Category Archives: Biogas

Biogas Sector in India: Perspectives

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Biogas is an often overlooked and neglected aspect of renewable energy in India. While solar, wind and hydropower dominate the discussion in the country, they are not the only options available. Biogas is a lesser known but highly important option to foster sustainable development in agriculture-based economies, such as India.

What is Biogas

Briefly speaking, biogas is the production of gaseous fuel, usually methane, by fermentation of organic material. It is an anaerobic process or one that takes place in the absence of oxygen. Technically, the yeast that causes your bread to rise or the alcohol in beer to ferment is a form of biogas. We don’t use it in the same way that we would use other renewable sources, but the idea is similar. Biogas can be used for cooking, lighting, heating, power generation and much more. Infact, biogas is an excellent and effective to promote development of rural and marginalized communities in all developing countries.

This presents a problem, however. The organic matter is putting off a gas, and to use it, we have to turn it into a liquid. This requires work, machinery and manpower. Research is still being done to figure out the most efficient methods to make it work, but there is a great deal of progress that has been made, and the technology is no longer new.

Fossil Fuel Imports

India has a rapidly expanding economy and the population to fit. This has created problems with electricity supplies to expanding areas. Like most countries, India mainly uses fossil fuels. However, as oil prices fluctuate and the country’s demand for oil grows, the supply doesn’t always keep up with the demand. In the past, India has primarily imported oil from the Middle East, specifically Saudi Arabia and Iraq.

Without a steady and sustainable fossil fuels supply, India has looking more seriously into renewable sources they can produce within the country. Biogas is an excellent candidate to meet those requirements and has been used for this goal before.

Biogas in India

There are significant differences between biogas and fossil fuels, but for India, one of the biggest is that you can create biogas at home. It’s pretty tricky to find, dig up and transform crude oil into gas, but biogas doesn’t have the same barriers. In fact, many farmers who those who have gardens or greenhouses could benefit with proper water management and temperature control so that plants can be grown year round, It still takes some learning and investment, but for many people, especially those who live in rural places, it’s doable.

This would be the most beneficial to people in India because it would help ease the strain of delivering reliable energy sources based on fossil fuels, and would allow the country to become more energy independent. Plus, the rural areas are places where the raw materials for biogas will be more available, such animal manure, crop residues and poultry litter. But this isn’t the first time most people there are hearing about it.

Biogas in India has been around for a long time. In the 1970’s the country began a program called the National Biogas and Manure Management Program (NBMMP) to deal with the same problem — a gas shortage. The country did a great deal of research and implemented a wide variety of ideas to help their people become more self-sufficient, regardless of the availability of traditional gasoline and other fossil fuel based products.

The original program was pioneering for its time, but the Chinese quickly followed suit and have been able to top the market in biogas production in relatively little time. Comparatively, India’s production of biogas is quite small. It only produces about 2.07 billion m3/year of biogas, while it’s estimated that it could produce as much as 48 billion m3/year. This means that there are various issues with the current method’s India is using in its biogas production.

Biogas_Animal

Biogas has the potential to rejuvenate India’s agricultural sector

The original planning in the NBMMP involved scientists who tried to create the most efficient biogas generators. This was good, but it slowed people’s abilities to adopt the techniques individually. China, on the other hand, explicitly worked to help their most rural areas create biogas. This allowed the country to spread the development of biogas to the most people with the lowest barriers to its proliferation.

If India can learn from the strategy that China has employed, they may be able to give their biogas production a significant boost which will also help in the rejuvenation of biomass sector in the country. Doing so will require the help and willingness of both the people and the government. Either way, this is an industry with a lot of room for growth.

