# Can Biochar Improve the Sustainability of Animal Production?
## 5 Manure Storage and Treatment
### Biochar and Manure Storage  
Liquid manure can be a source of gaseous emissions, including ammonia, sulfides, VOCs, and greenhouse gasses (GHG), including methane and nitrous oxide. [PERSON] et al. [100] studied the potential for different biochars to mitigate odor/gas emissions and improve nutrient uptake when applied as a surface cover for dairy manure. Two biochars were tested: gasified wood chips at 650 \({}^{\circ}\)C (BC1) and wood bark via slow pyrolysis at 600 \({}^{\circ}\)C (BC2). The BC2 cover reduced headspace NH\({}_{3}\) emissions by 72-80%, whereas no significant difference was noticed for BC1. However, BC1 increased nutrient uptake from 0.21 to 4.88 mg N g\({}^{-1}\) biochar and 0.64 to 2.70 mg P g\({}^{-1}\) biochar compared to BC2. This was desirable as it could translate to the slow release of nutrients when land applied. These differing results were attributed to the high pH of BC1 (9.32) compared to BC2 (7.28). Additionally, BC2 was more hydrophobic than BC1 allowing it to float better on the surface. They reported a trade-off between the biochar potential for NH\({}_{3}\) emission reduction and for nutrient absorption with increased hydrophobicity aiding biochar floatability and, consequently, the surface NH\({}_{3}\) reduction but reducing its nutrient absorption. In evaluating biochar from need canary pellets (torrefied, 300 \({}^{\circ}\)C) as an NH\({}_{3}\)-emission-control measure in manure digestate storage, [PERSON] et al. [101] observed significant reductions in cumulative  
Figure 4: GC-MS results for as-received cattle manure (**a**) and manure with biochar treatment (**b**). Reprinted with permission from [PERSON] et al. [97]. 2021, Agapios Agapiou. NH\({}_{3}\) emissions after biochar addition, with acidified biochar outperforming untreated biochar, and surface application reducing emissions more than in mixed addition. [PERSON] et al. [102] hypothesized that biweekly biochar application as a surface cover would remedy the decline in the biochar mitigation impact over time. They conducted an eight-week study in deep-pit swine storage structures. Weekly tests revealed that the bi-weekly reapplication of biochar was more effective than a one-time application and that a higher application rate did not impact the emission and odor reduction. Ammonia decreased by 33%, 25%, and 53% for one-time 2 kg m\({}^{-2}\) h\({}^{-1}\), one-time 4 kg m\({}^{-2}\) h\({}^{-1}\), and bi-weekly 2 kg m\({}^{-2}\) h\({}^{-1}\), respectively, all with \(p\)-values < 0.05. Additionally, the NH\({}_{3}\) levels dropped close to zero immediately after reapplication. Odor reduction doubled from 11% to 22%, and CH\({}_{4}\) production tripled from 15% to 45% in bi-weekly applications versus both one-time applications. While increased CH\({}_{4}\) production is a trade-off between reduced odor (NH3 emission) and increased greenhouse gas (GHG) emissions, it can be valuable in an AD. [PERSON] et al. [103] conducted a study on emission reduction in deep-pit swine storage structures. Red oak biochar was surface-applied at 0.64 cm (0.25 in) thickness to stored swine manure to reduce NH\({}_{3}\), H\({}_{2}\)S, VOCs, and GHGs. The biochar significantly reduced \(p\)-cresol by 66-78% over the three week trial. The NH\({}_{3}\) and H\({}_{2}\)S emissions were reduced by 19-39% and 16-23% over the duration of the experiment. Additionally, the odor intensity for the biochar-treated manure was reduced by 17-30% over the duration of the experiment. This experiment also proved that biochar could float on manure for days to weeks at a time. [PERSON] et al. [104] applied the positive results from [PERSON] et al. [103] to investigate reducing short-term release of H\({}_{2}\)S emissions in deep-pit swine storage during agitation and pump-out. Two thicknesses of the same read oak biochar, 6 and 12 mm, were applied to the manure surface and then manually agitated while measuring the H\({}_{2}\)S fluxes before and after (Figure 5).