Global Fuel Sources and How To Reach Energy Sustainability

By Sterling Ericsson and Preston Hurst

Energy demand and supply has been a continuous topic in the world of fuel production. As populations expand and advanced technologies become more ubiquitous, the demand for more energy in the form of electricity, transportation fuel, and more multiplies. From 1971 to 2014, worldwide total energy supply enlarged from just under 6,000 Mtoe (millions of tons of oil equivalent) to nearly 14,000 Mtoe.[1]

Then, as now, fossil fuels composed most of that production, with renewables and biofuels only contributing 15% to global supply. But the gears have slowly begun to shift. The OECD region known for its fossil fuel production furnished over 60% of global needs in the 1970’s. Now that has shrunk to less than 40%, with China and the rest of Asia being the new up and comers. The core of that change, the story of the transition to finding more sustainable options, is the story of fuels themselves. So, in light of that, we shall investigate each piece of that story in turn.[1][2]

Fossil Fuels Around The World

Global consumption of fossil fuels as an energy source continues to be the primary power producer for much of the world. With an increasing average energy consumption of 1-2% per year, this places the greatest strain on the three main fossil fuel sources: oil, natural gas, and coal. Their output needs to therefore increase to cover for this deficiency or other energy sources must take their place.[3]

Of these, oil remains the most consequential in energy supplies, making up 32.9% of global consumption in 2016. In general, oil has seen a steady decline in usage over the past two decades, with 2016 being the first improvement (1.9%) since 1999. This can likely be attributed to a rebounding of oil prices in early 2015, accelerating consumption enough, primarily in Europe, even to offset the USA’s continued decline of oil utilization.[3]

Natural gas also saw an extreme uptick of 1.7%, with there being a 5.4% boost alone in the US. But the OECD region remained the primary driver of natural gas expenditures at 53.5% of all gas consumed in the world. This all coincided with a boom in international gas trade, especially in pipeline importation.[3]

Out of the three available options, coal fared the worst in 2015-6, with global consumption and production falling by several percentage points. The US saw the greatest volumetric decline at 12.7%, possibly due to the replacement of coal sources with natural gas as a viable alternative.[3]

A variety of measurements have been employed to determine the future of energy usage and what that might entail for the future of fossil fuels. One recent study attempted a model that combined economic impacts with global energy consumption and how climate change effects will play a role. It was estimated that global energy requirements will more than double by 2100 and that fossil fuels will likely play some sort of dominant role in total energy supply until the mid-century mark.[4]

Oil will feature sustained growth until 2060, but thereafter will have its energy input fall precipitously. Coal will see a small amount of increase, but will ultimately fall off the energy map by 2030. Natural gas will see a longer lasting lifespan, due to its involvement in electrical output, but will hit a similar 2060 cap as seen by oil. The cause of the eventual dropoff will be thanks to the increasingly untenable prices that the three fuel sources will go for until their swift replacement.[5]

This model more or less corroborates expected diminishing of fossil fuel reserves, with oil and gas reaching their stretched limit within 35-40 years. The fuels will still exist after this point, but the quantities needed will not be possible to supply and will force other fuels to come to the forefront. Other models suggest that this will happen even sooner, with all three being phased out by 2025 or 2030. Whether such rapidity in fuel substitution will come to fruition is uncertain at this point.[6]

A final thing to note about fossil fuels on a global setting are the subsidies that many nations pay to keep them competitive and operational. Without these, the decline of such fuels would surely have happened sooner than any modern model predicts. So, these subsidies sitting at over $5 trillion worldwide (Over 6% of total GDP internationally) should be mentioned as an unpredictable element in all the predictive systems we apply to the problem. If multiple nations decided to reduce or entirely rescind their subsidies for fossil fuels, that would have a commensurate shift in the timeline models just discussed.[7]

The Productivity of Renewables

In a world dealing with an increasingly more volatile energy crisis and a reliance on a fuel source producing harmful byproducts in the atmosphere, renewable sources of energy with minimal impact have been a long sought-after goal. Therefore, expanding production of electrical energy sources such as wind, solar, hydroelectric, and nuclear have become variable focuses depending on the country and region of the world.

