Jiwu LI, Le LI

1. Hainan State Farms Academy of Sciences, Haikou 570206, China;

2. College of Environment and Plant Protection, Hainan University, Haikou 570228, China

Banana is a kind of fruit with the 4thlargest yield in China[1]. Banana stems refer to the remaining part of banana plant after banana harvest. Their moisture content is usually higher than 90%. Due to strong toughness, banana stems are difficult to be processed.So in agricultural production, the majority of banana stems is discarded at random[2],resulting in enormous waste of resources and serious pollution of environment[3]. Agricultural waste is a major source of environmental pollution.Meanwhile, it is also a huge potential base for biomass resources. Its dualism should be fully understood[4-6].The development of recycling utilization model characterized by “resourcesproducts-waste-renewable resources”for banana stems waste can promote the coordinated development of economy and the environment, and it has great environmental, economic and social benefits. However, the current comprehensive utilization of banana stems lacks of detailed and reasonable collection method, resulting in very high transportation costs that cannot be borne by companies. Even worse,the harvesting time of bananas is relatively concentrated, and the fresh banana stems cannot bear longtime storage. Thus the banana stems processing enterprises cannot obtain continuous supply of raw materials. In this study,based on the understanding about distribution and scale of banana stem resource in Hainan, the collection,low-cost transportation and storage methods for banana stems were studied so as to lay a solid foundation for the comprehensive utilization of banana stem resource[7].

Material and Methods

Material

The banana stems,in diameter of 30 cm and height of 80 cm, were collected from a farm in Wenchang City,Hainan Province.

Equipment and instruments

The used equipment and instruments in this study included multipletool high-speed rotary crusher (Yijin 420), presser, cutting machine, elec-tronic balance, thermostatic drier box,platform scale,and so on.

Treatments

A total of 8 treatments were designed. In the 8 treatments, fresh banana stems were all desiccated naturally on 100-mesh stainless steel strainers with a slope of 5% for 8 d.There were 3 replicates for each treatment.The fresh banana stems basically in the same length were sampled for determination of moisture content(90.5%).In Treatment 1,fresh banana stems were desiccated horizontally on an outdoor strainer; in Treatment 2,fresh banana stems were desiccated vertically on an outdoor strainer; in Treatment 3,fresh banana stems were first crushed and then desiccated on an outdoor strainer; in Treatment 4,fresh banana stems were crushed,compressed and desiccated on an outdoor strainer; in Treatment 5, fresh banana stems were first torn up and then desiccated on an outdoor strainer;in Treatment 6,fresh banana stems were directly desiccated on an indoor strainer; in Treatment 7, fresh banana stems were first crushed and then desiccated on an indoor strainer; in Treatment 8,fresh banana stems were crushed, compressed and desiccated on an indoor strainer.

A total of 100 banana plants were selected randomly, and after the harvest of bananas, the plants were cut down. The average moisture content in banana stems was determined.The banana stems were then crushed by a multiple-tool crusher (minimum width of inlet of 30 cm, cutting speed of 2 000 r/min) and compressed by a presser. Subsequently, the banana stems were transported on 100-mesh stainless steel strainers with a slope of 5%. All the strainers were placed in a field arranged with drainage ditches.All the banana stems were air dried for 8 d. There were 3 replicates for each treatment.In Treatment A,the banana stems were covered and stored for 3 months; in Treatment B, the banana stems were covered and stored for 4 months; in Treatment C, the banana stems were covered and stored for 6 months.

Results and Analysis

Effect of different treatment on weight of banana stems

Banana stems are bulky and heavy, and are difficult to be transported. So they usually take up large spaces. The variations of banana stems weights in different treatment groups were shown in Fig.1.As shown in Fig.1, in the initial stage, there were no significant differences in banana stems weight among different treatment groups, but after 8-d desiccation,the banana stems weights ranked as Treatment 6 ＞Treatment 7 ＞Treatment 8 ＞Treatment 1 ＞Treatment 2 ＞Treatment 5＞Treatment 3＞Treatment 4. The weight of banana stems in the Treatment 4 was reduced most greatly, and it was reduced from 822.03 to 203.92 g.The weight of banana stems in the Treatment 4 was reduced by 75.19%after the desiccation.After the processes of crushing and compression, the weight of banana stems was reduced by 52.78%.The decrement of banana stems weight in the Treatment 3 ranked third, and the weight of banana stems was reduced from 845.92 g to 413.74 g. Among all the 8 treatment groups, the decrement of banana stems weight was smallest in the Treatment 6, where the weight of banana stems was reduced from 855.84 g to 829.72 g with a percentage of 3.05%. Based on the results above, it could be concluded that the desiccation effect of crushing, compression and drying on outdoor strainer was best for banana stems.

Effect of different treatment on moisture content in banana stems

Banana stems have high moisture content, so they are intolerant to longtime storage and are very perishable.The variations of moisture contents in banana stems of different treatment groups were shown in Fig.2.As shown in Fig.2,the initial moisture contents in banana stems of the 8 treatment groups were all 90.5%, and after 8-d desiccation, the moisture contents ranked as Treatment 6＞Treatment 7＞Treatment 8＞Treatment 1＞Treatment 2 ＞Treatment 5 ＞Treatment 3 ＞Treatment 4.The moisture content was lowest in Treatment 4,and it was reduced to 19.93%; while the moisture content was highest in Treatment 6,and it was reduced to only 87.45%.The moisture contents in banana stems which had been dried in outdoor were reduced most greatly on the 1std since the starting of the desiccation, which was most obvious in banana stems of Treatment 4. However, in banana stems which had been dried in indoor,the decrements of moisture contents were relatively small.

