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21-27 

21 

 

 

 

Review 

Sustainable energy and digital currencies: 

challenges and future prospect 
Seyed Ehsan Hosseini1* , Hesam Kamyab2  

1Department of Mechanical Engineering, Arkansas Tech University, 1811 N Boulder Ave, Russellville, AR, 72801, USA 
2Malaysia-Japan International Institute of Technology Universiti Teknologi Malaysia, Jalan Sultan Yahya Petra, 54100 
Kuala Lumpur, Malaysia 

 
A R T I C L E   I N F O 
 

Article history: 
Received 02 March 2022  
Received in revised form 
01 April 2022 
Accepted 05 April 2022 
 
Keywords: 
Cryptocurrency, Digital mining, Sustainability, 
Electricity, Renewable energy 
 
*Corresponding author 
Email address: seyed.ehsan.hosseini@gmail.com 
 
DOI: 10.55670/fpll.futech.1.1.4 

A B S T R A C T 
 

Due to the impressive growth in digital coins trading, most cryptocurrencies' 
market cap has increased drastically. Therefore, more people are engaged in the 
mining process, causing a significant increase in electrical power consumption. 
To make cryptocurrency technology sustainable, using renewables such as 
photovoltaic solar power, wind energy, tidal power, geothermal power, 
hydroelectric power, fuel cell, and biomass has been implemented. Moreover, 
to decrease electrical power consumption in the cooling process of mining 
systems and computers, using phase change material (PCM) has been 
recommended. Since the cryptocurrency mining process is very competitive, 
only those miners will survive who employ the most competitive mining 
systems and benefit from the lowest electrical power costs. While the 
profitability of renewable electricity-based mining is lower than grid-based 
mining, the latter method compensates for better sustainability in 
cryptocurrency and lower environmental costs. This paper reviews the possible 
ways to make the cryptocurrency mining process clean and environmentally 
friendly. 
 

 
 

 
1. Introduction  

In 2009, the world’s first Blockchain was created by 
Satoshi Nakamoto by introducing Bitcoin (BTC) with the 
hope of developing an independent and decentralized 
monetary system. Blockchain is an exposed, distributed 
ledger that records transactions between parties in a 
verifiable and permanent manner [1]. Due to impressive 
growth in BTC trading, the BTC market cap is currently more 
than $ 630 billion, and many discussions have been made on 
BTC and its pros and cons [2]. Transparency and anonymity, 
as well as no central authority, are the essential advantages 
[3], while security, scalability [4], double spending [5], 
sustainability of the market structure, and energy 
consumption are the most disadvantages of the 
cryptocurrency [6]. Since cryptocurrency does not exist in a 
physical form, it is a peer-to-peer payment system. 
Consumers have an extraordinary ability to pull cash out of 
cryptocurrency ATMs, buy goods and services with 
cryptocurrency at online retailers, and use cryptocurrency 
at some brick-and-mortar stores. The currency is tradeable 
on various exchanges, and initial coin offerings (ICOs) draw 
interest across the investment spectrum. There is no central 

exclusive manager of the ledger in cryptocurrency 
technology, with significant responsibility for updates, 
storage, and verification of transactions. In contrast, all 
participants of the cryptocurrency network hold a copy of 
the ledger, and all transactions are transparent and visible 
to all users. Cryptocurrencies have passed a long journey 
from their obscure origins. While cryptocurrencies were 
disdained as a gadget for speculators and criminals by the 
mainstream financial world, significant progress has been 
made in the industry, and cryptocurrency has proven itself a 
legitimate and world-changing financial tool [7]. The BTC 
[8], Ethereum (ETH) [9], Binance (BNB) [10] have 
experienced massive growth in users and price; however, 
there are still doubts about the outcomes of wide 
cryptocurrency adoption. Particularly, huge concerns about 
electrical power consumption in the cryptocurrency mining 
process have raised skeptics among environmentalists due 
to realizing carbon emissions in the power generation 
process. It is claimed that just BTC mining is responsible for 
0.5 percent of global electricity consumption [11]. Marcel 
Thum [12] believes that cryptocurrency mining is a waste of 
resources. It is claimed the BTC itself might consume as 

 

 

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S.E. Hosseini, H. Kamyab/Future Technology                                                                               May 2022| Volume 01 | Issue 01 | Pages 21-27 

22 

 

much energy as all global data centers [13]. Calculations 
indicate that one dollar’s worth of BTC requires seventeen 
megajoules of energy, which is more than double the amount 
of the required energy to extract one dollar’s worth of 
copper, gold, and platinum [14]. Mora et al. [15] pointed out 
that the cryptocurrency mining process actively contributes 
to global warming, where BTC mining itself could push 
global warming above 2oC. Tomlinson et al. [16] stipulated 
that current Blockchain projects do not contribute to a 
sustainable future due to technical issues and a conceptual 
framing that favors the status quo rather than 
transformative alter. Carbon emission modeling of the BTC 
mining process in China demonstrated that the energy 
consumption of this process is expected to peak in 2024 at 
296.59 Twh and emit 130.50 million metric tons of carbon 
emission [17].  

