DEVELOPMENT OF A CLOSED PRODUCTION PROCESS OF TAPIOCA INDUSTRY.

production consumes large amount of energy to process cassava Most used is energy in the that affect In addition to main products, tapioca industry also generates certain amount of by-products such as cassava's peel, stockpile and wastewater that potentially be utilized as an energy source. This research aimed to develop a model of a closed system of energy independent production process of tapioca through reusing the by-product as the energy source. Development of a closed system model was based on the mass balance, assessing energy content of by-products, and build a closed system of tapioca production process. This study used secondary data of processing stages and primary data of material balance from a tapioca industry. The results showed that the achievable yield of tapioca was 32%. The tapioca industry with 1,000 ton of cassava per day has the potential energy of 1,407,714,408 kcal per day derived from cassava stockpiles


Type and Source of Data
The data used were primary and secondary data. Primary data onto a factory were obtained from direct observation of the production process at a tapioca factory in Lampung (Southern Sumatera, Indonesia). Secondary data was obtained from literature studies in the form of books, journals, theses, electronic articles and other scientific articles.

System Boundary
The tapioca flour production process consists of five main compartments namely stripping station, size reduction (grating) station, extraction station, drying station, and milling station. The main input are 1,000 tons cassava per day and water. The main products are tapioca flour and by-products in the form of cassava peel, wastewater, piles and steam. Cassava peel and wastewater are the output of the first compartment (the stripping station), the pile is the output of the third compartment (the extraction station), and water vapor is the output of the fourth compartment (the drying station).

Model Description
Mass balance models were developed based on mass flows that describe the real production process. These models connect inputs as independent variables and outputs as dependent variables using the ratio (efficiency coefficient) of both based on the principle of linear equations. The calculation tool used was Microsoft Excel. The flow of tapioca production capacity of 1,000 ton of cassava per day was used as the reference. Calculation results from the model were compared with the real data onto tapioca processing industry in Lampung, then used to calculate the potential amount of energy from by-products as alternative energy sources to meet the needs of the production process. Model that has a high level of accuracy and in accordance with the real production process were used as a basis for calculating energy potential from the by-products to develop an independent energy tapioca production process model.

Mass Balance Model and By-product Energy Content
Modeling mass balances started by identifying compartments to describe the production process, then the model was formed into the mass balance equation that connects inputs (cassava and additional materials) and output (tapioca). The by-products are wastes that were assumed to be recovered. Secondary data onto mass flows of tapioca production process were used to find efficiency equations. After the mass balance equation and efficiency can be formed, the value of the efficiency factor and the mass balance was determined. The proposed models consist of two type that are simple and complex models.
The equation below was used to calculate by-product energy potential: Energy potency (kcal) = Mass (kg) x Calorific value (kcal/kg)

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The calorific value was obtained from the literature and mass of the by-products was calculated using the mass balance model.

Simple Model
The simple model assumes that all process stages in one single compartment. This model explains the total number of inputs and outputs in the system only in general ( Figure 1).

Figure 1:-Simple model of tapioca processing
Notes: I= input, P= product, W= waste I = P +W Mass balance equation is made by assuming the input is equal to output. The expected process efficiency is close to 100%, that is, all mass flows in the conversion process can be known, identified and calculated. The equation that describes a mass balance is: Where (a) is the ratio which value is between 0 to 1

