# Can Biochar Improve the Sustainability of Animal Production?
## 5 Manure Storage and Treatment
### Biochar and Manure Composting  
Composting transforms manure into a stable and safe final product that offers a nutrient source to enhance plant growth [106]. The physicochemical properties of biochar make it a desirable compost additive to absorb gaseous emissions. Table 2 summarizes some research efforts that have demonstrated the effects of biochar as a compost addi  
Figure 5: Swine manure surface: control (**left**), biochar evenly applied to surface (**center left**), 6 mm biochar layer after agitation (**center right**), and 12 mm biochar layer after agitation (**right**) with patches of open manure circled in red. Reprinted with permission from [PERSON] et al. [104]. 2020, [PERSON]. tive for gaseous emission control. A more detailed review by [PERSON] [107] provides additional details. [PERSON] et al. [114] studied the effect of rice-husk biochar addition and dosage on the peak CH\({}_{4}\) and CO\({}_{2}\) emissions from chicken manure composite. The experiment was conducted for 43 days in 500 mL glass bottles at varying ratios of manure, biochar, and sawdust. Daily headspace gas spaces were collected and processed in a GC-MS. Although the experiment was not directly testing for NH\({}_{3}\) emissions, they noticed that the concentrations were very high at the beginning of the process while the compost was established. This was due to a sharp increase in pH from about 8.0 to 9.0 for all treatments over the first five days, though the biochar did increase the pH more than the control. The 20% biochar treatment resulted in a 54.9% reduction in peak CH\({}_{4}\) emissions. This reduction was attributed to three possible causes: (1) the high porosity of biochar and its potential to increase aeration in the compost mixture, (2) high porosity and surface area resulting in the greater adsorption and retention of CH\({}_{4}\), and (3) the higher pH in biochar-amended compost. For some of the same reasons that biochar might have decreased CH\({}_{4}\) emissions, it also contributed to a 148% increase in CO\({}_{2}\) emissions. The increased aeration due to the porosity of the biochar supports aerobic decomposition, resulting in increased CO\({}_{2}\) respiration from these microorganisms. [PERSON] et al. [117] produced similar results with increased CO\({}_{2}\) emissions from biochar as a compost additive. This study tested the cumulative gas flux instead of peak gas flux as [PERSON] et al. did [114]. Wood-based biochar was added to poultry manure at 5% and 10% addition rates in 165 L reactors for 42 days. Cumulative CO\({}_{2}\) emissions increased by 6.9 and 7.4% for the 5 and 10% addition rates, respectively, compared to the control. [PERSON] et al. [118] attributed this increase to the high porosity of the biochar, which created better aeration conditions for the compost. This resulted in possibly abiotic oxidation of the biochar but, more likely, an additional carbon source for microorganisms thereby increasing the CO\({}_{2}\) respiration. While there are numerous studies on the effects of biochar as a compost additive, it is important to understand the mechanisms of adsorption for this application to achieve the desired effects. An area that still needs to be explored further is the ability of biochar to increase certain emissions while decreasing others. Additionally, further research is needed on composing with higher-moisture-content manure, possibly in the form of a slurry or pumpable liquid, as well as the effect of biochar post modifications for a more uniform reduction of gaseous emissions.