Biogas, gas & methane

Biogas is mostly methane (around 60%) with carbon dioxide (around 40%) and a little hydrogen and hydrogen sulphide. It is made by anaerobic bacteria breaking down organic matter in the absence of oxygen (when the organic matter is waterlogged – i.e. a slurry). Biogas is generated naturally in the mud at the bottom of marshes; it is called marsh gas, and often ignites. The process also occurs in landfill sites, and in the digestive system of humans and other animals (yes, farts are biogas). But we can make it ourselves from plant and animal wastes, and even human waste; soft material is better than twigs / woody material. It can be burnt to drive a generator, or on a smaller scale, for cooking or lighting gas lamps. Also, biogas engines have been developed for transport. The equipment in which the organic matter breaks down anaerobically is called a digester, and there is also some sort of storage container for the gas produced. Raw biogas can be 'scrubbed' by passing it through slaked lime, which removes most of the CO2 and increases its calorific value.

The two main types of digesters are the continuous and the batch. Continuous digesters have a constant throughput of material, and batch digesters extract the gas from a contained batch of material, which is then emptied and a new batch added. Biogas digesters are already widely used in developing countries, especially India and China, as firewood for cooking becomes scarce. By the end of the nineties, there were millions of small family plants in India and China. In the West, digesters tend to be larger-scale, taking animal slurries and human sewage. But they can be domestic-scale, for individuals looking to reduce their dependency on fossil fuels.

what are the benefits?

reduces CO2 emissions: because it is a substitute for natural gas. Because CO2 from biogas is from recently-alive plant matter (even if it was fed to animals), it is part of a cycle – i.e. CO2 given off by burning biogas is absorbed by plants that will provide future biogas. reduces methane emissions: animal manures release methane into the atmosphere – about 10% of methane emissions in the US come from animals, according to one survey. When methane is burnt it releases CO2, but methane is a more potent greenhouse gas than CO2, so it is a good idea to burn it rather than release it. However, it's better for organic waste to be separated and put into an anaerobic digester instead of collecting methane from landfill sites; and it would save more energy if all organic waste, including paper, was recycled instead of landfilled – plus it would prevent leaching of contaminants into groundwater and soil.

reduces resource use: biogas doesn't need millions of miles of pipes to deliver it, and doesn't need to be liquefied and shipped across the world, with all the resources and energy that these things entail. Plus it saves trees (for firewood). Natural gas is finite, so won't last forever – and there will probably be wars for it as it runs out. creates two renewable resources: sewage sludge and animal slurries usually end up as fertiliser anyway – so it's better to obtain fuel from it first, and prevent runoff and methane emissions at the same time – and you still get fertiliser at the end of the process. It's the missing link for those wanting to switch from fossil fuels – many people heat their homes with wood and their water with solar, and get their electricity from wind and solar – but cooking is a problem; it's too expensive with electricity, and agas are expensive, take a long time to fire up, will make your space too hot in the summer. Gas is best, and now it can be done without gas bills. nb: as with other biofuels, we think that the feedstock (raw materials) should be waste material. We don't think it's a good idea to set aside large areas of land for growing fuels when much of the world doesn't have enough food (although the waste from food crops is fine). See Biofuel Watch. Also, large-scale digesters need to be fed by large operations like factory farms or sewage plants. These bring their own problems, such as hormones, treatment of animals, and energy-intensive transport and chemicals. We think that the best solution is usually the smallest scale possible – in this case the domestic scale.

what can I do

setting up: batch digesters based on some kind of drum / container such as the one in the top photo are feasible on the domestic scale. Continuous digesters are popular in Asia (right) - an inlet and outlet pit with a concrete or steel gas container. You can build your own – see links page or come on a LILI course. sizing: in India, for a family of 8 with a few animals (say 8-10 cows), a 10m³ digester is recommended, with 2 m³ gas storage. But a typical small family digester will be around one cubic metre. For cooking and lighting, you don't need much; every kg of biodegradable material will yield around 0.4 m³ (400l) of gas, and gas lights need around 100l per hour. 2 gas rings for a couple of hours a day will use between 1-2 m³, so if you have some livestock, plus kitchen and human waste, you can do this easily. When it comes to driving any kind of engine (e.g. a generator or a pump) it's a different matter, and is way beyond the domestic-scale. How long you leave the material in a batch digester depends on temperature (2 weeks at 50°C up to 2 months at 15°C). The average is around 1 month, so gauge how much material you will add each day, and multiply it by 30 to calculate the size of the digester. using: the waste input must be a slurry – so add water if it's too solid. Try and keep the temperature over 30°C if possible; it generates a little heat, but in colder countries the digester will need insulation and even a little extra heat in the winter (which could be provided by some of the biogas). A greenhouse is a good place for it. safety: methane is explosive – see Adelaide University's website for safety considerations.

In these articles the author has endeavoured to explain why biogas is green and renewable when used as an energy source, and how it is produced by the anaerobic digestion (AD) process. A number of methods of producing methane biogas using AD are also discussed, so that the reader will understand exactly what biogas methane is and the implications for our planet of its creation and use.