Because of the environmental effects of fossil fuels used 
in the BTC mining process, the Tesla company suspended 
vehicle purchases using BTC [18]. In contrast, 
cryptocurrency advocates have claimed that BTC and other 
cryptocurrencies are the crucial part of deploying a carbon-
neutral grid. They believe that cryptocurrency miners are 
flexible and unique energy buyers with a fixed location 
requiring only an internet connection and easily 
interruptible load [19]. Recently, using Blockchain in the 
development of smart cities has been considered by the 
researchers [20].  It is believed that cryptocurrency has 
considerable advantages over centralized currencies 
because it does not rely on any trusted intermediary or 
single point of failure [21]. Double spending is crucial in 
cryptocurrency because the tokens can be easily copied and 
double-spent without an appropriate security mechanism. 
This issue could devaluate cryptocurrency and threat 
customers' trust in the currency [5]. However, this problem 
has been solved using only upspent outputs of the previous 
transaction as an input of a subsequent transaction. 
Meanwhile, the order of transactions is specifying by their 
sequential order in the Blockchain [3]. This process 
effectively timestamps transactions by hashing them into an 
ongoing hash-based Proof of Work (POW) chain. Therefore, 
the POW not only discourages spam but also is considered 
an easy way to check the proof of computational effort [22]. 
However, this solution comes at high computational and 
energic costs and has become one of the crucial criticisms of 
cryptocurrency in recent years [23]. 

2. Cryptocurrency mining process 

Same as gold, Bitcoin, the most widely-known crypto 

network, cannot simply be created arbitrarily, and it 

requires energy to extract [24]. Bitcoin is created through a 

computational process known as mining, and it has not been 

issued, endorsed, or regulated by any central bank. Since 

cryptocurrency has no bank to regulate it, the mining 

systems are employed to verify transactions by solving 

cryptographic problems, similar to complex math problems 

[25]. While cryptocurrency appears to be a well-established 

trading method, there are still so many energy and 

environmental issues. While gold is extracted from the earth, 

crypto must be mined via a computer-generated process. 

Cryptocurrency mining has become an attractive business 

since it offers a robust financial incentive. For mining each 

block, the miner receives a block reward and the transaction 

fees of the transactions in the block. However, 

cryptocurrency mining is a costly and challenging activity. 

Initially, general computers were employed to mine 

cryptocurrency, but they switched to advanced hardware, 

offering higher performance and lower energy costs. Large-

scale mining companies must pay to build mining farms 

capable of vast amounts of processing power, and then the 

mining process itself requires large quantities of electricity. 

With mining operations for Bitcoin and other 

cryptocurrencies taking up the same share of electricity as 

many countries, miners must be careful not to spend more 

than they make.  

Several factors should be considered to choose the most 

appropriate mining hardware and software. The first 

criteria is the mining equipment price (measured per GHs), 

which is influenced by the hash rate and the lead time. The 

energy cost is another factor that is considered by 

cryptocurrency miners. Efficient equipment with the lowest 

electrical power consumption and minimum heat emission 

is preferred. The difficulty (an arbitrary dimensionless value 

that measures how difficult finding a hash below a given 

target is) is the third factor [26]. Over the past few years, the 

required electricity for the energy-hungry cryptocurrency 

mining process has become a controversial topic [27]. The 

electrical energy required for a single Bitcoin transaction is 

1775 kWh, equivalent to the power consumption of an 

average U.S. household over 60.84 days. The related carbon 

footprint is about 843.12 kgCO2, equal to the carbon 

footprint of 1,868,656 VISA transactions or 140,521 hours of 

watching YouTube. In July 2021, the energy consumption of 

the Bitcoin mining process was reported 135.12 TWh, 

comparable to the power consumption of Sweden, and the 

released CO2 emission was estimated 64.18 Mt, comparable 

to the carbon footprint of Serbia & Montenegro [28]. Figure 

1 illustrates Bitcoin's energy consumption since Jan 2017 

[29].  
 

