Module 4
Module Four – Biogas If you do not live in an area where wind power is an option, or you are just not interested in generating electricity in this manner, then biogas might be for you. In any case, it is certainly worth looking into. While it is theoretically possible to make your own biogas digester, as you will see when we start describing the process, there’s actually quite a lot to it. For this reason, unless you are just extremely adept at building and machining, going the do-it-yourself route is NOT recommended. Methane is deadly. You do not want to try making a homemade system and put your family at risk. Fortunately, there are several great turnkey systems available commercially. These will save you an enormous amount of time and effort, plus take all the guesswork out of the equation.
Are Permits Needed? If you live inside the city limits, there may be some permit requirements, so you will want to check before you get too deeply involved in the project. Also, if you live in a neighborhood that has a home owner’s association, you will definitely need to check their bylaws to see if this kind of thing is allowed.
Also bear in mind that there’s some odor involved with setting up this system. You are essentially cooking garbage and getting methane as a result of it. This is a micro-version of the
same system that landfills use to generate methane. That is one of the ways that landfills help defray their costs. The garbage is piled high enough that the debris most deeply buried stays hot enough to begin to digest in the same way it does in the digester system you mean to set up. That is why landfills are always constructed with underground pipes that “vent” the methane to the surface. The landfills then use this to power their operation, and sometimes sell the excess to the community. You are doing the same, exact thing, but on a much smaller scale. The potential problem though, is that it carries all the same downsides, and your neighbors may not appreciate your stinky attempts at generating your own power.
How It Works Biogas works by creating methane, then turning that methane into useable power. In practice, what ultimately gets produced in the tank is about two thirds methane and one third CO2. Without doing anything else to it, the gas you will produce using such a system can be used to power any machinery or appliance that was designed to run on natural gas. If you do not have any appliances that run on natural gas, then you can use the gas produced to power a generator that will ultimately provide electricity. Note that if you decide you want to pursue this angle, then you will probably WANT to start investing in appliances that run on natural gas. The two biggest contenders here would be your water heater and/or your kitchen stove, though there are other options as well.
To give you an idea of what’s available, here are some examples of the gas powered stoves and water heaters you might be interested in:
Stoves: http://www.amazon.com/Frigidaire-FFGF3015L-Freestanding-Ready-SelectControls/dp/B003JFT3XI/ref=sr_1_1?ie=UTF8&qid=1428339236&sr=81&keywords=gas+powered+kitchen+stove
Gas powered tankless heater: http://www.amazon.com/Eccotemp-L10-Deluxe-TanklessHeater/dp/B001IBQN9M/ref=sr_1_8?ie=UTF8&qid=1428339279&sr=88&keywords=gas+powered+water+heater
A complete system: http://www.amazon.com/AO-Smith-GNR-40-ResidentialNatural/dp/B008DC1OYI/ref=sr_1_20?ie=UTF8&qid=1428339400&sr=820&keywords=gas+powered+water+heater
The centerpiece of any biogas system is the digester. A digester is simply a tank into which biomass is fed in order to be “digested.” It is essentially the same thing as a compost pile, but totally enclosed to capture the methane gas that is being created. The organic process is the same as well, as it is bacteria which are breaking down the biomass and turning it into useful methane gas.
The digester tank is actually composed of two tanks – an inner one and an outer one. The inner tank is the one where you feed the organic material to be digested. Typically, this includes things like kitchen waste, grass cuttings and other non-woody garden waste. You can even use manure (human, animal, or both), and in fact, this is recommended.
You will want to create a “slurry” out of these components. To do that, simply mix your waste materials with a bit of water. In order to get the best results, you will want to grind the waste before it enters the tank. If you have decided to buy a turnkey system, you are in luck, because these will almost always come with a “feedstock preparation chamber.” That fancy name refers to nothing more than a food grinder, which works much like the garbage disposal under a kitchen sink. It grinds all the biomaterial added to fine particles, so that they can be digested and converted into methane gas faster.
Once the digester is filled with slurry, the next step is cooking. The biomass slurry needs time to cook at around 37 degrees Celsius (98.6 degrees Fahrenheit). This is the ideal temperature for the bacteria which are performing the process of breaking down the biomass. At this "cooking" temperature their metabolism is the highest and they consume the most. As a result of consuming the biomass, they produce the methane you will be using for power. Temperature regulation is a fairly important part of the digestion process. Too hot, and the heat can kill the bacteria that are fermenting the slurry. Not hot enough and the bacteria's metabolism is slowed, leaving you with nothing but a big, smelly tank of goo.
Turnkey systems come with an on-board heating system that helps regulate the temperature of the cooking chamber to a precise degree. Herein is the benefit in buying a turnkey system, rather than attempting to build your own. As the mixture cooks, gas flows from the digestion chamber into the secondary chamber, then into your home via pipes. At some point between the digester and your home there will be a small overflow chamber to catch water buried in the ground. Invariably, there’s at least a little bit of water vapor in the gas that gets produced, and this small tank simply catches that vapor. While there are trace elements of methane and other chemicals in the water that collects, there’s not a high enough concentration to be dangerous.
