Biogas in Pakistan

Biogas in Pakistan – some facts and figures

By Engr. Naeem ul Zaman & Engr. Asim bin Aziz
BIOGAS IS produced by anaerobic (absence of air) decomposition of organic matter by a bacteria present in the stomach of animals including buffalos, cows etc. Bio Gas is also known as Gobar Gas or Marsh Gas. Chemically it consists of 60-65% Methane (CH4), 35-40% Carbon Dioxide (CO2), and traces of Hydrogen Sulfide, Water Vapors, Nitrogen and other gases.
Because of its Methane content, it burns just like natural gas but has a lower heating value of nearly 600 BTUs/cft as compared to 925 BTUs/cft of natural gas (commonly known as Sui gas) which is more than 98% Methane.
Theoretically, it is very simple and easy to produce biogas by mixing equal amounts of fresh buffalo dung and water and put this in a vessel where there is no air. In summer, the gas will appear within few days time and in winter or in cold climate, it may take a little longer. The bacteria; present in the dung does all the work.
Despite the fact that it looks so simple, the production of biogas is not so popular in Pakistan. Large scale efforts were made to popularize biogas production during 1980s and lot of money was spent by the government, but after some time the efforts died down and only a few biogas plants installed at that time are still in production. At present Pakistan Council of Renewable Energy Technology (PCRET) is trying to propagate biogas production but on low key basis. A number of NGOs as well as commercial organizations are also working on biogas production.
Gas produced in a small bio-digester which contains about 20 kg of dung should be enough to meet the fuel requirement of a small family. Based on these calculations, a bio-digester for any number of animals can be designed.  The thumb rule is one cubic meter (35.5 cft) digester volume for 10 Kg of cow dung (one cow).
Large size digesters use different type of biomass such as potato waste, chicken droppings, tannery waste, green silage (leaves, corn etc), food scrapes, bakery waste, molasses, slaughter house waste (poultry and other) fats and greases to produce biogas at industrial scale, both for electrical power generation as well as for heating purposes.
A biogas production facility is basically a gas tight vessel with possibility of adding fresh slurry and removal of gas and waste slurry. For intermittent use of gas such as domestic needs, gas storage is necessary. In case of industrial use, either a separate storage tank is used or excess gas is flared (burned). Storage may be an integral part of the digester or it may be a separate facility.
For domestic purposes, biogas is produced at very low pressure that is a few inches of water column. It can safely be transported through flexible plastic pipes recommended for natural gas. For transferring gas for a couple of small size burners over a short distance of few feet, heavy duty plastic tube of 6 mm bore can be used. Since biogas is produced in water slurry in relatively warm condition, it is saturated with water vapors and may also contain traces of foul smelling vapors.
Biogas is 60% methane and 40% Carbon Dioxide with traces of hydrogen sulfide, water vapors and sometimes foul smelling substances. For use of biogas as fuel on domestic level, no treatment is required. When large quantity of gas is consumed as fuel, condensate removal and flame arresters may be required for trouble free use.
In case biogas is used as fuel for internal combustion engines for power production, the impurities present in biogas may be undesirable. Some engine manufactures offer engines that accept raw gas; otherwise the advice of engine manufacture may be sought.

In case it is desired to store and use biogas for automobile use (as it is being done elsewhere) the gas should be purified before compression. There are a number of methods available for purification of bio gas (chemical treatment, membrane separation etc)
Nearly 10,000 BTUs of thermal energy is required to generate one KWt of electricity by internal combustion engines. Since the heating value of bio gas is close to 600 BTUs per cft, to generate one KWt of electricity, 17 cft or 0.5 M3 of biogas is required. Thus to run a 5 KWt generator for one hour, 85 cft (2.5 M3) of biogas is required. To operate a 5 KWt water pump for five hours a day, 425 cft or 12.5 M3 of gas is required. This quantity of gas can be generated from the cow dung of twenty cows. In case of dairy farms with high milk yield cows, the power production would be much higher.
Bio gas can run a petrol engine without any major modification. Even a diesel engine (Peter Engine) can run on a mixture of 50:50 diesel and biogas. There is a lot of potential of power generation from biogas in our rural areas and the economics of farmers can be improved.
Refrigeration units running on gas are available in the market. These units are ideal for chilling milk and preserving agro products before these are sent to the market.
The cow dung contains 16 % dry matter and nearly half of this is converted into gas. Since the slurry to the digester is fed with 8% solids the slurry leaving the digester contains only 4% solid organic matter. While planning a biogas plant, the disposal of this slurry must be accounted for. Totally composted and free from pathogens, it is an ideal crop food.
The biogas digester produces slurry daily; however, the requirement in the fields is intermittent, therefore, the storage of slurry is a must. In case of small bio digesters, the slurry is sun dried and stored in the open before it is used. In case of lager installations, the slurry may be stored in large size ponds. In case of large size dairy farms, where the slurry cannot be consumed in house, it may be dewatered, blended with chemically produced N P K, pelletized and sold as biofertiliser.

