Tuesday, February 24, 2015

Confronting the Fear of a Biogas Digester Turning Sour

Nobody talks about what happens when a biogas digester turns sour. It's costly, can mean turning away clients, and the extra hydrogen sulphide produced can be very dangerous...

We must start confronting the fear of a Biogas Digester Turning Sour!

As more and more biogas plants are built, many organisations and plant operators will be tasked with the responsibility for reliable operation of these intricate pieces of equipment. There is a danger that unless the biogas industry airs its past errors in public, the anaerobic digestion industry will be set back by lack of understanding of the nature of the problems that can occur if biogas plants are not continually monitored and well run.

It is perfectly natural for a young industry, such as this to want to move forward and not talk about past mistakes, but on the other hand it is only by understanding the past that repeating past errors can be avoided.

For that reason, in this article we will discuss that most unpleasant outcome of poor or inexperienced biogas plant operation, which is known as a digester turning sour.

What is actually meant by this term, is when a biogas reactor is allowed to diverge sufficiently from its target pH, and intended alkalinity concentration for the methanogens (methanogenic organisms) to be killed (in effect poisoned), and other unwanted organisms to thrive. Significant quantities of dangerous hydrogen sulphide are likely to be produced in such circumstances.

To describe this as a "fearful event", is not an overstatement. The consequences in terms of lost production from a biogas plant in these circumstances are substantial. In fact it is quite possible that plant managers and/ or operators will have faced disciplinary action due to such events.

Those that sell these plants naturally like to provide the impression that these plants run themselves.  While they may appear to do so when run by experienced operators, behind the scenes there is always activity. Biogas plants should never be considered to be "black boxes" in which waste enters and methane leaves like clockwork. It simply cannot be like that!

These are complex biochemical reactors. Those that study biochemistry and microbiology will appreciate that there are at least three stages taking place, each of which has to progress successfully before biogas is produced. Phase changes are needed from solids to liquid to gas, and the right healthy micro-organisms need to be present at every stage.

The equipment can fail in a multitude of ways. Sensors can lose calibration, but still appear to be working. Pumps can, at times appear to be running but are in fact delivering no flow.

A delicate balance needs to be maintained and while it is, all goes well. However, feed materials are always changing both in their nature, and seasonally. This means that regular monitoring of digester health is always absolutely essential, and beyond that so is a proactive plant operator needed, to ensure that manual and automatic adjustments are carried out, hour by hour, day by day, year in, year out.

Wise biogas plant designers/contractors install automatic equipment and train operating and maintenance staff, to maintain that delicate balance, as a matter of routine.

But, it is vital that management and staff at every biogas facility remain vigilant, because should a digester fail and turn sour it is a lengthy procedure to bring it back to health. The worst case scenario is that the whole digester tank has to be dug out, and the whole biological commissioning process started again. The consequences of this in terms of cost, the ability to comply with contractual duties, and lost goodwill, are massive. Not to mention the dangers of the likely odour escape, the health and safety of personnel, and the risk of polluting the local environment while disposing of the contents of a "sour" reactor, which hardly need stressing.

Short of that, in most cases when it happens, it is caught in time to implement procedures to bring the reactor back to a healthy condition, while retaining the substrate in-situ. This is a slow process and may take 4 weeks or more to achieve even the recommencement of substrate feeding feed, even at a low fow rate.

Subsequently, over some weeks, the feed flow rate must be progressively increased. This must be done rapidly enough to encourage the growth of a healthy compliment of fermentation micro-organisms, but never so rapidly as to cause organic overload. Organic overload could push the reactor back into the chemical conditions which caused the problem originally, so care is needed throughout.

Once the bulk of the methanogenic organisms are lost, for example, they must be replaced. The methanogens are slow growing and have to be teased back into health, over a long period when no treatment can take place. In short, the microbiologcal system has to be allowed its own time, to recover itself, and that process cannot be rushed.

In view of the large loss of revenue and inevitable disruption which would be caused to the waste producers if their waste could not be removed by the biogas plant operator, the avoidable event of a sour digester needs to be continually borne in-mind by all those involved in the industry.

Monitoring and control systems are improving all the time in reliability and sophistication, so with time the threat is becoming easier to manage. However, the AD industry must never forget the consequences of a sour digester.

It is only when organisations in this industry continuously confront the fear of a sour digester, which should be instilled in the culture of all biogas companies, that it can be avoided. That mildly felt apprehension, needs to be ever-present throughout the company from the managing director, at all levels down to the pump fitter.