Biogas from Slaughterhouse Wastes

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Slaughterhouse waste (or abattoir waste) disposal has been a major environmental challenge in all parts of the world. The chemical properties of slaughterhouse wastes are similar to that of municipal sewage, however the former is highly concentrated wastewater with 45% soluble and 55% suspended organic composition. Blood has a very high COD of around 375,000 mg/L and is one of the major dissolved pollutants in slaughterhouse wastewater.

slaughterhouse-waste

In most of the developing countries, there is no organized strategy for disposal of solid as well as liquid wastes generated in abattoirs. The solid slaughterhouse waste is collected and dumped in landfills or open areas while the liquid waste is sent to municipal sewerage system or water bodies, thus endangering public health as well as terrestrial and aquatic life. Wastewater from slaughterhouses is known to cause an increase in the BOD, COD, total solids, pH, temperature and turbidity, and may even cause deoxygenation of water bodies.

Anaerobic Digestion of Slaughterhouse Wastes

There are several methods for beneficial use of slaughterhouse wastes including biogas generation, fertilizer production and utilization as animal feed. Anaerobic digestion is one of the best options for slaughterhouse waste management which will lead to production of energy-rich biogas, reduction in GHGs emissions and effective pollution control in abattoirs.

Anaerobic digestion can achieve a high degree of COD and BOD removal from slaughterhouse effluent at a significantly lower cost than comparable aerobic systems. The biogas potential of slaughterhouse waste is higher than animal manure, and reported to be in the range of 120-160 m3 biogas per ton of wastes. However the C:N ratio of slaughterhouse waste is quite low (4:1) which demands its co-digestion with high C:N substrates like animal manure, food waste, crop residues, poultry litter etc.

Slaughterhouse effluent has high COD, high BOD, and high moisture content which make it well-suited to anaerobic digestion process. Slaughterhouse wastewater also contains high concentrations of suspended organic solids including pieces of fat, grease, hair, feathers, manure, grit, and undigested feed which will contribute the slowly biodegradable of organic matter. Amongst anaerobic treatment processes, the up-flow anaerobic sludge blanket (UASB) process is widely used in developing countries for biogas production from abattoir wastes.

Slaughterhouse waste is a protein-rich substrate and may result in sulfide formation during anaerobic degradation. The increased concentration of sulfides in the digester can lead to higher concentrations of hydrogen sulfide in the biogas which may inhibit methanogens. In addition to sulfides, ammonia is also formed during the anaerobic digestion process which may increase the pH in the digester (>8.0) which can be growth limiting for some VFA-consuming methanogens.

Anaerobic Digestion of Animal Manure

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Animal manure is a valuable source of nutrients and renewable energy. However, most of the manure is collected in lagoons or left to decompose in the open which pose a significant environmental hazard. The air pollutants emitted from manure include methane, nitrous oxide, ammonia, hydrogen sulfide, volatile organic compounds and particulate matter, which can cause serious environmental concerns and health problems.

In the past, livestock waste was recovered and sold as a fertilizer or simply spread onto agricultural land. The introduction of tighter environmental controls on odour and water pollution means that some form of waste management is necessary, which provides further incentives for biomass-to-energy conversion.

cow-manure-biogas-plant

Anaerobic digestion is a unique treatment solution for animal manure management as it can  deliver  positive  benefits,  including  renewable  energy,  water pollution, and air emissions. Anaerobic digestion of animal manure is gaining popularity as a means to protect the environment and to recycle materials efficiently into the farming systems.

Waste-to-Energy (WTE) plants, based on anaerobic digestion of cow manure, are highly efficient in harnessing the untapped renewable energy potential of organic waste by converting the biodegradable fraction of the waste into high calorific value gases.

The establishment of anaerobic digestion systems for livestock manure stabilization and energy production has accelerated substantially in the past several years. There are thousands of digesters operating at commercial livestock facilities in Europe, United States,  Asia and elsewhere. which are generating clean energy and fuel. Many of the projects that generate electricity also capture waste heat for various in-house requirements.

Important Factors

The main factors that influence biogas production from livestock manure are pH and temperature of the feedstock. It is well established that a biogas plant works optimally at neutral pH level and mesophilic temperature of around 35o C. Carbon-nitrogen ratio of the feed material is also an important factor and should be in the range of 20:1 to 30:1. Animal manure has a carbon – nitrogen ratio of 25:1 and is considered ideal for maximum gas production.

