## 2 What Is Terrestrial Storage of Biomass (TSB)?
### Bioethanol from Corn  
The preferred biomass source for bioethanol in the US is corn. Corn obtains its carbon from CO\({}_{2}\) in the atmosphere via photosynthesis. When bioethanol is burned, its carbon goes back into the atmosphere as CO\({}_{2}\). Thus, the bioethanol product itself is not a NET. It is at best a \"renewable\". Corn starch fermentation produces CO\({}_{2}\) as a coproduct. That is why beer and champaign are bubbly. Most of the over 200 bioethanol plants in the US vent CO\({}_{2}\) into the atmosphere. The CO\({}_{2}\) coproduct is of a high purity. Thus, this CO\({}_{2}\) has been viewed as a low-hanging fruit that could contribute as a NET if CCS equipment and energy is added to purify and compress it, and a pipeline is added to transport it to a location for permanent underground storage. This brings up several issues relevant to all CO\({}_{2}\) mitigation technologies. The first is cost. Pipelines are required to send CO\({}_{2}\) to storage in underground aquifers or spent oil or gas wells. Archer Daniels Midland (ADM) has one pipeline in operation that sends CO\({}_{2}\) to an aquifer in downstate Illinois ([PERSON] and Lisi [33]). That pipeline has a design capacity of 1 million short tons per year and a cost of USD 208 million dollars, with 68% of the cost paid by the US Department of Energy. Two other pipelines have been proposed. A 1200-mile Valero/Black Rock pipeline with a capacity of 5 million tons/yr would span the US Midwest and also send CO\({}_{2}\) to an aquifer in downstate Illinois (Businesswire [34]). The cost has not been disclosed. Pipelines were proposed to send CO\({}_{2}\) gathered from a portion (about 20%, not 100%) of the bioethanol plants in the US Midwest for storage in underground aquifers in Illinois and North Dakota ([PERSON], [PERSON] [35]). The cost of these pipelines alone would be billions of dollars. Public resistance has emerged as another issue in achieving net zero. The proposed pipeline to North Dakota has just been shelved due to push back from farmers and indigenous peoples (\"not on my land\") (Associated Press [36]). The government needs to educate the public on what will be necessary to solve global warming and make the tough decisions to make it happen. When starting with the entire corn plant, bioethanol from corn has been shown to be very carbon and energy inefficient ([PERSON] and [PERSON] [6]). The societal effect and the effect on the US gasoline pool, as well as US gasoline and oil exports, has also been discussed. Thus, these will only be summarized here. In the corn bioethanol process, corn starch in the kernels is hydrolyzed and fermented. Hydrolysis breaks the starch polymer into its six carbon glucose sugar monomer units. Fermentation converts four of these carbons into ethanol and two of the carbons into CO\({}_{2}\). Right away, this reduces the renewable carbon efficiency, not counting the process inefficiencies, to 4/6 or 66%. However, if the process boundary starts with the entire corn plant, the kernels are only about 65-70 wt% starch, and the corn plant is only about 35 wt% corn kernels. Thus, the \"renewable\" corn efficiency of the bioethanol product is at most about 16%. If the CO\({}_{2}\) byproduct is captured and stored underground, it would contribute a NET efficiency of only about 8%. It takes a lot of energy to separate bioethanol from water in the fermentation broth. The energy to remove ethanol by distillation just up to the ethanol/water azeotrope is about 18% of the heat of the combustion of the bioethanol product ([PERSON] and [PERSON] [37]). The energy needed to run the rest of the plant increases the total energy demand to about 35% of the heat of combustion of the bioethanol product ([PERSON] et al. [18]). Corn bioethanol is also a good case for why it is also necessary to consider the environmental and societal impact of CO\({}_{2}\) mitigation technologies.