KESC's biogas energy project

 Karachi Electric Supply Company biogas energy project 

BR Research met Evan Chrapko, CEO of Highmark Renewables and Omer Ghaznavi, General Manager Corporate Strategy & Business Development at KESC to discuss about the upcoming renewable power project base primarily on animal waste. Following are the edited transcripts of the conversation BR Research: How did the biogas idea come up in presence of the more fashionable renewable soures such as wind and solar energy?

Evan Chrapko & Omer Ghaznavi: We started the work on this project about 18 months ago. Initially the focus was on wind power, solar power and the regular stuff that we keep hearing about. But the problem with wind and solar was that the pricing was too high. There were a lot of technology issues, everything had to be imported, it was not proving to be economical enough for us for a variety of reasons.

The idea was to bring the prices down in the future instead of going up all the time. We started looking around for options and one project that we came across was the Landhi bio gas project. The project we have taken is the biggest in the world and dealing with 3000 tons of waste a day to produce 25 MW. To handle that, you need to know what you are doing and need to be able to prove that the thing will work because it is a matter of $60-70 million of investment.

BRR: What advantages does biogas energy have over more conventional sources and what expertise does Highmark offer? EC & OG: We spoke to a lot of German and North Americans firms in the beginning but most of them were hesitant to work in Pakistan back then. Then we heard about Highmark and a couple of projects that they were doing. We contacted them and started searching for different sites. Landhi was the best option as it is very concentrated and generates a lot of waste.

The waste which is dumped into the open sea has huge impact on the environment. The concept was to move to a more sustainable process without much dependency on imported material and equipment at a much lower price. The beauty of the model is that the majority of the equipment can be sourced locally, reducing the import dependency.

While the line work, layout and the engineering will be done remotely by Highmark, the implementation on the ground will be done by the local contractor. We have our options open for equipment, we can either source it locally or import it from US or Far East, whatever suits us.

We have now brought in a testing container to get an idea of what kind of and how much gas can be produced. We have three months of testing going on, after which we will work on design. At the same time, we are working on the financial close, the investors have shown interest but we obviously need the data to support the case.

We are hoping to reach the financial close by the end of the year. For financing, we are talking to a lot of international financing institutions like ADB. IFC etc. Local financing is a bit dicey and it makes almost impossible to look for that.

BRR: Is biogas energy any friendlier to the environment than the other renewable sources?

EC & OG: The good thing about the project is that other than producing power that will be environmental friendly we will also be producing 400 tons of organic fertiliser, which is only slightly smaller than Fatima Fertiliser.

It will not be a direct substitute to urea but will be a complimentary product. While urea is suitable for extracting more growth, this organic fertiliser would be used on eroded soil which has lost its utility and where urea won't be effective.

And Pakistan faces that soil problem a lot, so there is a market for organic fertiliser to be tapped. That is why we are hoping to talk to the likes of Fatima, Engro or the Faujis and let them deal with the fertiliser side of things.

There is no point KESC trying to become a fertiliser firm. The core thing that attracted towards Highmark was their capability to utilise all kind of waste like animal waste, metro waste etc.

BRR: Are there other sites in Karachi from where the raw material can be sourced?

EC& OG: Yes there are a few places near Sohrab Goth - but they won't be as big as Landhi. Landhis's advantage is its concentration and huge amount of waste which is why it is getting international attention.

The current largest project comparable in the world is 8-9 MW. So this project is going to be the largest in the world by a mile. We have a lot of interest on how much could be done socially and on humanitarian grounds. This is a high quality product and very sustainable and reliable in comparison to wind or solar which is very vulnerable and fluctuates highly.

This is energy plus fuel - so we are cleaning up the by-product in a way that allows the environment to stay clean. We are working with KESC because we see the strategic leadership and vision there - they are very serious and ken about the project which is why we are moving ahead swiftly.

All the solar and wind projects do generate electricity but the social and environmental aspect is largely ignored. It is not that we are doing some rocket science work - it is a combination of some very old and some relatively new laboratory technology and this combines in a unique way to get something that is very reliable.

BRR: Will it be local people working on the project or will it be a mix of foreigners and local both?

EC & OG: All construction, operation, everything will be locally done. The only thing that comes from Highmark is the design.

The idea behind it is not to deal with the load shedding issue with this project - it is to bring about a change in the local community over there. We will be working with our CSR team towards providing health and education services to the local community.

The biggest thing is that you need to collect 3000 tons of we waste from the sites every day, we will be picking waste form restaurants and even from the Sabzi Mandi - but the biggest chunk (95 percent) will be the animal waste and we will be mixing it altogether.

