Feasibility Study on Anaerobic Digester

Feasibility study on anaerobic digester 1
FEASIBILITY STUDY ON ANAEROBIC BIODIGESTER FROM COW DUNG WASTE FOR A
SLAUGHTERHOUSE FIRM IN EDO STATE, NIGERIA
By Name
Course
Instructor
Institution
Location
Date

Feasibility study on anaerobic digester 2
Executive summary
The ever-increasing demand, health impacts and abnormal costs of utilizing energy which is
obtained from compounds of hydrocarbon has necessitated the need for alternative sources of
energy which is cleaner and cheap. In other terms energy source that promote sustainability. One
of the most appropriate alternatives in the recent research has proved to be cow dung .This
research study has exclusively covered a project that utilizes cow dung for the purposes of biogas
production located in Edo estate, Nigeria. The utilization of biogas provides many benefits both
to the individual, society and the environment and generally promotes sustainability. It greatly
helps in solving the problems arising from waste management and thus it is recommended that
biogas plants be implemented in large scale projects for a better future (Artto, 2011).
Key terms
Biogas, manure, digester

Feasibility study on anaerobic digester 3
Contents
Abstract...................................................................................................................... 2
Introduction................................................................................................................ 4
Study background................................................................................................... 4
Structure of biogas plant......................................................................................... 5
Biogas unit components.......................................................................................... 6
Types of digester..................................................................................................... 7
Building materials and dimensions........................................................................10
Site preparation..................................................................................................... 10
Facility layout..................................................................................................... 10
Dimension marking............................................................................................ 11
Excavation works............................................................................................... 11
Preparation of the digester’s bottom.................................................................12
Construction of the digester............................................................................... 12
Placement of the heating tubes.........................................................................13
Installation technology.......................................................................................... 13
Insulation technology......................................................................................... 14
Mechanization and information technology..............................................................14
Gas processing unit............................................................................................... 16
Mixing technology................................................................................................. 16
Monitor and controlling...................................................................................... 17
Running the plant.................................................................................................. 17
Constraints in integrating biogas plants into farms...............................................18
Economic benefits of the biogas plants.................................................................19
Advantages and Benefits of Biogas.......................................................................20
Financial analysis..................................................................................................... 21
Project costs and revenue..................................................................................... 21
System productivity.............................................................................................. 22
DESIGN..................................................................................................................... 30
Introduction........................................................................................................... 30
FACTORS INVOLVED IN OPTIMUM BIOGAS PRODUCTION.......................................32
DESIGN CONCEPT OF THE BIODIGESTER...............................................................36
Selection of construction materials.......................................................................41

Feasibility study on anaerobic digester 4
Recommendations.................................................................................................... 42
Conclusion................................................................................................................ 42

Feasibility study on anaerobic digester 5
Feasibility study
Introduction
Study background
The utilization of fossil fuels as the chief source of energy has resulted in a number of impacts
such as environmental degradation, climate change, and health impacts. Besides, the
management of waste is one major contributing factor to the hindrance of effective
development .This majorly is as a result of the increased commercial, agricultural and industrial
activities creating huge amounts of wastes .These wastes usually are not properly disposed
thereby creating health discomfort and also ratification of the environment .Nevertheless, these
wastes when properly managed can be converted into a useful substance to the society. For
instance, the waste substances can be converted into a form known as biogas. Biogas generally
are products that are obtained after the breakdown of organic substances in the absence of
oxygen. Its raw materials are usually readily available and thus it is a renewable source of energy
.This technique stand to be among the efficient energy sources and since livestock waste
management has been a major challenge in most countries, it appears to be the best solution to
this stalemate (Brenda, 2015). Huge volume of cow dung generated are usually disposed in the
landfills or applied on the farms without any proper treatment. Nigeria alone generates
approximately 230000 tons of fresh cow dung annually and since only one kilogram of the dung
can produce 0.03m3 of gas daily, meaning that on a daily basis, the total amount of biogas
produced can be 6.8miliom m3.The biogas produced after fermentation has many applications
including households heating and cooling, electrical power generation and also running of
engines. (Berridge, 2014)
Below is a graph showing the sludge production in regards to the retention time and temperature

Feasibility study on anaerobic digester 6
The graph shows that the production of biogas is proportional to the temperature and the
retention time such that the longer the retention time and higher temperatures, the increased
amount of biogas produced.
Structure of biogas plant
The plant generally comprises of two parts which are the storage and the digestion chamber.
Some plants have pre-chamber for the mixing of the products and post chamber for the
allowance of the products to fully ripen. The figure below represents the parts of the biogas
chamber (Bishop, 2013).

Feasibility study on anaerobic digester 7
Biogas unit components
The biogas unit comprises of the following components;
 Overflow tank
 Reception tank
 Gas holder
 Fermenter or digester
Size of the biogas unit
There are several factors which determine the size of the biogas unit. These factors include
 The utilization demand of the of the natural gas and the pattern of consumption
 The nature of the soil on the site and also the ground level
 The expertise’s of the biogas plant operators as well as the technology used
 The type and quantity of waste that is supposed to be disposed on the digester
 The main aim of disposing the waste into the digester
 The temperature of air in the specific region (Bishop, 2013)
Besides, there are some mathematical calculations which need to be performed such as;
Digester size (m³) = Daily feed-in (m³ day-1) × Retention time (day)
The total size of the biogas unit defines the size of the digester which comprises of the total
volume that is occupied by the fermented material and also the gas stored in the digester.
Usually, the daily feed material consists of water and the cow dung or the manure that is usually
added at a certain percentage so as to average the concentration of the solids present therein. An

Feasibility study on anaerobic digester 8
intricate and reliable design of a biogas digester plant takes into account some various
parameters. For instance
 The retention of the added materials to the total volume of waste
 The total number of cows in the site
 The average amount of cow dung material that is produced by each cow monthly
 Amount of liquid mater that is deposited on a daily basis to the digester
 The quality of the organic matter deposited daily
 The retention time (Board, 2013)
 The digester load
 The empty part of the tank available for the substrates, this space is usually 10 percent of
the total tank volume
Types of digester
Various kinds of digester have been developed over the past few months. These types of digester
include different kinds such as batch flow, contact flow, continuous flow, and plug flow among
others. Usually, the available digesters are designed in a way such that no mechanism is
incorporated so as to minimize the time of retention when the biogas is less active. Normally,
these systems are discontinuously fed or continuously fed. The discontinuously fed systems are
the batch digesters while the continuously fed systems are continuous flow digester. The batch
digester is usually filed once and then maintained for a longer period; thereafter the organic
matter is offloaded at a later period. It has few operational requirements and installation can
always be done in one anaerobic tank or more depending on the demand of the biogas and also
materials available (Brandt, 2014)