Some "fear" should especially be felt by the accountant/ maintenance budget holders who might otherwise require that essential maintenance be deferred to improve company cash-flow, just for a few months, but with dire consequences.

Paradoxically, it can be the best run biogas companies which fall hardest. It is perfectly possible for a site team to make biogas plant operation look to higher-management to be simple, and by achieving reliable plant operation for many years, to result in a loss of understanding of the duties of the plant operational staff. This is easy to creep-up on an organisation over time, and after many staff changes.

A gradual erosion of respect for the work of the site operational staff, can easily lead to corner-cutting. This can reduce monitoring and maintenance, while the site staff suffer in silence, mending and managing on reduced man-hours, and pared-back budgets. Eventually, if not corrected, this can result in a crisis, and a large plant failure.

Yes. Even the very best run companies can fall prey to this...

So, our conclusion is that the "black box" concept of a biogas plant, must always be held in-check by a willingness not to brush this age-old problem of biogas plant operation "under the carpet". You can never switch-on a biogas plant and walk away!

Instead, all in the anaerobic digestion industry must in their own ways, continuously remain open to the fear of biogas plant micro-organism failure (a "sour" digester), when operating conditions stray a long way away from healthy conditions for the unseen microbial populations, which are essential for plant operation.

Achieve that, and the problem doesn't actually recur - and the biogas industry will thrive.

Thursday, February 19, 2015

US Rendering Plant Gets State-of-the-Art GasMix Biogas Mixing Technology

(Image: Courtesy Landia)

Landia’s GasMix state of the art biogas digester mixing technology has just been successfully installed at North State Rendering in Oroville, California for the best possible biogas yield. To achieve that, very thorough mixing of the bio-reactor is essential.

Only by achieving heterogenous mixing can the micro-organisms that produce biogas methane get at all the food they can extract from the substrate, and the GasMix system (which we have described previously here) is particularly ingenious in the way it achieves that.

The rendering industry is seldom publicized.  What it does is not exactly glamorous and little usually happens in the industry to promote more general interest.  However, at North State Rendering they now have something which is making them a star of the U.S. biogas industry.

(Image: Courtesy Landia)

Biogas Energy is the company that has been contracted to build an anaerobic digestion facility for North State Energy, where Landia's gas mixing equipment is helping to pay peak dividends.

They are now achieving uninterrupted biogas production, generating electricity 24/7, fuelling the rendering company's trucks, and creating heat to run their boilers. Plus, they have estimated that they will be able to reduce by 75% their diesel costs, by introducing a gas-cleaning skid to create a natural gas grid-ready quality biomethane, that is then compressed to become their own source of CNG fuel.

Rendering waste is a high energy producing substrate, so their bio-reactor produces a lot of energy. This means so that the economic benefit of this new plant is seriously cutting their business costs.

Not only that, at times when they do not need all the power to plant produces, they can further process and sell the spare energy, and the plant also provides a form of wastewater treatment ready for its discharge and use.

This has to be a notable first for the industry in North America!

(Image: Courtesy Landia)

Brian Gannon of Biogas Energy said recently that:

"For a rendering plant, biogas is a natural fit”.

“North State Rendering were looking for ways to cut costs, secure new waste supply contracts, and improve wastewater treatment, so creating their own on-site biogas facility was a wise move.  Fuel and energy are a significant operational cost for the business, so investing in technology that eliminates electricity bills, slashes diesel costs and reduces natural gas imports all makes sense.  Modifying the anaerobic digestion process to integrate with a rendering plant took some fine tuning, including a very positive modification to the digester’s mixing system, but now, we see how we got it right”.

Renderers commonly find that food waste from kitchens, grease trap waste, plus restaurant and food processing waste, can be expensive to render, and yet it is ideal for anaerobic digestion.  The biogas plant allows them to divert such wastes from their existing and new waste disposal contracts, freeing up rendering capacity for rendering more suitable materials.

By configuring their waste reception facility flexibly they now divert their existing incoming materials to the most efficient type of process, either to the rendering plant or to the biogas plant.

The digester processes materials such as, food and yard waste and high-liquid content grease trap materials.  Wastewater produced by the rendering process is also sent to the biogas plant, as is also any dead livestock tissue, after suitable preparation. This is particularly useful during hot weather, when rendering may become difficult due to the rapid degradation of this material.

