Bio-Gas from Coconut Husk Retting

ABSTRACT

“Earth does not belong to man but man belongs to earth; what man does to earth is itself

what he does to himself”. Energy utilisation is one of the prominent issues to be

discussed in the present scenario. In the past few decades there has been a drastic hike in

energy demand since energy has plays a vital role in a society’s upliftment and helped in

evolution of energy deficit. The depletion of world petroleum reserves coupled with

global environmental problem stimulated the search for alternative source for petroleum

fuel. Biogas recovery from coconut husk is one such candidate for the exploitation as an

alternative to conventional fuels. A large quantity of coconut husk is retted in back waters

of kerela to extract coir fibre. Coconut husk retting is a bacteriological process which

decomposes the binding material that hold the fibres together in the husk. Retting takes

places under anoxic conditions. Husk which normally is considered as waste and thrown

in open dumpsites will allow for the recovery of methane which otherwise will simply go

into the atmosphere if left to decay in open fields. The project activity is thus considered

a both a renewable energy and waste management solution. This project will also comply

with government solid waste management act and clean air act to protect environment by

avoiding open field dumping of waste. Using waste bio mass to produce energy can

reduce green house emission and reduce pollution and waste management problem which

has high potential in addressing energy security of the country.

BY: G.ARUN GOWTHAM K. SHANKAR REDDY MECHANICAL III YEAR TKRCET,HYD.

INTRODUCTION

The discovery of fossil fuels and the extensive use of them limited the vision and role of

other options and areas of harnessing energy. However, with time, the extensive use of

these fuels has led to the depletion of them. Also the noteworthy dangers due to usage of

these fuels have sent out a distress signal to search for an alternative source. As an

alternative, biomass plays an important role in quenching our thirst for energy. ‘History

repeats itself’ and man has once more gone back in time to learn from his ancestors.

Throughout history humans have used fuels made from plant and animal matter for

heating and cooking.

Moreover today’s technological advances and society’s increasing demand for energy

have led to an expanded role for these biomass fuels. Biomass is material derived from

recently living organisms. It includes plants, animals and their by-products. For example,

manure, garden waste and crop residues are all sources of biomass. It is a renewable

source based on the carbon cycle, unlike other natural resources such as petroleum, coal,

and nuclear fuels.

Biomass fuels get their energy from the sun. Photosynthesis converts solar energy

striking the leaves of plants into chemical energy, which is stored in the plants

themselves. Animals that eat plants store some of this energy in their bodies; some of it is

also ultimately stored in manure and other wastes. Biomass fuels are renewable because

the raw materials can be replaced within a human lifetime simply by growing more crops

or collecting more waste. The energy content of biomass fuels is usually measured in Btu

(British thermal units). The energy produced by a lit match is roughly equal to one Btu.

This biofuels can be widely categorized into: alcohol fuels and agricultural fuels

Alcohol Fuels

Certain plants can be used to produce liquid alcohol fuels such as ethanol (grain alcohol)

and methanol (wood alcohol). Ethanol can be produced by fermenting crops such as corn,

sugar beets, or grasses, or by fermenting by-products of cheese and paper manufacturing.

Methanol can be produced by heating wood in an enclosure that has little air and then

using chemicals to convert the gases given off by the heated wood into a liquid. Both

ethanol and methanol can be used to run cars, trucks, and buses.

Agricultural fuels

Agricultural products specifically grown for bio-fuel production include corn and

soybeans, primarily in the United States; rapeseed, wheat and sugarbeet primarily in

Europe; sugarcane in Brazil; palm oil in South-East Asia; and jatropha in India. In

Hawaii and Brazil, bagasse, a residue left over after sugarcane is harvested and

processed, is burned in power plants to produce electricity. In Denmark, straw is burned

to produce heat for farms. Biodegradable outputs from industry, agriculture, forestry and

households can be used for bio-fuel production, either using anaerobic digestion to

produce biogas, or using second generation bio-fuel processes; examples include straw,

timber, manure, rice husks, sewage, and food waste. The use of biomass fuels can

therefore contribute to waste management as well as fuel security and climate change.

Bio-fuels and other forms of renewable energy aim to be carbon neutral.

This means that the carbon released during the use of the fuel, e.g. through burning, to

power transport or generate electricity, is reabsorbed and balanced by the carbon

absorbed by new plant growth. These plants are then harvested to make the next batch of

fuel. Carbon neutral fuels lead to no net increases in atmospheric carbon dioxide levels,

which mean that global warming need not get any worse.

