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Mass and Energy Balances of Dry Thermophilic Anaerobic Digestion Treating Swine Manure Mixed with Rice Straw.

Zhou S, Zhang J, Zou G, Riya S, Hosomi M - Biotechnol Res Int (2015)

Bottom Line: The results suggest that methane yield using the proposed DT-AD system increased with a higher C/N ratio and shorter SRT.However, the biogas yield increased when the SRT was shortened to 40 days, and the generated energy was greater than consumed energy when C/N ratio was 20 : 1 and 30 : 1.The results suggest that with the correct optimization of C/N ratio and SRT, the proposed DT-AD system, followed by using digestate for forage rice production, can attain energy self-sufficiency.

View Article: PubMed Central - PubMed

Affiliation: Eco-Environmental Protection Research Institute, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China.

ABSTRACT
To evaluate the feasibility of swine manure treatment by a proposed Dry Thermophilic Anaerobic Digestion (DT-AD) system, we evaluated the methane yield of swine manure treated using a DT-AD method with rice straw under different C/N ratios and solid retention time (SRT) and calculated the mass and energy balances when the DT-AD system is used for swine manure treatment from a model farm with 1000 pigs and the digested residue is used for forage rice production. A traditional swine manure treatment Oxidation Ditch system was used as the study control. The results suggest that methane yield using the proposed DT-AD system increased with a higher C/N ratio and shorter SRT. Correspondently, for the DT-AD system running with SRT of 80 days, the net energy yields for all treatments were negative, due to low biogas production and high heat loss of digestion tank. However, the biogas yield increased when the SRT was shortened to 40 days, and the generated energy was greater than consumed energy when C/N ratio was 20 : 1 and 30 : 1. The results suggest that with the correct optimization of C/N ratio and SRT, the proposed DT-AD system, followed by using digestate for forage rice production, can attain energy self-sufficiency.

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Biogas and methane yields under different C/N ratios under a SRT of 80 days.
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fig2: Biogas and methane yields under different C/N ratios under a SRT of 80 days.

Mentions: Each treatment maintained a relatively stable biogas yield. Different levels of biogas were produced at different C/N ratios after 80 days following the start of the experiment, with an SRT of 80 days (Figure 2(a)). The average biogas yield at the CN10 treatment level was 177 ± 80 mL/g VSadded between 80 days and 300 days, which was half the yield of the other two CN treatments. Treatments with C/N ratios greater than 20 produced relatively high biogas yields, mostly greater than 400 mL/g VSadded. When these higher levels are compared with CN10, the benefit of adding more rice straw to assist in anaerobic digestion of swine manure is clear, with increases up to approximately 2 and 3 times the average biogas production of CN20 (386 ± 139 mL/g VSadded) and CN30 (474 ± 99 mL/g VSadded). Biogas production in CN30 showed a higher and stable level, which is generally in agreement with the literature and indicates an optimal C/N ratio of 25–35 for rice straw [23, 24]. Conversely, biogas production of CN10 remained at an “inhibited steady state,” which is a condition where the process is stable, but with a low methane yield [10, 25], suggesting that the C/N ratio should be well balanced to avoid process failure by ammonia accumulation.


Mass and Energy Balances of Dry Thermophilic Anaerobic Digestion Treating Swine Manure Mixed with Rice Straw.

Zhou S, Zhang J, Zou G, Riya S, Hosomi M - Biotechnol Res Int (2015)

Biogas and methane yields under different C/N ratios under a SRT of 80 days.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4644824&req=5

fig2: Biogas and methane yields under different C/N ratios under a SRT of 80 days.
Mentions: Each treatment maintained a relatively stable biogas yield. Different levels of biogas were produced at different C/N ratios after 80 days following the start of the experiment, with an SRT of 80 days (Figure 2(a)). The average biogas yield at the CN10 treatment level was 177 ± 80 mL/g VSadded between 80 days and 300 days, which was half the yield of the other two CN treatments. Treatments with C/N ratios greater than 20 produced relatively high biogas yields, mostly greater than 400 mL/g VSadded. When these higher levels are compared with CN10, the benefit of adding more rice straw to assist in anaerobic digestion of swine manure is clear, with increases up to approximately 2 and 3 times the average biogas production of CN20 (386 ± 139 mL/g VSadded) and CN30 (474 ± 99 mL/g VSadded). Biogas production in CN30 showed a higher and stable level, which is generally in agreement with the literature and indicates an optimal C/N ratio of 25–35 for rice straw [23, 24]. Conversely, biogas production of CN10 remained at an “inhibited steady state,” which is a condition where the process is stable, but with a low methane yield [10, 25], suggesting that the C/N ratio should be well balanced to avoid process failure by ammonia accumulation.

Bottom Line: The results suggest that methane yield using the proposed DT-AD system increased with a higher C/N ratio and shorter SRT.However, the biogas yield increased when the SRT was shortened to 40 days, and the generated energy was greater than consumed energy when C/N ratio was 20 : 1 and 30 : 1.The results suggest that with the correct optimization of C/N ratio and SRT, the proposed DT-AD system, followed by using digestate for forage rice production, can attain energy self-sufficiency.

View Article: PubMed Central - PubMed

Affiliation: Eco-Environmental Protection Research Institute, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China.

ABSTRACT
To evaluate the feasibility of swine manure treatment by a proposed Dry Thermophilic Anaerobic Digestion (DT-AD) system, we evaluated the methane yield of swine manure treated using a DT-AD method with rice straw under different C/N ratios and solid retention time (SRT) and calculated the mass and energy balances when the DT-AD system is used for swine manure treatment from a model farm with 1000 pigs and the digested residue is used for forage rice production. A traditional swine manure treatment Oxidation Ditch system was used as the study control. The results suggest that methane yield using the proposed DT-AD system increased with a higher C/N ratio and shorter SRT. Correspondently, for the DT-AD system running with SRT of 80 days, the net energy yields for all treatments were negative, due to low biogas production and high heat loss of digestion tank. However, the biogas yield increased when the SRT was shortened to 40 days, and the generated energy was greater than consumed energy when C/N ratio was 20 : 1 and 30 : 1. The results suggest that with the correct optimization of C/N ratio and SRT, the proposed DT-AD system, followed by using digestate for forage rice production, can attain energy self-sufficiency.

No MeSH data available.


Related in: MedlinePlus