From the Field

Community gets free biogas and bioslurry

Sun-dried bioslurry to be used as organic fertilizer
Biogas fuelled generator saves pig farmer 50% on electricity bill

In the Thai province of Phattalung, 18 pig farmers, feeding their pig slurry into a biodigester, donate their surplus biogas free of charge to the local community. The 2,822 cubic meter central gas storage connects to a plastic piped grid reaching 1,500 households in the Praekha community. Bio-digestion is a compulsory manure treatment for pig farmers with 5,000 pigs or more, and is recommended to all pig farmers contracted by Charoen Pokphand Foods in Thailand.

The farmers use the biogas mainly to generate electricity to provide lighting and to operate equipment and appliances within their farms. One farmer reported saving up to 50 percent of his electricity expense. He also gained extra income by selling sun-dried bioslurry as organic fertilizer. Bioslurry from other digesters is distributed through pipelines, again free of charge, to fertilize nearby palm oil orchards. Important co-benefits of the digestion of pig slurry include the elimination of unpleasant odour and the prevention of waste water leaching to the environment.

It is estimated that villagers substituting LPG with biogas, save over 10 US dollars per household per month; adding up to 180,000 US dollars per year for the whole community. The villagers only pay a small maintenance fee to use the local grid. The central gas storage has been funded by the provincial office of energy.

Picture report digester construction

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Construction of a fixed-dome digester requires skilled labor. For many good reasons the production of biogas is highly promoted in tropical regions, and therefore many qualified masons are needed. The LMMC project supported two trainings in digester construction. Click on the picture to open the picture report of a training in Malawi.

Biogas contains about 65% methane, a powerful greenhouse gas, which is formed during the decomposition of biomass in an oxygen-free environment. Livestock manure is biomass. And since bio-digestion does not alter the nutrient content, the bio-slurry, the coproduct of bio-digestion, remains a perfect organic fertilizer. To ease handling and transport many smallholder farmers prefer to compost the often rather liquid bio-slurry.

The benefits of biogas are diverse. For family use, biogas substitutes for fossil or biomass fuel, thus saving time and money. Non-oil producing countries save on foreign currency for fuel imports. And government targets on the mitigation of greenhouse gases become easier within reach.

Related news: How to construct a fixed-dome bio-digester

Goat urine as nitrogen fertilizer

Goat pen with slatted floor (photograph: Geraldina Herrera)
Manure and urine collection (photograph: Betty Londergan)

From 2004 to 2010 more than 1,600 families with a small child have received goat units under auspices of the Save the Children’s goat program In Guatemala‘s Western Highlands. A single goat produces enough for one glass of milk a day for that child. The units comprise of a milk goat and a small pen (2 meters x 2 meters) built with an elevated slatted floor in order to keep the animals dry and to collect manure and urine.

The solid manure is used to fertilize the agriculture plots with maize and beans, home gardens and to sell of surplus. The urine sifts through the solid droppings on a waterproof sheet of canvas which is hanging under the slatted floor. At the lowest point the urine drips through the perforated canvas into a small container. The collected urine is subsequently re-packed in recycled plastic bottles and either used or sold as urea-rich fertilizer. Notwithstanding that this type of urine collection is on a small scale and specifically with dairy goats in confinement, it demonstrates that urine collection is not always impossible. Urine is a valuable nitrogen fertilizer provided it is collected within a few hours of deposition to prevent nitrogen loss due to ammonia volatilization.

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Extension Works in Viet Nam

Vietnamese farmer fills up a barrel with bioslurry for transport.
A bioslurry pit near the field saves transport.

Recently Vietnamese agriculture expert Le Thi Xuan Thu, asked farmers in the five Vietnamese provinces about their current manure management practices and the bottlenecks for improving it. Her final remark underlines the importance of a well-trained extension service with qualified extension workers. “Farmers with access to active extension services show a strong willingness to practice integrated manure management, including producing biogas and using bioslurry for crop fertilization.” She continues: “Even without subsidies farmers are willing to invest in bio-digesters. Farmers with mixed crop-livestock systems are willing to invest on bio-slurry pits and related facilities so that they can store sufficient slurry and use it for their crops efficiently.”

But it is not all ‘milk and honey’. Currently most Vietnamese landless livestock farmers discharge manure to the sewage system. Many farmers with bio-digesters lack the labor to transport and apply their bioslurry to their crops on often faraway fields; in which case they also discharge the slurry. Some farmers with a mixed crop-livestock system collect solid manure and make compost.

So, what are the drivers for integrated manure management? Thu: “Farmers inherited knowledge in manure management and farming practices from their ancestors. But the economic and environmental circumstances have changed.” According to Thu many farmers first cite the health benefits of bio-digestion. Secondly, the biogas and bioslurry help to reduce household expenses and synthetic fertilizers purchase. Biogas production is currently the main intervention through which farmers deal with manure in Viet Nam.