In practice, bio-fuels are not carbon neutral. This is because energy is required to grow

crops and process them into fuel. Examples of energy use during the production of bio-

fuels include: fertilizer manufacture, fuel used to power machinery, and fuel used to

transport crops and fuels to and from bio-fuel processing plants. The amount of fuel used

during bio-fuel production has a large impact on the overall greenhouse gas emissions

savings achieved by bio-fuels.

Carbon emissions

The carbon emissions produced by bio-fuels are calculated using a technique called Life

Cycle Analysis (LCA). This uses a "cradle to grave" approach to calculate the total

amount of carbon dioxide and other greenhouse gases emitted during bio-fuel production,

from putting seed in the ground to using the fuel in cars and trucks. The majority of LCA

studies show that bio-fuels provide significant greenhouse gas emissions savings when

compared to fossil fuels such as petroleum and diesel. Therefore, using bio-fuels to

replace a proportion of the fossil fuels that are burned for transportation can reduce

overall greenhouse gas emissions. These fuels are mainly classified into first- generation

and second-generation bio-fuels.

First generation biofuels

First-generation fuels refer to biofuels made from sugar, starch, vegetable oil, or animal

fats using conventional technology.

The most common first generation bio-fuels are listed below.

Vegetable oil

Vegetable oil can be used for either food or fuel; the quality of the oil may be lower for

fuel use. Vegetable oil can be used in many older diesel engines (equipped with indirect

injection systems).

Biodiesel

Biodiesel is the most common biofuel in Europe. It is produced from oils or fats using

transesterification and is a liquid similar in composition to mineral diesel.

Bioethanol

Ethanol is the most common biofuel worldwide. It is an alcohol fuel. It is produced by

fermentation of sugars derived from wheat, corn, sugarbeet.

Butanol

Butanol is often claimed to provide a direct replacement for gasoline. It is not in

widespread production, and engine manufacturers have not made statements about its

use.

Methanol

Methanol is currently produced from naturalgas, a fossil fuel. It can also be produced

from biomass.

BioGas

Biogas is produced by the process of anaerobic digestion of organic material by

anaerobes. It can be produced either from biodegradable waste materials or by the use of

energy crops fed into anaerobic digesters to supplement gas yields. The solid byproduct,

digestate, can be used as a biofuel or a fertiliser.

Biogas contains methane and can be recovered from industrial anaerobic digesters and

mechanical biological treatment systems. Landfill gas is a less clean form of biogas

which is produced in landfills through naturally occurring anaerobic digestion.

Second generation biofuels

Second generation biofuels use biomass to liquid technology. The following second

generation biofuels are under development:

BioHydrogen

Bio-DME

Biomethanol

DMF

HTU diesel

Fischer-Tropsch diesel

Mixed alcohols (i.e., mixture of mostly ethanol, propanol and butanol, with some

pentanol, hexanol, heptanol and octanol)

The analysis for bio-fuels has shown that first generation biofuels can save up to 60%

carbon emission and second generation biofuels can save up to 80% as opposed to using

fossil fuels.

BIOGAS RECOVERY FROM COCONUT HUSK

We will now concentrate on a particular source of biogas which is unique and

very easily available for extraction of biogas- COCONUT HUSK.

Coconut husk is nothing but the outer thick layer of coconut which when dried has a

brown color to it.

This organic husk has been conventionally used to make ropes and fibers. When

coconuts are used in a commercial sense this husk is simply scraped off and thrown away

or left to decompose. The easy availability and growth of coconut trees in most parts of

the country makes it a viable source of biogas. Also it is practical as the procedure to

extract biogas from coconut husk is very simple.

Preparation

The procedure of extracting biogas from coconut husk is very similar to the extraction of

biogas from animal and plant waste by land filling.

This method is widely employed in the backwaters of Kerala. A large volume of coconut

husk is first collected. This husk is soaked in water body e.g. a pond or a man made tank.

This is called retting of husk. Coconut husk retting is a bacteriological process which

decomposes the binding material that holds the fiber together in the husk. This process

takes place under anoxic conditions. This procedure is fundamentally used for

manufacturing fibers and ropes. Methane gas is developed from the soaking of the husk.

This methane has been for years let off into the atmosphere. Methane is the second most

important greenhouse gas after carbon dioxide, and is expected to contribute nearly 18%

of the total global warming during the present half-century. Wetlands are the largest

natural source of methane. Kerala has a total of 127,930 ha of wetland area.

