Comprehensive Benefit Analysis on Development Models of Circular Agriculture in Wangcang County of Sichuan Province

Yuanyuan CHU，Shunqiang SUN

College of Economics and Management，Southwest University，Chongqing 400715，China

From 2003，Wangcang County of Sichuan Province started developing circular agricultural economy with biogas as link in all suitable towns．With more than 10 years of development，circular agriculture of Wangcang County has begun to take shape，but there are still problems of slow development and low efficiency．Through cost benefit analysis on development models of circular agriculture in Wangcang County from the perspective of sustainable development of county-wide agriculture，it is expected to come up with pertinent recommendations for efficient advance and scientific development of circular agriculture in Wangcang County．

1 Documentary overview

1．1 Overview of circular agricultural economic models of Sichuan ProvinceTypical models of circular agriculture in Sichuan Province are＂pig-biogas-fruit＂ecological agriculture and its derivative models．Zeng Xiaolan（2009）stated that natural conditions of Sichuan Province is suitable for developing＂pigbiogas-fruit＂model with biogas as the link．This model mainly uses mountain area，farmland，water and courtyard resources，combines biogas pool，hogpen，toilet，focuses on leading industry，and carries out comprehensive use of biogas，biogas dregs，and biogas liquid．Taking Shehong County as an example，Luo Qing and Deng Ziyuan（2009）pointed out that circular agriculture in central Sichuan mainly takes biogas as the link and is based on superior industries．For example，pig raising，grain crop planting and wine making are superior industries in Shehong County，so major models of Shehong County is＂grain-pig-biogas-fruit＂and＂grain-wine-biogas-grain＂．Zhao Jianjun and Guo Lingli（2009）stated that＂pig-biogas-fruit＂is a typical model in southern rural areas．The development of circular agriculture in Sichuan Province is mainly based on biogas．

1．2 Overview of benefit analysis methodsIn evaluation and analysis of circular agriculture in Sichuan Province，most researches touch upon overall circular agriculture of the whole province，while few are related to county-wide agricultural economic model．Liu Xiaoling（2012）made evaluation and analysis on benefits of utilization of biogas pools in Huixian County．Yang Lirong，Chen Wenkuan and Mu Peisong（2009）studied agricultural economic efficiency of Shehong County based on data envelopment analysis（DEA）［1］．

In the evaluation of circular economy of agriculture in Sichuan Province，different scholars adopted different analysis methods，mainly including Delphimethod，Analytic Hierarchy Process（AHP），comprehensive index evaluation method，and DEAmethod．Sun Yanling and LiMing（2009）made evaluation of sustainability of agriculture in Sichuan，revealed existing problems in Sichuan，and came up with recommendations and policies for strengthening sustainable development ability of Sichuan Province in accordance with actual situations of China and Sichuan Province，using DEA method．Using fuzzy comprehensive evaluation method and combining actual situations of agricultural development in two model areas，Huang Caian（2012）established a pertinent performance evaluation indicator system for circular agriculture，and made performance evaluation on circular agriculture of Ya'an City using AHPand Delphi method．The above analyses are established on the basis of massive data．

In benefit analysis method of county-wide agricultural circular economical models，most use cost benefit method and analyze ecological and social benefits in a quantitative way．In the evaluation of benefits of biogas pool utilization in Huixian County，Liu Xiaoling（2012）held that economic benefits should combine with cost benefit analysis method and emergy analysis，ecological benefits are analyzed by AHP，and energy replacement benefits and social benefits are discussed by comparative analysis on the basis of survey［2］．In the benefite valuation and analysis of biogas in Jiangyou City，Zhao Jianjun and Guo Lingli（2009）stated that economic benefits can be measured by money，while it is difficult to accurately measure social and ecological benefits［3］．They made technical economic analysis on＂pig-biogas-fruit＂model using cost benefit analysis method．