Solid concentration in the feed material is also crucial to ensure sufficient gas production, as well as easy mixing and handling. Hydraulic retention time (HRT) is the most important factor in determining the volume of the digester which in turn determines the cost of the plant; the larger the retention period, higher the construction cost.

Description of Biogas Plant Working on Animal Manure

The fresh animal manure is stored in a collection tank before its processing to the homogenization tank which is equipped with a mixer to facilitate homogenization of the waste stream. The uniformly mixed waste is passed through a macerator to obtain uniform particle size of 5-10 mm and pumped into suitable-capacity anaerobic digesters where stabilization of organic waste takes place.

In anaerobic digestion, organic material is converted to biogas by a series of bacteria groups into methane and carbon dioxide. The majority of commercially operating digesters are plug flow and complete-mix reactors operating at mesophilic temperatures. The type of digester used varies with the consistency and solids content of the feedstock, with capital investment factors and with the primary purpose of digestion.

Biogas contain significant amount of hydrogen sulfide (H2S) gas which needs to be stripped off due to its highly corrosive nature. The removal of H2S takes place in a biological desulphurization unit in which a limited quantity of air is added to biogas in the presence of specialized aerobic bacteria which oxidizes H2S into elemental sulfur.

Biogas can be used as domestic cooking, industrial heating, combined heat and power (CHP) generation as well as a vehicle fuel. The digested substrate is passed through screw presses for dewatering and then subjected to solar drying and conditioning to give high-quality organic fertilizer.

Biochemical Conversion of Biomass

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Biochemical conversion of biomass involves use of bacteria, microorganisms and enzymes to breakdown biomass into gaseous or liquid fuels, such as biogas or bioethanol. The most popular biochemical technologies are anaerobic digestion (or biomethanation) and fermentation. Anaerobic digestion is a series of chemical reactions during which organic material such as human waste is decomposed through is decomposed through the metabolic pathways of naturally occurring microorganisms in an oxygen depleted environment.

Biomass wastes can also yield liquid fuels, such as cellulosic ethanol, which can be used to replace petroleum-based fuels.If you are writing an essay related to this topic experts from the best custom essay service in usa advise you to read and analyze the information provided in this article.

Anaerobic Digestion

Anaerobic digestion is the natural biological process which stabilizes organic waste in the absence of air and transforms it into biofertilizer and biogas. Anaerobic digestion is a reliable technology for the treatment of wet, organic waste. Organic waste from various sources is biochemically degraded in highly controlled, oxygen-free conditions circumstances resulting in the production of biogas which can be used to produce both electricity and heat. Biomass conversion technologies are slowing being built for home boilers also.

The team over at The Solar Advantage says this, ‘”Almost any organic material can be processed with anaerobic digestion. This includes biodegradable waste materials such as municipal solid waste, animal manure, poultry litter, food wastes, sewage and industrial wastes.”

An anaerobic digestion plant produces two outputs, biogas and digestate, both can be further processed or utilized to produce secondary outputs. Biogas can be used for producing electricity and heat, as a natural gas substitute and also a transportation fuel. A combined heat and power plant system (CHP) not only generates power but also produces heat for in-house requirements to maintain desired temperature level in the digester during cold season. In Sweden, the compressed biogas is used as a transportation fuel for cars and buses. Biogas can also be upgraded and used in gas supply networks. You can find learnerships in these specialised fields for those interested in a career in this sector.

Working of Anaerobic Digestion Process

Digestate can be further processed to produce liquor and a fibrous material. The fiber, which can be processed into compost, is a bulky material with low levels of nutrients and can be used as a soil conditioner or a low level fertilizer. A high proportion of the nutrients remain in the liquor, which can be used as a liquid fertilizer. Many companies are use R&D tax credits to carry out these initiatives.