Brian Gannon also said:

“We had been using submersible propeller mixers inside our main digester, but with our re-design of the tank, we switched to a new system that meets all of our needs.  One of the main issues with submersible digester mixing systems is that the equipment is inside the tank, which from a maintenance point of view is a nightmare.  The downtime caused by having to open the digester to lift the mixers out for repairs and maintenance caused serious process interruptions and safety issues."

“We now have a Landia digester mixing system, which is mounted externally, so maintenance is much easier.  Even during commissioning when the AD biology was at a delicate stage, we were able to carry out some tweaks without any interruption whatsoever to the biogas production process.  With submersible mixers we would have had to start over again, which would have been very expensive and used up a ton of manpower”.

Ease of maintenance is not the only benefit from the Landia GasMix system, Brian also explains that the Landia (patent-pending) system is able to agitate and mix into the entirety of the digester tank (even one as big as this - at 64 feet high!), whereas competing systems frequently fail to prevent a hard-pan (or "crust") from forming on the surface of the tank’s contents.

Brian also said that:

“The anaerobic digestion facility is designed to process a very wide range of feedstock”, he said, “so its pumps and mixers have to cope. The Landia chopper pumps, which form part of the GasMix system, are absolute troopers. They just keep on working.  We wouldn’t be achieving what we are now without them”.

The GasMix system installed comprises, two 30-HP chopper pumps and a self-aspirating system. That, coupled to a clever sequencing control system ensures that the action of the meathnogenic micro-organisms is much more effective in reducing the volatile organic solids content to produce more methane, and does it in a much reduced time period.

Landia’s GasMix which is uniquely designed specifically for AD and biogas reactors, is simple to operate, and has a low energy requirement, because it only needs to run for up to 30% of the installed capacity of the equipment, in normal use.

Brian Gannon concluded:

“Renderers have a big head-start over other companies trying to develop new waste-to-energy facilities.  Unlike newcomers, renderers already have the necessary permits in place to process waste material.  They also have the trucks to collect waste, and the energy consumption that biogas facilities can help fuel."

“As energy and fuel prices climb and wastewater discharge fees escalate, waste processors can turn waste into an asset.  For Biogas Energy, our experience at North State Rendering and the introduction of Landia’s GasMix digester mixing system means that we can help our clients generate renewable energy with a system that maximizes production while facilitating operations and maintenance”.

For more information contact:
Landia: www.landiainc.com
T: +1 (919) 466 0603
Biogas Energy: www.biogas-energy.com
T: +1 (815) 301 3432

Tuesday, January 13, 2015

Renewable Natural GasTo Be a Major Contributor to Improved Sustainability of Transport

Natural gas offers huge opportunities for reducing the use of petroleum in transportation. One highly sustainable source of natural gas is biomethane, and that, by definition, is made from organic (usually waste) materials. 

The method by which biomethane is made is to first create biogas, using the anaerobic digestion process, and then remove the unwanted impurities (such as carbon dioxide), and the small trace amounts of compounds which would not be found in natural gas extracted from fossil fuel sources.

That is done in a process known to the energy industry as “biogas upgrading” and there have been important innovations in the technology for doing this in recent years. Not least in the development of efficient membranes for this purpose.

The Scale of this Opportunity

The potential impact that replacing gasoline (petrol) vehicles with natural gas (CNG) fuelled vehicles, can be appreciated when one considers medium and heavy-duty fleets. These have a significant potential for natural gas use, and they currently consume more than a third of the petroleum used for transportation in the U.S.

Natural gas is an excellent fuel for a wide range of heavy-duty transport vehicle applications, especially transit buses, refuse haulers, and Class 8 long-haul or delivery trucks. In addition, natural gas can be a very good choice at the moment for light-duty vehicle fleets which have the ability to use central refuelling. In other words, work out of a base, and can fill the tanks when then come home each night).

The Extent of US Government Support

The US Vehicle Technologies Office (VTO) has been supporting the development of natural gas engines and research into renewable natural gas production, for some time now. In fact, VTO has supported the development of natural gas engines for heavy-duty vehicles since 1992. We can go further than that to force this point home, as well, because nearly all heavy-duty natural gas engines on sale in the U.S. today can trace their origins to the US DOE's support for research and if not through research, through partnerships between the VTO and industry.

Work to Increase the Sustainability of Natural Gas Use

Natural gas is known to be the cleanest burning and lowest carbon dioxide producing of the major fuels in use today. New methods of natural gas extraction such as fracking are increasing its availability, but not its sustainability. To increase the sustainability of natural gas, the US VTO has also been supporting research into the production of renewable natural gas.