2 Development models of circular agriculture in Wangcang County of Sichuan Province

2．1 General situations of agricultural economic development of Wangcang CountyWangcang County（105°58′24″E-106°46′2″E，31°58′45″N-32°42′24″）is situated in northern Sichuan Province and contiguous to Shaanxi Province．With subtropical humid monsoon climate，it features distinct vertical climate，large annual temperature range but small monthly temperature range，average annual temperature is16．2℃，annual sunshine hours is 1352．52 hours，annual rainfall is 1142 mm，and average annual frost-free period is266 days．The soil is mainly mountainous yellow soil and mountainous yellow brown soil，with total area of 2976 km2．Wangcang County is a state-level poverty stricken county and its agricultural economic development is lower than the average national level．In 2014，per capita net income of farmers in Wangcang County was7812 yuan，while the per capita net income of rural residents in the whole country was 9892 yuan，showing a certain gap．Grain crops in Wangcang County are mainly rice and corn，and cash crops are mainly tea，fruit trees and traditional Chinese medicinal plants．Animal husbandry，forest and fruit，sericulture，and traditional Chinese medicinal plant industries are five largest industries supporting county-wide rural economy．By 2014，there have been 9 agricultural model parks in Wangcang County，the construction area was up to 100000mu，and increase of farmers' income exceeded 2000 yuan on average．

2．2 Development models of circular agriculture in Wangcang County of Sichuan ProvinceMajor models of circular agriculture in Wangcang County include＂pig-biogas-fruit＂，＂pig-biogas-vegetable＂，and＂pig-biogas-tea＂．In recent years，rural biogas projects implemented in Wangcang County are mainly national debt，provincial level，and conceding the land to forestry．The subsidy amount is respectively 2000 yuan，1200 yuan and 1500 yuan for a biogas pool at central government and provincial finance level，and farmers only need 2000－2500 yuan．

The development of biogas industry in Wangcang County is excellent．From agricultural information network of Wangcang County，from 2003，energy-saving technology with rural biogas as major part was gradually known and accepted by farmers．The number of biogas pools built in the whole year was7000；in 2008，it rose to 190000 and the biogas household entrance rate reached 18%；in 2010，it completed construction of biogas pools for 8589 households and the whole county has built31000 biogas pools；in 2013，the whole county built 45922 biogas pools，accounting for 81%of total households suitable for construction of biogas pools；by 2014，the whole county has built 48000 biogas pools and the penetration rate was up to 83%．As shown in Fig．1，it takes on gradual growth trend．

2．2．1 Pig-biogas-tea model．The pig-biogas-tea model takes pigmanure and domesticmanure as raw materials of fermentation to generate biogas，biogas liquid and dregs．Generated biogas can be used for domestic use，biogas liquid and dregs are used as nutrients of tea trees，and biogas liquid can feed pigs．

2．2．2 Pig-biogas-fruit model．The pig-biogas-fruit model takes pigmanure and domesticmanure as rawmaterials of fermentation to generate biogas，biogas liquid and dregs．Generated biogas can be used for domestic use，biogas liquid and dregs are used as nutrients of fruit trees，and biogas liquid can feed pigs．Wangcang County is situated in subtropical humid monsoon climate zone，suitable for planting orange，walnut and peach trees．Cultivation range is mainly distributed in Donghe Town and downstream townships with lower altitude．

2．2．3 Pig-biogas-vegetable model．The only difference with the above model is that biogas dregs and liquid are used for ma-nure of various vegetables planted by farmers．However，this model is more adapted and widely applied in rural areas of Wangcang County．Rural areas with too low temperature and too high altitude are not suitable for installing biogas facilities，because generation of biogas needs certain temperature condition．

3 Cost benefit analysis of circular agriculture in Wangcang County of Sichuan Province

3．1 Economic benefits

3．1．1 Costs．（i）Construction of biogas pools．In recent years，farmers in Wangcang County generally build 8 m3biogas pools．Here，only costs for construction of biogas pools are calculated，excluding costs for three kinds of transformation and neglecting difference in freights of distribution areas．Construction costs include building material（equipment，cement，sand，and standard bricks）cost，labor cost and freight．The total costs are 4250 yuan approximately，including 2450 yuan material cost，1200 yuan labor cost，and 600 yuan freight．

Table 1 Estimation of investment of rural household biogas pools

（ii）Management cost and maintenance expenses．Management cost mainly includes labor cost for maintenance of biogas pool（once every two years）and labor cost for complete discharge（once every year），about 200 yuan annually；maintenance cost mainly includes costs for replacing materials and elements of biogas pools and auxiliary facilities，about 50 yuan annually．Management and maintenance costs constitute operating costs of biogas pool，about250 yuan annually．

3．1．2 Benefits．According to calculation，building a 8 m3biogas pool in Wangcang County and raising 3－5 pigs，it is able to provide 350m3biogas and provide 16－20m3biogas fertilizer．

（i）The biogas can satisfy more than 80%living fuel demands for a family with 3－5members for one year．In Wangcang County，farmers generally adopt firewood as fuels．Using biogas will save firewood as high as2．5 tons annually．Without considering saving the time for cutting firewood and ecological benefits，it can save lighting expenses as much as100 yuan annually．