Biofuel Production

A variety of fuels can be produced from waste resources including liquid fuels, such as ethanol, methanol, biodiesel, Fischer-Tropsch diesel, and gaseous fuels, such as hydrogen and methane. The resource base for biofuel production is composed of a wide variety of forestry and agricultural resources, industrial processing residues, and municipal solid and urban wood residues. Globally, biofuels are most commonly used to power vehicles, heat homes, and for cooking, apart from powering home boilers.

The largest potential feedstock for ethanol is lignocellulosic biomass wastes, which includes materials such as agricultural residues (corn stover, crop straws and bagasse), herbaceous crops (alfalfa, switchgrass), short rotation woody crops, forestry residues, waste paper and other wastes (municipal and industrial). Bioethanol production from these feedstocks could be an attractive alternative for disposal of these residues. Importantly, lignocellulosic feedstocks do not interfere with food security.

Ethanol from lignocellulosic biomass is produced mainly via biochemical routes. The three major steps involved are pretreatment, enzymatic hydrolysis, and fermentation. Biomass is pretreated to improve the accessibility of enzymes. After pretreatment, biomass undergoes enzymatic hydrolysis for conversion of polysaccharides into monomer sugars, such as glucose and xylose. Subsequently, sugars are fermented to ethanol by the use of different microorganisms.

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The Need for Speciality Membrane Covers

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Biogas containment is a critical safety component. When handling biogas, you must ensure the storage area is properly covered to prevent contamination. Membrane covers are a reliable solution. They are made using polymers, such as polyvinyl, polyethylene and polypropylene. A biogas cover is also suitable in water treatment plants, where it’s necessary to prevent odour and gas from escaping. Waste-to-energy projects leverage uniquely designed membranes to collect biogas and use it as fuel. Whether you are storing liquids or gases, Biogas Membrane provides several benefits that make it a valuable investment, particularly for large-scale projects.

finding the right membrane cover for biogas projects

Improved Safety

Areas that handle chemicals and toxic gases have strict safety standards. Membrane covers are some of them. The linings are resistant to chemicals, meaning no hazardous compounds can get in or out of the storage section. In a case where a membrane covers water in an open area, rainwater can’t permeate the material. It gathers on top of the membrane, ensuring the covered water is safe to use. The cover also keeps out waste from avian life, dust, debris and other contaminants.

Biogas storage membranes are strong and tear-proof. Since they can resist punctures, you don’t have to worry about contamination, even when people walk on top of them. Additionally, they safeguard against UV rays, which can compromise the composition of various gases and liquids.

Low Maintenance

After installing a geomembrane, you won’t have to worry about servicing it regularly. Membrane covers for water silos, biogas digestors and water treatment plants are flexible, yet strong. Regardless if it’s a single or double membrane, expect a robust material that cleans easily. The covers are built to withstand extreme weather conditions. So, no matter how hot it cold it gets, the membrane provides excellent temperature control. Due to the minimal supervision and maintenance required, the membrane liners reduce costs.

Compared to the cost of acquiring and maintaining full storage tanks and closed cisterns, membranes are economical. The installation is uncomplicated, as well. Although some covers require peripherals, like inner support struts, the setup is not hard and doesn’t disrupt operations.

Diverse Applications

Perhaps the biggest advantage of membrane covers is their versatility. Through customisation, covers can serve different uses. They are suitable for collecting biogas to convert into green energy, capping landfills after they reach their capacities and controlling vapours and fumes in wastewater treatment plants. The specific requirements determine the ideal membrane. Therefore, you must understand particular storage needs before settling on a biogas liner.

biogas-crop

Finding the Right Membrane Covers

Geomembranes come in different materials. When picking a liner, learn how suitable a certain material is for your storage. For instance, the aggressive conditions of a biogas digestor demand a heavy-duty polypropylene cover that can take the punishment.

