Assessment For Typical Modes Of Circular Agriculture In The Central Of Shaanxi

The production practice and theoretical research of circular agriculture is a research hotspot in the field of agriculture in China.Studies and practices on circular agriculture has been currently the research focus of agriculture research in China.Presently,the central region of Shaanxi is making full efforts to promote the utilization of breeding wastes,actively carrying out the production practices of cultivation and breeding combination and agriculture and animal husbandry cycle,which resulting in various production modes of circular agriculture.While the weak theoretical research on circular agriculture and the limited mastering of material cycle characteristics,energy flow characteristics,capital flow characteristics,ecological environmental benefits,etc.in the process of circular agricultural production lead to the lack of the insight into the characteristics of circular agriculture practices.It's significantly important to design a comprehensive assessment method for the circular agriculture.We selected the typical circular agricultural production mode in the central of Shaanxi including circular agricultural production mode based on rural courtyard including the"pig-biogas-grain"circular agricultural production mode?rural courtyard mode i?,"pig-biogas-fruit"circular agricultural production mode?rural courtyard mode ii?,circular agricultural production mode with Fengrun Ecological Agricultural Development Co.,Ltd.ecological demonstration park as the main body?agricultural park mode i?and Circular agricultural production mode with Yijun compound planting and breeding ecological demonstration park as the main body?agricultural park mode ii?,and circular agricultural production mode based on leading enterprise?leading enterprise mode?as the research objects.Through the follow-up investigation of each mode,the collection and arrangement of relevant data,in-depth analyses were performed on the energy production efficiency,material conversion efficiency,economic benefits,environmental pollution reduction,ecological sustainability and etc of the selected modes using material flow analysis,energy flow analysis,capital flow analysis,life cycle analysis and emergy analysis by follow-up survey and data collection from farmers,to comprehensively evaluate the economic benefits,the environmental benefits and the ecological benefits of each mode.The following conclusions are obtained:?1?The circular agriculture production mode had significant advantages of reusing and recycling the materials and nitrogen in the systems,it could recycle and reuse some wastes generated by the system and realize the recycling and reuse of materials and nitrogen in the mode.But the main source of materials and nitrogen for the modes in this study was still the market which mainly included water,feed and fertilizer.Using digestate as a fertilizer on arable land could replace part of the chemical pollution and enhance nutrient recycling.While the agricultural part mode ii and leading enterprise mode had replaced all the fertilizers by digestate,it is conducive to the harmless production of agriculture.However,nitrogen deficit occurred in the planting subsystem of both modes.Leading enterprise mode had the highest material conversion efficiency?0.89?,that was 2.6 times and 25.6 times of the rural courtyard mode ii and agricultural part mode ii separately,but its nitrogen conversion efficiency was only 65.0%and 41.5%of the rural courtyard mode ii and agricultural part mode ii.Besides,excessive nitrogen fertilizer application in the planting subsystem in agricultural part mode i resulted in a high nitrogen surplus,and the nitrogen conversion efficiency of this mode was only 0.23 which was the lowest among the modes.?2?The organic energy had the greatest contribution to the total input of the circular agriculture production modes.The organic/inorganic energy of leading enterprise mode was 188.9,which was 4.3 times that of agricultural park mode ii.The energy flow cycle index was 0.99,and the energy flow density was 3.47 MJ/?m²·a?which showed a strong system self-sustaining ability and stability.Through the feed self-sufficiency and fertilizer self-sufficiency,rural courtyard mode i and agricultural park mode ii showed a high degree of intra system dependence,which was 6.0 times and 4.1 times that of agricultural park mode i.Each subsystem of agricultural park mode i showed good energy conversion efficiency,and the energy production investment ratio of the whole mode was 0.99,which was 1.4 times,2.1 times,2.4 times and 2.3 times that of Rural Courtyard mode i,Rural Courtyard mode ii,agricultural park mode ii and leading enterprise mode respectively.?3?With the expansion of production scale,the capital flow level of circular agricultural production modes had greatly improved,and the investment recovery period and the investment risk of the mode had increased accordingly.The total cost and total revenue of the leading enterprise mode were the highest among the circular modes.The cumulative net cash flow of the 30-year simulation was 47.2 million yuan,which was 2.5times higher than the agricultural park mode i.Besides,the annual savings by using biogas and electric power generated in leading enterprise mode was estimated as 445000 yuan.The purchase of feed was the main operating costs in each mode.In the leading enterprise mode,the total costs of the feed in 30 years would account for 90%of the total input.The agricultural park mode ii made full use of the waste from the planting subsystem as livestock feed,reduced the feed cost and made the mode show better cost profit rate,economic production investment ratio,annual return rate and capital profit rate.?4?The total biogas output of the large-scale biogas project?LBP?in the leading enterprise mode was about twice that of the household biogas project?HBP?in rural courtyard modes.The biogas,electricity and biogas manure produced by the LBP could replace 66 tons of coal,157000 k Wh of thermal power generation and 22 tons of chemical fertilizer which reduced the energy consumption?EC?of 4.60E+6 MJ/FU,the global warming potential?GWP?of 4.22E+5 kg CO₂-eq/FU,the acidification potential?AP?of2281 kg SO₂-eq/FU,the eutrophication potential?EP?of 151 kg NO₃^--eq/FU,the photochemical oxidation potential?POP?of 88 kg C₂H₄-eq/FU,and the human toxicity potential?HTP?of 378 kg 1,4-DCB/FU.The pollution emissions in the biogas project were concentrated in the biogas combustion stage,biogas manure management and fertilization stage.Biogas project showed significant advantages of reducing the environmental impacts of EC,GWP,AP,EP,and HTP with the consideration of environmental emissions and emissions avoided,but increased the impact of POP.The agricultural park mode i with low biogas manure output decreasing the impacts of AP and EP during the biogas manure management and fertilization stage which resulted in the highest comprehensive environmental impact value as 186.57,followed by leading enterprise mode as 132.95.?5?The emergy of non renewable resources accounted for a large proportion in the agricultural park modes and the leading enterprise mode,made the modes show higher risk of non renewable resources depletion and pressure on the environment than the rural courtyard modes.The rural courtyard mode i and the agricultural park mode ii showed better self-sufficiency in emergy due to the producing feedstuff of the residue,and the feedback rate of the output emergy was 4.4 and 2.4 times that of the leading enterprise mode.Considering the environmental loading ratio,emergy yield ratio and emergy trading in the market,the rural courtyard modes had the best ecological sustainability.Generally,this study had completed the comprehensive evaluation of the material cycle effect,energy cycle effect,expected economic benefit,energy saving and emission reduction level and ecological sustainability of the typical circular agriculture production modes centered on the utilization of breeding wastes in the central of Shaanxi.It could provide a reference for the further development of regional circular agriculture.