Once the gas hits your house, you can use it as is, if you have appliances that run on natural gas, or, if you need to convert it into electrical power, you can feed the methane into a small generator that runs on natural gas to provide electricity for your home. In that case, during
installation, you will want to route the pipe that runs from the digester to your home to the wherever you plan to locate the generator (in your garage, in an outbuilding near the home, etc.). In summary then, if you invest in a turnkey system, you will need the system itself, like this one: http://hestiahomebiogas.com/products/
And possibly a generator that runs on natural gas, like this: http://www.amazon.com/Powerland-PD3G10000E-Tri-Fuel-PortableGenerator/dp/B005NHQXDI/ref=sr_1_3?ie=UTF8&qid=1428187702&sr=83&keywords=natural+gas+powered+generator
That is it. That is really all there is to putting this type of system together. The hardest part is actually running the pipes to carry the methane gas you produce into your home. Unless you’ve worked with natural gas before, you may want to hire a contractor to assist you with the installation. It is necessary that these pipes don't leak at all, to avoid any potential safety problems.
Scaling Up Your Gas Production How much electricity you can make using this method depends entirely on how much scrap biomass (kitchen scraps, non-woody gardening debris, and manure) you generate on any given day. A typical family is not going to produce enough biomass per day to keep the system running at a rate that produces enough methane to meet your home's needs. It is necessary to
have a few acres of land, along with a modest amount of livestock, in order to produce sufficient biomass to generate the methane you will burn on a daily basis, even without using it for electrical power.
Of course, that means collecting the manure from your livestock to feed to your biogas digester. If this sounds distasteful to you, this may not be the best system for you to use. There are other options which might be more appropriate to your needs.
The other issue here is that although you may not outright NEED significant acreage in order to build the system, the more land you have, the less likely you will be to offend your neighbors (a point we talked above above), but there are other reasons this system is better suited to people with acreage. If you and your family have a small farm, then the manure from any livestock or other animals you may have on your property will only add to the amount of biomass you generate to feed into the digester.
You CAN make arrangements with your neighbors, offering to collect their unwanted biomass to further add to your stock and increase production, but here you may wind up ultimately being a victim of your own success. If they start to see what you are able to do with it, they’re likely to want to set up their own system, and then you will lose your supply. That is kind of a happy dilemma though, because it means that you are system is working and other people are SEEING it working and want in on your success.
In any case, as we’ve explained, it is a great system, though like any other, it has its plusses and minuses, strengths and weaknesses. If you play to those strengths, you will be miles ahead.
Are Permits Needed? If you live inside the city limits, there may be some permit requirements, so you will want to check before you get too deeply involved in the project. Also, if you live in a neighborhood that has a home owner’s association, you will definitely need to check their bylaws to see if this kind of thing is allowed.
Also bear in mind that there’s some odor involved with setting up this system. You are essentially cooking garbage and getting methane as a result of it. This is a micro-version of the
same system that landfills use to generate methane. That is one of the ways that landfills help defray their costs. The garbage is piled high enough that the debris most deeply buried stays hot enough to begin to digest in the same way it does in the digester system you mean to set up. That is why landfills are always constructed with underground pipes that “vent” the methane to the surface. The landfills then use this to power their operation, and sometimes sell the excess to the community. You are doing the same, exact thing, but on a much smaller scale. The potential problem though, is that it carries all the same downsides, and your neighbors may not appreciate your stinky attempts at generating your own power.
How It Works Biogas works by creating methane, then turning that methane into useable power. In practice, what ultimately gets produced in the tank is about two thirds methane and one third CO2. Without doing anything else to it, the gas you will produce using such a system can be used to power any machinery or appliance that was designed to run on natural gas. If you do not have any appliances that run on natural gas, then you can use the gas produced to power a generator that will ultimately provide electricity. Note that if you decide you want to pursue this angle, then you will probably WANT to start investing in appliances that run on natural gas. The two biggest contenders here would be your water heater and/or your kitchen stove, though there are other options as well.
To give you an idea of what’s available, here are some examples of the gas powered stoves and water heaters you might be interested in:
Stoves: http://www.amazon.com/Frigidaire-FFGF3015L-Freestanding-Ready-SelectControls/dp/B003JFT3XI/ref=sr_1_1?ie=UTF8&qid=1428339236&sr=81&keywords=gas+powered+kitchen+stove
Gas powered tankless heater: http://www.amazon.com/Eccotemp-L10-Deluxe-TanklessHeater/dp/B001IBQN9M/ref=sr_1_8?ie=UTF8&qid=1428339279&sr=88&keywords=gas+powered+water+heater
A complete system: http://www.amazon.com/AO-Smith-GNR-40-ResidentialNatural/dp/B008DC1OYI/ref=sr_1_20?ie=UTF8&qid=1428339400&sr=820&keywords=gas+powered+water+heater
The centerpiece of any biogas system is the digester. A digester is simply a tank into which biomass is fed in order to be “digested.” It is essentially the same thing as a compost pile, but totally enclosed to capture the methane gas that is being created. The organic process is the same as well, as it is bacteria which are breaking down the biomass and turning it into useful methane gas.