Consider the thickness because it dictates its durability. You want the cover to be as thick as possible without affecting flexibility or functionality.

The most important part of selecting a membrane lining is ensuring it matches the project. It should satisfy the product’s chemical composition and the necessary technical specifications.

Whether your project involves wastewater, clean water or biogas, you need reliable, durable and effective coverage solutions. With geomembranes or biogas membranes, you guarantee safety and quality.

Biogas in Agriculture Sector in India: Key Challenges

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Although the conversion of agriculture waste – cattle dung and crop residues –  to biogas and digested slurry is an established and well-proven technology in India, it has been under-used, probably because until recently, firewood was easily available and chemical fertilizer was relatively affordable to most of the farmers in India.

The National Biogas and Manure Management Programme (NBMMP) was put in place to lower the environmental degradation and prevent greenhouse gas emissions, like carbon dioxide and methane, into the atmosphere. However, this objective of the program is less likely to motivate the farmers and their families to install biogas plants.

This program rolled out by Ministry of Non-Conventional Energy Sources (now Ministry of New and Renewable Energy), New Delhi, with heavy subsidies for family-type biogas plants to increase adoption, was successful with lakhs of biogas plants being installed across the country till now.

It was realised that due to poor dissemination of information and unsatisfactory communication about the plant operation & application of the digested biogas slurry, and unable to perceive the return in terms of value resulted in discontinuation of lakhs of biogas plants across the country.

The entire biogas technology marketing efforts failed to highlight major advantage – an increased revenue from agriculture with the use of high quality and a low-cost homegrown digested biogas slurry as fertiliser. Another advantage was to help farmers’ understand that their land quality and output per acre will increase over the years by the use of digested biogas slurry which has been degraded from the rampant use of chemical fertiliser and pesticides.

Challenges to be addressed

The farmer’s communities today are required to made to understand that their revenue from agriculture is decreasing year on year due to increasing deforestation, degradation of land quality, rampant use of chemical fertiliser and pesticides, lack of farm cattle, injudicious use of water for irrigation, and use heavy vehicles for ploughing.

These ill-advised decisions have made the farmers poorer, impacted the health of their families and the rural environment of villages. The years ahead are crucial if this trend is not reversed.

Unending benefits of biogas technology

Most of the rural and semi-urban areas have a poor perception of the Anaerobic Digestion (or biogas or biomethanation) technology. This technology offers benefits to all spheres of society but have a particular emphasis on the needs of the farmers in rural areas.

Farmers with dairy animals generally have free access to animal waste (dung), which provide input feed for the biogas digesters. Normally, these farmers stock-pile the dung obtained from their cattle as a plant fertilizer, but this has lower nitrogen content than the digested biogas slurry created by the biogas digestion process, which is odorless and makes a better fertilizer to substitute chemical fertilizers. They can use the gas for cooking or heating, for running power generators. The biogas technology helps farmers reduce their burden to buy LPG and harmful chemical fertilizers and pesticides.

In short, biogas technology is an integrated solution for sustainable agriculture, improving health and lowering environment degradation.

The promise of biogas technology

Biogas technology can help in the following manner:

  • Enhance bio-security for dairy animals – being fully fermented, bio-slurry is odorless and does not attract flies, repels termites and pests that are attracted to raw dung.
  • Provides high quality and low-cost homegrown fertiliser for sustainable agriculture.
  • Reduce energy poverty and ensure energy security.
  • Digested biogas slurry is an excellent soil conditioner with humic acid.
  • Save time for women for education and livelihood activities.
  • Increase forest cover as less firewood would be needed on a daily basis.
  • Reduce weed growth

Importance of Government Efforts

The agriculture sector is playing a major role in India economy and it comprises a huge vote bank. Our government has launched various initiatives like GOBAR-DHAN (Galvanizing Organic Bio-Agro Resources Dhan), Sustainable Alternative towards Affordable Transportation (SATAT), and New National Biogas and Organic Manure Programme (NNBOMP) in attempt to revive interest in biogas technology for farmers and entrepreneurs.

rice-straw-biogas

Agricultural residues, such as rice straw, are an important carbon source for anaerobic digestion

These initiatives are aimed at developmental efforts that would benefit the farmers, vehicle-users, and entrepreneurs. These initiatives also hold a great promise for efficient solid waste management and tackling problems of indoor air pollution caused by use of firewood, deforestation and methane gas release in the atmosphere due to open piling of cattle dung.

