# The Environmental Stake of Bitcoin Mining: Present and Future Challenges
## 1 Introduction  
### Climate Change and Cryptocurrencies  
Climate change is one of the biggest concerns of the modern era, due to the proven impacts on human health [1; 2; 3] and ecosystems [4; 5; 6]. An increasing awareness of the influence of human activities on climate change has captured the attention of both politics and society [7] and pushed the research towards reaching a net-zero greenhouse gas (GHG) emission goal [8; 9] by taking actions to boost the implementation of sustainable processes and technologies [10; 11; 12; 13]. A worldwide picture of the cumulative CO\({}_{2}\) emissions from 1750 to 2022 is reported in Figure 1, representing the amount already emitted into the atmosphere. Although theglobal CO2 emissions are \"only\" slightly increased in 2023 compared to 2022 [14], the concentration of CO2 in the atmosphere reached 427 ppm (June 2024) [15], stressing the need for proper and timely mitigation actions. To tackle the issue of present and future emissions, beyond the transition to low-carbon technologies and universal efforts towards greener industrial systems, it is essential to identify the major sources of GHG emissions. Historically, transportation, building, and industry have covered most of the GHG emissions, mainly due to energy requirements. However, today, new sectors are growing, the impact of which remains little investigated, if at all. Of relevance here, in a world increasingly oriented towards digitalization, cryptocurrencies have been widely discussed in recent years, because of their potential implications on the monetary system [17; 18; 19; 20; 21], by removing the middlemen and establishing trust between unknown parties [22]. Cryptocurrencies have also been placed under investigation due to several environmental implications [23]. Here, the Bitcoin mining activity is particularly noteworthy, reporting that in 2021, the mining network globally consumed 89.00 TWh of electricity [24], which represents about 0.3% of the total electricity consumed worldwide [25]. [PERSON] and colleagues (2023) recognized the significance of the impactful energy consumption and consequent carbon intensity of the cryptocurrency system. They also reported the existence of several implications that may affect both energy consumption and emission trends, such as, for instance, the price of Bitcoin [26], whose relationship with the total energy consumption is suggested to be \"chaotic\" and \"nonlinear\" [27]. The close link between CO2 emissions relative to the use of Bitcoin was also confirmed by [PERSON] and [PERSON] [28] by means of a Bayesian analysis and quantile cointegrated vector autoregression investigation, which corroborates a Bitcoin use/carbon emissions \"causal effect\" existing between them. In particular, the contribution of Bitcoin mining to the total global carbon emissions in 2016 was estimated to be around 0.19% [29], a value which is highly dependent on different factors, especially the electricity mix employed. Figure 1: Cumulative CO2 emissions from 1750 until 2022 [16]. In recent years, researchers have attempted to assess the environmental impact of cryptocurrencies [22; 23; 30; 31; 32; 33]. However, to the best of our knowledge, there is a lack of adequate discussion on how this market fits into the pathway toward carbon neutrality predicted for the coming decades. In fact, [PERSON] et al. (2019) [22] and [PERSON] et al. (2023) [23] presented a comprehensive model that included the evaluation of spatial variability by detailing all the countries involved, but they did not project GHG emissions for the coming years. [PERSON] et al. [32] accounted for the positive implications of mining alongside its effects on climate change. However, in this study as well, the impacts were neither assessed based on future projections nor was spatial variability considered. [PERSON] et al.