To improve the livelihoods of local farm communities Thu stresses the need for a combination of environmental standards and regulations, and agricultural programs in which the development of an extension system plays an important part.

A step further up the awareness ladder is the linkage between integrated manure management with food security and climate change. Thu is clear on that: “Not many farmers are aware of climate change. Food security and climate change issues are normally introduced to farmers via extension trainings and mass media. In communities with an active extension service, farmers do have some general knowledge about the issues.”

Le Thi Xuan Thu’s farm visits in five provinces were part of the Vietnamese Opportunity for Practice Change. The identified bottlenecks will subsequently be addressed in a training of 100 extension workers. Hereafter these extension workers will disseminate this knowledge in field-based-schooling sessions to an estimated 4,000 farmers.

The trainings are a concerted action of SNV Viet Nam and the Vietnamese National Biogas Program.

Bio-slurry feeds coffee, vegetables and fish

Bio-slurry to be mixed with straw and ashes.
Sprinklers irrigate the vegetables with diluted bio-slurry.

Vietnamese Nguyen Xuan Khoat has been using bio-slurry for 11 years in which period he learned how to optimize its use to his farm needs. Each day his 80 pigs produce about 120 kg of fresh dung. Nguyen collects the dung to produce compost and biogas. Forty kg is stored in a brick pit where it is mixed with straw and ash to turn into compost fertilizer for use in his coffee garden.

The remaining 80 kg is diluted as part of the cleaning process and fed into a bio-digester. Biogas is used for household cooking. After digestion the bio-slurry (digestate) first flows in a slurry pit also to be mixed with straw and ash. Through an overflow, 80% of the remaining liquid slurry flows into a second pit to irrigate the coffee and vegetable gardens via spraying system. The remainder 20% flows into a pond with fish for home consumption. The mixed bio-slurry from the first pit is dried and applied to the soil. Nguyen decided to invest in a bio-digester as he has been aware of high quality nutrients in bio-slurry and its advantage of a continuous supply to his crops. Each year, he now saves 30%, or 100 kg of NPK synthetic fertilizers purchase, while each month his family saves up to 12 kg of LPG for cooking.

Note: in order to avoid human health risks bio-slurry should not be applied on vegetables and fruits for fresh consumption.

Feedlot Compost

The composting area with compost heaps on the background
Feedlots to finish beef cattle

Because of their size and the large daily produced quantity of fresh manure many feedlots for finishing beef cattle struggle with sound manure management often leading to environmental pollution and a waste of valuable resources. The Argentinian brothers del Barrio, owning the El Trébol farm enterprise with about 30,000 heads of beef cattle, of which 12,500 are kept on feedlots, successfully utilize these valuable resources; not because it generates additional income but because it reduces pollution of their environment.

Every day they scrape off the top layer of the 50 feedlots and pile-up this mixture of manure and topsoil to be composted. The final product is compost containing 65% organic matter and many valuable crop nutrients. The compost is sold as organic fertilizer to horticulturists and retailers in the area of Buenos Aires. The del Barrio brothers herewith demonstrate that even in high density cattle situations like the feedlots manure management is possible and profitable.

El Trébol is partner of the National Feedlot Chamber, of which Guillermo del Barrio is at present the vice president. In this position he is promoting the development of a manual of good environment practices.

Chicken feed fish

Fish line up to feed on the chicken manure. (Photo courtesy: www.thairath.co.th)

Layer hens are known to produce nutrient rich manure. Thai poultry and fish farmer Sattha Ponpaipan uses this knowledge effectively. The manure nutrients from his layer hens are completely used up to feed his fish. Sattha raises over 20,000 layer hens in four separate houses that are built over ponds which house over 300,000 fish. The hens are fed at 5 am and 1 pm so they produce feces that correspond to the need of the fish during the daytime. Through metal slatted battery cages, feces drop directly into the ponds. Turbines are used to push water with nutrients from under the hen houses to the connecting ponds. The use of chicken manure to feed fish helps Sattha to reduce his spending on pellet fish food by half and to effectively dispose all the chicken feces. Since the fresh chicken manure is used immediately after excretion, this system avoids any possible losses to the environment. The phosphate-rich sediment of the ponds is regularly removed and used to fertilize nearby trees.

Educational farm important to show-case profits of Manure Management

1,500 kg of fresh manure per day supplies 50% of electricity demand.
250 m3 bio-digester produces 30 m3 of biogas per day.

