Tag Archives: biogas

The True Function of a Biogas Plant | Benefits Listed by Real Farmers

The question of function of biogas plant. Many people new to the industry would say that the true function of a Biogas Plant is surely simply to make biogas… Full stop! end of discussion.

And yet, this would be at odds with the long list of other AD Plant benefits invariably listed by real farmers who have their own on-farm anaerobic digestion facilities.

We have found that farmers appreciate the benefits of on-farm biogas production, but their experience of their own anaerobic digestion plants reveals many other benefits.

It is with that in mind that we were fascinated to read the Royal Agricultural Society of England report authored by Angela Bywater, titled: “A Review of Anaerobic Digestion Plants on UK Farms – Barriers, Benefits and Case Studies”, which is available on their website as a pdf download. This article, and the embedded video, were written by us to highlight just one small part of this report which talks about the real-life experiences of real farmers, while using their biogas plants.

We have reproduced part of the executive summary below, but we suggest that you watch our video below first as an introduction to this subject, and afterwards return and SCROLL DOWN for the full content of our article:

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“All of the farmers involved in the case studies in a Royal Agricultural Society of England study, lauded the numerous benefits of AD which included:

• improved slurry handling;
• the ability to target crop nutrients;
• increased nutrient uptake;
• increased spreading windows;
• less crop taint and decreased re-grazing times;
• significant odour reduction when compared with slurries;
• a reduced or nil reliance on fossil based fertilisers;
• reduced reliance on fossil fuel-derived heat;
• a vastly decreased potential for watercourse pollution;
• fewer emissions to air (odour, ammonia and GHGs);
• environmentally friendly farm diversification.

In other words, on-farm anaerobic digestion offers a significant step towards more sustainable farming. It is for these reasons that the UK Government and the agriculture industry see anaerobic digestion as the ideal way to treat slurry. As stated in DEFRA’s Shared Vision for Anaerobic Digestion, the NFU would like to see 1000 on-farm digesters by
2020.

Work done by the RASE and AEA Group indicates that for the greatest impact, low-cost AD plant should be targeted at dairy farms, starting from about 100 cows and upwards.”

Source: The above excerpt is from: “A Review of Anaerobic Digestion Plants on UK Farms – Barriers, Benefits and Case Studies”; Supporting Sustainable Agriculture, By Angela Bywater, Royal Agricultural Society of England – Executive Summary.

When government subsidies such as the FiT (Feed-in Tariff) Scheme for England were first introduced there was great disappointment that small farm AD plants were at the last minute apparently omitted when the lowest band of subsidy eligibility was set just above the rate of power generation small farms could achieve.

It is not known why such a great opportunity to assist small farm businesses had been passed over. It was done without much comment, and even less warning by Defra, and only really apparent when the regulation’s small-print was issued. It truly was a wasted opportunity.

Is it too much to hope that the resurrected FiT and RHI schemes promised will be set to benefit small farmers? These would be seen as payments, NOT AS A SUBSIDY. But, money paid by the nation for the service the farmers with AD plants provide toward the sustainability of farming.

In other words an investment in the future heath of farming. A way in which marginal farms can diversify, raise their income and improve the financial security of their businesses, meaning that they will not need assistance from the national purse in the form of welfare payments to low-earners (income supplements), and other benefits for the poor.

Other Function of Biogas Plant References Online:

Biogas Defined and the Function of AD Systems from Wikipedia

Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste. Biogas is a renewable energy source.

Biogas can be produced by anaerobic digestion with anaerobic organisms, which digest material inside a closed system, or fermentation of biodegradable materials.

