## 10 Conclusions  
Terrestrial Storage of Biomass (TSB) is a Negative Emission Technology (NET) for removing CO\({}_{\text{2}}\) \"already\" in the air. In TSB, nature does the work of CO\({}_{\text{2}}\) removal by growing biomass via photosynthesis. The key to permanent carbon sequestration is to bury the biomass in underground pits designed to minimize degradation. The chemistry of biomass formation and decomposition was reviewed to provide guidance on pit design to minimize the decomposition. These include the following: (1) surrounding the biomass with clay of a low oxygen and water permeability to starve the biomass of those elements which are needed for decomposition; (2) segregating the thin topsoil where bacteria, worms, and other organisms reside that provide the enzyme catalysts required for degradation; (3) using the excess clay that is available due to the volume occupied by the buried biomass \begin{table}
\begin{tabular}{c c c} \hline \hline
**CDR Method** & \multicolumn{2}{c}{**Weighted Average Price (S)**} \\  & **2022** & **2023** \\ \hline Afforestation/reforestation & 12 & 16 \\ Bioenergy with carbon capture and storage (BECCS) & No data & 300 \\ Biochar & 212 & 131 \\ Biomass burial & 92 & 111 \\ Bio-oil storage & 600 & 505 \\ Direct air carbon capture and storage (DAC) & 1261 & 715 \\ Direct ocean carbon capture and storage & 984 & 1402 \\ Enhanced rock weathering & 434 & 371 \\ Forest management & 15 & 12 \\ Mineral products & 471 & No data \\ Ocean alkalinity enhancement & No data & 1608 \\ \hline \hline \end{tabular} Data Source: [PERSON] et al. [53].  
\end{table} 
Table 1: Cost Comparison of Carbon Dioxide Removal Technologies. to form a peaked roof over the pits, which sheds rainwater and keeps any neighboring groundwater from infiltrating the pits. With a proper pit design, less than 8.8% of the asymptotic decomposition, assumed in the recently released Puro.Earth methodology for TSB, should be achievable. While it is too early to tell the long-term carbon efficiency, insignificant degradation has been observed in projects where biomass has been buried for several years. TSB is shown to have advantages relative to other methods for the net reduction in atmospheric CO\({}_{2}\). These include other NETs such as DAC, biochar, and ocean pH manipulation via the addition of olivine. The biochar yield is an issue. It depends on the biomass source and the charring conditions, and, in particular, the temperature. The biochar yield may only be 20-40%, which means that the process generates 1-4 times as much byproducts as the primary product, for which there must be an economic and environmentally friendly home. This compares to the greater than 90% carbon efficiency of TSB. The chemistry of ocean pH manipulation was reviewed to show why MRV has been a challenge for this technique. TSB was also compared to bioethanol from corn to show the importance of setting proper system boundaries and educating policy makers of all the impacts of new technologies. Bioethanol fuel itself is claimed to be renewable. However, when proper system boundaries are drawn, bioethanol is shown to be both carbon and energy inefficient. When carbon efficiency is calculated based on the carbon in the entire corn plant, bioethanol fuel is shown to have a \"renewable\" carbon efficiency of only about 16%. Bioethanol also produces CO\({}_{2}\) in the fermentation process. Most existing bioethanol plants vent this CO\({}_{2}\) into the atmosphere. Capturing it and storing underground would provide a low-hanging fruit NET, but the NET carbon efficiency would only be about 8%. Pipelines to transport and store of this CO\({}_{2}\) have met public resistance by farmers and indigenous peoples (not in my backyard). Corn bioethanol is also energy inefficient. It takes about 18% of the heat of the combustion of the final bioethanol product to distill the ethanol from the fermentation mix and about 35% to run the entire process.