The Role of Anaerobic Digestion

Renewable natural gas is a purified version of biomethane that results from the anaerobic digestion process which occurs without any encouragement in the decomposition of landfills, and is the product produced by wastewater treatment plants where the sludge is digested in in a “biogas digester” (or biogas plant), and also at livestock facilities where a biogas plant is in use.

A Surprisingly Level of Reduction of Greenhouse Gas Emissions!

The US VTO has provided the following amazing quotation about the use of renewable natural gas:

“When it [renewable natural gas] is used in vehicles in place of diesel, it reduces greenhouse gas emissions by 88 percent or more.” www.energy.gov/eere/vehicles/vehicle-technologies-office-natural-gas-research

We think that this is a quite astonishing improvement! We are surprised that this fact isn't being sung from the rooftops by all those in the biogas industry...

Reducing vehicle emissions is also vital for human health, as many thousands of people die annually in our big cities, who otherwise would live on, due to vehicle fume particulate pollution. It also does this without the parasitic drag on performance produced by the pollution prevention devices which have to be fitted to petrol and diesel vehicles. Most people who read the above statistic will say that it is crazy not to use much more natural gas in place of petroleum and diesel, especially when the US has so much natural gas available now, and for the foreseeable future.

So, What is Being Done to Raise Natural Gas Use for Vehicle Transport?

The US VTO explains, on their website that through collaborating with industry and national laboratories, the VTO has done a great deal already. It has demonstrated the feasibility of purifying biomethane from landfills.

The Big US Push to Utilize Landfill Gas Sourced Biogas as Transport Fuel

As a result of this project the government identified more than 300 landfills which are currently producing biomethane. Furthermore, on average it was found that they could each produce up to 20,000 gallons of liquefied natural gas per day. The EPA is now assisting the waste management industry in promoting the installation of as many landfill gas extraction and biomethane production facilities, which have biomethane upgrading plant installed on landfills throughout the US, as possible.

Huge US Development Program for 11,000 NewAgricultural Biogas Plants

Since then, further research has identified more than 8,000 livestock units that could also support renewable natural gas production within economically viable anaerobic digestion plants. Although a number of agricultural/ dairy industry businesses were already installing their own biogas to biomethane production facilities, many more will soon be implementing this sustainable energy producing technology in accordance with the USDA “Roadmap for Renewable Energy” which aims for the creation of 11,000 new agricultural waste fed biogas plant installations by 2020.


The result is that landfills and livestock facilities are using anaerobic digestion technology to produce fuel and to power renewable natural gas vehicle fleets, led by the refuse haulers, and milk haulers, but now also being followed by the first transit bus fleet operators.


Having read this article we hope that our readers now appreciate the huge advantages of renewable natural gas as a transport fuel. It is number one for sustainability, but is followed by the substantial benefits of using natural gas from carbonaceous sources as a bigger part of the nation’s transport fuel consumption.

This is especially true when compared with diesel fuel use, and the real public health damage being caused currently by urban air pollution from vehicle exhausts.

Finally, we do suggest to our readers that they go and visit  the link above to the US government's article in which it states that "renewable natural gas reduces greenhouse gas emissions by 88% or more".

Can it really be true? An 88% reduction! If it is, why isn't it a fact on everyone's lips? Surely, everyone that calls themselves "green" should be shouting about this from the rooftops! Your comments are appreciated.

Wednesday, December 31, 2014

2014: A Great Year for Anaerobic Digestion and Biogas in the U.S.

2014 will probably be seen in years to come as a turning point in the development of the anaerobic digestion and biogas energy industry in the U.S.: The year when their industry came of age and finally began to take-off in terms of business.

Last year the USDA, with the EPA and DOE at their side, published a Biogas Opportunities Roadmap report. It described the steps that these three Federal Agencies will take to increase the uptake of the anaerobic digestion with the development of many more biogas plants in the United States, on a scale hardly even imagined previously.

Will 2014 be seen as the year when this "banana power" prediction finally
became accepted in the mind of US businesses?
Their "Roadmap" outlines the ways in which those that want to promote waste fed anaerobic digestion projects will be able to overcome the current regulatory restrictions which have been holding back the development of a healthy (energy from waste) biogas industry in the U.S.

There is no doubt that this will end up creating new jobs, and injecting cash into the nations economy. At the same time these agencies recognise, that an important part of the Roadmap is in its aims to educate the public on the benefits which will flow from biogas development. Within these benefits is of course the ability of these biogas plants to reduce Greenhouse Gas emissions, and in this and in other ways lead to improvement in the nation's environmental quality.