Complex Model Process and Material Flows
The complex mass balance model consists of independent variables as mass inputs and dependent variables as the output of the process. This model has 21 variables consisting of 5 independent variables (I 11 , I 12 , I 41 , I 51, and I 61 ) and 16 dependent variables (X 1 , X 2 , X 3 , X 21 , X 4 , X 5 , X 6 , X 7 ; P 91 ; and W 11 to W 81 ). Dependent variable X 8 can be ignored, because it acts as explanations of the flow of the production process. The process at the sifting station is a direct flow, so there is no flow out of the system ( Figure 2).  Table 1 and 2 for symbols explanation) (Notes: Compartment IX is neglected bacause very small mass flow out of it).
524  Peeled cassava X 2 Grated cassava X 3 Rasped cassava X 21 Scattered cassava X 4 1 st extraction of cassava pulp X 5 2 nd extraction of cassava pulp X 6 Cassava slurry results from separation X 7 Wet Starch X 8 Rough Tapioca W 11 Cassava peel W 12 Wastewater Fine tapioca The process in Compartment I is whole cassava brought to the root peeler hopper. During the stripping and cleaning process, the root peeler rotates, resulting in friction between the walls of the root peeler and cassava, and friction between the cassava. This friction results in the erosion of the cassava skin. The peeled cassava is then flowed to the washer (still in Compartment I). Washing is done using a washing tub equipped with a propeller arrangement. The propeller rotates so that the friction/thrust forces make the cassava washed and continuously move it to the cassava carrier screw to the next stage.
The next stage (Compartment II) is the cutting and crushing phase which aims to reduce the size of cassava tubers before the process of dissolution (Compartment III). The tool used is chopper. At the stage of dissolution (Compartment III) using a rasper, which is a rotating cylinder with saw blades.
Extraction is the stage of separating starch components from non starch components such as fiber. The working principle of the extraction process is to separate the starch suspension from cassava pulp with the help of a filter and centrifugal force. Extraction is divided into two parts, namely pulp extraction (Compartment IV) and milk extraction (Compartment V). The separation step (Compartment VI) aims to precipitate the starch suspension and separate it with water and impurities which may still be carried after the extraction process as well as non-starch components 525 such as protein and fat. The tool used is separator. This tool is precipitating the starch suspension based on its specific gravity of the help of centrifugal force. The process of reducing water content (Compartment VII) is carried out using a Dewatering Centrifuge (DC). The working principle is to separate free water from the material based on particle size of the help of centrifugal force and filter cloth to produce wet starch.
The drying process (Compartment VIII) is carried out using a flash dryer, which is a chimney equipped with a blower at one end as an air suction, heat exchanger (steam or oil) for air heating, input of wet starch, and cyclone to separate air with tapioca. The drying medium used is heated air. The drying temperature ranges from 190 o C-210 o C. Tapioca which has dried then sieved on a shiver with 80 mesh sieve sizes. The sieving machine uses a vibration and vertical movement system to separate fine tapioca with crust. The crust is a dry starch that does not pass through the 80 mesh sieve.

The Equations
The equation needed to solve the problem is equal to the number of dependent variables, namely 16 equations. One mass balance equation can be made from each compartment to obtain 8 equations. The remaining 8 equations were made as efficiency equations. According to Fauzi et al. (2008), the process of cassava stripping contained the remains of scattered cassava which is 2 kg out of a total of 80 kg of the cutting process. The percentage of grated cassava is 98% of chopped cassava, the value of a 3 is 0.98.

Mass Balance Model
The mass balance model was developed following compartments and sub-compartments that describe machines/processes at each station, so that the details of mass changes will be seen more clearly and detail. The model calculates a yield of 32% which is higher than Garbalet al. (2012) and Rahmatulet al. (2013) as much as 20-30% and larger than factory actual data. The yield difference is caused by a more detailed and complex mass flow, so the model is more accurate and consistent. This detailed calculation reduces output that is not identified, so that mass flow has a system efficiency of 100%. This better yield is due to the looping system on the remaining scattered cassava (W 21 ) in Compartment 3, which is brought back to the cutting process (Compartment 2). At this level of yielding the amount of stockpile produced is 53.5%. The mass flows of tapioca production is shown at Figure 3. 527 Figure 3;-Material flows of tapioca productionthe model output (symbols description in Table 2)

