Biomass Energy for Bitcoin Mining: Evaluating its Feasibility and Environmental Impacts

Sustainable energy series, pt. 4

Introduction

Welcome to part 4 of our sustainable energy for bitcoin mining series! In this part, we examine the potential of biomass as a possible sustainable energy source for the mining of bitcoin and other blockchain related activities that require large amounts of energy. 

Biomass is often viewed as a sustainable source of energy because its main source, wood, can be regrown, in contrast to finite sources such as fossil fuels. However, there is also serious criticism on the label “sustainable” for biomass, because it can come with high emissions. In this article, we will examine both sides of this energy source, listing its advantages and disadvantages in order to explore if it is truly a sustainable source of energy for bitcoin mining. 

About biomass energy

What is biomass energy?

Biomass is one of the oldest sources of energy in the world, originating from the moment people first started burning wood for cooking and heating purposes. Today, wood is still the largest source of biomass for biomass energy production, as trees can be easily regrown. Other sources of biomass for energy production include agricultural residues, food crops, oil-rich algae, and organic components from household and industrial waste.

How is biomass turned into energy?

Generating energy from biomass usually happens through combustion or decomposition of the organic materials. There are multiple methods for doing this. We will briefly discuss the four most common ones. 

1. Direct combustion: The direct burning of biomass produces heat and/or steam, which can be used for heating purposes, generating electricity through steam turbines, or powering industrial processes. A common way of generating energy from wood biomass is by processing the harvested trees into wood pallets; little compressed chips of wood. These wood pallets are then used as the fuel for the burning process that generates energy.
2. Cogeneration: This process involves the simultaneous production of heat and electricity from biomass. Heat generated during electricity production is captured and utilized for space heating, water heating, or other industrial applications.
3. Anaerobic digestion: Microorganisms can process organic matter in an oxygen deprived environment, which results in the production of several components, including biogas. This biogas can then be used as fuel for generating heat or electricity. 
4. Biochemical conversion: Biomass can also be converted into liquid fuels, such as ethanol or biodiesel, through biochemical processes like fermentation or transesterification. These fuels can be used as alternatives to fossil fuels in transportation or other applications.

Wood as biomass source

A very common source for large biomass plants is wood. There are two common ways in which companies can obtain wood biomass for the production of energy. Wood can be grown in and harvested from forests or forest plantations specifically for the purpose of biomass production, or the wood biomass can originate from wood residues. Wood residues stem from waste and by-products of saw mills and wood processing facilities, and also from trees themselves: the branches, tops, and parts of the trunk that have compromised wood quality are usually not suitable for use in construction or other high end applications, and can thus be used as biomass.

Is biomass sustainable?

There has been a lot of discourse about the question whether the use of wood biomass for energy production is sustainable or not. In this section, we shed light on both sides of the argument, attempting to evaluate the extent to which biomass can be seen as a sustainable energy source for bitcoin mining.

Carbon neutral in theory: emissions equal uptake of CO2

The strongest argument in favor of biomass being a sustainable energy source is the fact that this type of energy is more or less carbon neutral in theory. Though the burning process releases carbon into the atmosphere, the trees that the wood comes from have previously taken this carbon out of the atmosphere during photosynthesis. Photosynthesis is the process by which plants convert sunlight, CO2, and water into sugars that they need for their growth. Plants release oxygen as a byproduct of photosynthesis. 

Because the CO2 that is emitted during the burning of biomass has previously been taken up from the air, no net CO2 is added to the atmosphere. This would make biomass a sustainable energy source, as opposed to the burning of fossil fuels, whose CO2 uptake from the atmosphere has taken place so long ago (hundreds of millions of years ago) that it is no longer compensating for our current atmospheric CO2-levels.

Renewable fuel source

Unlike fossil fuels, which took millions of years to form, many biomass sources can be grown over the course of months (e.g. grasses) to a few decades (e.g. trees). This makes biomass a renewable source of fuel, if managed in a sustainable manner of course. If more trees are being harvested for biomass than planted, the biomass reserves of wood will deplete too.

Utilization of biomass waste and residues

Another way in which biomass can be viewed as sustainable is through its potential to use waste and residuals from other processes, such as harvesting of trees, the processing of wood into construction materials, and agricultural waste. By using these by-products that would otherwise be discarded or left to decompose, biomass energy contributes to waste reduction and promotes sustainable waste management practices.

Criticism on the sustainability of biomass

Biomass is not truly that carbon neutral

Even though in theory it seems simple that the amount of CO2 emitted during the burning process is the same as the amount of CO2 taken up by the trees, the reality is much more complex – and a lot less positive in regard to the sustainability of biomass. Many studies have shown that biomass is not truly carbon neutral. Moreover, if biomass plants use the inappropriate type of tree species, biomass generated electricity can even become quite carbon intensive. 

Furthermore, the emissions from the use of biomass for energy are not limited to the burning process. The trees have to be harvested from the forest, transported to processing facilities where they are turned into wood pallets, and those pallets then have to be transported to the location where the actual burning takes place. All the machinery involved in the harvesting, processing and transportation processes also emits CO2, which is not accounted for in the uptake by the trees. 