A herd of 155 milk-producing cows populate the milk production unit of CATIE's commercial farm in Costa Rica. The cows are stabled for 6 hours per day, during which time they produce about 1,500 kg of fresh manure. The manure is separated into solid and liquid parts: The liquid is channeled into a 250 m3 bio-digester. The digester produces 30 m3 of biogas (consisting in 60-65% methane) each day. A generator converts the biogas into electricity, yielding about 67 kWh or 50% of the electricity used daily to operate the milking equipment. The liquid bio-slurry is used to fertilize the pastures. The solid manure is composted and used to fertilize the cut-and-carry pastures and CATIE’s sugar cane and coffee cultivation. The on-farm use of the liquid and solid manure products reduced the farm’s bill for synthetic fertilizer by at least 25%. It has also reduced the emission of greenhouse gases, mainly nitrous oxide, from the farm’s livestock.

The farm is an important center and showcase for education and environmental awareness in the region. Diverse groups of students, farmers, extension workers, policy makers, and members of civil society participate regularly in trainings and other events on environmentally friendly livestock production.

700 pigs and no waste!

Pigs like to cool down in the flush area.
Solid manure is partly sold for crop fertilization.

The medium-scale Ear Long pig farm in Thailand integrates pig meat production with crop production and aquaculture. It shows well thought through manure management.

The 700 pigs are kept on a concrete floor with water flush area. The solid excretions are shoveled out daily. They are either sold or used as organic fertiliser for crops and the ponds with larger fish.

The flush water drains into a lagoon with zooplankton. This uses the remaining nutrients in the flush water, thereby improving water quality and again providing feed for aquaculture. From here the water is oxygenated as it overflows to the second, third and fourth lagoon. Finally the water flows through a shallow pond with buffer plants before being released outside the farm.

Separating the solid manure and the much diluted flushing water pays off. Methane emissions are reduced compared to the normal use of mixing dung, urine and flushing water. The solid manure is utilized more efficiently compared to liquid manures, while the remaining nutrients in the flush water are recycled as fish feed.

Surplus biogas for sale

The only weight to carry is the bag since the gas weighs practically nothing.
Putting some pressure on the bag is enough to make the gas flow.

Bio-digesters may produce more biogas than needed for daily family use i.e. cooking and lighting. When a distribution network is lacking, this surplus gas is either discharged into the air or flared off. This is a waste of valuable renewable energy and a harmful contribution to global warming! But how to store it instead? Portable gasbags offer a cheap and easy to handle solution. The bag (as shown) contains 2 cubic meters of biogas, enough for 4 hours household cooking. With the bags comes the opportunity to sell the gas to families without a bio-digester; so they can cook clean also.

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Biogas as peace keeper

Simple 1” pipes distribute biogas to the villagers.
Cooking stoves for natural gas are adapted for using biogas.

Poultry farmer Aram Uprajong in Western Thailand had a choice. Either close his farm or restore the friendship with his neighbours. Wisely he chose for the last. Over the years the manure of his 6,000 layer hens caused heavy problems with odour and flies for the neighbouring villagers. In response to the increasing complaints Aram installed a bio-digester, thus preventing a forced closure of his farm. After satisfying his farm and own family’s energy needs, Aram now distributes the surplus of biogas free of charge to dozens of houses in the village. The villagers only pay a small maintenance fee to use the plastic-piped local grid. The digestate is sun-dried and sold as fertilizer. But most importantly: the bad odours as well as the flies are gone! And last but not least, the captured methane from the manure substitutes the fossil fuel used in many households before.

Bio-slurry of the hill

Waterhoses transport the bio-slurry to downhill pastures.
A fixed 2” pipe transports the bio-slurry uphill to be released through the waterhoses.

Slurry from dairy cattle manure after bio-digestion always tends to be very liquid. Liquid bio-slurry is often difficult to apply on small scale farms, especially when the spreading area is not close to the farm. Costa Rican dairy farmer Carlos Gomez and his daughter Karla in the highlands of Turrialba came up with a simple and effective solution. “We let gravity do the job!” They fertilise the hilly pastures using garden hoses; downhill simply by gravity; uphill by pumping it up first. The biogas is used for household cooking and in the small milk processing unit for local cheese production.

No wasted manure

Steep hills complicate the use organic fertilizer.
A small garden machine mixes the manure to dry and allows manual spreading on pastures and crops.

In the highlands of Turrialba Costa Rican Glen Aguilar runs a middle size dairy farm. The 20 cows are confined in a plastic covered kraal for app. 8 hrs. per day. Mechanized manure application on his pastures is practically impossible due to the steep slopes and abundant rainfall. Therefore most farmers use synthetic fertilizer and discharge their manure as waste (ending up in surface waters). Not Glen Aguilar. He invested in a small horticulture machine to mix and turn the topsoil of the kraal consisting of app. 90% manure. Fresh dung is mixed with the old dung twice per week and subsequently air dried, providing dry bedding for the cows and an easy to store and to handle organic fertilizer for his pastures, thus saving on synthetic fertilizers. Although some nitrogen may be lost in the process; drying manure is a very effective method to prevent methane emissions. Given the circumstances (steep slopes and high rainfall) the application of dry solid manure to the grassland ensures an optimal use of the valuable nutrients.