 

 
It should be noted that Bitcoin energy consumption is 

just related to the mining process, and the energy 
consumption of cooling systems, third parties (wallets, 
exchanges, and payment solution providers), and Bitcoin 
ATMs were not considered. As a reference of comparison, the 
annual energy required for the entire banking sector is 
estimated 650 TWh, including data centers that process 
transactions, branches, and ATMs. Nevertheless, Alex de Vries 
[30] believes that the digital currency energy consumption is 
underestimated and proposed a market dynamic approach to 
evaluate the exact amounts of the required energy for BTC 
mining. Corber et al. [31] investigated the influences of BTC 
price volatility as well as the dynamics of cryptocurrency 

Figure 1. Bitcoin energy consumption [29] 

 



S.E. Hosseini, H. Kamyab/Future Technology                                                                               May 2022| Volume 01 | Issue 01 | Pages 21-27 

23 

 

mining characteristics on the utility companies and 
underlying energy markets. It is stipulated that BTC prices 
have a significant impact on the mining process and 
consequently its energy consumption [32]. While the BTC 
price rises, more people are engaged in the mining process, 
causing a significant increase in energy consumption [33].  

It should be noted that BTC is accounted for 2/3 of the 
total cryptocurrency energy consumption, and the mining of 
the other digital coins should be considered in energy and 
environmental studies [34]. To get rid of generated heat in the 
cryptocurrency mining process, a cooling system should be 
employed that burdens additional electrical power 
expenditure. Using phase change material (PCM) in 
cryptocurrency mining devices and computers, as well as 
mining warehouses, could be helpful to minimize the 
electrical power required for cooling systems in the mining 
process. The idea of using PCMs in electronic devices [35], 
refrigeration systems [36], solar power generation systems 
[37], and residential buildings [38] was developed by several 
researchers, and the benefits of the PCMs in terms of energy-
saving were highlighted; however, it has not been 
investigated in cryptocurrency mining process yet. 

3. Digital currencies mining and renewables 

It is claimed that the annual Bitcoin network energy uses 

as much as the country of Argentina, and the Ethereum 

network demand is as much electrical power as the entire 

nation of Qatar [39]. Approximately 65% of bitcoin mining 

systems are located in China, where most of the country’s 

energy demand is generated from coal [40]. About 48% of the 

worldwide mining capacity is situated in the Sichuan 

province in China, where electricity is cheap [41]. Coal and 

other non-renewable energy sources are currently the major 

electrical power sources throughout the world, both for 

cryptocurrency mining operations and other industries. 

However, burning fossil fuels is a significant contributor to 

global warming due to the carbon dioxide (CO2) emission. The 

Bitcoin mining process accounts for approximately 35.95 

million tons of annual CO2 emissions, the same amount as 

New Zealand [42].  

To make the mining process greener, implementing a 

carbon tax on the BTC miners was suggested. However, a 

carbon tax would make BTC mining less attractive and 

decrease the price of BTC [43]. Because of the environmental 

issues, large-scale miners have started to employ renewables 

in the rigs to mitigate mining costs and make the most 

significant profit possible. Based on Adjeleian et al. [44], the 

application of Blockchain could be helpful for the 

development of renewable energy and has the capability to 

reshape the sustainable energy market. Application of 

decentralized energy systems such as wind turbines, 

photovoltaic solar power generation, tidal power for clean 

power generation for mining systems has been developed in 

the research [45]. In solar-powered mining systems, once the 

solar panel itself is paid, the miners get rid of a hefty 

electricity bill, and the cost of mining becomes free, and 

consequently, the mining process becomes more profitable. 

Although utilization of solar energy has been noticed by the 

Governments in recent years, solar still accounts for 2.3% of 

the total energy demand in the United States. Considering 

wind power, hydropower and biomass, approximately 19.8% 

of the total U.S energy demand is generated by renewables 

[46]. The promising news is that according to the 

International Energy Agency (IEA), the cost per megawatt to 

build solar plants is recently dropped below fossil fuels 

worldwide for the first time [47]. Crypto Climate Accord [48] 

aims to achieve net-zero emissions from electrical power 

consumption associated with all of their respective crypto-

related operations by 2030. In June 2021, Blockstream 

mining company announced its collaboration with American-

based Square.Inc company for solar-powered BTC mining 

[49]. In this cooperation, five million dollars is invested in the 

facilities by Square.Inc and the 100% renewable energy-

based mining infrastructure is going to be completed by 

Blockstream. The wind-based electricity generation in the 

U.S. increased threefold in 2020 compared to 2011, reached 

to 118.3 gigawatts. 