Our technology is unique that it will accept all kinds of organic waste. We have put in a lot of research to get to this technology as the waste here is not 'clean' and contains lots of impurities.

BRR: Will the electricity produced be attached to the national grid or will it be for Landhi only?

EC & OG: We will identify industrial users in Landhi, Korangi and nearby areas. We will try not to throw it on the grid in order to avoid line losses etc. The tariff for biogas is already set by Nepra at 8.5 cents per unit, which we hope will be feasible enough.

We do not want to be dependent on government doling out money - we plan to subsidise it form carbon credits and sale of fertilisers.

BRR: What is the project's estimated cost? Are there any plans to expand?

EC & OG: The project's estimated cost is $65-70 million. This is a KESC project but we don't want it to be confined to KESC only - we want the bigger players to come in and share. If we can show it successfully in Karachi - then it can work elsewhere in Pakistan too.

It may not resolve your 5000 MW shortage - but t it will get power to the remote areas and provide cleaner energy. And will also provide bio fertilisers which are very good for the farmland. It is certainly better than using raw manure.

KESC can only do Karachi but that is why we don't want to do it solely on our own, we want other partners to work with us. We are hoping that in the next decade we have three or four such facilities in Karachi as there are other waste sites in the city - where human or metropolitan waste could be used.

We have great incentives on renewable energy - there are no taxes - repatriation of money is easy. We are hoping to start generating electricity by 2013 - fingers crossed.

Source: http://www.brecorder.com/articles-a-letters/single/626/0/1192816/?date=2011-05-26

Biogas Plant in Pakistan | Biogas in urdu

Biogas Plant in Pakistan | Biogas article in urdu

Source: http://www.columnpk.com/urdu-article-what-is-biogas-plant-and-how-it-works/

Initial Environmental Examination for Pakistan Domestic Biogas Program
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Summary	The report presents the finding of the Initial Environment Examination (IEE) conducted for the Pakistan Domestic Biogas Program, proposed to be implemented by the Rural Support Program Network (RSPN), Pakistan. The program envisions setting up 300,000 domestic biogas plants across Pakistan within 10 years of time. Potential impacts likely to arise from the construction and subsequent operation of the domestic biogas digester units on physical and socio economic and environment was assessed and the mitigation measured identified to reduce the possible impact likely to cause its operation. An Environmental checklist has also been developed to implement the recommendation of IEE. On the basis of the assessment, the report concludes that since Pakistan is an energy deficient country, whose major supply is imported, there is an urgent need to provide an alternative source of energy and the proposed domestic biogas program seems to help fulfil this objective without resulting in any potential environmental impact. No adverse effect on the environment was identified because of this program. Detailed findings and conclusions can be found in the report along with the adopted IEE methodology, identified potential impacts and the mitigation measures and the environmental checklist developed to overcome the impacts.
Pages	54
Region(s)	Asia
Country	Pakistan
Year	2010
Thematic area	Renewable Energy
Sub-sector	Domestic biogas
Topic	Programme management
Author(s)	N/A
Publisher(s)	RSPN

Biogas in Pakistan

With the energy crisis in Pakistan getting worse day by day, biogas plants in rural areas can play a major role in decreasing the burden on the national energy grids. Even in the developed countries like UK, biogas plants are being built and encouraged with the help of government funds and many other incentives. In our neighbouring country India, there are almost two millions biogas plants.

Pakistan�s 70 percent population lives in the rural areas. Most farmers have two or more cows/buffalos. The dung from these cattle mixed with an equal proportion of water can be used to produce biogas in a biogas plant. This biogas can then be used for cooking purposes or to generate electricity through a gas fired engine whereas the residue from this plant can be used as a fertiliser. Typically, 50 kg cow dung is required to produce 100 cubic feet of biogas that is sufficient to fulfil the daily requirements of a family of five or six members.

About 4,137 biogas plants were installed in Pakistan with the help of the government in the period 1974 to 1987. The government fully funded the first 100 installations and later on withdrew the financial support. Since then, the growth rate of this technology dropped drastically and only 6,000 biogas plants were installed till the end of 2006. Pakistan Centre for Renewable Energy Technologies (PCRET) has already installed and supported 4,000 biogas plants with only 50 percent financial contribution from beneficiaries.

There are significant social, economic and environmental benefits of biogas technology. The government of Pakistan through PCRET and Alternative Energy Development Board (AEDB) should take the initiative and announce more funds and support for this proven technology to be a part of our rural society. In parallel, the media should raise the level of awareness among the rural community by highlighting the benefits of this technology. NGOs and foreign investors should be encouraged to invest in this sector too.