Harvesting of trees affects CO2 reserves in the soil

In addition to the extra emissions from harvesting and transportation, forests soils also release CO2 when trees have been harvested. Soils are a very important carbon sink worldwide, so the leeching of CO2 from soils due to intensive harvesting practices is concerning. Furthermore, with the current global warming every bit of added CO2 is a step closer to the point where we can no longer significantly reduce climate change.

Temporal gap between emission and uptake

While woody biomass is derived from renewable sources, there can be a significant time lag between the carbon dioxide emissions from biomass combustion and the regrowth of biomass to reabsorb that carbon dioxide. This time lag creates a temporary increase in atmospheric carbon dioxide levels, leading to a “carbon debt.” It can take years or even decades for new biomass growth to offset the emissions from biomass combustion, depending on the growth rates of the biomass feedstocks. We do not have the luxury to wait a few more decades before excess CO2 from current biomass burning is taken up by new trees.

Intensive forestry can exhaust soils

The potentially negative impacts of biomass production are not restricted to emissions and global warming. Intensive forestry practices, such as the continuous regrowing of forest plantations for biomass production, can lead to soil exhaustion. Exhaustion of soils can come in the forms of depletion of nutrients, acidification, reduced water retention capacity, and increased susceptibility to erosion. Additionally, intensive forestry practices can disrupt soil structure and compaction, especially when heavy machinery is used, impairing root growth and limiting the ability of plants to access water and nutrients. It can easily take a hundred years before an area of soil has recovered from disturbance and compaction by heavy vehicles. 

The depletion and degradation of soils can be limited or prevented if forest owners implement sustainable harvesting practices. An example is the planning of logging roads through a forest patch. The heavy machinery should stay on these roads to limit soil disturbance of heavy machinery.

Low nature value of plantation forests

Though a plantation forest is still way better than an urban environment or parking lot, these type of forests generally have low natural values and are not that great for maintaining and increasing biodiversity. Plantation forests are often composed of even aged stands, with little to no vertical heterogeneity and little undergrowth. They lack the ecological diversity and natural dynamics found in natural forests. This uniformity limits habitat diversity and reduces the availability of varied food sources, nesting sites, and shelter for a wide range of species. Plantations often lack the complex structure, diverse understory vegetation, and natural succession processes found in native forests, which are essential for providing niches for different plant and animal species. 

There are many ways of managing plantation forests in a manner that better reflects a natural situation. Implementing these might increase the nature value of plantation forests and boost their role in biodiversity conservation. 

The potential of biomass as energy source for bitcoin mining

After the sustainability arguments and counterarguments, we will now evaluate whether biomass has potential as a sustainable energy source for the mining of bitcoin and other blockchain-related applications.

Advantages of biomass energy for bitcoin mining

Despite biomass not being that carbon neutral as is often theorized, if forestry and harvesting practices are done right and in a responsible manner, biomass is still a less harmful fuel source for electricity than fossil fuels. Biomass is also a fuel source that can replace coal relatively easily and quickly in power plants operating on coal. Generally, there are no expensive adaptations necessary to make the switch. 

Another advantage of biomass energy is that the amount of electricity generated can be steered to match demand. If more energy is needed, a power plant can burn more fuel to increase electricity levels, and the other way around, in contrast to sustainable energy sources such as wind, solar power, hydropower and geothermal energy.

Disadvantages of biomass energy for bitcoin mining

Aside from the fact that the sustainability of biomass is questionable, there are several disadvantages that might make biomass a less attractive source of energy for bitcoin mining purposes. 

Firstly, biomass energy conversion processes are often a lot less effective than other energy sources such as fossil fuels and renewable energy technologies (e.g. solar and wind energy). This means that a high quantity of biomass is required to generate electricity, which can make it costly and which increases the impact on the environment. 

Secondly, it is difficult to tailor biomass energy to the needs of an individual bitcoin mining plant. Unlike solar panels or (smaller) wind turbines, a biomass plant is not that easy to construct and comes with great expenses. 

Furthermore, scaling up biomass production for large-scale bitcoin mining operations would require significant amounts of land and water resources. This could lead to competition with other land uses, such as agriculture or conservation, and put additional pressure on water supplies and soil quality.

Conclusion

In this article, we evaluated the potential that biomass energy can have as a sustainable energy source for bitcoin mining. Though biomass is a step forward from fossil fuels in terms of sustainability, especially if grown, managed, and harvested in a responsible way, it is not as sustainable as some of the other energy sources we discussed in this series. It is also not the most effective way to generate energy, as it requires large amounts of fuel input. Therefore, for bitcoin mining, there are better alternatives when it comes to sustainable energy sources, such as wind and solar energy.

Sources / further reading

Ahamer, G. (2022). Why Biomass Fuels Are Principally Not Carbon Neutral. Energies, 15(24), 9619. https://doi.org/10.3390/en15249619

James, J., & Harrison, R. (2016). The effect of harvest on forest soil carbon: A meta-analysis. Forests, 7(12), 308. https://doi.org/10.3390/f7120308