Graphyte, an American climate tech company founded in 2023, has developed a Biomass Carbon Removal and Storage (BiCRS) method to remove atmospheric CO₂. Their solution enables biomass to be stored in dry conditions for over 1,000 years without significant CO₂ and methane emissions. The company aims to achieve production costs under $100 per ton of CO₂ sequestered.
(This article contains 3 diagrams and 1302 words.)
Challenges: CO₂ removal
Since the early 1900s, carbon dioxide (CO₂) levels in the atmosphere have increased by 50% due to human activities. When fossil fuels (such as coal, oil, and natural gas) are burned for energy production, transportation, and industrial processes, CO₂ is released into the atmosphere. This excess CO₂ acts as a greenhouse gas, trapping heat and causing the air and ocean temperatures to rise. CO₂ emissions play a crucial role in driving climate change.
This warming effect has caused the global average temperature to rise by about 1.1 ºC since the pre-industrial period. This has led to rising in the frequency and intensity of extreme weather events, melting of polar ice caps and glaciers and rising sea levels, shifts in species ranges and increased risk of species extinction, agriculture and food security, and ocean acidification.
To mitigate these impacts, the Paris Agreement aims to limit global warming to well below 2 ºC above pre-industrial levels. The Intergovernmental Panel on Climate Change (IPCC) estimates that a “carbon budget” of about 500 GtCO₂, which corresponds to about ten years at current emission rates, provides a 66% chance of limiting global warming to 1.5 ºC. This requires carbon negative options which remove CO₂ from the atmosphere.
Graphyte Technology
One approach to achieving carbon negativity is Biomass Carbon Removal and Storage (BiCRS), which involves capturing and storing organic carbon converted from atmospheric CO₂ by plants and trees through photosynthesis.
BiCRS differs from Direct Air Capture (DAC), a technology that uses machines to directly capture CO₂ from the air and sequester it underground. While DAC is currently expensive, many companies are demonstrating its feasibility. BiCRS leverages plants to remove CO₂ from the atmosphere through photosynthesis. The process involves growing and harvesting woody biomass, then burying it in trenches under soil, effectively sequestering CO₂ in biolandfills. This method offers a cost-effective approach to removing significant amounts of CO₂ from the atmosphere.
Storing harvested biomass underground in wet anaerobic environments has been found to be a net greenhouse gas emitter rather than a carbon-negative solution. In these conditions, groundwater promotes microbial growth that degrades the biomass, generating CO₂ and methane (CH₄). The IPCC estimates that 50% of wood degrades in wet landfill environments, releasing significant amounts of CH₄, which is 25 times more potent as a greenhouse gas than CO₂. Consequently, simple underground storage of biomass in wet environments is not considered a viable solution to global warming.
Graphyte is developing dry biolandfill methods for safely, verifiably, efficiently, and economically storing carbon in biomass without significant degradation for centuries to millennia. These dry biolandfills can offset 1.3 to 1.8 metric tons of CO₂ per metric ton of dry biomass sequestered. Graphyte's solutions are easily scalable, with the potential to remove billions of tons of carbon, helping to offset CO₂ emissions and mitigate climate change. Compared to other carbon removal approaches like DAC, Graphyte's biolandfill solutions are relatively inexpensive, estimated at under $100 per ton of CO₂ sequestered.
How Graphite uses carbon casting to store biomass
The company has developed a method called Carbon Casting, as illustrated in the diagram below.
The Carbon Casting method involves the following steps:
- Collecting biomass, including timber and crop residues;
- Crushing, drying, and sterilizing the biomass to eliminate microbial activity;
- Compressing biomass into dense carbon blocks to improve mechanical stability, minimize water-holding volumes, limit water vapor mass transfer, reduce degradation rates, and enhance economics;
- Wrapping carbon blocks with polymer barriers to prevent decomposition; and
- Storing the encapsulated carbon blocks and monitoring biomass decomposition.
Compared to DAC methods that use 8-12 GJ/ton CO₂e, Graphyte’s method uses a total energy of about 0.8 GJ/ton CO₂e.
How Graphite uses dry tomb to store biomass
Graphyte has developed an alternative method using dry tomb biolandfills to store carbon blocks, as shown in the diagram. This approach eliminates the need to encapsulate each carbon block with a polymer barrier.