Biogas is primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulfide (H2S), moisture and siloxanes. The gases methane, hydrogen, and carbon monoxide (CO) can be combusted or oxidized with oxygen. This energy release allows biogas to be used as a fuel; it can be used for any heating purpose, such as cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat. via Biogas – Wikipedia

The microscopic organisms that produce biogas, known as Archaea, are among the oldest life forms on Earth. Much less oxygen-breathing and CO2-absorbing plant life …

Function of Biogas Plant Operation in Principle

In airtight fermentation vessels – the so-called digesters – use a function of biogas plant operation, namely a fermentation process. This is stimulated and produces biogas using bacteria. The bacteria are similar to those which can also be found in the digestive tract of a cow. Main products of anaerobic degradation are energy-rich methane and carbon dioxide. Since both are gaseous, they separate from the fermentation substrate and form the main components of biogas. Carbon dioxide is not oxidised, but then can be supplied together with the energy-rich methane cogeneration power stations of combustion and fed into each locally existing heat network. via EnviTec Biogas AG

The Function of Biogas Plant Operation shall be to control the digester’s chemical environment as follows:

4. pH of the digester-: Neutral pH is an important parameter in anaerobic digestion, just as it is for aerobic composting. If pH is measured at the inlet, it will be slightly lower than neutral — usually around 5.5 — as fresh material is converted into acids. The pH will neutralise as these acids are converted into methane gas. By the time the liquid bio-fertilizer comes out the digester, it should be 7. If the pH of the bio-fertiliser is lower than this, it is an indicator the digester has been over-fed and is at risk to “sour,” or stop working due to low pH. If the pH at the inlet goes below 5.5, it is necessary to add some wood ashes or lime to buffer the digester. A function of biogas plant operation is to prevent soured digester has no bubble activity and instead of producing gas, instead it draws air into it. The top will be sucked in tightly against the surface of the liquid and if a brewer’s airlock is being used, the water in the airlock will be sucked into the digester. Restarting a soured digester is time consuming, severely compromising the function of biogas plant effected, and in most cases it is simpler to dump it out and start over.

5. Feedstock -: Biogas production is best at the 25:1 C:N ratio as aerobic composting. Cattle manure is most common feedstock for biogas because cattle manure is naturally the perfect 25:1 carbon-to-nitrogen ratio. Cattle manure makes an excellent feedstock to begin

These above factors are controlled by digester loading.

After these five steps, it is important to know that for the first 48 hours for a small digester or up to a couple of weeks for a larger system, the digester will only produce carbon dioxide (CO2). Carbon dioxide is of course used in fire extinguishers. When you put a match to the gas to test for flammability, it will be blown out with an audible “hiss” and a wisp of black smoke. As the biogas begins to come on, the hiss and black smoke will be gone and you will smell the distinct “rotten eggs” scent of the hydrogen sulfide (H2S). This odour is the signal to begin capturing your gas, as it is either flammable or soon will be. This “CO2 Phase” has caused many people to abandon projects that might have been flammable if they had waited a short time longer. via Structure and purpose of AD plants

The post The True Function of a Biogas Plant | Benefits Listed by Real Farmers appeared first on The Anaerobic Digestion Biofuels Blog.

4 Biogas Generator Types

A type of biogas generator is illustrated here.

As a general rule Americans are all big biogas generators, if they only knew it. So, is every citizen of every wealthy country.  We  throw away several pounds (about 2kg in fact) of waste every day, and still  55% of all that trash generated in the United States goes into landfills.  Many other nations are just as bad.

1 – Landfills as Biogas Generators

But, we can ALSO burn Grandpa’s trash too, using the gas which pours out of landfills! That’s why we say we are all biogas generators.

In 1986 there were over 7,600 small dumps, today there are around 1900 mega-dumps which should have enough capacity for centuries of garbage. We could also call these “biogas generators” because in 2008, power from landfills exceeded solar power production in New York and New Jersey, and biogas collected from landfills has expanded significantly in the years since.

Of the 1900 landfills (or should we call them biogas generators!) over 640 have added the technology to harness the power of landfill gases (LFGs) and converting them to energy. LFG is produced by anaerobic bacteria (bacteria that doesn’t need oxygen) buried deep within landfills.

The anaerobic bacteria munch on our trash and poop out methane which would NORMALLY be real bad for the planet.

