generating 4,333 TWh in 2019. Not fantastic news for the world’s current largest renewable energy source.

Second, there are many regions that don’t have access to water bodies that could prove good dam locations. Even if hydroelectric dams can help supply select regions of the world with nearly all their electricity, not everyone can follow suit. For hydroelectricity to dominate the electricity mix, we’d need plentiful access to rivers combined with sufficient unpopulated space and biodiversity to spare. Unfortunately, the Earth’s surface is fully booked at the moment.

Third, dams are often at the mercy of precipitation. With increasing global temperatures, droughts are becoming more frequent and intense. That forces regions to rely more heavily on fossil fuels during times of drought – when the dam’s water elevation isn’t high enough to produce more electricity than the dam uses to operate.

Fourth, hydroelectric dams create reservoirs of decaying organic matter. Just upstream of the dam, loads of dead vegetation and animals accumulate on the reservoir floor. The decay process consumes oxygen and releases GHGs. This can significantly lower the oxygen content of the water, which is kind of a bummer for fish downstream since they depend on oxygen as much as we do. The GHG emissions are also far from negligible. While better reservoir management practices can significantly reduce those emissions, many dams aren’t up to par. This explains why certain regions of the world have cleaner hydropower systems than others, which has made it difficult to quantify hydroelectricity’s emissions [ranging from roughly 0.162.4% of the world’s yearly GHG emissions].

Although hydroelectric dams are a great alternative to fossil fuels in select locations, they have serious side effects to consider. Installing a new dam would prove costly for biodiversity, while maximizing efficiency on the existing ones would not be without consequences either.


Biomass can be considered renewable, but it’s certainly not a clean fuel source. Biomass [for energy production purposes] is just wood and other organic matter grown from farms or forests that end up producing energy [e.g. biomass burnt at power plants, ethanol from corn mixed in gasoline, etc…]. Biomass may seem renewable, but we certainly don’t have time to make the industry sustainable.

Governments around the world are considering using biomass to slightly reduce their dependence on fossil fuels. Unfortunately, that wouldn’t make sense from a carbon emission standpoint. For an equivalent energy output, burning wood [including a proper life-cycle analysis] can be 2-3 times as carbon emitting as fossil fuels.

It’s true that this carbon was initially absorbed from the atmosphere, so we could make biomass renewable if we started planting vegetation for that purpose. However, it would take too much time and space to start this process now, for something that really doesn’t provide that much energy. In addition, planting ‘compensation forests’ would assume that the vegetation being cut down for energy production has the same value as the vegetation being planted to compensate – which isn’t true since vegetation plays many important roles in an ecosystem [i.e. not just in the carbon cycle]. For example, replacing a tree cut down in Brazil with another tree planted in Finland isn’t really a fair deal as far as Brazilian biodiversity is concerned.

Biomass also uses a considerable amount of arable land, which is not something we have the luxury to spare. When burned, it can release other pollutants in the atmosphere as well, just like fossil fuels. To truly help the environment, we should help preserve vegetation while it’s still alive – a much more efficient way to mitigate climate change and biodiversity loss rather than burning our environment.

One of the only good reasons to use biomass and harness its energy is if the biomass would instead be wasted. And one of the best ways of converting organic matter into energy and fertilizer is by producing renewable natural gas.

Renewable Natural Gas

Renewable natural gas [RNG] sure has an interesting name. It’s mainly produced by landfills, industrial manure ponds, and anaerobic digester plants [e.g. for sewage treatment] during the decomposition of trash and organic waste. This RNG can then be injected into the natural gas grid to be burned like ‘normal’ natural gas. When burned, RNG still releases CO2, so what’s so renewable about it?

The renewable aspect comes from the assumption that RNG can replace some natural gas in the grid, thus lowering ‘normal’ natural gas consumption. This logic only holds if we assume that the amount of energy supplied by the RNG would have been supplied by natural gas anyway. It also only makes sense if we assume that the RNG would have been released in the environment if it hadn’t been captured and burned.

Those are 2 pretty reliable assumptions. With RNG eventually being consumed [releasing energy and CO2], the assumed RNG emissions are reduced by a factor of around 28, since the main component of RNG [methane] is 28 times more greenhousy than CO2. While that’s great for general types of landfills, this waste-to-energy process might not be the best for organic matter. Quite simply, because there are other ways to deal with organic waste that don’t produce methane in the first place.

One of the other ways to deal with organic waste is by composting it. This process produces some CO2 instead of methane and helps us respect nutrient cycles – an essential component of sustainable agriculture. We should note that anaerobic digester plants can also recover nutrients from organic matter, so the main difference between both methods of dealing with organic waste is the fact that RNG is produced in anaerobic [i.e. oxygen-less] conditions.

