Mass flow and energy balance plus economic analysis of a full-scale biogas plant in the rice-wine-pig system.

This paper presents mass flow and energy balance as well as an economic analysis for a biogas plant in a rice-wine-pig system at a practical rather than laboratory scale. Results showed feeding amount was 65.30 t d(-1) (total solid matter (TSM) 1.3%) for the normal temperature continuous stirred tank reactor (CSTR), and 16.20 t d(-1) (TSM 8.4%) for the mesophilic CSTR. The digestion produced 80.50 t d(-1) of mass, with 76.41 t d(-1) flowing into rice fields and 4.49 t d(-1) into composting. Energy consumption of this plant fluctuated with seasons, and surplus energy was 823, 221 kWh/year. Thus, biogas plant was critical for material recycling and energy transformation of this agro-ecosystem. The economic analysis showed that the payback time of the plant was 10.9 years. It also revealed application of biogas as a conventional energy replacement would be attractive for a crop-wine-livestock ecosystem with anaerobic digestion of manure.

Semi-continuous anaerobic co-digestion of dairy manure with three crop residues for biogas production.

The characteristics of anaerobic semi-continuous co-digestion of dairy manure (DM) with three crop straw residues (SRs), rice straw, corn stalks and wheat straw under five mass mixing ratios (SRs/DM) were investigated. During the anaerobic digestion (AD) process, four periods were identified: startup, first stage of stabilization, second stage of stabilization, and suppression. Following the four periods, the biogas production rate varied between 101 and 576mL L(-1)d(-1). A high CH4 content and volatile solid reduction was maintained at the SRs/DM mass mixing ratio 1:9. The highest cumulative biogas production of more than 19L was obtained at ratio 5:5. However, ratio 9:1 performed worst in the whole process. Systematic analysis of the elements revealed nitrogen, phosphorus, and trace elements contents were important for the AD. Overall, the semi-continuous AD is efficient within a wide range of SRs/DM mass mixing ratios.

The effects of dietary fiber level on nutrient digestibility in growing pigs.

The objective of this study was to investigate the effects of total dietary fiber level on nutrient digestibility and the relationship between apparent total tract digestibility of total dietary fiber, and soluble dietary fiber, insoluble dietary fiber and available energy. Sugar beet pulp was as the only fiber source. The experiment was designed as a 6 × 6 Latin square with an adaptation period of 7 d followed by a 5-d total collection of feces and urine. Feed intake tended to decrease (P =0.10) as total dietary fiber level increased. The apparent total tract digestibility of dry matter, crude protein and gross energy decreased (P <0.01) when total dietary fiber increased but the digestibility of soluble dietary fiber and insoluble dietary fiber increased (P <0.01). The digestible energy and metabolizable energy content of diets decreased (P <0.01) as the total dietary fiber increased.

[Analysis on the sustainability of Amomum villosum cultivation under the tropical rainforest in Xishuangbanna].

Amomum villosum has been cultivated under tropic rainforest in Xishuangbanna area since 1970s. The cultivation area of Amomum villosum had expanded to 5811 hm2 by 1998, and the dry fruit yield had reached to 542 t. In this study, the ecological and economical benefits of this cultivation model were analyzed. The results showed that plant diversity, litter, soil humidity, and soil fertility of rainforest decreased at different levels after Amomum villosum cultivated under rainforest, and the distribution of nutrition had been changed in the soil. The economical benefits had an obvious downtrend after 7-8 years cultivating due to irrational management. So, the present cultivation model of Amomum villosum under the tropical rainforest was not sustainable. For the objectives of harmonizing the ecological, economic, and social benefits and sustainable utilization of the rainforest, and improved model was also discussed in this study.