LOCATIONAL OPTIMIZATION OF BIOGAS DIGESTER
According to the Business Standard Report, approximately 40 % of the food produced in India is being wasted daily and this percentage touches 50% on special occasions. It is approximated that the quantity of daily food waste generated in India is about 750–1000 tones and it is estimated that 33% of all agri-food production is lost in the form of waste. The percentage contribution to this number is high in metropolitan city and major district headquarters. But food waste is not equally distributed among different parts of society and it depends on the habitat of the humans can be the concluding statement. Hence before setting up Biogas plant a proper survey has to be made based on quantity of waste generated in particular location by considering all the facts related to installation procedure and this method is called as “Locational Optimization” and the constraints placed on setting up biogas plant are economic, environmental and social objectives and decision is made based on the weights of individual criteria and sub criteria. Hence optimization of the selected site is necessary for maximization of the profit and sustainability of the plant.
The aim of locational optimization is to customize the actual condition of a process by considering individual property through selective adaption of influencing aspects to attain a distinct target state. In conventional way, optimization of the location and biogas plant operation is dependent on Social, Economic and Environmental aspects. These areas mutually influence each other and thus cannot be optimized independently. An optimization problem is expected to have host of different solutions, various possible solutions shall be compared with each other on the basis of evaluation criteria and adoption of the solution is solely dependent on the weightage.
The criteria used for evaluation can include costs, for example gas yield or minimization of environmental impacts. Depending on the overriding objective the evaluation criteria then need to be weighted, so that a final assessment can be made and a judgement on which criteria importance to be given. Practically, each and every dependable criteria of a biogas plant must aim to attain the overall optimum that is attainable under the given conditions. Infrastructure challenges, Environmental factors and societal conditions are significant considerations because biomass to energy scheme is extremely dependent on feedstock availability hotspots and transportation facility. Pooling of organic waste or feedstock from hotels, restaurants, kitchens or any other related spots is referred as “off load points”. But the fact is off-loading points and biogas demand is often widely separated by distance. Improper collection, poor segregation, a lack of transportation facilities and inadequate waste transportation upsurge the possibility of supply chain disturbance and create difficulty in employing waste in production of biogas. Thus, locating appropriate sites for biogas plant setup and installation, which minimizes transportation distance and a total supply chain cost is of high importance.
The plant needs abundant water reserves for biogas digesters; especially anaerobic digestion necessitates abundant water with a proportion equal to 1:1 of the amount of water and feedstock to be loaded into the digester. Thus site has to be near to aquifer surface and site has to be excluded if waterline is 150 m away from site. Specific ecology criteria to be studied are quality of soil, slope of selected site, area size, and local traffic change, its data, and access to local public infrastructure, transportation are major considerations. Soil quality is one of the indicators for qualitative analysis of the site conception. The soil characteristics decides drainage conditions with smooth relief, deep water table and good soil support capacity and these aspects are also considered to be suitable for engineering works.
Some of the social challenges are the behavior of the society towards biogas plant. Absence of knowledge, intelligence or communication and limited interaction with potential adopters could be another reason for the low level of information among people. The residents must be convinced about the importance of the biogas plant. Thus, rural economy should be the cause of awareness of environmental protection, economy of resources and health improvement among rural households, thus contributing to success of biogas plant installation. Thus an expertise person in this path is important. Insufficiency of public contribution and consumer interest are the most important society’s cultural barrier.
The optimization of technical methods and procedures in a biogas plant is meant to raise the accessibility of the technology by minimizing interruptions and guaranteeing smooth running of the bio gas generation process. This objective correspondingly has secondary effects for the economics of the plant, because the plant can only meet its operation objective if it has a high-pitched capacity utilization rate. Contrarily, a high-pitched technological input relates to high budget, so a cost-benefit examination must be performed in the perspective of economic optimization.
The quantity of biogas yielded in a biogas plant is strictly associated with purity of substrates. Source sorted organic waste is technically cleaner than mechanically sorted feedstock. Additional important argument connected to substrate condition concern is the stability and optimization of supply of feedstock coupled with transportation to the site. Transporting moisture biomass from the off-load point to the production site becomes unfavorable due to building pressure and hence it is advised to reduce the moisture before loading into vehicles. At site, suitable pretreatment is mandatory before storage of feedstock to avoid biodegradation and loss of heating value. At least three months of survey is necessary to study the average waste generated in the selected location and based on that the size of the bio digester can be decided. The generated biogas has to be stored before applications, because the gas to undergo filtration to remove the adulterant gas compositions to improve the performance. The quantity of biogas produced is a function of atmospheric temperature and humidity. In order to generate constant biogas, the digester temperature and pressure must be uniform irrespective atmospheric conditions.
It should always be remembered that each biogas plant is a system that consists of a large number of individual components that have to be fine-tuned to each other. Efforts must therefore be made as early as the planning phase to ensure that the chain works as a unified system.
