Optimization Of Bio-Fertilizer Production From Watermelon Peels Using Response Surface

The continuous use of chemical fertilizer affects the environment and soil fertility. Bio-fertilizer helps in safeguarding soil fertility and reduce environmental pollution. This research focuses on the optimization of production of bio-fertilizer from watermelon peels. Central Composite Design (CCD) under the Response Surface Methodology (RSM) of the Design Expert software version 6.0 was used to optimize the retention days and water ratio, (factors), while Nitrogen(N), Phosphorous (P) and potassium (K) were the responses. Watermelon peel was blended and fermented for different days based on the experimental design obtained. The optimum values obtained after optimization for retention days and water ratio are 20 days and 400 ml respectively, while N. P and K contents are 26.2824, 94.5099 and 0.0005, respectively. The use of bio-fertilizers will be more economical and safer for farming activities.


BACKGROUND
Bio-fertilizers are products from agro-waste which consist of some micro-organism like bacteria, fungi and algae. Basically they are cost efficient, not harmful to the environment & natural source of nutrients [8].
Presently, there is a growing concern about the negative impact and threats to sustainable agriculture resulting for chemical agents such as chemical fertilizer. The continuous use of bio-fertilizers proves to be economical in terms of production, eco-friendly in terms of use, more efficient, productive and attainable to farmers over chemical fertilizers. [5] Bio-fertilizer is favourably the need for present day agriculture, since it is safe and residue free food is increasing on daily basis. In view of the shifting focus towards organic farming and reduction of negative effects and residues in the ecosystem, it is necessary to promote the production of bio-fertilizers in large scale in order to meet the present demand. Bio-fertilizers became popular due to high negative impact of chemical fertilizers [16].
Environmentalists are requiring immediate action by society for a shift to more environmentally friendly method of farming. Organic farming tends to be more environmentally sustainable form of agricultural production. similarly it emphasizes on good physical and mental state of animal and the prevention of synthetic chemical inputs such as fertilizers and genetically modified organisms (GMOs). [10] For a sustainable agriculture system, it is essential to use natural resources, renewable inputs which are more helpful to the plant and cause less environment hazard[10]. Agro-wastes are made up of waste which is formed from various agricultural products. Agro-wastes consist of fruits,vegetables, weeds and organic manure. The accumulation of agro-waste is harmful to the ecosystem and causes some environmental hazards. In order to avoid this, proper and safe waste management are undertaken.
The agro-wastes can be used in the production of Bio-fertilizer using fermentation method such as solid state fermentation which is a simple and cost efficient method [14].
In the times past, the farmers were keen in the usage of chemical fertilizer as it result to high yield. But eventually, they realized that chemical fertilizer affects the soil nutrients and kills the essential microbes which enhance the growth of crops. The negative impact faced using chemical fertilizers were affecting not only the soil but also human beings who eat these farm products [13]. Generally agricultural products which includes bio-fertilizer are used to replace the usage of chemical fertilizers as it does not contain any toxic substance and makes the soil enriched[1]

Sustainability of Bio-fertilizers.
The environmental hazards resulting from the frequent use and application of mineral fertilizers, and the negative environmental impacts of chemical fertilizers and their rising costs, enhances the application of bio-fertilizer which is valuable in the sustainable agricultural practices. The continuous application of bio-fertilizer encouraged plant growth and productivity [5] due to the presence of different strain groups such as nitrogen fixer, nutrient mobilization microorganisms which help in increasing the availability of minerals and their forms in composted minerals and increase levels of extractable of macro or micro-nutrients has increased significance effect of bio-fertilizers in different crop plants [2] [4]. Bio-fertilizer can be processed through Solid-state fermentation [5][12]. Usually the retention period for the anaerobic digestion of agro-wastes at mesophilic temperature ranges between 20 to 40 days [8].
The major source of organic matter in soil is agro-wastes, because of the decaying part of plants.
Agricultural wastes are the cheapest form of raw material that can be used by farmers to improve the fertility of soil due to it availability. [3]

Problem Statement
The continuous use of chemical fertilizers affects the environment, soil fertility and kills the beneficial microbes which enhances the growth of the crops. Hence, the use of natural products like bio-fertilizers in crop cultivation will help in safeguarding the soil health, reduce environmental pollution and yield quality products.