These initiatives aren’t marketing the value which solves a major challenge – degradation of agriculture land for farming in rural India. The initiative and efforts are majorly focused on waste management, environment and towards behavioral change. These changes are of global importance and can be managed effortlessly by generating tangible results for farmers.

India has an aspiring young workforce which is moving to urban settlements in hope for better opportunities, therefore, productivity and revenue from agriculture needs to grow. The biogas sector in India can restore agriculture productivity and strengthen revenue to make it attractive.

How Can You Produce Your Own Biogas?

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The idea of biogas is anything but new. People have been experimenting with making biogas for many generations. Biogas is made by converting organic waste into energy. It’s a huge win for the environment because it utilizes what is otherwise considered waste, but it’s a big win for pocketbooks too.

Organic waste includes the byproducts of human food production (think potato peels, carrot peels, the tops of turnips, etc) but it also includes manure. Any manure is fair game, think about cows, pigs, chickens, rabbits, goats — virtually any farm animal produces mounds of this each day.

This manure produces very high levels of methane gas which is horrible for the environment. By using this manure to create biogas, we remove the danger of creating heat-trapping gases in our atmosphere that raises the temperature of the entire planet. Using it for biogas production can also help to reduce global warming.

How Do We Produce Biogas?

Biogas is produced from the breakdown of organic waste in an environment that is void of oxygen. We call this environment anaerobic and the process is process is called anaerobic digestion. Two products are created from this process. One is digestate. Digestate can be used for fertilizer and even as livestock bedding.  The other product is biogas. Biogas can be used for heating, electricity production and as a clean vehicle fuel.

It’s essentially like composting all of the materials, but in an environment without oxygen and in the temperature range of around 35 to 40 degrees Celsius and pH of around 7. This is optimal to produce biogas. Biogas can be converted into an upgraded form of gas by removal of carbon dioxide that can be used like natural gas. It can be used as-is as an engine fuel. It can be used as fuel in a vehicle, sometimes without modification.

How Can You Produce Your Own Biogas?

Just imagine being on your own off-grid property, running a hundred head of cattle, growing your own food and canning it. You’ve got meat covered, your food is stocked and you are prepared for just about anything. But what about fuel? Imagine what a game-changer it could be if you were able to produce your own fuel from the waste from your cattle and your garden scraps or food residuals! You can!

The Biogas Digester makes it possible, and fairly easy, for you to start producing your own biogas. Buy a ready-made biodigester for around $700-$1000 dollars and start producing your own biogas to meet your fuel requirements. They are containers designed to do the work for you and help you collect the fruits of your composted and digested waste.

Build your own! China has approximately 30 million Biodigesters in use in its rural areas. Rural Chinese areas are far removed from cities that have gas stations. It simply isn’t accessible as it is in the US. Many rural people have learned to make their own biodigesters to fill their fuel needs.

offgrid-biodigester

You need a tank that is sealed with an access hole on one side for adding organic waste. You have another access to an outlet. That is where you collect the liquid run-off that can be used for fuel.

The bottom of the main unit is the digestion chamber. From that is an outlet where the digestate can be collected and used as fertilizer. The main chamber typically has a domed top to allow for the room that will be necessary for the expansion of the gases formed inside. By being sealed, the unit creates that all-important anaerobic environment.

