Frequently Asked Questions

 Biogas is the type of gas that is produced in an anaerobic digester. Biogas is mainly made of methane and carbon dioxide plus small amounts of some other gases. Biogas generally contains 55%-75% methane and 44%-24% carbon dioxide, with the other gases making up 1% or less of the mixture. Since biogas is made from organic material, it is sometimes also called “renewable natural gas”. 

 Biogas is lighter than liquid and rises to the top of the digester. From the top of the digester, tubes, and pipes allow the biogas to slowly release from the tank into a container so it isn’t released into the air. Biogas can be used as fuel for a boiler to generate hot water or steam, or for an engine to power an electric generator to generate electricity. Biogas can also be“scrubbed,” meaning the carbon dioxide andother non-methane “contaminants” are removed, leaving purer methane gas. Methane is the prime component of natural gas so this scrubbed biogas can then be pressurized and injected in an existing natural gas pipeline, liquefied for other storage or even used as a vehicle fuel .

 You shouldn’t breathe biogas. Biogas, due to its methane content, is flammable and should be dealt with in a safe and secure manner. Some of the trace gases that make up about 1% or less of biogas are acidic and can be corrosive to certain kinds of metals and need to be dealt with carefully .

 Yes. Anaerobic digester technology is employed worldwide to create renewable energy. Biogas produced from an anaerobic digester is comprised primarily of methane gas, which can be used instead of fossil fuels to produce energy. This “renewable natural gas” can substitute for fossil fuel natural gas for any need including heating, cooking and driving. Biogas can also be used as fuel to make clean electricity. All of these options provide us with the opportunity to turn organic “waste” into a valuable renewable energy resource in a sustainable manner.

 Methane is a greenhouse gas that is more than 20 times as damaging to the environment as carbon dioxide, but it has to be released into the air and atmosphere to take part in the “greenhouse effect.” That is why people who run anaerobic digesters are very careful to contain the biogas and not let it be released into the air—it should be used for energy! One of the benefits of anaerobic digestion is its ability to capture the methane that would normally be emitted into the air if the organic material was left to decompose in an uncontrolled landfill. 

 Anaerobic digestion is the process by which naturally occurring bacteria, which can only live in places where there is no air, break down organic, biodegradable material over time and converts it to biogas and a natural fertilizer. Infact, anaerobic means “no oxygen”.  

 From the size of a large refrigerator to the size of a small building. The size of the digester depends on how much organic material will be fed into the digester, and how quickly that specific digester can breakdown the organic material 

 The U.S. has over 2,200 sites producing biogas: 250 anaerobic digesters on farms, 1,269 wastewater treatment plants using an anaerobic digester (~860 currently use the biogas they produce), 66 stand-alone (non-agriculture and non-wastewater. The potential U.S.dairy and that not using Europe has) anaerobic digesters, and 652 landfill gas projects. The potential for U.S growth is huge. We count nearly 13,500 sites ripe for development today: 8,241 dairyand swine farms and 3,888 wastewater treatment plants (including ~380 who are making biogas but not using it) which could support a digester and 440 untapped landfill gas projects. For comparison, Europe has over 10,000 operating digesters and some communities are essentially fossil fuel free because of them. If fully realized, these biogas systems could produce enough energy to power 3.5 million American homes and reduce emissions equivalent to removing 800,000 to 11 million passenger vehicles from the road. 

 It is hard to say exactly, but the number is in the hundreds of thousands or over a million. Anaerobic digesters are at work on every continent except Antarctica. Countries like India, China, and some Western European countries have been employing anaerobic digesters for decades 

 The key is to keep the microscopic bacteria, which break down the material fed into the digester, living and constantly multiplying inside the digester. The bacteria require a sufficient amount of organic feedstock, vitamins, supplements, and some water to live. The bacteria also thrive in a warm environment without large fluctuations in the acidity levels. Like all living things, the bacteria work better without toxins. 

 Certain crops like corn and grasses can be used to feed anaerobic digesters, but most organic waste materials like manure, and food scraps work even better than specially grown crops. 

