The effect of biochar and acid activated biochar on ammonia emissions during manure storage

The influence of using different types of modified vermiculite cover on ammonia mitigation from animal slurry storage: The role of sulfuric acid

Animal slurry storage is an important ammonia (NH3) emission source. Sulfuric acid (H2SO4)-modified vermiculite coverage is a new promising technology for controlling NH3 emission from slurry storage. However, the underlying mechanisms in controlling the mitigation effect remain unclear. Here, a series of experiments to determine the effect of H2SO4 on the modified vermiculite properties, floating persistence, and NH3 mitigation effect was conducted. Results showed that abundant H2SO4 and sulfate remained on the outer surface and in the extended inner pores of the vermiculite with acidifying H+ concentrations higher than 5 M. An initial strong instantaneous acidification of surface slurry released rich carbon dioxide bubbles, strengthening cover floating performance. An acidification in the vermiculite cover layer and a good coverage inhibition interacted, being the two leading mechanisms for mitigating NH3 during initial 40-50 days of storage. The bacterial-amoA gene dominated the conversion of NH3 to nitrous oxide after 50 days of storage. Vermiculite with 5 M H+ modification reduced the NH3 emissions by 90 % within the first month of slurry storage and achieved a 64 % mitigation efficiency throughout the 84 days period. With the development of the aerial spraying equipment such as agricultural drones, acidifying vermiculite coverage hold promise as an effective method for reducing NH3 emission while absorbing nutrients from liquid slurry storage tank or lagoon. This design should now be tested under field conditions.

Biochar-enhanced anaerobic mixed culture for biodegradation of 1,2-dichloroethane: Microbial community, mechanisms, and techno-economics

While anaerobic digestion (AD) has been employed for the degradation of chlorinated aliphatic hydrocarbons, the associated digester performance might suffer from volatile fatty acids accumulation, insufficient substrate-microbes interaction, and lower biogas yields. To overcome these limitations, this study is the first to augment the hydrocarbon-degrading microbial capacities by adding agricultural waste-based biochar to the digestion medium. 1,2-dichloroethane (1,2-DCA) was selected as the target pollutant because it is discharged in large quantities from oil refining, petrochemical, and chemical industries, causing serious environmental and human health concerns. A multi-chamber anaerobic reactor (MAR) was operated at a 1,2-DCA loading rate of 1.13 g/L/d, glucose dosage (as an electron donor) range of 200-700 mg/L, and hydraulic retention time of 11.2 h, giving dechlorination = 32.2 ± 6.9% and biogas yield = 210 ± 30 mL/g CODremoved. These values increased after biochar supplementation (100 mg/g volatile solids, VS, as an inoculum carrier) up to 60.2 ± 11.5% and 290 ± 40 mL/g CODremoved, respectively, owing to the enhancement of dehydrogenase enzyme activities. Burkholderiales (15.3%), Clostridiales (2.3%), Bacteroidales (3.5%), Xanthomonadales (3.3%), and Rhodobacterales (6.1%) involved in 1,2-DCA degradation were dominant in the reactor supplemented with biochar. It's suggested that biochar played a major role in facilitating the direct interspecies electron transfer (DIET) between syntrophic bacteria and methanogens, where chloride, ethylene glycol, and acetate derived from 1,2-DCA dechlorination could be further used to promote methanogenesis and methane production. The synergetic effect of adsorption and dechlorination towards 1,2-DCA removal was validated at various biochar dosages (50-120 mg/g) and 1,2-DCA concentrations (50-1000 mg/L). The techno-economic results showed that the cost of treating 1,2-DCA-laden discharge (100 m3/d) by the MAR module could be 0.83 USD/m3 with a payback period of 6.24 years (NPV = 2840 USD and IRR = 10%), retrieving profits from pollution reduction (9542 USD/yr), biogas selling (10418 USD/yr), and carbon credit (10294 USD/yr).

Digestate-derived carbonized char and activated carbon: Application perspective

The flourishment of anaerobic digestion (AD) on waste treatment emphasizes the importance of digestate valorization, which plays an essential role in determining the benefits provided by the AD process. The perception of digestate gradually shifts from waste to products to realize the concept of circular economy and maximize the benefits of digestate valorization. This review first outlined the current status of digestate valorization, focusing on thermal-chemical methods. The novel valorization methods were then summarized from the recent research, illustrating prospects for digestate valorization. Limits and perspectives are finally addressed. Methods for preparing digestate-derived activated carbon and impurity effects were elucidated. Inherent mineral content/inorganic impurity could be a niche for downstream use. High surface area and well-developed pore structure are essential for satisfying downstream use performance, but they are not the only factors. Digestate char applications other than use as an energy fuel are suggested.

Co-composting poultry carcasses with wood-based, distillers' grain and cow manure biochar to increase core compost temperatures and reduce leachate's COD

Composting has been recognized as a viable method to dispose of animal carcasses. Common concerns related to the composting process include low core temperatures, leachate generation, and ammonia emissions. This study tested co-composting full-size poultry carcasses with commercially available biochars at an aeration rate of 0.8 L∙min^-1. Biochars prepared by gasifying wood pallets, distillers' grains, and cow manure were added to the composting bins at the 13% rate (by volume). Results showed that poultry carcasses with wood-based and cow manure biochar increased temperatures by 2.0 to 3.3 °C. All biochar-amended bins met the time-temperature criteria to eliminate avian influenza (H7N1) viruses, which could not be achieved without biochar addition. Wood-based biochar amendment lowered the cumulative chemical oxygen demand of the leachate samples by 87% (P = 0.02). At the rate studied, the biochar amendment did not significantly affect ammonia emissions (P = 0.56). BET surface area of wood-based biochar was 1.4 and 28 times greater than that of cow manure and distillers' grain biochar, respectively. Compared to no biochar addition, wood-based biochar resulted in significantly higher compost temperatures (P = 0.02), lower leachate COD values (P = 0.02), and a higher total nitrogen content (P = 0.01) while it did not cause an increase in sodium content (P = 0.94) of the finished compost. In conclusion, amending the poultry carcass composting process with wood-based biochar (13% by volume) is recommended, especially to eliminate disease-causing agents.