The digester tank is actually composed of two tanks – an inner one and an outer one. The inner tank is the one where you feed the organic material to be digested. Typically, this includes things like kitchen waste, grass cuttings and other non-woody garden waste. You can even use manure (human, animal, or both), and in fact, this is recommended.
You will want to create a “slurry” out of these components. To do that, simply mix your waste materials with a bit of water. In order to get the best results, you will want to grind the waste before it enters the tank. If you have decided to buy a turnkey system, you are in luck, because these will almost always come with a “feedstock preparation chamber.” That fancy name refers to nothing more than a food grinder, which works much like the garbage disposal under a kitchen sink. It grinds all the biomaterial added to fine particles, so that they can be digested and converted into methane gas faster.
Once the digester is filled with slurry, the next step is cooking. The biomass slurry needs time to cook at around 37 degrees Celsius (98.6 degrees Fahrenheit). This is the ideal temperature for the bacteria which are performing the process of breaking down the biomass. At this "cooking" temperature their metabolism is the highest and they consume the most. As a result of consuming the biomass, they produce the methane you will be using for power. Temperature regulation is a fairly important part of the digestion process. Too hot, and the heat can kill the bacteria that are fermenting the slurry. Not hot enough and the bacteria's metabolism is slowed, leaving you with nothing but a big, smelly tank of goo.
Turnkey systems come with an on-board heating system that helps regulate the temperature of the cooking chamber to a precise degree. Herein is the benefit in buying a turnkey system, rather than attempting to build your own. As the mixture cooks, gas flows from the digestion chamber into the secondary chamber, then into your home via pipes. At some point between the digester and your home there will be a small overflow chamber to catch water buried in the ground. Invariably, there’s at least a little bit of water vapor in the gas that gets produced, and this small tank simply catches that vapor. While there are trace elements of methane and other chemicals in the water that collects, there’s not a high enough concentration to be dangerous.
Once the gas hits your house, you can use it as is, if you have appliances that run on natural gas, or, if you need to convert it into electrical power, you can feed the methane into a small generator that runs on natural gas to provide electricity for your home. In that case, during
installation, you will want to route the pipe that runs from the digester to your home to the wherever you plan to locate the generator (in your garage, in an outbuilding near the home, etc.). In summary then, if you invest in a turnkey system, you will need the system itself, like this one: http://hestiahomebiogas.com/products/
And possibly a generator that runs on natural gas, like this: http://www.amazon.com/Powerland-PD3G10000E-Tri-Fuel-PortableGenerator/dp/B005NHQXDI/ref=sr_1_3?ie=UTF8&qid=1428187702&sr=83&keywords=natural+gas+powered+generator
That is it. That is really all there is to putting this type of system together. The hardest part is actually running the pipes to carry the methane gas you produce into your home. Unless you’ve worked with natural gas before, you may want to hire a contractor to assist you with the installation. It is necessary that these pipes don't leak at all, to avoid any potential safety problems.
Scaling Up Your Gas Production How much electricity you can make using this method depends entirely on how much scrap biomass (kitchen scraps, non-woody gardening debris, and manure) you generate on any given day. A typical family is not going to produce enough biomass per day to keep the system running at a rate that produces enough methane to meet your home's needs. It is necessary to
have a few acres of land, along with a modest amount of livestock, in order to produce sufficient biomass to generate the methane you will burn on a daily basis, even without using it for electrical power.
Of course, that means collecting the manure from your livestock to feed to your biogas digester. If this sounds distasteful to you, this may not be the best system for you to use. There are other options which might be more appropriate to your needs.
The other issue here is that although you may not outright NEED significant acreage in order to build the system, the more land you have, the less likely you will be to offend your neighbors (a point we talked above above), but there are other reasons this system is better suited to people with acreage. If you and your family have a small farm, then the manure from any livestock or other animals you may have on your property will only add to the amount of biomass you generate to feed into the digester.
You CAN make arrangements with your neighbors, offering to collect their unwanted biomass to further add to your stock and increase production, but here you may wind up ultimately being a victim of your own success. If they start to see what you are able to do with it, they’re likely to want to set up their own system, and then you will lose your supply. That is kind of a happy dilemma though, because it means that you are system is working and other people are SEEING it working and want in on your success.
In any case, as we’ve explained, it is a great system, though like any other, it has its plusses and minuses, strengths and weaknesses. If you play to those strengths, you will be miles ahead.