 To keep the right bacteria alive and multiplying, many of the larger digesters are kept at or above 30 to 38 degrees Celsius or 86 to 100 degrees Fahrenheit. Digesters can also work at temperatures that are both lower and higher than this. Because the bacteria working in the digester are very sensitive to temperature, cooler digesters take more time to break down the biodegradable feedstock, while hotterones may break down the biodegradable feedstock more quickly. 

 Theoretically, any organic material can be broken down through anaerobic digestion. Wasted or spoiled food, plant clippings, animal manure, meat trimmings, and sewage after it’s been treated are especially well suited to this type of digestion. Inorganic material such as rocks and dirt, and man-made materials such as plastic, metal cans, and glass, will not be broken down through anaerobic digestion. In addition, woody wastes do not digest well because their strong fibers are naturally resistant to degradation and also an aerobicbacteria. 

 It varies based on the type of organic material you feed into the digester and the design of the digester. Simpler organic compounds, such as simple sugars, fats, and proteins, will digest fairly quickly. More complex organic compounds may take 30 plus days to completely digest, especially fibrous materials like cellulose, the major constituent of paper, paperboard, and card stock and of textiles made from cotton, linen, and other plant fibers). The operating temperature of the digester also has a significant impact onthe time it will take to break down the material. 

 Organic material is something that was living and can decay. Wasted or spoiled food, plant clippings, animal manure, meat trimmings, and sewage are common types of organic material used with Anaerobic digestion. In contrast, inorganic material includes things like rocks, dirt, plastic, metal and glass.

 No.  By “organic” we mean what chemists refer to as an “organic” material–the carbon-based material from which all living things are made. Man-made materials such as plastic and glass, and some other natural materials like rock, sand, metals, and dirt are called “inorganic materials”. Inorganic materials will not be broken down in an anaerobic digester. 

 When put into adigester, fats, oils and greases (industry lingo: FOGs) and food waste create the most biogas. For this reason, many dairy farms that have digesters add local food scraps to the manure in their digesters to increase the amount of biogas produced. Digesting different materials is called co-digestion. 

 Typically, the producer can expect to receive avoided cost of cogeneration (COG,i.e., the commodity price) plus a negotiated percentage of the value realized from the sale of the RIN (renewable identification number attached to the gallon equivalent of fuel) and LCFS (low carbon fuel standard) credit, if in CA, associated with the amount of gas produced. That price will of course be variable month to month. A fixed, wholesale price for RNG that will be soldas vehicle fuel doesn’t exist at this time. To create it, any seller of RNG vehicle fuel would have to risk (or  somehow hedge) their exposure to variable RIN, LCFS and NG commodity pricing (which is based on what the market will bear at any one time) in order to offer a fixed price to the producer. 

 Biogas systems are one of the most effective solutions for waste management. They protect our climate, air, water, and soil by recycling organic material, like food waste and manure, into renewable energy and soil products while also reducing GHG emissions. Without biogas systems, tons of carbon emissions would be released into our air, and more fossil fuelswould be used to fuel our economy and create synthetic fertilizers to grow our crops. When operated properly, biogas systems create healthier soils by returning nutrients to the earth and producing reliable,carbon-offsetting, baseload renewable energy. While there are many sources for renewable electricity, and the U.S. has large stores of natural gas, biogas systems do something these other sources can’t–recycle the massive volumes of food waste in this country, which makes up 30-40% of all garbage in theU.S., as well as other organic wastes from farms and water treatment facilities. Without biogas systems, these waste streams, when unmanaged, create a host of environmental issues. 

 Biogas systems dramatically reduce odor from common waste materials and treat other air contaminants, like hydrogen sulfide, while reducing greenhouse gas (GHG) emissions. Moving manure from open lagoons to a covered, airtight biogas system significantly reduces naturally occurring GH Gemissions via its capture and conversion to renewable electrical, thermal, or liquid forms of energy orfuel. Most biogas systems reduce carbon emissions in transportation by about half compared to fossilfuels. The least GHG emitting biogas systems are so carbon negative they reduce carbon emissions sixtimes more than a battery-electric vehicle running on 100% wind or solar power compared to a gasoline vehicle. 