Methane is 20 times more potent a greenhouse gas than CO2, and according to the EPA, municipal solid waste (MSW) is the third-largest source of human-related methane emissions in the US.

But, if we capture it before it floats up and makes climate change worse, we can use it for good because by using the energy we don’t need to use the oil we would otherwise have needed to use.

Methane is an odourless, colourless hydrocarbon (CH4), and because the bacteria are trapped underground, companies can drill wells into the rubbish and suck it out with vacuum pipes.

Once collected, the methane is cooled, cleaned, and mixed with mercaptan to give it a detectable odour before they send it out to natural gas plants to be burned for fuel.

Yep, natural gas normally comes from fossil fuels come from rock, or oil deposits, and depending upon the source it’s a “dirty” natural gas. Typically, a mix of 99 percent methane with some propane, ethane and sulphur and helium mixed in.

The biomass methane also needs cleaning up to be just CH4.

The EPA’s Landfill Methane Outreach Program is hoping to encourage companies to set up on top of landfills and suck in as much methane as possible, because otherwise we’re just letting dollars float away.

As of 2018, LFG captured energy was powering several million US homes.

So just to recap, we throw away a lot of stuff and just let it sit there, but thanks to these technologies getting trashy could clean up the world.

As found on Youtube.

2 – A Simple Home Biogas Generator

Here is a our second biogas generator, and it is using a home anaerobic digestion system to generate biogas.

The whole idea is to create biogas which is such a good green, clean, and sustainable energy methane.

Here, we are going to show you today four different ways. You can go as simple or as high-tech as you want to go with this.

Here is one real simple method right here. You take two cylinders, and as you put food waste and your manure and everything else in there, as you churn it up, the methane bubbles to the top and forces an upper cylinder up, which is good for several purposes.

It holds the methane, and it pressurises the biogas generated. Meaning that you can send it back to your utilities gas supply, or whatever you are going to use it for.

You put in your rotten vegetables, and your manure, and whatever organic waste you’ve got which can be ground up, and you put it in here.

As the methane builds up under this chamber, it raises up slowly, until it would eventually fall off. it won’t fall off though because you will use it for cooking. That’s why it truly is a great “biogas generator”.

As the cylinder rises up, you turn your cook stove on or your electricity generator. This biogas storage device sinks back down. It is all very simple, and I call it our biogas generator concept 2.

3 – Small Farm Scale Biogas Generator also for Smallholdings and 3 – Community Anaerobic Digestion (AD) Projects

Next, we are going to do the same thing, for a biogas generator at a much bigger scale.

We got some old fuel tanks from a farm, had them welded together, made one a lot bigger. They just happened to just fit neatly inside each other.

So, here is another concept. Here is a whole other way. The whole idea is to have a sealed chamber that seals off the oxygen.

This is what we have done with three tanks. You put the food scraps, manure etc., in, as before.

But, this time an electric powered thing grinds them up, and sends them down a pipe and the food stays for on average about 30 days where it just rots by fermentation without free oxygen being present.

The digester is at the heart of this biogas generator and must be completely sealed.

The whole idea is to starve the rotting stuff of oxygen to generate biogas. That’s what anaerobic composting is all about.

Use products like the Uniseal range to prevent wastage from leaking biogas, during the pilot stage in the storage period.

I am just going to use it. They are not too expensive. We are going to take the years organic waste, such as rotten apples, and rotten vegetables, and turn them into methane by grinding them up in our methane digester, and letting them rot.

For larger biogas generation plants you can generate biogas at a larger scale. One potential good move (US based) is a 3/4 horsepower in-sink macerator.

I just ground up a whole box of rotting apples in like thirty seconds to a minute, straight into an (past its use-by date!) apple sauce.

The great thing about using rotten vegetables is you are getting it before it is halfway digested. A lot of people use methane digesters. They will throw cow dung in there, which is good. But, that stuff is halfway already used. The cow has already used it. One time, they hooked up a balloon to one of these cows. That cow, in one day, filled up a balloon full of methane the size of the cow.