As an example, smaller nations with abundant waterways have bee-lined for hydroelectric power as their renewable of choice. Lesotho, Albania, and Paraguay have managed to achieve nearly 100% renewable energy reliance thanks to the dams and waterways in their areas of influence, with other countries like Iceland having a mixture between the former and their unique geothermal energy production due to the volcanic activity in the region.

Renewables as a whole, outside of nuclear and hydroelectric sources, grew to 2.8% of global energy consumption (and 6.7% of global power generation) in 2015, with a power generation increase of 15.2% within the electricity supplied by renewables themselves. This is close to the decade long average of 15.9% increase per year. The countries that saw the most improvement in this field were Germany (23.5%) and China (20.9%), reflecting the intense attention both have been paying to funding renewables over the past several years.[3]

For wind and solar installation, the United States has seen significant improvement, with wind making up 27% of the energy production increase for the country in 2016. Though Germany in the previous year, per its position of most renewables investment, saw a double amount of 53.4%. Solar has also seen the US come third in the world in 2015, with a 41.8% change, surpassed by China and Japan.[3]

Nuclear as an energy production option saw more modest alterations, with only a 1.3% global output enhancement, centered almost entirely on the actions of China with its 28.9% gain of nuclear power. This has resulted in it reaching fourth in the world, past South Korea, as a nuclear electricity provider.[3]

Hydroelectric did the worst out of the available options, elevating by less than a percent globally. China remains the largest producer of hydroelectric power and even it only saw a 5% difference in the power output in 2015. One of the likely primary reasons for this stagnation in many regions is due to an ongoing worldwide drought caused by higher and fluctuating temperatures. When dealing with the effect and aftermath of such conditions, there is little need or desire to increase hydroelectric productivity.[3]

A major question facing renewables is how effective they can be at covering the energy demand requirements currently controlled by the fossil fuel market. Based on how many renewables work, whereby power generation is restricted to environmental conditions, there is concern that they will never be able to be used beyond incidental and outlying energy. When what is needed currently is a replacement base power system that can successfully shoulder the energy demand load and minimize or eliminate the need for fossil fuels.[8]

Hydroelectric can fill this gap, as several countries have shown, but not every region has enough sources of such power to make up a base power system. Thanks to this, out of all the available choices in renewables, nuclear will likely prove the best option for base power. But improvement in this realm is reliant on enactment of new nuclear power projects by governments, something that is not in favor in many nations today.

Regardless, the energy production of other renewables will continue into the future, picking up a necessary chunk of the annual increase in demand. By 2020, electricity generation from renewables is expected to increase by 50-75% of the amount in 2010 and it is expected to double the former even by 2035. The vast majority of this increase will be in wind power and a lesser amount for solar.[9][10]

At minimum, any amount of power generation that is taken from fossil fuels will result in a reduction in greenhouse gas emissions. So, even if renewables won’t directly be the source for base power in the future, they will benefit the planet anyways by providing low cost, environmentally friendly electrical alternatives.

First Generation Biofuels Break Open Energy Options

While technology continues to advance apace, new energy solutions will obviously emerge to fill gaps and openings in global demand. Biofuels, in turn, have come onto the scene as one of the most rapidly ballooning fields in energy production. In many places, their usage is still limited and not totally adopted by national governments, but that has also been changing swiftly over the past two decades.