 Biogas systems, when properly operated, can help the farmer to optimize the volume and ratio of nutrients used in the soil. During the digestion process, several physical, chemical, and biological conversions take place. The resulting digestate has odor and pathogens virtually eliminated and more importantly produces a readily available form of nutrients in the soil. This may allow farmers to targetmore precise application of these nutrients. This provides the potential for increased crop yields while reducing environmental losses. Additionally, the qualities of the digestate facilitate the use of solids/nutrient separation technologies that can further aid optimization of nutrient application in thesoil and reduce the needs for synthetic fertilizers produced from fossil fuels. 

 Biogas is made up of methane and carbon dioxide, which are powerful greenhouse gases. If not processed in a biogas system, the organic waste our society produces would naturally generate these gases. Anaerobic digesters are designed to not only capture these gases, so they do not escape to the atmosphere, but use them to also offset the use of fossil fuels for energy. This is a win-win for climate change because methane is removed from the atmosphere and less fossil fuel is used by renewable biogas-generated electricity, heat or fuel. This is how many biogas systems are carbon negative, meaning they remove more carbon from the atmosphere than they ever put into it. Biogas systems help address not only the climate but also other environmental challenges simultaneously. 

 Biogas is a renewable source of energy that is a direct replacement for non-renewable, carbon-intensive fossil fuels. Without biogas systems, tons of carbon emissions would be released into our air from the waste our society produces, and more fossil fuels would be used to create synthetic fertilizers to grow our crops. Additionally, biogas systems reduce carbon emissions in transportation by at least halfcompared to fossil fuels. Vehicles fueled by renewable natural gas can reduce carbon emissions six times faster than wind or solar charged battery-electric vehicle. 

 No. Biogas systems are one of the most effective solutions for reducing GHG emissions, while also addressing our need to manage our waste. Biogas systems protect our air, water, and soil by recycling organic material, like food waste and manure, into renewable energy and soil products, while also reducing GHG emissions. In fact, Biogas systems reduce carbon emissions in transportation byat leasthalf compared to fossil fuels. And vehicles fueled by renewable natural gas can reduce carbon emissions six times faster than wind or solar charged battery-electric vehicle. 

 Livestock’s role in greenhouse gases often gets overstated. Livestock contributes to about 6% of emissions worldwide and 4% in the U.S., whereas the majority of GHG emissions are driven by the energy and transportation sectors. Additionally, with genetic and other technological advancements within the livestock industry, the number of animals providing our food products is decreasing, thus reducing GHG emissions and bringing the livestock industry closer to net zero carbon emissions. The use of anaerobic digesters to capture methane that would otherwise be emitted by farms has led to a 30% reduction ofCalifornia dairy emissions already, and many more can be built increasing that reduction. Further, feed additives could help reduce methane emissions from cows directly. It’s thanks to biogas systems and other environmental solutions that the U.S. dairy industry has set a commitment to achieve carbon neutrality, optimized water usage and improved water quality by 2050. 

 Unlike conventional natural gas, RNG is not a fossil fuel and does not involve drilling. It is a renewable gas made from biogas that is fully interchangeable with natural gas. No matter how much we reduce waste, as long as we flush toilets, let food spoil, don’t eat onion peels, and raise animals, we will produce the waste that can be turned into biogas and in turn, RNG. Just like conventional gas, RNG can be used to create electricity, powering homes and businesses, and fueling vehicles. RNG is created from biogas, which is mostly methane and carbon dioxide. When the carbon dioxide and some trace elements in the biogas are removed, 95-99% pure methane remains, the same as conventional natural gas, except RNG been renewably produced by recycling organic material. 