Useful Links

A tank that demonstrates the size and simplicity of a tank that can be purchased and used in the backyard.

https://www.etsy.com/listing/705458580/portable-home-biogas?gpla=1&gao=1&

This is a very in-depth article with directions for creating your own biodigester from Science Direct – https://www.sciencedirect.com/topics/engineering/biogas-digester

Biogas from Crop Wastes vs Energy Crops: European Perspectives

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Most, if not all of Europe has a suitable climate for biogas production. The specific type of system depends on the regional climate. Regions with harsher winters may rely more on animal waste and other readily available materials compared to warmer climates, which may have access to more crop waste or organic material.

biogas-crop

Regardless of suitability, European opinions vary on the most ethical and appropriate materials to use for biogas production. Multiple proponents argue biogas production should be limited to waste materials derived from crops and animals, while others claim crops should be grown with the intention of being used for biogas production.

Biogas Production From Crops

Europeans in favor of biogas production from energy crops argue the crops improve the quality of the soil. Additionally, they point to the fact that biogas is a renewable energy resource compared to fossil fuels. Crops can be rotated in fields and grown year after year as a sustainable source of fuel.

Extra crops can also improve air quality. Plants respire carbon dioxide and can help reduce harmful greenhouse gasses in the air which contribute to global climate change.

Energy crops can also improve water quality because of plant absorption. Crops grown in otherwise open fields reduce the volume of water runoff which makes it to lakes, streams and rivers. The flow of water and harmful pollutants is impeded by the plants and eventually absorbed into the soil, where it is purified.

Urban residents can also contribute to biogas production by growing rooftop or vertical gardens in their homes. Waste from tomatoes, beans and other vegetables is an excellent source of biogas material. Residents will benefit from improved air quality and improved water quality as well by reducing runoff.

Proponents of biogas production from crops aren’t against using organic waste material for biogas production in addition to crop material. They believe crops offer another means of using more sustainable energy resources.

Biogas Production From Agricultural Waste

Opponents to growing crops for biogas argue the crops used for biogas production degrade soil quality, making it less efficient for growing crops for human consumption. They also argue the overall emissions from biogas production from crops will be higher compared to fossil fuels.

Growing crops can be a labor-intensive process. Land must be cleared, fertilized and then seeded. While crops are growing, pesticides and additional fertilizers may be used to promote crop growth and decrease losses from pests. Excess chemicals can run off of fields and degrade the water quality of streams, lakes and rivers and kill off marine life.

Once crops reach maturity, they must be harvested and processed to be used for biogas material. Biogas is less efficient compared to fossil fuels, which means it requires more material to yield the same amount of energy. Opponents argue that when the entire supply chain is evaluated, biogas from crops creates higher rates of emissions and is more harmful to the environment.

Agricultural residues, such as rice straw, are an important carbon source for anaerobic digestion

In Europe, the supply chain for biogas from agricultural waste is more efficient compared to crop materials. Regardless of whether or not the organic waste is reused, it must be disposed of appropriately to prevent any detrimental environmental impacts. When crop residues are used for biogas production, it creates an economical means of generating useful electricity from material which would otherwise be disposed of.

Rural farms which are further away from the electric grid can create their own sources of energy through biogas production from agriculture wastes as well. The cost of the energy will be less expensive and more eco-friendly as it doesn’t have the associated transportation costs.

Although perspectives differ on the type of materials which should be used for biogas production, both sides agree biogas offers an environmentally friendly and sustainable alternative to using fossil fuels.

Biomethane – The Green Gas

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Biomethane, also known as the green gas, is a well-known and well-proven source of clean energy, and is witnessing increasing demand worldwide, especially in European countries, as it is one of the most cost-effective and eco-friendly replacement for natural gas and diesel.

Advantages of Biomethane

The key advantage of biomethane is that it is less corrosive than biogas which makes it more flexible in its application than raw biogas. It can be injected directly into the existing natural gas grid leading to energy-efficient and cost-effective transport, besides allowing natural gas grid operators to persuade consumers to make a smooth transition to a renewable source of natural gas.