Within the Roadmap there are more than 10,000 farms where it is estimated one of these new alternative energy producing waste processing plants should be built in just a few short years, so the young biogas industry will have plenty to be doing. This news has been welcomed by the American Biogas Association, which is the main industry trade body.

For years, third world ranchers have been using methane from manure to run electrical generators down on the farm. This low pollutant emitting biogas is not only a good local fuel in countries with little or no infrastructure, now even countries like the U.S. will be reaping energy from what is otherwise a very smelly resource.

About 80 percent of the estimated only 160 biogas energy projects in the U.S. are currently installed on dairy farms, which then combust the gas to generate electricity. The combined installed capacity of all dairy farm projects is now nearly 60 MW, and should now rise rapidly.

Until now the value of biogas was not properly understood. Because of that there has been an absence of training and regulation standards. Biogas industry data is under-developed and it has been difficult to secure finance, but in 2015 that should all start to change.

In huge tanks, bacteria will turn waste into methane gas, which is burned in turbines or engines that generate electric power. Each large biogas plant can generate as much as a wind turbine, but this energy is far more valauble as it is generated continuously and is not weather dependent. After methanization, the "digestate" produced is further composted and turned into fertilizer that is used by farms in the region.

Looking back at the last 12 months we wanted to share another biogas development which was one of our favorite moments.

In a recent issue of Biomass Magazine, it was explained that there has been staggering growth in the use of cellulosis renewable information number (RIN) market. To you and me this means that existing alternative energy plants are making much more of it, from compressed natural gas (CNG) to liquified natural gas (LNG). In fact, this renewable energy output surged from 3.5 million in August 2014 to 7.5 million in September 2014, presumably due to new plants coming on-stream.

Also, in 2014, municipalities and others who have long been looking for ways to make the best possible use of landfill gas (LFG) created by anaerobic processes at their landfills, will have been further encouraged to go ahead with landfill gas collection schemes. In 2015 and beyond, many more of these should now be equipped with biogas upgrading equipment, and be used to fuel waste collection fleets, or simply sell the compressed biomethane as CNG.

http://images.anaerobic-digestion.com/meme/view/Biogas Explosion!/535ab20138acfhttp://images.anaerobic-digestion.com/meme/view/Wikifibs Funny History of Biogas No. 1/52ee606582163 http://images.anaerobic-digestion.com/meme/view/Biogas Engines Run On A Futureproof Fuel: Her Lifetimes Energy Could Be Guaranteed.../52eee957a55c1

Another feature in 2014, has been the number of bodies such as universities and computer data-centre operators that have "gone green", and are generating their own electricity from organic waste. Many have installed their own biogas plants, and a number of those are using fuel cells. These fuel cells convert biogas to electricity through an electrochemical process that also reduces nitrogen oxide, sulfur dioxide and particulate matter emissions, usually by more than 70%.

The California Energy Commission was also in the news and is promoting the production of biomethane through regulatory measures. So, California is also keen to see increased uptake of biogas and is seeking ways to capitalize on the emerging high energy feedstocks available in the state. These include wastewater, municipal solid waste and industrial food waste. 2014 has seen them exploring how to encourage  utility businesses to install biogas plants, and get the potential consumers of this new alternative energy to use it. This has produced much needed publicity on the market prospects for biomethane, not least in the natural gas powered vehicle market.

In the 1985 blockbuster “Back to the Future” there was a scene when a banana peel was needed to fuel a Delorean.

Not much happened to bring such a prediction into reality in the US until around 2012 when several major project developments were successfully brought on-stream, across the United States. The first food waste digesters were also coming online at that time, and since then they have shown their worth.

Move on to 2014, and finally all the "technology talk" of previous years seems to be being brought forward to real action on the ground. Throughout 2014, federal, state, and local market involvements have been propelling developments forward in anaerobic digestion and biogas plant implementation.

We hope you enjoyed this article, and wish all our readers a very HAPPY NEW YEAR! Don't forget that we do have a comments section below this blog! Did we get our opinion of US events in 2014 right? Your feedback is important to us.

Tuesday, December 09, 2014

Why Better Digestate Enhancement and Treatment is What the Biogas Industry Needs

Digestate Enhancement is Important!

The operating capacity of biogas plants in the UK is rising faster all the time. The technology has recently also been extended from the original use on farms with energy crops, into new areas. Two of these rapidly expanding Anaerobic Digestion (AD) Plant sectors, in the UK, are in sewage sludge treatment, and food waste disposal.