The contribution of wind and hydropower to the U.S. 

electrical supply is 7.1% and 7%, respectively, where the 

most wind power is generated in Texas and the Midwest. 

Further development of wind and hydroelectric power could 

pave the road to deliver more transparent energy usage and 

sustainability metrics in the cryptocurrency. In June 2021, 

China Government increased its regulatory squeeze on 

cryptocurrencies to shut down up to 90% of the BTC mining 

capacity in the country [50]. The China central bank 

stipulated cryptocurrencies have disrupted the regular order 

of the economy and increased the risks of illegal cross-border 

transfers of assets and illegal activities such as money 

laundering. This decision made BTC's price and the whole 

cryptocurrency market fallen by 20% and 12%, respectively, 

due to uncertainty about the cryptocurrency future. 

Nevertheless, cryptocurrency mining won’t cease due to this 

crackdown, and the operators will relocate their mining 

systems elsewhere. Texas, USA, is one of the best candidates 

for large-scale mining systems that could benefit from the 

new restrictions in China due to its low-cost electrical power 

and the unique regulatory environment [51]. Due to 

electricity price volatility in Brazil, Bastian-Pinto et al. [52] 

suggested hedging electricity price risk by investing in the 

digital coin mining facility to generate new mined 

cryptocurrency. Recently, El Salvador Government 

announced this country is going to adopt BTC as legal tender 

and develop the geothermal electric companies to come up 

with a plan for volcano-powered BTC mining [53]. In 

southwest China, where the local electrical power demand is 

relatively low, a large amount of hydroelectrical power is 

generated [54]. However, the power export capacity of this 

region is limited due to the lack of high-quality grid 

infrastructure. Therefore, Yunnan and Sichuan provinces are 

suitable regions for industries with high-demand electrical 

power, and mining cryptocurrency in these provinces could 

be a clean and environmentally friendly process. The only 

issue here is seasonal variability in hydroelectric power due 

to the variation in water availability through 

droughts/floods/rain. For instance, in Sichuan province, the 

average electrical power generation in the wet seasons is 

three times that of the dry season. To balance these 

hydroelectrical power fluctuations, other types of electricity 

generation should be employed, and coal-based power 

generation is the most available candidate. Consequently, the 

cryptocurrency mining process in this region is not 

technically 100% green. On the other hand, the digiconomist’s 

results prove that the development of cryptocurrency could 



S.E. Hosseini, H. Kamyab/Future Technology                                                                               May 2022| Volume 01 | Issue 01 | Pages 21-27 

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lead to huge environmental issues. De Vries [55] believes that 

these environmental dilemmas will not be solved by 

renewable and sustainable energy and suggested changing 

the POW algorithm with “Proof of Stake” (POS) as the best 

solution. The POS protocol was proposed by ETH, the world’s 

second-largest digital coin behind BTC. This protocol was 

developed to address environmental concerns about the POW 

system by omitting competition between miners. Without the 

competition, there is no computing power arms race for 

miners to participate in [56]. The next generation of 

cryptocurrency needs to focus more on the problems related 

to scalability, interoperability, and sustainability on crypto 

platforms [57]. Imran [58] pointed out that it is not correct to 

compare Blockchain mining energy consumption with VISA’s 

energy utilization per transaction because, while VISA 

consumes this energy specifically for the transaction, 

Bitcoin’s electricity consumption is dedicated to protecting all 

transactions dating back to 2010. He concluded that in the 

long-term mining process, renewable energy would become 

profitable. It is believed that the marginal cost of renewable 

electricity generation continues to decrease relative to the 

marginal costs of fossil fuel-based electricity generation, 

which can enhance the miners’ incentive to shift towards 

sustainable energy [59]. Turby [23] investigated the 

possibility of sustainable development of cryptocurrency 

without damaging this sector. The author discussed several 

regulatory and fiscal approaches to restrict the digital 

currency’s energy utilization and its ecological implications. 

It was indicated that since cryptocurrency’s success is due to 

miners and incentivizing investors to earn profits, using these 

incentives to change the energy consumption pattern by fiscal 

means can help the digital currency to obtain environmental 

targets.  The price of cryptocurrency is not only decided by 

the traders, but the price is also related to the electrical power 

price. The cryptocurrency mining competition has led to the 

deployment of more energy-efficient hardware to be 

financially viable [60]. The energy demand of the digital coins 

mining process is typically supplied by the electrical power 

from the grid. This method is best suited for use in countries 

with low electrical power prices, such as China, Russia, and 

Iran. However, the necessity of exploiting power generating 

systems with better performance than fossil fuel-based 

power generation systems is felt. 