The apparatus you are going to build uses a discarded 18 litre water container as the “digester.” A mixture of water and animal manure will generate the methane, which you will collect in a plastic balloon. The 18 litre water container performs the same task as the stomach of a livestock animal by providing the warm, wet conditions favored by the bacteria that make the methane.

Basic introduction to the world of energy.

1. Introduction
2. Electricity in Circuit
3. Natural Gas
4. Petroleum
5. Nuclear Energy
6. Hydropower
7. Geothermal Energy
8. Golar Energy
9. Wind Energy
10. Biomass - a Renewable Energy
11. Diesel
12. Famous People in Energy
13. Alternative Energy
14. Thermodynamics
15. Tidal Energy
16. Glossary

It was slightly more than a quarter century ago that biogas plants first appeared as a practical source of renewable alternative energy. The idea took time to catch on and to be accepted, but these plants are now in world-wide use. In a recent fiveyear plan India set itself the task of installing 25,000 cowdung gas plants a year. China claims at present the present moment to have some 7,000,000 biogas plants scattered all over the country, ranging from small family plants to huge government installations for running buses, trucks and diesel-electric generators, besides steadily providing a collosal amount of rich fertilizer and humus for field and garden. The welcome given to FUEL GAS FROM COWDUNG by readers around the world has been very heartening. Since it first appeared it has several times been reprinted at the special request of UNICEF. We have the pleasure in offering the public the present third edition, which we hope will be still more useful to readers in developing countries. In preparing this edition we (the authors) have borrowed rather freely from articles which have appeared in the BIOGAS NEWSLETTER of Nepal. For permission to do so we are grateful to the Editors. We wish also to thank the Development and Consulting Services (D.C.S.) of Butwal, Nepal, for kindly allowing us to include designs of several appliances produced and perfected by them.

People living in remote areas of South-East Asia, or other tropical or sub-tropical countries, where electricty is not available and fuel is hard to get, have a very cheap, abundant and efficient fuel in the gas produced from ordinary cowdung. This gas (marsh gas or methane) is generated with the greatest ease simply by letting a slurry of cowdung and water ferment in a ;Yell-like pit without exposure to air. The gas rises LO the surface and collects in a drum, whence it is piped to the kitchen stove. A farmer with a couple of bulls or buffaloes for ploughing and one or two cos for milk gets enough dung every day to produce sufficient gas for all the cooking needs of a village family of six. The cooking is clean and hygienic, the pots do not get black, there is no smoke or smell, and the gas is non-toxic. And after extracting the gas to cook his food, and to light his house at night, the farmer still has all the dung left, well fermented and rotted, to fertilize his fields.

Fresh cowdung, or other animal dung (from horses, mules, donkeys, buffaloes, yaks, Pigs, pou3try) diluted with water and fermented by bacterium methanogenes, without exposure to air, delivers 90% of its potential gas within a period of four weeks, more than half of it within the first eight or ten days. Six weeks of fermentaticn produces about 98%. Hence the fermenting pit, in which daily additions \,f slurry enter at the bottom and gradually raise to overflow at the top, should be large enough to hold each day's addition for a minimum of four weeks or a maximum of six, i.e. from 30 to 40 days. In other words, the volume of the pit should be at least 30 times, or better 40 times, the volume of siurrjr added daily.

Building a steam engine is tough. Finding a dynamo simpler. But I don't want to be around a homemade boiler. There's a good chance that it's a bomb waiting to go off.

There's a simpler way. Instead of burning coal or wood to make steam in an external combustion engine, the smart thing to do is to convert the fuel to gas and send it into a commercial internal combustion engine driving an alternator. The system might be nothing more than a 5 hp Briggs & Stratton engine and a truck alternator charging 12 volt batteries. No boiler to build. No engine to build. No gasoline to buy. Just build a simple cooker and fire it up.

This is was done in 1905 when Mathot showed people how to use those new "high-tech" one lung engines, powering them with gas generated by cooking wood and coal.

Chapters include selection of an engine, installation, foundation and exhaust, water circulation, lubrication, perfect operation, how to start the engine, perturbations in the operation, producer gas engine, producer gas, pressure gas-producers, suction gas-producers, oil and volatile hydrocarbon engines, and selection of an engine.

The beauty of this book is in details provided for many different gas generators. You get drawings of a Simplex generator, a Dowson unit, a Fichet-Heurtey producer with rotating bed-plate, a Gardie unit, a sawdust purifier, a gas holder and washer, a Fange-Chavanon inverted-combustion producer and many, many more. You'll find more about gas production here than in a dozen other books.

This is not only valuable material to the homesteader and survivalist, but especially to the guy who wants to run his auto on coal and wood. Scaled down versions of these digesters were used all over the world during WWII and the years following due to petroleum shortages. And antique engine fans will find interesting details on early engines, ignitions systems, and more. No promises, but it may be that details here could help you run an engine on methane generated by rotting manure and organic material in a digester.