（ii）Biogas dregs and liquid can be used as fertilizer and save 25%chemical fertilizers．Farmers in Wangcang County have 2．5 mu farmland on average and apply chemical fertilizer about 1000 yuan annually．Using biogas dregs and liquid can save 250 yuan for chemical fertilizer．Besides，using biogas dregs and liquid can improve quality of agricultural products and increase the benefits about100 yuan．

（iii）Biog as liquid can be taken as feeds of chicken，fishes，pigs，and cattle and can save feeds about 20%．The annual feed cost of each household is about1000 yuan，using biogas dregs and liquid can save feeds about200 yuan，and it can increase benefits about300 yuan through selling the pigs．

In sum，the annual economic benefit is about950 yuan．

The service life of biogas pool is20 years．According to current loan rate，the base earnings ratio is6%．In recent years，rural biogas projects implemented in Wangcang County are mainly national debt，provincial level，and conceding the land to forestry．The subsidy amount is respectively 2000 yuan，1200 yuan and 1500 yuan for a biogas pool at central government and provincial finance level，and farmers only need 2250－2500 yuan．Therefore，costs and benefits of biogas pool with government subsidies are shown in Table 2．

3．1．3 Payback period of investment．The payback period of investment refers to the time required for the return on an investment to repay the sum of the original investment．According to the above values，the payback period of investment＝（4－1）＋｜－128．9｜／（425．57＋128．9）＝3．23 years．

From the above calculation，we know that the net present value of building an 8m3biogas pool with government subsidies is 6029 yuan，and it is able to recover the cost in 3．23 years．Such circular agriculture with biogas poolas link has excellent economic benefits．

3．2 Ecological benefitsDeveloping circular agriculture not only brings economic benefits，but also brings ecological benefits．Construction of biogas pools in rural areas can transform farmers' traditional production and living style and improve their living conditions．An 8m3biogas pool can generate biogas as much as 350 m3．This can basically satisfy living energy demands of a three member family，effectively transform rural energy consumption structure，replace 2500 kg firewood，protect forest land 3．5 mu，reduce water and soil loss2m3，and reduce CO2emission 2 tons．Farmers in Wangcang County generally use firewood as fuels．With biogas developed，farmers will cut down less firewood，forest land will be protected to a certain extent，and water and soil loss will also be reduced to a certain extent．Besides，it will reduce pollution of CO2and SO2 to air．In addition，use of biogas manure reduces chemical fertilizers and pesticide，reduces farmland pollution and water pollution．Also，it reduces incidence of rural diseases and improves farmers' living environment．

Table2 Cost benefit analysis with government subsidies

3．3 Social benefitsAccording to local characteristics of Wangcang County，the＂pig-biogas-fruit＂，＂pig-biogas-veget able＂，and pig-biogas-tea＂models have a lot of social benefits．Since the circular agriculture with biogas as link was advocated in 2003，farmers'living conditions have been greatly improved．Developing rural biogas realizes change of firewood to gas as fuel，effectively solves the problem of random stacking of coal and dust，reduces multiplication of mosquitoes and flies，and brings rural areas to develop towards healthy，sanitary and clean direction．Besides，use of biogas supplements energy for living，saves time for firewood cutting and tending the kitchen fire，liberates women from heavy housework，increases labor，and creates favorable conditions for accelerating transfer of rural surplus labor，increasing farmers' income， and maintaining social stability，showing considerable social benefits．

3．4 Graphic analysisAs shown in the graph，farmers' demands are definite and F denotes utilization volume of resources．In this study，it refers to take firewood and coal as living fuels．F*stands for optimum utilization volume of the society．In this study，it refers to use of biogas pool under the leadership of government．Obviously，in spontaneous action of farmers，resources are used excessively，FF*is the part of excessive use and stands for marginal social cost．When government advocates building biogas pools and provides certain amount of subsidies，F will gradually move towards F*and the reduced marginal cost will become ecological，social and economic benefits．

4 Existing problems in development of circular agriculture in Wangcang County of Sichuan Province

4．1 Low amount of state subsidiesIn recent years，rural biogas projects implemented in Wangcang County are mainly national debt，provincial level，and conceding the land to forestry．The subsidy amount is respectively 2000 yuan，1200 yuan and 1500 yuan for a biogas pool．In recent years，building a biogas pool needs higher input，because costs for bricks，sand，stones，cement and steel bars and labor costs are constantly rising．Apart from government subsidies，farmers need inputting 2000-2500 yuan．