RNG – Conclusion

In both scenarios, CO2 ends up being released into the atmosphere. In the case of RNG replacing natural gas in the grid, the CO2 released by consumed RNG can technically be considered as offset, since natural gas would have been consumed anyway. In the case of composting, the CO2 doesn’t offset anything – but well-balanced composting processes can prevent a good share of those emissions by locking up organic waste’s carbon into the compost product. Composting also has other benefits. Notably, the fact that it can provide nutrients in a much simpler process, which avoids inefficiencies and additional impacts [e.g. anaerobic digester plant construction, RNG leaks, etc…].

RNG production from anaerobic digester plants can offset some GHG emissions from energy production in the short term, while providing the nutrients required for low-GHG farming to take place in the long term. That being said, RNG is produced from waste [and it should stay that way – see biomass], which means it’s already limited in terms of how much energy it can provide.


All these examples reflect an important problem in our societies: we simply consume too much energy for renewables to be able to replace fossil fuels. Lowering our energy demand worldwide will help renewables take a more important share of the energy mix. Failure to do so would lead to the continued domination of the Big 3 in the energy mix for many decades.

Alternatively [without reducing consumption], attempts to replace all the energy supplied by fossil fuels would lead to the rapid depletion of other natural resources through any combination of the renewable solutions mentioned above. Keep in mind that global energy demand is projected to increase by 30% between 2017 and 2040. It remains to be seen if that 30% can even be covered by renewables or efficiency advances, or if we’ll have to increase raw fossil fuel consumption to keep up with demand.

We’re well aware of the negative aspects of fossil fuels and agree they can no longer be burned. Unfortunately, each renewable solution comes with its own set of limitations. The current response to these limitations seems to be “innovation will find a way”. Oddly enough, we rarely come to the conclusion that this clean energy supply problem might not be one we can solve. Living on a planet with finite resources won’t allow us to produce infinite amounts of energy or the materials needed to harness renewable energy sources for very long.

Don’t Get It Twisted

We need to establish our priorities. Decarbonizing our atmosphere is vital, and this is something all renewable energy sources can help us with. However, we have to accept that this will have serious consequences – like increasing mining activity and biodiversity loss.

That’s okay because we’re currently in a race against global warming and climate change, but looking at the small picture risks creating a lot more problems later – especially as we increase our dependence on finite resources like metals.

P.S. – Individuals

Renewables will be important as we attempt to transition from fossil fuels to these new technologies, but they aren’t great solutions at the individual scale. With finite resources, we shouldn’t expect to each have our own electric vehicle or solar panels – in fact it might be best not to. Instead, reducing our demand for energy and materials are concrete steps that guarantee results. On top of that, those of us that wish to source our energy from renewables can just purchase renewable energy ‘certificates’ from large-scale suppliers.

Now this isn’t always the case, especially in underdeveloped countries where large chunks of the population rely heavily on extremely polluting fossil fuels. In these types of scenarios, mini-grids and off-grid renewables are small scale solutions that can play a significant role in cleaning up the electricity mix.

Getting back to developed countries, individualized renewable solutions can be problematic for numerous reasons [including but not limited to]:

  • Individualized solutions are taking up materials from a finite resource pool. So that means less is available for others who might need it more [e.g. in underdeveloped regions where mini-grids/off-grid renewables could replace fossil-fuels].
  • These technologies have significant impacts on the planet, and the benefits that some of these solutions bring may not be enough to make up for their life-cycle impacts. For example, installing a solar array on a rooftop can actually increase one’s impacts if the region’s electricity grid is already dominated by renewables. It’s best to let experts figure out where renewables would be beneficial.
  • Renewables will be much more efficient and eco-friendlier if employed at a large scale [or at least at the mini-grid scale] by experts, as they will have more knowledge on maintenance, recycling programs, and more. As such, rooftop solar for example – when managed by the grid – can be a very attractive solution. Additionally, policy changes can force a quick transition to better ‘renewable energy management’, yet another reason for renewables to be part of a large-scale system.
  • Individualized solutions don’t usually lead to energy consumption reductions – it often has the adverse effect. With peace of mind that the technology is completely clean [which isn’t the case], owners may not see any point in limiting energy consumption anymore.
  • These solutions can distract us from the real solutions by promising an unchanged world [e.g. same level of energy consumption] – but where the environmental crisis is solved. As we’ve seen, that just can’t work. There are far more effective measures out there that can actually help us reduce our impacts, and it shouldn’t come as a surprise that our unsustainable daily routines need to change a bit [we’ll see many examples in the main sections].

In the end, we will need these new technologies. However, we have to realize that many rely on energy-intensive industries – and quite simply have limited energy generation potential compared to our current consumption. So we’ll have to reduce consumption and use renewables as efficiently as possible.

We should also note that we don’t have time to just wait around for research to make efficiency advances for these technologies while we do nothing. Hoping for the best is good for waking up in the morning, but so is the prospect of implementing concrete solutions that are guaranteed to make a difference.