Great, raw, rare energy information from a simpler time begging to be adapted to today's world. We've been consuming oil faster than we've been finding it for many years now. Shortages are on the way. This might be a way around the problem. Interesting stuff.

 

Problem: Cooking fuel, waste disposal, inefficiency of traditional biogas cattle dung digesters

Idea: A very efficient process of biomethanisation thanks to high calorie content of the waste used for the bacteriological digestion. The system is usable by any household.

Difficulty:Construction: easy to medium, use: easy. The digester should be kept at temperatures between 32 & 37°C (89.6-98.6°F)

• Price Range: About 100$ with new material
• Material Needed: 2 plastic water tanks, one of 1cubic meter, the other of 0,75 cubic meter content, flexible pipe, stable
• horizontal base, frame to stop the gas tank rise, inlet and outlet fittings
• Geographic Area: Global, in temperate to cold climates, the plant has to be heated
• Competencies: Simple plumbing skills
• How Many people? 2
• How Long does it take? From three to max. ten hours construction time, two weeks to start the methan production

A Backwoods Home Anthology ALTERNATIVE ENERGY Is methane production on your homestead practical? By Jim Tracy for a Homesteaders searching power source of energy independent of grids and pipelines may have to look no farther than the manure in the barn. This”waste”is teeming with bacteria that produce energy through a process that is almost as old as life itself. In the absence of oxygen, certain types of bacteria break down organic material and give off methane gas, the chief constituent in the natural gas utilities sell.

An overview of methane production from manure on farms. Covers how it works and the major issues involved.

150 page pdf document.

Growth and concentration of the livestock industry create opportunities for the proper disposal of the large quantities of manures generated at dairy, swine, and poultry farms. Pollutants from unmanaged livestock wastes can degrade the environment, and methane emitted from decomposing manure may contribute to global climate change. One management system not only provides pollution prevention but also can convert a manure problem into a new profit center. Economic evaluations and case studies of operating systems indicate that the anaerobic digestion (AD) of livestock manures is a commercially available bioconversion technology with considerable potential for providing profitable coproducts, including a cost-effective renewable fuel for livestock production operations. This Casebook examines some of the current opportunities for the recovery of methane from the AD animal manures. U.S. livestock operations currently employ four types of anaerobic digester technology: slurry, plug-flow, complete-mix, and covered lagoon. An introduction to the engineering economies of these technologies is provided, and possible end-use applications for the methane gas generated by the digestion process are discussed. The economic evaluations are based on engineering studies of digesters that generate electricity from the recovered methane. Case studies of operating digesters, with project and maintenance histories and the operators “lessons learned,” are included as reality checks. Factors necessary for successful projects, as well as a list of reasons explaining why some AD projects fail, are provided. The role of farm management is key; not only must digesters be well engineered and built with high-quality components, they must also be sited at farms willing to incorporate the uncertainties of a new technology. More than two decades of research has provided much information about how manure can be converted to an energy source; however, the American farmer has not been motivated to adopt new practices. More cost-effective and easily managed manure management techniques are still needed to encourage farmers to use animal manure for conversion into energy and nutrients, especially for smaller farms. AD benefits farmers monetarily and mitigates possible manure pollution problems, thereby sustaining development while maintaining environmental quality. Moreover, rural economic development will benefit from the implicit multiplier effect resulting from jobs created by implementing digester systems. Promising future waste-to-profit activities may add to the economic performance of AD. New end-use applications, which provide added value to coproducts, are discussed.

Small Biogas Plant Plans from Nepal. Nice construction manual written some time ago but with drawing and some b&w photographs.

About the author

David MacKay is a Professor in the Department of Physics at the University of Cambridge. He studied Natural Sciences at Cambridge and then obtained his PhD in Computation and Neural Systems at the California Institute of Technology. He returned to Cambridge as a Royal Society research fellow at Darwin College. He is internationally known for his research in machine learning, information theory, and communication systems, including the invention of Dasher, a software interface that enables efficient communication in any language with any muscle. He has taught Physics in Cambridge since 1995. Since 2005, he has devoted much of his time to public teaching about energy. He is a member of the World Economic Forum Global Agenda Council on Climate Change. He was elected a Fellow of the Royal Society on 14 May 2009.

About the "free book" license

This is a free book. I didn't write this book to make money. I wrote it because sustainable energy is important. If you would like to have the book for free for your own use, please help yourself to any of the electronic versions on this website. There's pdf and html versions (thanks to William Sigmund!); we are working on other formats.

This is a free book in a second sense: you are free to use all the material in this book, except for the cartoons and the photos with a named photographer, under the Creative Commons Attribution-Non-Commercial-Share-Alike 2.0 UK: England & Wales Licence. (The cartoons and photos are excepted because the authors have generally given me permission only to include their work, not to share it under a Creative Commons license.) You are especially welcome to use my materials for educational purposes. This website includes links to separate high-quality files for each of the figures in the book.

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