Biofuel production over the past decade alone has seen annual gains of 14.3% on average, with the US and Brazil having a strong attention on expansion. Though first generation biofuels, being so reliant on crop farming, are subject to the whims of the global market as well. In 2015, this resulted in only a 0.9% change, far off from the decade average. This was due to Indonesia and Argentina seeing huge 25 and 45 percent losses in their output.[3]

For the former, this was thanks to a massive influx of palm oil as an energy source, killing the biofuel market for that year, though this was later offset with a government subsidy. Argentina, meanwhile, has seen a freeze in their soy exports to China in 2015 that caused a serious hit to biofuels. Though, in both cases, the issues were resolved by 2016, allowing the biofuel field’s growth to continue.[11]

First generation biofuels, with the varieties of subfields making up different uses of plant matter for bioethanol, biodiesel, or solid fuels or the side products of animal agriculture used to mitigate methane exposure to the atmosphere like with biogas, are targeted to the different kinds of agriculture and the commodities they make. It is no surprise then that greenhouse gases (GHGs) and climate change influence are a main topic of discussion for them.[12]

Since 2000, biofuels have grown to make up, in one part, 4% of transportation fuels worldwide. Second generation biofuels in recent years have begun to quickly outstrip their predecessor, but first generation fuels continue to be used for a majority of the 25 billion gallons of bioethanol created in 2016. And, as previously noted, having the US and Brazil be the producers of 85% of that using corn and sugarcane.[13][14]

Even so, many scientists and industry professionals currently view first generation biofuels as just an initial step toward better technologies and a way to perfect things like fermentation machines and other devices that can be used with second generation biofuels and beyond. Because of the interactions between food and feed costs, land use, and water requirements (2-3% of global water and arable land use go to biofuels), there are several restrictions on wider scale application of bioethanol, biodiesel, and biogas. Increasing yield is one method to make the costs more efficient and to drive down concerns of GHG emissions, along with utilizing bioenergy crop species directly to avoid entanglement with food supplies.[15]

For current usage, at least, first generation biofuels will continue to play a considerable role in the biofuels field as a whole. And biogas, as a fuel production option that only deals with already existing animal raising anyways, will likely be expanded on all farms using animal agriculture. Italy saw a 10-fold increase in livestock farms using biogas alternatives, from 56 farms to 521 farms, in a period between 2001 and 2011, with more contemporary years seeing a greater and greater jump. Developed and developing nations that have a reliance on meat production may see a turn to biogas as an energy source to complement this.[16]

The biofuel field, even though its beginning dates to several decades back, is still seen as an emerging energy option in the world today. It has yet to gain the heights that many recognize it eventually will. But first generation biofuels have certainly left their mark on energy dependency in the world, particularly as a replacement for oil and diesel as a transportation fuel. The future for these fuels is uncertain.

They may continue to grow and overtake other industries as they do so or they may end up being outclassed by the later generations of energy production in their very own field. At this point in time, there are too many possibilities to tell and disparate regions of the world may make their own choices that change this outcome. Even so, it is clear that first generation biofuels will continue to be used for now for several years to come.

Second Generation Biofuels

The next section covers what have come to be known as second generation biofuels. In a broad sense, this label covers biofuels produced from non-edible plant components[17]. From a sustainability perspective, this category of biofuel removes the tradeoff between direct food supply and fuel production that is faced by first generation biofuel production. However, other sustainability challenges are involved in their production. We will look at two prominent sources of second generation biofuels, and discuss their application, and the implications on global energy sustainability.

Lignocellulosic Ethanol

There are four general steps to obtaining ethanol from lignocellulosic feedstocks[18]: First, is breakdown of the lignin-cellulose matrix; second, the enzymatic breakdown of cellulose to form glucose; next, the glucose is converted to ethanol; and lastly, the mixture is processed/refined into a form of usable fuel[18].

What makes second generation biofuels a more sustainable option than first generation is the type of feedstock used. Rather than using an edible product, such as maize grain, we may use biomass products that are not a component of the food supply. Feedstock examples include straw and stover left behind after grain harvest, as well as woody by-products of the lumber industry[19]. This may also include ‘energy crops’; species that are planted for the harvest of their biomass, but which are not sources of food, thus will not increase global food demand. These may be perennial species such as some trees[20].

