# Carbon Footprint Assessment on the Viability of Utilizing Brewer's Spent Grain to Produce Biochar
## 3 Results  
### BSG-to-Biochar Process Inputs and Outputs  
Data collection was categorized by the industrial phases (1-5) outlined in Section 2.3.1. Data were collected from the laboratory-scale protocol utilized by the researcher and from publications on similar processes.  
Figure 2: System boundaries for a greenhouse gas assessment on making biochar from BSG.  
The major inputs for phase 1, soaking, were the electricity required for operation of a funnel hood and the electricity required for operation of a scale. The Lawrence Berkeley National laboratory calculator found that the closed fume hood would use 71.4 kWh/day, which is equivalent to 257 MJ [25]. The volume was adapted to consider the functional unit of 1 kg of unprocessed BSG. Specifically, 1 kg of BSG is equivalent to 220 cm\({}^{2}\), while the fume hood volume is 11,600 cm\({}^{2}\). Therefore, 1 kg of BSG requires 9.74 MJ for 48 h of soaking. Utilizing a scale with 10-watt power for 30 min required 0.018 MJ.  
Phase 2, drying, considered the electricity for heating as the major input, and water vapor dissipated off of the BSG as the major output. At the laboratory scale, 1 kg of unprocessed BSG was equivalent to 2.2 L; therefore per 1 kg of BSG, the oven utilized 0.915 MJ. At the laboratory scale, BSG lost 70-75% of its weight after drying. It was assumed that the water vapor produced from BSG drying was 0.7 kg per 1 kg of unprocessed BSG.  
The major input for grinding, phase 3, was the electricity required to power the coffee grinder. After drying, 1 kg of unprocessed BSG was equivalent to 0.3 kg of processed BSG. A 300-watt coffee grinder used for 1 min was suitable for 0.3 kg of dry BSG, requiring 0.018 MJ for use. There was some minor dust associated with this protocol; however, the total volume was considered negligible as an environmental burden. After this stage, 1 kg of unprocessed BSG was equivalent to 0.299 kg of pretreated, dried, ground BSG.  
The major input for weighing, phase 4, was the electricity used to power the scale. Utilizing a scale with 10-watt power for 15 min required 0.009 MJ. There was no considerable output for this phase.  
Phase 5, pyrolysis, required nitrogen gas and electricity as the major inputs. Based on the assumptions provided in Section 2.2. GHGA Model Assumptions and Equations, it was determined that 137 kg of nitrogen were utilized per 1 kg of unprocessed BSG. Therefore, bio-oil production was determined to be 0.192 kg; syngas was 0.018 kg per kg of unprocessed BSG.  
Figure 3 provides an overview of the mass flows for the BSG to biochar process. The major outputs of phase 1 were wastewater drained off the grain after soaking and the vented fumes. Per 1 kg of unprocessed BSG, 1.02 L of wastewater was drained via filtering the BSG solution over a cheesecloth. The filtrate had a pH value of 5.17, and, therefore, would require negligible neutralization treatment prior to discarding. In phase 1, BSG is maintained in a room-temperature, moist environment where naturally present microbes can readily metabolize and release greenhouse gasses. Because of this output, the BSG vessels were held in a well-ventilated area, the fume hood. The resulting volume for 1 kg of unprocessed BSG was 109 mL; this was assumed to be primarily CO\({}_{2}\), and, therefore, had a weight of 0.074 kg. A study found that after the fermentation of BSG, the total dissolved gas had a concentration of 0.72% dissolved CH\({}_{4}\); the remaining gas was CO\({}_{2}\)[29]. Because of the significant drop in pH and the increased presence of gaseous bubbles over the 48 h period, it was concluded that the main gas present in this study was CO\({}_{2}\) resulting from fermentation.