KHURAM PERVEZ

London, UK

Pakistan Council for Renewable Energy Technologies (PCRET) working on biogas plant projects

Pakistan Council for Renewable Energy Technologies (PCRET) working on biogas plant projects

biogas plant brochure by PCRET in urdu

BIOGAS FORMS  Brochure (Click here for Details) Plant Design (Click here for Details) Application Form (Click here for Details) Survey Form (Click here for Details) Biogas Technology - Experience of PCRET ::BIOGAS FOR COOKING, LIGHTING & IRRIGATION PURPOSE :: Introduction The Biogas Technology (BT) offers an efficient way of biomass utilization. It involves anaerobic fermentation of organic materials such as animal dung, agricultural wastes, aquatic weeds etc. to produce methane rich fuel gas and a value added organic fertilizer. Thus, it has considerable potential for providing fuel and fertilizer besides being on efficient system for recycling waste of prevention of pollution, ecological imbalance and improvement of sanitary conditions in the rural areas. PCRET: An Initiator Pakistan Council of Renewable Energy Technologies (PCRET) under took propagation of Biogas Technology as early as in 1976, based on imported Chinese Design and then initially installed 21 family size units. But afterward due to various factors such as gas pressure variables, lack of craftsmanship, leakage occurring in the dome, hindering good performance of gas produced through fermentation process, the council adjourned the programme. Thereafter Indian design was adapted with some modifications, suitable to local conditions and afterward a project for installation of 1,200 family size biogas plants on public - private cost – sharing basis was launched. In view of prompt and positive response of the people the project ended by installing 35% additional biogas plants than the target originally set forth in PC-1. (Actual 1,604 units installed against target of 1,200 units). Encouraged by positive public response, PCRET launched another project for installation of 2,500 biogas plants in 2007 with a subsidy component of Rs.17000/- per plant. In the last two years despite various financial constraints, about 2,000 biogas units have so far been installed successfully whereas work on other 500 units is in progress. Originally, biogas plants were constructed for cooking purpose only. But in view of the current energy crises i.e. rise in prices of fossil fuels; increase in electric utility tariff and heavy load shedding which has severely effected the life of common man and the economy, possibilities were further work up for utilization of biogas on commercial scale. Thus over the period, demand from the public has compelled PCRET to explore ways and means of using biogas for lighting as well as irrigation purposes. Keeping this aspect in view, PCRET came forward to make possible the usage of biogas in generating power for lighting, refrigeration, electric fans, mobile charging, running washing machine and iron for pressing clothes etc. Besides the galloping prices of diesel coupled with its irregular supply has compelled agriculturist to use biogas as duel fuel (diesel + biogas) for running their tube wells. For this purpose relatively a bigger size biogas plants (10M3, 15M3, 20M3 gas production capacity per day) have been designed and installed in Sialkot, Narowal, Jhang and other places. As per field reports, the success rate of such plants is very high. Biogas Potential in Pakistan As per recent livestock census, there are 51 million animals (Buffaloes, Cows, Bullocks) in Pakistan. Thus, 19.125 Million M3 biogas can be produced daily by anaerobic fermentation of dung through installation of about 3.825 million family size biogas plants, which could meet the cooking needs of about 50 million people. The total population of Pakistan is about 170 million, out of which 68% reside in the rural areas, which comes to be 98 million. Therefore we can meet the cooking / heating requirements of 44% rural masses from this single source of energy (biogas) besides, producing 57.4 million Kg of nitrogen enriched bio-fertilizer per day or 21.00 million tons of bio-fertilizer per year, which is an essential requirement for sustaining the fertility of agricultural lands. Best Option for Future In view of the prevailing situation, promotion of the biogas technology (B.T.) seems to be one of the best options which could, not only partially offset the fossil fuel and fuel wood consumption but also could facilitate recycling of agro-animal residues as a bio-fertilizer. Moreover, being clean and renewable, it would also contribute towards environment protection, sustenance of ecosystem and conservation of biodiversity. There is however, a tremendous need to promote public awareness, in particular, among youth and women, on the use of bio-energy (biogas) and bio-fertilizer and also to create awareness and know-how about eco-system management, conservation of bio-diversity and sustainable use of natural resources. Due to mass Social acceptance, the Government of Pakistan has asked PCRET to launch mega project on the biogas technology by installing 25,000 biogas units all over the country to not only cater the needs of cooking but also for agriculture and commercial purpose in order to meet the shortage of gas and electricity in the country. It is hoped that after approval from concerned quarters the project will pave way on mass-scale dissemination of an environment –friendly technology; which apart from being green has enormous benefits to the public at the country.