Justification
Presently, most communities in the rural areas in Nigeria are exposed to environmental issues, as a result of accumulation of agro-waste and continuous use of chemical fertilizer. In order to overcome the problems caused by continuous use of chemical fertilizers to the environment and soil, the focus of this research is to produce bio-fertilizer as a natural source against synthetic chemicals thereby reducing side effect resulting from the use of chemical fertilizer and waste in our environment through the concept of waste to wealth.
The application of Response surface methodology (RSM) to design optimization is aimed at reducing the cost of expensive analysis methods (e.g. finite element method or CFD analysis) and their associated numerical noise.
This research work is based optimization Of bio-fertilizer production from watermelon peels, in which Central Composite Design (CCD) under the Response Surface Methodology (RSM) was used to optimize the retention days and water ratio, (factors), while Nitrogen(N), Phosphorous (P) and potassium (K) were the responses.

MATERIAL AND METHOD
The raw material used for this study were sourced from yelwa market bauchi.while the chemicals used were of analytic reagent grade.

Experimental Design
Central composite design (CCD) method under the response surface methodology (RSM) of the design expert software were employed in the optimization of the production conditions such as retention time and water ratio. So as to determine the optimal condition for production of biofertilizer from watermelon peels.

Production Condition.
In order to study and determine the most feasible local environmental conditions for optimal production of biofertilizer from watermelon peel, 500 g of watermelon peel and different water ratio were used based on the experimental design table.

Preparation of Raw materials
Watermelon peels were collected from yelwa market,Bauchi. The raw materials were pre-treated by removal of unwanted materials, the watermelon peels were washed with water in order to remove impurities. The watermelon peels were blended using commercial blender.
Five hundred gram (500 g) of watermelon peel was measured using a weighing balance. The biomass were blended and mixed with water based on the experimental design values as stated. The essence of mixing the biomass with water is to allow the bacteria to move freely inside the fermenter (airtight container). The blended feed-stock was fed into the fermenter (airtight container) and closed after charging, so as to ensure airtight condition of the fermentation process. And it were allowed to ferment for different retention days at mesophilic temperature(with an optimum growth range from 20 to 45°C ). After the retention period of each of the sample, the substrate were collected and filtered. Then a sample of the soluble product were taken for elemental analysis.

Digestion
10 ml of the sample were measured into a beaker and 8 g of K2SO4 and 1g of CuSO4 were add to the sample, then 15 ml of H2SO4 was slowly added and then the beaker was then placed on heating mantle and was heated until it boiled. The boiled sample was allowed to cool and were diluted with 100 ml of distill water, which was then filtered using filter paper.

Distillation
50 ml of the filtered sample solution were measured and 30ml of NaOH were added and used for distillation. After distillation, 15 ml of the distillate were used for titration.

Titration
10 ml of boric acid and 10ml of sodium hydroxide (NaOH) were added to the 15 ml of the distillate and 2-3 drops of methyl orange were droped into it and mixed, then titration were carried out until the titrant turns pale pink. The burrete reading were then taken and percentage Nitrogen were calculated.

Determination of phosphorus (P)
50 ml of the sample were measured and 1 drop of phenolphthalein indicator were added to it, then 1 ml of 10 N H2SO4 and 0.5g of K2S2O8 were added to adjust the colour.

Determination of potassium (K)
20 ml of the sample were measured into a beaker and 5 ml of Hcl and 5ml of HNO3 were added to the sample, then 50 ml of distill water were added as well.
Then the sample solution were then heated until totally digested, after digestion it was then diluted with Then the concentration of potassium, were then determined using atomic absorption spectrophotometer.            ANOVA results for the cubic model were shown in Where N.P.K content is the response and the coded term A and B represent retention days and water ratio. It can be seen from the model equation that the linear terms A and B, and the interaction term AB in equation 4.1 and 4.2 are positive which denote positive contribution to N-content and P-content, while the quadratic and cubic terms A 2, B 2 A 3 B 3 and A 2 Bare negative, which denote negative contribution to both N and P content. While for equation 4.3, it could be seen that the cubic quadratic terms A 2 B 2 and A 3 are positive, which denote positive contribution to K-content. While the interaction term AB and A 2 B is negative which denotes negative contribution to K-content. From the numerical solution obtained these solution were picked which gave an optimum values, which are retention days20.00, water ratio4.01, N content26.2824, P content94.5099 and K content0.000495515.

CONCLUSION
Based on the analysis, design expert software 6.0, were used to optimize retention days and water ratio which gave an optimum value of N.P.K content at a good desirability level.
Bio fertilizer were produced from water melon peel after certain retention days with different water ratio based on the experimental design. The result obtained from this study shows that, the higher the retention days the higher the yield of bio-fertilize at a minimum water ratio while the lower the retention days the lower the yield. there for retention days plays a vital role in production of Bio-fertilizer from watermelon peels.