  

For instance, investigation about using electrical power 

generated by solid oxide fuel cell (SOFC) in the digital coins 

mining process has been investigated and claimed that SOFC 

has higher electrical efficiency [61]. The SOFC electrical 

power generation is in the early stage of commercialization; 

therefore, the initial cost of the SOFC-based mining process 

would likely be high. Nevertheless, using biogas instead of 

natural gas in the SOFC process would be cheaper and more 

affordable [62]. It is claimed that using biogas in SOFC is more 

economical than its exploitation in micro-gas turbines and 

internal combustion engines (ICE) [63]. Figure 2 

demonstrates the concept diagram of the cryptocurrency 

mining process using a biogas-based SOFC system for 

electrical power generation [61]. Electrical power generation 

by natural gas and biogas in the SOFC systems for the 

cryptocurrency mining process is affordable when the BTC 

price is higher than $20,000. The natural gas-based 

cryptocurrency mining process is better suited for the 

countries such as U.S. or Canada, where the electrical power 

price is high, but natural gas is cheap. The biogas-based 

cryptocurrency mining process is better suited for European 

countries and Japan, where the prices of natural gas and 

electrical power are high. Moreover, in Southeast Asian 

countries such as Indonesia, Malaysia, and Thailand, where a 

huge amount of biogas is available due to palm oil mill effluent 

(POME), this mining strategy could be affordable [64]. 

Indonesia and Malaysia have over 1,000 palm oil mills that 

produce almost 90% of the global palm oil supply that 

generates around 126 million tonnes of POME yearly [65]. 

Aside from POME, organic waste and animal manure can also 

act as feedstock for biogas production. The annual electricity 

potential of biogas from cattle, pig, and poultry waste in 

Indonesia and Malaysia is about 80 TWh and 10 TWh, 

respectively, which is more than sufficient to replace diesel 

fuel in the power sector [66]. The operating cost and the 

capital cost are two crucial factors considered by the miners. 

The deciding factor for the miners is operating costs in the 

countries where natural gas and electricity are expensive, 

while capital cost is the deciding factor in the countries with 

low natural gas and electricity prices. 

 

 

 

 

 

 

 

 

 

 

 

 

 

4. Conclusion Figure 2. Using SOFC to generate electrical power for cryptocurrency mining 



S.E. Hosseini, H. Kamyab/Future Technology                                                                               May 2022| Volume 01 | Issue 01 | Pages 21-27 

25 

 

Cryptocurrency technology is still in its infancy, and its 
future lies within speculation and hyperbole. Since the digital 
mining process is an energy-hungry technology, using energy 
consumption reduction methods such as phase change 
material in mining warehouses, mining systems, and 
computers is recommended to make it sustainable. 
Depending on the region, the required electrical power for the 
cryptocurrency mining process could be supplied by the grid 
(generated from fossil fuels) or renewables. Compared to 
fossil fuel-based electricity, electrical power generation by 
renewables have lower profitability at lower cryptocurrency 
prices due to the higher capital expenditure. However, 
considering operation expenditure, environmental costs, and 
sustainability issues for fossil fuel-based electricity, it can be 
concluded that renewables are beneficial options for the 
cryptocurrency mining process. The cryptocurrency mining 
process by renewables is affordable for miners when the 
cryptocurrency price is high. Ultimately, there is a need for 
digital coins to control the outrageous electrical power 
consumption to become green and sustainable.  

Ethical issue 
Authors are aware of and comply with best practices in 

publication ethics, specifically with regard to authorship 
(avoidance of guest authorship), dual submission, 
manipulation of figures, competing interests, and compliance 
with policies on research ethics. Authors adhere to 
publication requirements that the submitted work is original 
and has not been published elsewhere. 

Data availability statement 
Data sharing is not applicable to this article as no datasets 

were generated or analyzed during the current study. 

Conflict of interest 

The authors declare no potential conflict of interest. 

Authors’ contribution 

All authors of this study have a complete contribution to 

manuscript writing. 

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Abbreviations  
BNB: Binance 

BTC: Bitcoin 

ETH: Ethereum  

ICE: Internal combustion engines 

ICOs: Initial coin offerings 

IEA: International Energy Agency 

PCM: Phase change material  

POME: Palm oil mill effluent 

POS: Proof of Stake 

POW: Proof of Work 

SOFC: Solid oxide fuel cell 

 

 

 

 

 
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