Domestic Biogas Plant

Domestic Biogas Plant

Bio-gas plant diagram

Domestic Biogas Plants produce renewable fuel from organic biomass and are primarily used in developing countries and rural areas as an alternative to using fossil fuels, whose combustion contributes to global warming. Biogas is a carbon neutral fuel that is produced when bacteria degrade biological material in the absence of oxygen, a process known as anaerobic digestion, or fermentation of biodegradable materials such as biomass, manure, sewage, or municipal waste1 . The fuel consists primarily of methane (CH4 or natural gas) and carbon dioxide (CH4) mixed with trace gases and can be used to generate electricity for cooking and heating when it is burned.



The ability to capture methane and use it as a fuel source is important since methane is a significant contributor to global warming. Methane is 20 times more effective than CO2 at trapping heat in the atmosphere than CO2. Animal wastes are inherently anaerobic and release methane into the atmosphere during the process of decomposition unless they are managed2 .  Through the use of domestic biogas plants, the natural generation of methane can be captured and used as a clean, non toxic fuel source. Furthermore, the use of methane as a fuel source will offset the need for fossil fuels. Switching from fossil fuels to biogas will result in CO2 emission reductions as half of the green house gas emissions being released into the atmosphere are from CO2 from fossil fuel combustion3 .
Biogas history

Humans have been using anaerobic digestion has been used for centuries. Over 3,000 years ago, biogas was used to heat bath water in Assyria. In the late 19th century, biogas recovered from a sewage treatment facility fueled street lamps in Exeter, Devon in the United Kingdom. Biogas from sewage sludge was converted and used for fuel in automobiles in Germany in the 1950s4 . Today, biogas is being used worldwide, particularly in developing countries such as India, China, and Costa Rica.
Technical aspects

Domestic biogas plants (biodigesters) in developing nations convert livestock manure and night soil (human excreta) into biogas and fermented manure. The size of the plants varies, but most systems are feasible for households or small communities and use 110 lbs/50 kg manure per day, the amount produced by about 6 pigs or 3 cows. Manure must be collected, mixed with water and fed into the biodigester.  The optimal biodigester temperature of 97°F/36°C which promotes rapid anaerobic activity and allows for a smaller volume tank, makes biogas plants ideal for tropical climate locations5 .  As the manure ferments, the methane bubbles to the top of the container where it can be collected and piped to be used as fuel for a stove or lamp.

There are two types of conventional anaerobic digestion, a liquid and a solid process. In the “liquid” process, waste is mixed with water to facilitate digestion and in the “solid” process occurs on landfill sites and produces landfill gas (LFG)6 .  The liquid process is used for domestic biogas plants, however many biogas system designs and design variations exist.  

Types of biogas systems used in developing countries include:

    Home Biomass Systems (HBS) which are common in developing countries in tropical environments.
    China Fixed Dome (CFD) which are used in temperate and cold climates and are built underground
    India Floating Cover (IFC) uses cow manure as the main biomass input, the floating cover rises and falls with methane production and use7 .

Rural Costa Rican communities have built HBS of various designs . "Media bolsa” is a design that includes the basic construction elements of a domestic biogas plant and is used here as an example of a domestic biogas plant  The main component is a large underground tank which is covered by a large inflatable plastic sheet. This system includes an entrance tube, a mixing tub an exit tube, and a collection tub. In most biogas plants, water is necessary to turn biomass fluids into solution and immerse solids to create an anaerobic environment.  The media bolsa system requires a water-to-manure ratio of 2:1 for grazing livestock and a 1:1 ratio for grain-fed livestock.   Manure and water is put into the entrance tube which flows into the mixing tub. As the microbes digest the manure, the biogas bubbles up from the surface of the water/manure mixture and causes the plastic bag to inflate.  The methane can then be piped through a PVC tube connecting the tank to the kitchen stove for cooking or used for lighting purposes.
Domestic Biogas Plant Diagram

Diagram of a 50 m3 Biogas Digester
Source: http://www.smartinnova.com/index.php?p=re-biogas. Author: CITT, KIST. Permission: Smart Innovations.

Daily, manure and water are added to the system.  If the mixture in the fermenting tank is at the same level as the exit tube, the manure/water mixture introduced through the entrance tube will force the same volume of liquid out the exit tube and into the holding tank.  This fermented liquid can be used as a crop fertilizer and is rich in Nitrogen, Phosphorus, and Potassium. 8 .
Biogas plant construction and monitoring

In tropical environments, the biogas mixing tank may be constructed out of cement blocks, and is placed underground while the plastic bag is above ground.  In this type of design, building a roof over the digester is suggested to protect the plastic bag from the elements.

Constructing a domestic biogas plant requires basic building materials and can be done by hand.   Common materials include: a plastic bag, cement blocks, rebar, materials for building a roof over the digester, shovels for digging, PVC piping,  and a safety valve.  The average construction time using manual labor is about one week.
Biogas as a fuel
"Media Bolsa" Domestic Biogas Plant in Rural Costa Rica

"Media Bolsa" Domestic Biogas Plant in Rural Costa Rica
Source: http://www.ruralcostarica.com/biodigester.html. Author: Rural Costa Rica. Permission: Rural Costa Rica.