The use of energy crops may pose a problem in terms of sustainability. If arable land is planted with these species, then it will have the same effect on the global food economy as traditional bio-ethanol. As previously stated, leftovers and by-products are viable feedstock sources, but specific crops will likely be needed for these second generation biofuels to compete with fossil fuels and be produced at a scale that is economically viable[20]. The solution is to farm energy crops on land which is not productive for typical food crops.

Lignocellulosic crops show promise in increasing our world’s sustainable energy on both the environmental level as well as with food security. The question is can we implement the technology in an economically viable way[20]. Discovering ways to use existing infrastructure in the production chain, as well as finding value incentives for landowners to produce energy crops will help in making lignocellulosic ethanol a usable option for creating sustainable energy.

Algal Derived Biofuel

Another approach to producing fuel from non-edible plant sources is the use of algae. Algal cells are capable of producing biomass that contains high levels of sugars and lipids[21][22][23][26], which may be used as energy carriers for biofuel production[22][23].

Algae provide solutions to some of the sustainability challenges we face, yet they are not without their drawbacks. For example, compared to lignocellulosic sources, algal derived biofuel can produce ten to one-hundred times the amount of energy, yet it is more expensive[24]. Perhaps this trade-off is inherent due to the ability to harvest algae multiple times a year, as compared to the few, if not single, annual harvests we expect from typical cropping systems.

A key benefit of algal feedstock is the ability to utilize marginal land. Even deserts are able to produce algal growth, if the production infrastructure is built[22][23][25]. In addition, freshwater is not necessarily required, as seawater may be utilized by some species[26]. The ability to use marginal land and seawater are key to food supply sustainability, as neither of these resources will cause resource competition with traditional agriculture.

Limitations do exist in algal biofuel production. The efficiency of algal feedstock cultivation has been the target of much scrutiny[23][26][27][28]. Though there are several set-ups that can be used to grow algae, from raceway ponds to glass bioreactors, all need an external source of energy to be operational[23][27][28]. Targeted improvements to various process checkpoints are needed to make algal biodiesel a viable source of sustainable energy.

For example, using a harvesting system that uses sedimentation allows gravity to be a source of energy, thus increases the efficiency and the cost of the system as a whole[27]. The trade-off here is a lower harvest concentration, or in other words, a less efficient cultivation. Nonetheless, the use of lipids from algal extraction over soy/other oleoginous crops provides added sustainability to the food economy, if not to the fuel economy. Further advances in production and extraction technologies will allow algal biofuel to play a sustainable role in the global energy marketplace.


The growing human population will surely lead to not only an increased demand for energy, but for food as well. We face a great challenge in satiating the energy demand, without encroaching on resources needed for food production. Ultimately, renewable sources of fuel will need to be utilized if we are to have a 100% sustainable pool of energy.

Fossil fuels cannot be considered a sustainable option. They are a finite resource, not to mention environmentally deleterious due to CO2 emissions contribution to climate effects. Wind, solar and nuclear sources provide optimism that truly renewable, sustainable energy sources exist. Although they are not presently capable of relieving dependence on fossil fuels, we expect they will reduce total consumption as their use is broadened in coming years. However, traditional renewables cannot fill the need for liquid fuel, such as that used for transportation. This is where renewable biofuel, produced from crops, is important.

The sustainability issue facing bioethanol production is related to the food supply. Increases in global demand for food crops will lead to higher prices, raising ethical questions of how we should use the crops we grow. Innovations in the development of biofuels may provide answers. The second generation of biofuels are not made from edible plant products, so this makes them much more sustainable than corn ethanol and soy biodiesel, assuming they can be produced at a proper scale.

There is still a great amount of research needed, across the fields of engineering, chemistry and biology, in order for us to move to the theoretical maximum of 100% sustainable energy.


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Photo CCs: My Energetical from Wikimedia Commons

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