Energy and Water Potency of the Wastes
Stockpile, cassava peel, wastewater and evaporated water are the outputs of the cassava processing into tapioca with a considerable amount. The biomass (except water) contains energy so that they can be used as energy sources. Most tapioca factories in Indonesia only use stockpile and peels as a mixture of animal feed or processed into ethanol and biogas (Yu and  According to Balogun and Bawa (1997), cassava peels have a calorie of 19.1 MJ/kg. The chemical and nutritional components of cassava peels per 100 g are 8.11 g protein, 15.2 g crude fiber, 0.22 g pectin, 1.29 g fat and 0.63 g calcium (Rukmana 1997). High calorific value of stockpile and cassava peel can be burned on the steam boiler. The efficiency of using stockpile for furnace and boiler equipment is around 76.83% (Bora and Nakkeeran 2014).
A Boiler generates steam at very high pressures and temperature. High pressure steam is used to drive the turbine in the generator so that it can generate electricity. Wolowicz et al. (2012) stated that the efficiency of electrical and thermal energy conversion using steam turbine co-generation condensation could reach 43.5%. The electrical energy produced is used to supply the electricity needs of the tapioca production process. Calculation of potential byproducts can be seen in Table 4 using equation: Energy potential (kcal) = Mass x Calorific value. In the tapioca industry, electricity is needed for the process of producing tapioca. This process consists of cutting, cassava slurry separation process and dewatering process. The closed system model in the tapioca industry is an expression of self-reliance to meet energy without external input other than raw material and water input. Energy obtained from by-products is reused to meet electrical energy needs during the production process. By-products are converted into heat energy by the steam turbine system. Stockpile and peel are burned directly to produce steam 528 used in turbines to produce electrical energy. In theoretical calculations, the electrical energy produced from stockpile and peel is 11,734.82 kWh per day (Table 5).
In tapioca production, water is one of the important input materials. Mulyanto and Titiresmi (2008) stated that in the process of producing tapioca needs 7 m 3 of water per 1 ton of cassava. Another opinion, Mai (2006) stated that the water requirement is 10-30 m 3 , a more water used in the washing process will improve the quality of flour produced. The water needs can be reduced by reprocessing wastewater during the production process.
In addition to producing stockpiles and peels, the tapioca production generates wastewater containing nutrients (nitrogen, carbon, phosphorus, potassium, calcium, magnesium, sulfur, zinc, manganese, copper, iron and sodium) (Kurniawan 2009, Ubalua 2007 ) so that if it is discharged into public waters without processing, it will cause water pollution, which in turn will endanger aquatic biota and cause unpleasant odor. To minimize the risk of water pollution, many tapioca industries apply Wastewater Treatment Plant (WWTP).
Biogas production technology has been applied to tapioca wastewater treatment plants. The by-products in the form wastewater can generate electrical energy of 22,774 kWh (Table 6). However, the efficiency of gas generator is 35% (Wibowo 2016). Therefore, the electrical energy that can be produced from wastewater is 7,971 kWh. When added to the energy surplus from stockpile and cassava peels, a surplus of 19,705.84 kWh per day is obtained.
529  In addition to wastewater, processing cassava into tapioca produces water favour from dewatering station and pressing stockpile which when condensed can produce water. The water can be reused to meet the needs in processing cassava into tapioca. The source of water favour and its mass are presented in Table 7.  Table 7, the total of evaporated water only 32% meets the water demand of the industry from a total of 7,400 ton of water. If 2,353 ton of water were channeled into the extraction station, which requires 2,250 tons of water, then there were an excess of 103 ton of water that can be channeled into the separation station. 530 evaporated water requires a cool and filtering process to be clean water raw material and does not affect the tapioca production process (Figure 4).

Closed Production Sytem of Tapioca Industry
The tapioca production system produces by-products in the form of water vapor, stockpile, wastewater, and cassava peel. The by-products which still contain energy such as peel and stockpile can be reused as energy sources, but not all by-products can be reused due to high water content.
Water vapor produced from the drying process is collected by the condenser to produce water which can be reused as water input in the extraction and separation processes. Wastewater generated from the washing process, separation and dewatering can be reused to generate biogas that is converted into electrical energy. A closed production system of tapioca industry is shown in Figure 5, where all by-products are reused.

Conclusion and Recommendation:-Conclusion
The mass balance model can describe the real situation in tapioca factories. The results of water vapor can be reused as a water source at extraction and separation stations. Energy potential is obtained from wastes including peel, stockpile and wastewater. In tapioca industry with a capacity of 1,000 tons of cassava per day, it produces 117 ton of cassava peel, 533.4 ton of stockpile, and 4,825 ton of wastewater. Stockpile and peel can produce electrical energy equal to 110,996 kWh per day. Wastewater can produce electrical energy of 7,971 kWh per day. The plant's electricity needs are 99,261 kWh per day, so the tapioca industry can be independent of energy and there is still an electricity surplus of 19,706 kWh per day. The independent energy production model can be developed into tapioca industrial production systems that are energy independent and therefore can be developed into a closed production systems industry.

Recommendation:-
Further research in implementing this system needs to be done to adjust energy needs with various process technologies. This adjustment needs to be done because each industry has different machine operations and specifications so that energy requirements will also be different.