Since biogas is physically identical with natural gas, it can be used as fuel for vehicles. However, according to the University of Adelaide biogas website, biogas should be used directly for cooking, heating, lighting, or absorption refrigeration since electricity generation and compression of gas (for storage or vehicle use) uses large amounts of energy for a small output of useful energy. The biogas system works best as a stationary, not mobile fuel with a variable volume storage: such as a flexible bag or floating drum 9 .

 Developed countries also use biogas, but with modern technology.  Digesters are often stainless steel and the mixing system consists of two stainless steel propellers, powered by an electric motor operated by an inverter through the control panel. The digesters are equipped with temperature and pH probes to allow for easy system monitoring.  In European countries, anaerobic digestion is becoming increasingly widespread due to legislative tools aimed to increase biogas production and also to increasing energy prices10 .

Biogas methane content ranges from 50 – 80% 60%, 35% CO2, small amounts of water vapor, hydrogen sulphide H2S, carbon monoxide (CO) and N2 (Biogas China).
Benefits and advantages

Biogas plants have numerous advantages for household and community users.  First, biogas doubles as both a cheap fuel source and a sanitation device for waste11 .  Also, the decentralized biogas systems allow waste to be treated near the production source and sludge to be reused locally, which minimizes transport and initial capital cost compared to a centralized system.  In addition, biogas can replace the use of wood for fuel of indoor stoves.   Since biogas burns without smoke and is nontoxic, when it replaces wood as a fuel source, it can prevent respiratory distress and disease.  Futhermore, the relatively cheap cost of domestic biogas plants has lead to the widespread adapation in developing countries which allows rural people to have access to renewable fuel sources.  For example, in 2005, China had 17 M digesters and 50 M rural people were benefitting from biogas plant production12 .
Barriers and disadvantages

The main disadvantage of domestic biogas plants is the safety issue that the volatile nature of methane presents.  Biogas mixtures containing more than 50% methane are combustible.  Thus, naked flames should not be used near the digester and electrical equipment must be explosion proof.  In addition, the digester area must be well ventilated to minimize the risk of fires and explosions. 

Another risk is the potential for diseases to spread due to handling animal waste.  People should avoid contact with the digest contents and wash after working near the digester13 .
Costs

Since maintenance costs are low, the primary costs of domestic biogas plants are capital construction and labor costs.  These costs vary based on location and system design and size.  For instance, in Costa Rica due to the tropical location, costs range from $120 - 300 USD whereas in Asian countries, costs typically range between $300 - 600 USD due to the temperate climate14 .
Footnotes

"Media Bolsa" Domestic Biogas Plant in Rural Costa Rica

Source: http://www.ruralcostarica.com/biodigester.html.

1. Harris, Paul. Beginner’s Guide to Biogas. University of Adelaide, Australia. February 2010.

2. U.S. Environmental Protection Agency (EPA). In Brief: The U.S. Greenhouse Gas Inventory. May 2002.

3. Speth, James Gustave. Red Sky at Morning: America and the Crisis of the Global Environment.  New Haven: Yale University Press 2004.

4. U.S. EPA. Region 9: Waste Programs. Organics: Anaerobic Digestion. November 2009.

5. New Zealand Ministry of Agriculture and Forestry. Methane from Animal Waste Management Systems. October 2008.

6. University of Adelaide, Australia. Biogas: An Introduction. February 2010.

7. Biofuelswork.com. Biofuels. 2010.

8. Rural Costa Rica. Small-Scale Biogas Use with Biogidesters in Rural Costa RicaBiodigester Design & Construction. 2007.

9. University of Adelaide, Australia. Biogas: An Introduction. February 2010.

10. Comino, Elena, et al. Increasing Organic Loading Rate in the Co-Digestion of Energy Crops and Cow Manure Mix. Science Direct. September 2009.

11. Comino, Elena, et al. Increasing Organic Loading Rate in the Co-Digestion of Energy Crops and Cow Manure Mix. Science Direct. September 2009.

12. Institute of Science in Society. Biogas China. 2006.

13. University of Adelaide, Australia. Beginner's Guide to Biogas: Safety Page. 2010.

14. Institute of Science in Society. Biogas China. 2006.
Resources

 Deublein, Dieter and Steinhauser, Angelika.  Biogas from Waste and Renewable Resources: An Introduction. Weinheim, Germany: Wiley-VCH, 2008.