But, if your stuff is halfway digested, there is a problem because, about half the methane is gone already. If it is fresh it is best. Nothing produces methane better than anything with lots of sugar in it. Cantaloupes, apples etc, produce way more methane than just grass would.

So, what you should do? You should go out to some of the local restaurants, you know the ones right down the street. See if you can make a deal with them to get their leftover food waste to put in your biodigester. It is way better than just using cow dung or chicken waste. There is way more of it.

We went around, and after a while picked up 800 pounds of rotten food waste per load. If it was good, we would feed it to the chickens, but if it is super rotten stuff, we are just tossing in the macerator, grinding it up and mixing it in to a digester feedstock substrate (slurry). And it will, if needed, produce methane for seven or eight weeks. It will produce a lot of methane within two weeks.

Then, if it is for waste biogas generation, it just keeps going for about seven or eight weeks.

By the time it is fully digested, they fluid/ solid mix, almost comes out looking like a clear liquid.

This ends our biodigester blueprint.

4 – IBC Tanks Based Biogas Generators

These are our three IBC tanks: one, two, three. I wanted to build something that will take a hundred pounds of food scraps a day, move it on through.

The stuff that has been in there for a few days, will come off the top, go back into the bottom, swirl around.

The stuff that has been in here for a couple more weeks, will come off the top.

Then, by the time it gets digested to the end, it is almost fully eaten up and turned into a nice, almost clear liquid. That we can use for fertiliser.

Last thing we are going to do is install our overflow valve. We are going to put a hole, and put this uni-seal in right there. Shove it into the tank, and then we can come in and pull off about 100 gallons of fertiliser whenever we want it. We are going to pull off all these burrows and make that real clean. Use a really sharp hole saw if you can.

We recommend painting your biogas generator black, to soak up as much of the sun’s heat during the day as possible. That way you can keep that reaction going, and simultaneously use spare heat to warm the farm’s greenhouse during the winter time.

Experience we Gained from Running Our Biogas Generators

Alright, now we are going to get into the science of biogas generation at a micro-biological level.

What we found out on accident, because we guess nobody told us, or else we didn’t read the last few lines of the instruction manual.

You cannot just throw a bunch of rotten vegetables and rotten stuff and manure or whatever. You cannot just throw it into a chamber and expect it to automatically just create methane. You got several different variables and it is really easy to maintain; you just got to know some of the science.

We do not want to to make it sound super difficult, because it isn’t. But, the whole idea is you have two different kinds of bacteria.

One bacteria that eats your food and creates acid; the other that eats the acid and creates methane, a methanogenic bacteria.

Then, you have two different kinds of food to feed into the biogas generator. You have low-energy food, like what cows eat, namely grass.

Then, you got high-energy food like grain and at the highest levels, you have sugar.

So, what happens is if you put too much high-energy food in your chamber at once? If you feed the system too much, you will end up getting too much acid-producing bacteria or too much acid.

The acid bacteria will go crazy, and produce a bunch of acid and that acid is great, it is what the methane- producing bacteria eat to create methane. The problem is it shoots the pH so low.

Once you get below pH 6.0 you are done. Your methane bacteria start to die off and then you have to start over and build back up that methane population.

So, the question is, how do you start a methane digester? What is the best way?

The best way is to start it with cow manure. Not chicken manure; chicken manure has way too much high-energy grain, stuff that has not even been digested that just goes right through the chicken’s body. But, the cow, they have been eating grass and it is less likely to produce a spike in acid.

That is it for for this article intro. Check out our latest video on AD at: to follow soon

As found on Youtube

The post 4 Biogas Generator Types appeared first on The Anaerobic Digestion Biofuels Blog.

HomeBiogas: Transforms Your Food Waste Into Clean Energy

Samuel Alexander has an excellent review of the original Home Biogas unit over at Simplicity Collective. Check it out.

Here’s an overview of the Version 2.0 model, available here.