Design and performance test of a novel UAV air-assisted electrostatic centrifugal spraying system

Biochar is difficult to make pellets on its own. The pelleting of biochar mixed with livestock manure compost could have the following advantages: (1) use compost as a binder, (2) reduce the moisture content of compost for pelleting by simply mixing without drying, and (3) promote the application of biochar for carbon sequestration by simultaneous application with agricultural machinery for chemical fertilizers while preventing dust pollution and additional work for the farmer. Fertilizer pellets need to be produced in an economical manner. Therefore, we empirically examined the productivity of pelleting using a roller die pellet mill, which is characterized by high throughput and is commonly used in the mass production of multifertilizer and wood pellets. Although a feedstock with 25% biochar mixed with cattle manure compost produced fewer pellets than a feedstock consisting of only compost, the energy input per unit of production remained the same. The results suggest that the addition of biochar may not increase GHG emissions during the production of this new material. Durability and wettability showed similar or higher values in the mixed pellets, indicating that the new material can be used as a fertilizer in the same way as cattle manure pellets.

The green colonial microalga Botryococcus braunii produces large amounts of hydrocarbons and has attracted attention as a potential source of biofuel. When this freshwater microalga is cultured in a brackish medium, the hydrocarbon recovery rate increases; furthermore, the colony size becomes large. In this study, the effects of such changes on the energy balance of harvesting and hydrocarbon recovery were studied via filtrate experiments on an inclined separator and extraction from a concentrated slurry. The inclined separator was effective for harvesting large-colony-forming algae. The water content on the wire screen of slit sizes larger than 150 µm was 85% could be achieved. The input energy of the harvesting using the brackish medium with this separator was ≈44% of that using the freshwater medium with vacuum filtration, while the input energy of the hydrocarbon recovery using the brackish medium was ≈88% of that using the freshwater medium with pre-heating before n-hexane extraction. Furthermore, the energy profit ratio of the process in the brackish medium was 2.92, which was ≈1.2 times higher than that in the freshwater medium. This study demonstrated that filtration techniques and hydrocarbon recovery from B. braunii with a low energy input through culture in a brackish medium are viable.

Objective: The objective of this study was to evaluate the effect of waste cooking oil (WCO) addition on ammonia (NH3) emissions during the composting of dairy cattle manure under two aeration conditions.Methods: The composting tests were conducted using the laboratory-scale composting apparatuses (14 L of inner volume). Three composting treatments (Control, WCO1.5, and WCO3, with WCO added at 0 wt%, 1.5 wt%, and 3 wt% of manure, respectively) were performed in two composting tests: aeration rate during composting was changed from 0.55 to 0.45 L/min in Test 1, and fixed at 0.3 L/min in Test 2, respectively. The NH3 emitted and nitrogen losses during the composting were analyzed, and the effect of the addition of WCO on NH3 emissions were evaluated.Results: Both tests indicated that the composting mixture temperature increased while the weight and water content decreased with increasing WCO content of the composting mixtures. On the other hand, the NH3 emissions and nitrogen loss trends observed during composting in Tests 1 and 2 were different from each other. In Test 1, NH3 emissions and nitrogen losses during composting increased with increasing WCO contents of the composting samples. Conversely, in Test 2, they decreased as the WCO contents of the samples increased.Conclusion: The WCO addition showed different effect on NH3 emissions during composting under two aeration conditions: the increase in WCO addition ratio increased the emissions under the higher aeration rate in Test 1, and it decreased the emissions under the lower aeration rate in Test 2. To obtain reduction of NH3 emissions by adding WCO with the addition ratio ≤3 wt% of the manure, aeration should be considered.

Objective: In our previous study, we observed that the addition of waste cooking oil (WCO) reduced ammonia (NH3) emissions during laboratory-scale composting of dairy cattle manure under low-aeration condition. Therefore, this study aimed to evaluate the effect of addition of WCO on NH3 emissions reduction during pilot-scale composting of dairy cattle manure, which is close to the conditions of practical composting treatment.Methods: Composting tests were conducted using pilot-scale composting facilities (1.8 m3 of capacity). The composting mixtures were prepared from manure, sawdust, and WCO. Two treatments were set: without WCO (Control) and with WCO added to 3 wt% of manure (WCO3). Composting was conducted under continuous aeration at 40 L/min, corresponding to 22.2 L/(min‧m3) of the mixture at the start of composting. The changes in temperatures, NH3 concentrations in the exhaust gases, and contents of the composted mixtures were analyzed. Based on these analysis results, the effect of WCO addition on NH3 emissions and nitrogen loss during composting was evaluated.Results: During composting, the temperature increase of the composting mixture became higher, and the decreases of weight and water content of the mixture became larger in WCO3 than in Control. In the decrease of weight, and the residual weight and water content of the mixture, significant differences (p<0.05) were detected between the two treatments at the end of composting. The NH3 concentrations in the exhaust gases tended to be lower in WCO3 than in Control. Nitrogen loss was 21.5% lower in WCO3 than in Control.Conclusion: Reduction of NH3 emissions by the addition of WCO under low aeration condition was observed in pilot-scale composting, as well as in laboratory-scale composting. This result suggests that this method is effective in reducing NH3 emissions in practicalscale composting.