Source:http://climatelab.org/Domestic_Biogas_Plant

Biogas In Pakistan

Biogas In Pakistan

Source : http://paksc.org

Pakistan has low forest cover. About 4% of total area is covered by forest, in which only 5% area is protected. 90% of country’s wood production is used as fuel. About 7000 ha of land is reforested in Pakistan every year. To control reforestation adoption of biogas is a best technology in Pakistan. Biogas technology has proved to be very successful in Pakistan. These activities will not only be beneficial to the human health but will also have positive impact on the environment
Biogas is produced by mixing dung (Animal waste) and water in the absence of oxygen through fermentation process. Biogas can provide a clean, easily controlled source of renewable energy from organic waste materials for a small labour input, replacing firewood or fossil fuels (which are becoming more expensive as supply falls behind demand). During the conversion process pathogen levels are reduced and plant nutrients made more readily available, so better crops can be grown while existing resources are conserved.
Composition of Biogas

• Methane, CH4                              50-75%
• Carbon dioxide, CO2                   25-50%
• Nitrogen, N2                                 0-10 %
• Hydrogen, H2                               0-1 %
• Hydrogen sulphide, H2S              0-3 %
• Oxygen, O2                                  0-2 %

Composition depends upon the material feeded and process nature


Source :http://www.slbap.org/

• Information about Biogas Plant In Pakistan

• bio gas plant design for home (PDF)

• Bio Gas  (gobar gas) E project video.

• Build Your Own Bio Gas Plant (PDF) (science fair project)

• Information about Bioas plant, Gobar Gas Plant in Urdu
  

A.   Uses of Biogas.

·         For cooking and heating food.

·         For playing fan in summer.

·         For lighting.

·         Organic manure is its bye product.

The sludge product of anaerobic decomposition produces a better fertilizer and soil conditioner than raw manure. It nitrate e.g.  nitrogen, phosphorous, potassium, plus trace elements.

B.   Selection Criteria of Beneficiaries.

·         The plant will be allotted to individual household.

·         Land for construction of bio-gas plant should be available free of cost.

·         Enough water should be available for feeding purposes.

·         The individual household should have two buffaloes, preferably.

·         Direct sunshine should be there throughout the day time on the proposed site.

·         From environmental point of view, the plant should be out side of the boundary wall of the house. Plant should away  50 feet  from kitchen.

·          

C.   Location:

The most important consideration is the location of the plant.

·        DO NOT dig the digester pit within 13 meters of a well or spring used for drinking water.

·        If the water table is reached   when digging, then site should be changed or it will be necessary to cement the inside of
the digester pit.

·        Try to locate the digester near the stable excessive time is not spent transporting the manure because fresher manure produce more methane.

·        Be sure there is enough space to construct the digester. For 3 cubic meters of methane requires an area approximately 2 X 3 meters.

·        Arrange to have water readily available for mixing with the manure.

·        Plan for slurry storage. Although the gas plant itself takes up a very small area, the slurry should be stored either as is or dried. The slurry pits should be large and expandable.

·        Plan for a site that is open and exposed to the sun. The digester operates best and gives better gas production at high temperatures (35degrees)

·        Locate the gas plant as close as possible to the point of gas consumption. This tends to reduce costs and pressure losses in piping the gas. Methane can be stored fairly close to the house as there are few flies or mosquitoes or odor associated with gas production.

F. Design parameter:

i) Required Manure :

            One buffalo can produce about 20 to 22 kg manure per day. Average 4 No cows or 2 No            

            buffalos will produce about 45 kg manure per day .05 cubic meter. 

The ratio of manure and water is 1: 1.
45 kg manure + 45 kg water = 90kg
Total input per day  = 90 kg
Input for 5 weeks = 90 kg X 35 days = 3150 kg
1000kg = 1 cubic meter
3150 kg =3.1 cubic meters

So for a single household of average 7 people living is 3 cum plant is recommended

ii)  Temperature: Normally required temperature will be  20o c to 35 o c

iii) PH value: Neutral PH and ranges 6.8 to 7.2

G.  Construction Materials (For 3-Cubic-Meter Digester)

·         Bricks approximately 2700

·         Cement, 11 bags.

·         Sand, 74 cft.

·         Crush 9 cft.

·         Steel sheet for gas cap 20’x4’ of 16 gauge.

·         RCC pipe of 6 inch diameter,12 feet.

·         Angle iron 2 inch,10 feet.

·         Mild steel rods, approximately 18. feet (for bracing)

·         GI pipe  ½ inch dia, and fitting as per requirement.

·         Plastic pipe  ½ inch dia, as per requirement.

·         Stove 1 No.

·         Waterproof coating (paint, tar, asphalt, etc.), 4 liters (for  gas cap)

H.X- Section of 3M^3.

 

9. Design/Construction.

·         Prepare foundation.

·         Dig a pit 6.5 fee in diameter to a depth of 12 feet
Line the floor and walls of the pit with bricks and bound it with cement mortar with the ratio (1:5)

    

·         Put RCC pipe of 12 feet length from ground have one end of the input piping 3.5 feet above ground level and the other end 2 feet above the bottom of the pit.