Measurements show that methane fluxes from Kerala's coastal lakes have decreased

during the past decade. This could be due to the reduction in coconut husk retting activity

in these lakes. But one ton of methane produces the same greenhouse gas (GHG) effect as

23 tons of CO2. When methane burns the formula is CH4 + 2O2 = CO2 + 2H2O. So by

harvesting and burning landfill gas, its global warming potential is reduced a factor of 23,

in addition to providing energy for heat and power.

And so this large amount of methane can be directed and used as a fuel.

About 1000 tons of husk can undergo retting at once. This husk is left underwater for a

period of 20-25 days. The husk thus retted is diverted into an underwater tank. The husk

in this tank decomposes and releases marsh gas or methane. This methane gas is further

collected and distributed. The apparatus also consists of a gas sampling bottle wherein the

concentration of gases is analysed and temperature indicator is present to maintain the

optimum level of temperature in the tank. Further a gas flow meter is also installed to

check the flow and amount of supply of gas.

The gas that is obtained from the coconut husk has the following composition:

COMPONENT CONCENTRATION

(%BY VOLUME)

Methane 65.00

Carbon dioxide 30.00

Hydrogen sulphide 0.07

Others 4.93

It is evident that the main gas obtained from this procedure is methane. 1000 tons of

coconut husk can yield about 120 cubic meters of gas per day.

In some parts of our country this gas is being successfully used as fuel in stoves, lamps

and in IC engines.

Bio-waste management

Furthermore, a concrete waste management plan will also help us gain energy.Anaerobic

digestion can be used as a distinct waste management strategy to reduce the amount of

waste sent to landfill and generate methane, or biogas. Any form of biomass can be used

in anaerobic digestion and will break down to produce methane, which can be harvested

and burned to generate heat, power or to power certain automotive vehicles.

A 3 MW landfill power plant would power 1,900 homes. It would eliminate 6,000 tons

per year of methane from getting into the environment. It would eliminate 18,000 tons

per year of CO2 from fossil fuel replacement. This is the same as removing 25,000 cars

from the road, or planting 36,000 acres (146 km²) of forest, or not using 305,000 barrels

of oil per year. Biofuel industries are becoming established in many developing countries.

Many developing countries have extensive biomass resources that are becoming more

valuable as demand for biomass and biofuels increases. The approach to biofuel

development in different parts of the world varies. Countries such as India and China are

developing both bioethanol and biodiesel programs.

Oils and gases can be produced from various biological wastes:

Thermal depolymerization of waste can extract methane and other oils similar to

petroleum.

GreenFuel Technologies Corporation developed a patented bioreactor system that

uses nontoxic photosynthetic algae to take in smokestacks flue gases and produce

biofuels such as biodiesel, biogas and a dry fuel comparable to coal.

FUTURE

Recognizing the importance of implementing bioenergy, there are international

organizations such as IEA Bioenergy, established in 1978 by the International Energy

Agency (IEA), with the aim of improving cooperation and information exchange between

countries that have national programs in bioenergy research, development and

deployment.

In India, a bio-ethanol program calls for E5 blends throughout most of the country

targeting to raise this requirement to E10 and then E20. In China, the government is

making E10 blends mandatory in five provinces that account for 16% of the nation's

passenger cars. Biofuels can provide benefits including: reduction of greenhouse gas

emissions, reduction of fossil fuel use, increased national energy security, increased rural

development and a sustainable fuel supply for the future.

Environmental effects

Most mainstream environmental groups support biofuels as a significant step toward

slowing or stopping global climate change. However, biofuel production can threaten the

environment if it is not done sustainably.

Biofuels produce greenhouse gas emissions during their manufacture. The source of these

emissions are: fertilisers and agricultural processing, transportation of the biomass,

processing of the fuels, and transport and delivery of biofuels to the consumer. Some

biofuel production processes produce far fewer emissions than others; for example sugar

cane cultivation requires fewer fertiliser inputs than corn cultivation, therefore sugar cane

bioethanol reduces greenhouse gas emissions more effectively than corn derived

bioethanol. However, given the appropriate agricultural techniques and processing

strategies, biofuels can provide emissions savings of at least 50% when compared to

fossil fuels such as diesel and petroleum.

The increased manufacture of biofuels will require increasing land areas to be used for

agriculture. However, second generation biofuel processes can ease the pressure on land,

because they can use waste biomass, and existing (untapped) sources of biomass such as

crop residues and potentially even marine algae.

As the conservation of energy has become the need of the hour

these alternative sources of fuel need to be thought of and applied. Without the

development and the implementation of these methods we would not know what to

expect of the future. Also, acting upon on the method of alternative sources will help us

correct our mistakes in the future and will make way for brighter days ahead.

THANK YOU…