 Converting biogas to RNG is a multistep process, with different steps to remove different constituents in the biogas to leave almost pure methane. Because biogas consists of mostly methane and carbondioxide,with traces of other elements, producing RNG mostly consists of removing carbon dioxide. If the biogas has silicone compounds (from cosmetics and cleaning products in wastewater and landfill gas), or sulfur compounds (naturally occurring in our food wasteand manure), those are removed as well. Afterthe RNG is processed, it becomes interchangeable with traditional pipeline quality natural gas. You cannot tell an RNG molecule from a conventional gas molecule except the RNG was produced fromrenewable resources. RNG is versatile and can be used and delivered the same as conventional natural gas with a much better environmental footprint.

 Yes, biogas can replace any uses of conventional natural gas, a fossil fuel, and can help reduce dependency on natural resources. Methane is the principal gas in biogas, which is also the main component of natural gas. Therefore, biogas can replace natural gas in a variety of settings such as cooking, heating, steam production, electrical generation, vehicular fuel, and as a pipeline gas. Inaddition, when digested material is produced from a biogas system and used as a fertilizer, it replaces more fossil fuel since fossil fuel is used to make and transport all the chemical fertilizers used for agriculture and gardening.

 RNG can be either compressed or liquefied. Both forms are used for transportation fuel. 

 RNG can have many different carbon intensities depending on what waste resources it’s made from, how far it is transported, where it’s used, and how it is used. At worse, on a lifecycle basis, RNG produces halfthe carbon emissions of conventional natural gas. At best, it can remove 6-7 times more carbonemissions from the atmosphere than the use of natural gas and 6 times more than wind and solar used to power electric vehicles. That’s because emissions can be reduced by recycling waste that would otherwise emit methane emissions, and also by displacing fossil fuels in many ways.

 RNG can be used interchangeably with natural gas for heating, electricity, and the production of quality biomethane and transportation fuel. It can be injected into existing natural gas grids and used as asubstitute for conventional natural gas. RNG has the potential to replace at least 10 percent of the natural gas being used in the United States and in some cases, gas utilities can use RNG to help them reach net zero carbon goals. The use of RNG reduces greenhouse gas emissions and increases domestic energy production while improving waste management systems. 

 Biogas is commonly made from animal manure, sludge settled from wastewater, and at landfills containing organic wastes. However, biogas can also be made from almost any feedstock containing organic compounds, both wastes and biomass (energy crops). Carbohydrates, proteins and lipids are allreadily converted to biogas. Many wastewaters contain organic compounds that may be converted tobiogas including municipal wastewater, food processing wastewater and many industrial wastewaters.Solid and semi-solid materials that include plant or animal matter can be converted to biogas. 

 Biogas is being collected and used to generate electricity or steam at many landfills and wastewater plants,  food production plants. However, many opportunities for biogas production are yet to be implemented. Until recently, the low cost of fossil fuels has hindered the implementation of biogas production. There is limited awareness of the potential and advantages of biogas production bycitizens, government officials, and the business sector that has limited interest in biogas production. More education, demonstration, and investment in biogas technology would help overcome these barriers. 

 The broad types of wastes and biomass feedstock that are suitable for the production of biogas and limited data on production levels and biogas yields make it difficult to accurately calculate the totalamount of biogas, which can be produced in the state. If the annual biogas potential from only municipal wastewater, dairy manure, poultry manure, MSW, and energy crops is estimated, a rough potential of 116 billion cuft of natural gas inthe state of California alone!!! 

 Biogas production can reduce the pollution potential in wastewater by converting oxygen-demanding organic matter that could cause low oxygen levels in surface waters. Nutrients, like nitrogen and phosphorous, are conserved in biogas effluents and can be used to displace fertilizers in crop production. 

 While the combustion of biogas, like natural gas, produces carbon dioxide (CO2), a greenhouse gas, the carbon in biogas comes from plant matter that fixed this carbon from atmospheric CO2. Thus, biogas production is carbon-neutral and does not add to greenhouse gas emissions. Further, any consumptionof fossil fuels replaced by biogas will lower CO2 emissions.