4．2 Difficulty of farmers in raising funds restricts advance in three kinds of transformationsGovernment asks farmers to transform kitchens，toilets and hogpens，but provides no subsidies．To implement three transformations，farmers need spend 10000 yuan．This is far beyond their financial ability．Asa result，the rich people look down upon three transformations，while the poor people are incapable of building biogas pools．There are still no large scale three transformations in Wangcang County．

4．3 Weak awareness of farmers for sustainable development

In Wangcang County，most farmers still use firewood asmajor living fuels and keep using ground stove and wood-fired oven．Farmers have the tradition of using firewood for several thousand years and are difficult to adapt to use of new energies．Besides，a lot of farmers have biased opinion of construction of biogas pool project．They think that the cost for construction ofbiogas pools is too high，the construction is complicated，and biogas generation rate is low．As a result，they are unwilling to build biogas pools．

4．4 Technologies for building biogas pools are not perfect

At present，there are still many problems to be solved in the construction and use of biogas pools in Wangcang County．In the construction process，the installation is not specialized．In consequence，there is no generation of biogas in the subsequent use．Also，the maintenance and inspection system of biogas pools in Wangcang County is not well improved．In addition，lack of technicians makes the above problems difficult to be solved．As a result，many farmers abandon their biogas pools and it leads to huge waste of resources．

4．5 Too single model of circular agricultureThe model of circular agriculture in Wangcang County is too single and it is difficult to really realize sustainable agricultural development．Thus，circular agriculture with biogas pool as link can not be taken as the single model of circular agriculture in Wangcang County．With development of urbanization and constant increase of migrant workers，rural areas start to lack labors．Fewer and fewer farmers are willing to raise pigs．Lack of raw materials for fermentation，the utilization efficiency of biogas pools is low and leads to idle in a great number．This leads to waste of resources and restricts sustainable development of agriculture．Slow development of rural circular agriculture aggravates outflow of rural labor，forming a vicious circle．Besides，many areas are not suitable for building biogas pools，so it is necessary to develop new circular agriculture models in accordance with actual local conditions．Therefore，Wangcang County should introduce new circular agriculture models in accordance with local situations，to realize diversified development of circular agriculture．

5 Recommendations for promoting development of circular agriculture in Wangcang County of Sichuan Province

5．1 Increasing the amount of subsidies for building biogas poolsCircular agriculture of Wangcang County is mainly relied on biogas．This model not only brings huge economic，ecological and social benefits，but also promotes development of agricultural economy，and boosts development of secondary and tertiary industries to a certain extent．Therefore，to promote development of biogas project，government should increase the amount of subsidies for biogas construction especially in mountain areas，to ensure steady advance of biogas construction project．It is recommended to increase subsidy amount in the process of building biogas pools and transformations of kitchens，toilets and hogpens in accordance with actual situations of mountain areas．

5．2 Enhancing propaganda of biogas projectGovernment should enhance propaganda to raise awareness of farmers for sustainable development．It is recommended to spread propaganda through television and radio，to create favorable atmosphere．Besides，it is recommended to carry out one-to-one propaganda to farmers through going to and visiting villages．In addition，it is recommended to assign specialized technicians to make detailed explanation of principle and operation methods of biogas pool，to promote farmers to accept biogas pool project from the bottom of the heart．

5．3 Strengthening introduction of technologiesGovernment should introduce advanced technologies，personnel and methods to improve existing problems in construction and use of biogas pools．It is recommended to introduce advanced construction methods and improve unscientific process in the construction of biogas pools．Besides，it is recommended to arrange technicians to providemobile after-sales services in towns and villages，to solve possible problems in the use of biogas pools．

5．4 Improving the biogas pool service systemGovernment should establish and improve biogas service system，enhance service site construction，and expand coverage，to help every household to feed back and enjoy regular inspection and timely maintenance services．

5．5 Developing diversified models of circular agriculture in accordance with local situationsAt present，development of circular agriculture in Wangcang County is relatively backward and single．It is recommended to develop diversified models of circular agriculture．In areas with low temperature and altitude not suitable for building biogas pools，it is recommended to develop other models of circular agriculture，such as paddy field ecological breeding and integrated use of agricultural wastes［4］，and developing ecological farms in flat downstream areas［5］．Through diversified development in accordance with actual local situations，it is expected to really realize sustainable development of agriculture in the whole areas of the county．

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