·         Keep angle iron on the brick wall about 8 feet height from the floor on three sides  for the gas cap to rest on when it is empty.

·         Extend the brickwork up to  1 feet above ground level to bring the   total depth of the pit to approximately 12 feet.

·         Plaster inside the plant with the ratio (1:4)

·         Provide additional support for the pipe by fabricating across brace made from mild steel. 

J. Design of Gas Cap Drum

            The metal drum serving as a gas cap covers the fermentation tank and is the most expensive single item in the whole plant. The drum is made to hold between 60 and 70 percent of the volume of the total daily gas production. Usually drum from mild steel sheeting or galvanized iron sheeting of thickness 1.63mm (16 gauges). For 3 cum plant of 12 feet depth the height of the drum approximately one-third the depth which become 4 feet. Make the diameter of the drum 6 inch less than that of the pit (5 feet diameter).

            Using a flange, attach a 1.5 inch pipe to the inside top center. Fix the lower end of the pipe firmly in place with thin, iron tie rods or angle iron. The cap now looks like a hollow drum with a pipe, firmly fixed, running through the center. Cut a ¾ inch diameter hole, as shown in Figure 7, in the top of drum for out let of gas. Weld a 3/4 inch diameter pipe over the hole. Paint the outside and inside of the drum with a coat of paint or tar.

            Make sure the drum is airtight. One way to check this is to fill it with water and watch for leaks. Attach handles to either side of the drum. These don't have to be fancy, but they will prove very helpful for lifting the drum off and for turning the drum.
Weld a metal strip to each of the tie rod supports in a vertical position. These "teeth" will act as stirrers. By grasping the handles and rotating the drum it is possible to break up troublesome scum that forms on the slurry and tends to harden and prevent the passage of gas.

K. Prepare the Mixing and Effluent Tanks

          Build or improvise a mixing tank to be placed near the outside opening of the inlet pipe. Likewise, provide a container at the outlet to catch the effluent. Some provision may also be made for drying the effluent when the plant goes into full production. 

L. Operation

In order to start up the new digester, it is necessary to have 3 cubic meters (3000kg) of manure. Put the manure an equal amount of water into the mixing tank. Stir it into thick liquid called slurry. A good slurry is one in which the manure is broken up thoroughly to make a smooth, even mixture having the consistency of thin cream. If the slurry is too thin, the solid matter separates and falls to the bottom instead of remaining in suspension; if it is too thick, the gas cannot rise freely to the surface. In either case the output of gas is less. When filling the pit for the first time, pour the slurry equally into both halves to balance the pressure on the thin inner wall, or it may collapse.

            Mix 50 to 60kg fresh manure with same quantity of water and add it to the tank every day. The advantage of this model is that since the daily flow of slurry goes up the first side, where the insoluble matter rises, and down the second, where this matter naturally tends to fall, the outgoing slurry daily draws out with it any sludge found at the bottom. It can take four to six weeks from the time the digester is fully loaded before enough gas is produced and the gas plant becomes fully operational. The first drumful of gas will probably contain so much carbon dioxide that it will not burn.

            On the other hand, it may contain methane and air in the right proportion to explode if ignited.

M.  Test Gas Lines for Leaks 

            Checking for gas leaks is done by closing all gas taps, including the main gas tap beside the gas holder, except for one. Then to the open tap, a clear plastic pipe about a meter long is attached, and a "U" is formed. The lower half of the "U" is filled with water. Using a pipe attached to a second tap, pressure is applied until the water in the two legs of the "U" is different by 6 inch. The second tap is then closed.  If the water levels out when the second tap is closed, a leak is indicated and can be sought out by putting soapy water over possible leaks, such as joints, in the pipe work.

N.  Improved Stove 

            Because gas pressure is low, it will be necessary to modify existing equipment or build special burners for cooking and heating. A pressure stove burner will work satisfactorily only after certain modifications are made to the burner. The needle-thin jet should be enlarged to 1.5mm. To make a burner out of 1.5cm water pipe, choke the pipe with a metal disc having a center hole with a diameter of 1.5 to 2mm. An efficient burner is a tin can, filled with stones for balance, having six 1.5mm holes in the top.

            The gas enters through a pipe choked to a 2mm orifice. Or fill a chula or Lorena stove with stones and insert a pipe choked to a 2mm orifice. If possible, it is best to use a burner with an adjustable air inlet control. The addition or subtraction of air to the gas creates a hotter flame with better use of available gas.

O. Maintenance

            A digester of this type is almost maintenance free and has a life of approximately 25 years. As long as cow or other animal manure is used, there should be no problems.

 

Designed by : Muhammad Khaliq Rural Engineer SLBAP/LML