Bitcoin Mining is in short the hash-rate race between power-hungry computers. These machines require a lot of electric power to continue solving/computing complex mathematical puzzles. These cryptographic puzzles are created using memory intensive algorithm called the Proof-of-Work (PoW).

Miners validate transactions and add the next block on blockchain, thus keeping the system secure and running.

Due to increased competition, the difficulty of mining has increased to such an extent that now you require specialized hardware to achieve enough hash rate to at least participate in the system.

In 2009, 100 bitcoins could easily be mined within a day using CPU cycles of a simple home PC, but then as mining difficulty increased, miners moved to Graphics Processing Units called GPUs or Graphics Cards (used often to created gaming rigs) having a hash rate as high as 30MH/s and costing over $500 - $1,000 with power 200W.

GPUs are manufactured largely by companies like NVIDIA and AMD.

Then miners started developing even more specialized hardware called Application Specific Integrated Circuits (ASICs) having a hash rate over 10 TH/s and costing over $4,000 with power consumption over 1,400W (more consumption than a 1 tonne Split-Air-Conditioner).

Sounds cool? Lets now see true picture behind how noisy and environmentally poisonous can these machines get.

A single ASIC eats up as much power as 7 GPUs combined. ASICs give off serious heat and require multiple cooling fans that make a lot of noise. Just hear it yourself to see how noisy is the latest Bitcoin Antminer S9:

Miners increase the hash rate a hundred times by assembling several GPUs or ASICs together to create giant mining rigs (also called as a mining farm) as shown in the image below.

GPU mining rig

ASIC Mining rig

From environmental standpoint, a single BTC transaction pumps in about 500Kg of poisonous carbon footprint in air which equals to and wastes about 1MWh of precious electric power to create nothing out of something! Electricity consumed by a single BTC transaction can power over 30 luxury U.S households for a day.

The entire bitcoin network consumes over 60TWh electricity annually at present (14th April, 2018) which equals to more than four times the total electricity generated by one of the world’s largest hydroelectric power stations Tarbela Dam (13 TWh) in a year.

According to environmentalists increased CO2 in atmosphere due to unnecessary human activities of burning fossil fuels (like burning coal in case of Bitcoin mining) causes green house effect that ultimately give rise to global temperature rise. Thus resulting in glaciers melting, ocean level rising leading to hurricanes and floods. CO2 also causes acidic rain that further kills and destroys the marine life. Increased CO2 in atmosphere also causes over 20,000 premature human deaths annually. The list goes on..

“While it has long been known that carbon dioxide emissions contribute to climate change, the new study details how for each increase of one degree Celsius caused by carbon dioxide, the resulting air pollution would lead annually to about a thousand additional deaths and many more cases of respiratory illness and asthma in the United States, according to the paper by Mark Jacobson, a professor of civil and environmental engineering at Stanford. Worldwide, upward of 20,000 air-pollution-related deaths per year per degree Celsius may be due to this greenhouse gas.

For this study, Jacobson used the computer model to determine the amounts of ozone and airborne particles that result from temperature increases, caused by increases in carbon dioxide emissions. Ozone causes and worsens respiratory and cardiovascular illnesses, emphysema and asthma, and many published studies have associated increased ozone with higher mortality. "[Ozone] is a very corrosive gas, it erodes rubber and statues," Jacobson said. "It cracks tires. So you can imagine what it does to your lungs in high enough concentrations." Particles are responsible for cardiovascular and respiratory illness and asthma.”

— Science Daily

Even Hal Finney (closest friend of Nick Szabo (Nakamoto) who helped him fix Bitcoin bugs) admitted CO₂ emissions caused by Bitcoin mining and it got him so worried at such an early stage that he immediately tweeted his concerns in 2009 after mining bitcoin for just over two weeks:

Some crypto-enthusiasts may argue that this global warming thing is all myth and created by the elites to impose carbon-tax upon us. There is so much controversial stuff against climate change that for sometime even I started believing it. So I wont force anyone to believe on global warming thing without doing a thorough research.

• To create an inefficient trustless digital payment system that is over 9,000 times slower at maximum capacity compared to traditional payment processing systems like VISA.
• To create a new bogus fiat currency out of thin air that does not qualify any of the fundamental properties of money.
• To create an unregulated, borderless, anonymous and irreversible digital currency that has become the favorite currency of cyber-criminals, drug lords, child pornographers, darknet marketplaces, money launderers and tax evaders.

For me its the most long lasting deadliest poison ever created by mankind!