Under the same conditions, the moisture contents in banana stems which had been dried in outdoorranked as Treatment 1＞Treatment 2＞Treatment 5＞Treatment 3 ＞Treatment 4; the moisture contents in banana stems which had been dried in indoor ranked as Treatment 6＞Treatment 7＞Treatment 8. The moisture contents in banana stems dried in outdoor were all lower than those in banana stems dried in indoor; the moisture contents in banana stems which had been crushed and compressed were lower than those in banana stems which had been only crushed; the moisture contents in banana stems which had been crushed were lower than those in banana stems which had been decayed naturally.

Table 1 Effect of different storage time on moisture content in banana stems %

Concentrated collection model for banana stems waste

Table 1 showed the changes in moisture content and volume of banana stems in different concentrated collection treatment group.In the initial stage,the moisture contents in banana stems were all more than 90%. After the compression, the moisture contents were reduced to 45%-55%, and the volumes were reduced to 30%-40% of the initial volumes. After the natural drying, the moisture content in banana stems was reduced to 25% or less. The moisture content in banana stems was not changed significantly after 6-month storage. Therefore, the process of banana plants-cutting down-crushing-compression-transportation-desiccation-storage was basically formed. After crushing and compression, the volume and weight of banana stems will be reduced,thereby facilitating transportation. After desiccation, banana stems can be stored for a very long time, which solves the problem of raw material supply for banana stems processing enterprises.Thus the concentrated collection and resource utilization of banana stems waste are ultimately achieved.

Conclusions and Suggestions

The processes of crushing, compression and outdoor drying on strainers showed the best desiccation effect,and the moisture content in banana stems was reduced from 90.5% to 19.93%, and the weight was reduced by 75.2%.After 3 to 6-month storage,the moisture contents in banana stems ranged from 17%to 20%,and the volumes were reduced to 30%-40% of the initial volumes,which basically met the requirements by dry storage. The plant-cutting down-crushing-compression-transportation-desiccation-storage production model was initially developed for desiccation and concentrated collection of banana stems,which would lay a certain foundation for the utilization of banana stem resource by enterprises.

However, the industrialization of concentrated collection and utilization of banana stems is affected by many factors. Although some preliminary research results have been obtained in this study, some deficits still exist.Therefore, further researches in this field are still required. First, the relevant departments can be cooperated with enterprises to carry out researches on process monitoring of concentrated collection and utilization of banana stems. The compressed density of raw material, transformation products, resources conversion, large -scale processing equipment and integrated effectiveness all needed to be studied. The acquisition of raw materials, transport vehicles, storage, production site layout and the like are arranged according to the distribution and harvesting time of bananas in Hainan Province. Second, the social benefits of banana stems comprehensive utilization and biomass conversion are more obvious than their economic benefits,so enterprises are usually lack of an impetus. For this, the government should strengthen policy support and invest corresponding financial support. In addition, the government should also coordinate the relationship between farmers and enterprises. From the perspective of comprehensive utilization and overall effectiveness, a unified and rational production model of collection, crushing, transportation and storage should be established for banana stems waste, transforming banana stem waste into renewable resources and energy by enterprises,thereby promoting the commercial and industrial application of banana stems waste.

[1]CHEN XJ(陳新建),CHEN DM(陳道明).Trade situation and development strategies for Chinese tropical fruit production(中國熱帶水果生產(chǎn)貿(mào)易現(xiàn)狀及發(fā)展對策)[J].China Tropical Agriculture (中國熱帶農(nóng)業(yè)),2010,3:14-17.

[2]YANG YZ(楊永智),WANG SM(王樹明),YANG C (楊岑).Development and utilization of banana stalk-leaves resources(香蕉莖葉資源的開發(fā)利用研究)[J]. Science of Resources and Environment(資源與環(huán)境科學(xué)), 2012, 4: 294-295.

[3]LIU Y (劉洋). Rural circular economy value discussion of China (我國農(nóng)村循環(huán)經(jīng)濟的價值探討)[D]. Dalian: Dalian Maritime University (大連: 大連海事大學(xué)),2012.

[4]LI ZG (李志剛),TAN LH (譚樂和).Utilization of tropical agricultural wastes in Hainan Province (海南省熱帶農(nóng)業(yè)廢棄物資源化利用狀況及對策)[J]. Chinese Journal of Tropical Agriculture(熱帶農(nóng)業(yè)科學(xué)),2009,29(8):47-50.

[5]SUN YM (孫永明), LI GX (李國學(xué)),ZHANG FD (張夫道), et al. Status quo and developmental strategy of agricultural residues resources in China (中國農(nóng)業(yè)廢棄物資源化現(xiàn)狀與發(fā)展戰(zhàn)略)[J].Transactions of the CSAE (農(nóng)業(yè)工程學(xué)報),2005,08:169-173.

[6]WANG SL (王松林).Study on resource utilization of agricultural waste(農(nóng)業(yè)廢棄物資源化利用研究)[D].Hainan:Hainan University(海南: 海南大學(xué)),2008.

[7]DENG YG(鄧怡國), SUN WS(孫偉生),WANG JL(王金麗),et al.Utilization status and analysis of tropical agricultural waste resources: comprehensive utilization of banana leaves(熱帶農(nóng)業(yè)廢棄物資源利用現(xiàn)狀與分析——香焦莖葉綜合利用)[J].Guangdong Agricultural Sciences(廣東農(nóng)業(yè)科學(xué)),2011,1:79-80.