Biogas can be upgraded to biomethane and injected into the natural gas grid to substitute natural gas or can be compressed and fuelled via a pumping station at the place of production. Biomethane can be injected and distributed through the natural gas grid, after it has been compressed to the pipeline pressure.

The injected biomethane can be used at any ratio with natural gas as vehicle fuel. In many EU countries, the access to the gas grid is guaranteed for all biogas suppliers.

A major advantage of using natural gas grid for biomethane distribution is that the grid connects the production site of biomethane, which is usually in rural areas, with more densely populated areas. This enables biogas to reach new customers.

Storage of Biomethane

Biomethane can be converted either into liquefied biomethane (LBM) or compressed biomethane (CBM) in order to facilitate its long-term storage and transportation. LBM can be transported relatively easily and can be dispensed through LNG vehicles or CNG vehicles. Liquid biomethane is transported in the same manner as LNG, that is, via insulated tanker trucks designed for transportation of cryogenic liquids.

Biomethane can be stored as CBM to save space. The gas is stored in steel cylinders such as those typically used for storage of other commercial gases.

Applications of Biomethane

Biomethane can be used to generate electricity and heating from within smaller decentralized, or large centrally-located combined heat and power plants. It can be used by heating systems with a highly efficient fuel value, and employed as a regenerative power source in gas-powered vehicles.

Biomethane, as a transportation fuel, is most suitable for vehicles having engines that are based on natural gas (CNG or LNG). Once biogas is cleaned and upgraded to biomethane, it is virtually the same as natural gas.

Because biomethane has a lower energy density than NG, due to the high CO2 content, in some circumstances, changes to natural gas-based vehicle’s fuel injection system are required to use the biomethane effectively.

Description of a Biogas Power Plant

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A biogas plant is a decentralized energy system, which can lead to self-sufficiency in heat and power needs, and at the same time reduces environmental pollution. The key components of a modern biogas power (or anaerobic digestion) plant include: manure collection, anaerobic digester, effluent treatment, biogas storage, and biogas use/electricity generating equipment.

anaerobic_digestion_plant

Working of a Biogas Plant

The fresh organic waste is stored in a collection tank before its processing to the homogenization tank which is equipped with a mixer to facilitate homogenization of the waste stream. The uniformly mixed waste is passed through a macerator to obtain uniform particle size of 5-10 mm and pumped into suitable-capacity anaerobic digester where stabilization of organic waste takes place.

In anaerobic digestion, organic material is converted to biogas by a series of bacteria groups into methane and carbon dioxide. The majority of commercially operating digesters are plug flow and complete-mix reactors operating at mesophilic temperatures. The type of digester used varies with the consistency and solids content of the feedstock, with capital investment factors and with the primary purpose of digestion.

Biogas Cleanup

Biogas contain significant amount of hydrogen sulfide (H2S) gas which needs to be stripped off due to its highly corrosive nature. The removal of H2S takes place in a biological desulphurization unit in which a limited quantity of air is added to biogas in the presence of specialized aerobic bacteria which oxidizes H2S into elemental sulfur.

Utilization of Biogas

Biogas is dried and vented into a CHP unit to a generator to produce electricity and heat. The size of the CHP system depends on the amount of biogas produced daily.

Treatment of Digestate

The digested substrate is passed through screw presses for dewatering and then subjected to solar drying and conditioning to give high-quality organic fertilizer.  The press water is treated in an effluent treatment plant based on activated sludge process which consists of an aeration tank and a secondary clarifier. The treated wastewater is recycled to meet in-house plant requirements.

Monitoring of Environmental Parameters

A chemical laboratory is necessary to continuously monitor important environmental parameters such as BOD, COD, VFA, pH, ammonia, C:N ratio at different locations for efficient and proper functioning of the process.

Control System

The continuous monitoring of the biogas plant is achieved by using a remote control system such as Supervisory Control and Data Acquisition (SCADA) system. This remote system facilitates immediate feedback and adjustment, which can result in energy savings.