Both of these applications for AD makes real sense due to the energy that this releases which can be used in turn to power the wastewater treatment works at which the AD facility is located, and similar uses also exist at facilities accepting food waste

In our opinion this goes further because of the use of biogas digesters for the treatment of sewage sludge with the ability to pay for the AD Plant, at least in part, from the sale of the biogas or electricity generated from it. This is now becoming the accepted practise in the UK, and we are certain that the same applies in a number of other nations.

However, using biogas digesters for organic wastes from sources such as food waste has much less of a proven performance history. In fact, only in 2011, there were concerns that completely food waste fed anaerobic digestion plants might not be feasible in the long term due to process instability problems.

This anticipated obstacle has been eliminated by the results of published studies carried out by the University of Southampton, however, this example just goes to show how very recently the scientific community was still talking about whether this kind of biogas digester would work dependably, or go sour! Fast foward to today, we still are no more than 2 to 3 years after that event, and many large food waste biogas plants have actually now already been commissioned! In addition it is likely that in less than 5 years there will be legislation in the UK which will legally require that food waste be separately collected by all councils, and anaerobically digested.

The end-result of this rapid take-up of a new technological application, has in-truth been that there has actually been hardly any time for much study work to be  done on digestate disposal and/ or sales/ product improvements, when compared to other aspects of biogas manufacturing.

It is an inescapable fact that 90 to 95 % of the original feed product which goes into a biogas digester re-appears as digestate from the digester as digestate, and if the digester is running properly the mass decrease is merely the mass of the biogas created. the techniques by which any AD Plant handles digestate is therefore of big relevance to plant operation and to the financial practicality of each plant.

With the undeniable increased popularity of waste digestion, the need to enhance the available strategies for managing digestate, as a helpful resource, and not just as a waste for disposal, is pressing.

The next breakthrough the Anaerobic Digestion industry badly now needs is certainly in improving the optimization of digestate by inventing better techniques, and treatment, with the aim being to open-up this product to new, much bigger, and more rewarding markets.

Barriers encountered in the UK to finding better ways to enhance and treat digestate were identified in a recent study for WRAP. Read more abut those barriers to digestate enhancement here. 

Saturday, October 11, 2014

5 Most Critical Factors in the Design of Every Biogas Plant - Xergi List

The five design factors which can make or break the success of a Biogas Plant Project, is a list inspired by a pdf available on the Xergi website. Our interpretation of their list follows:

The 5 most essential aspects of the design of any anaerobic digestion plant can be listed as:

1. A High Degree of Flexibility

Biogas plants are complex even without consideration of the fact that the feed materials are waste products. They vary not only seasonally, but according to market forces and what the waste producer is doing in their business at any time. Not only that, as any biogas plant operator will tell you, it is necessary to feed the digester with the right mix of "woody" and "green" at all times.

If you perfer to view this on the YouTube website click here for this Xergi Biogas Top Design Success Factors video.

So, all biogas plant designs need to come with a huge dose of flexibility across just about any parameter that you consider. This is essential, when it comes to providing a plant which will be sufficiently adaptable to the clients needs throughout the lifetime of the biogas plant.

2. Dosing Equipment With The Ability To Handle All Types Of Feed Materials

No biogas plant can work well for long unless the operator is able to set the relative feed materials (substrate) proportions and overall input flows to what is needed for the good of the biomass in the digesters at any time, and for the equipment to reliably deliver that dose.

In most processes the input (raw material) is known (because it is bought-in to a specification). Waste deliveries to an AD Plant are the complete opposite. Nothing is the same for two days running when it is waste that is the raw material and is collected from the public and businesses.

This is a challenge for dosing equipment designers, and not all of them are up to scratch on the ability of their pre-treatment of waste arriving at the biogas plant to sort, mix, and break the material down into a transportable/ pump-able quantity of biogas plant feed accurately, and daily over long periods in-between maintenance dates.

3. Adopting an Ideal Process Temperature

Thermophilic AD Plants provide optimum gas yields within the shortest period of time (average particle residence time in the reactor), so it is important for the economic benefit of the biogas project that the best rates of reaction are achieved, and by experience a company like Xergi is well versed in balancing demanding cost factors for choice the best process operating temperature.

4. High Efficiency Mixing

Mixing demands are hard to meet in the fermentation process, as the mixture has a comparatively high viscosity, and fibrous materials can cause reduced equipment availability.

Within the biogas industry there are many ways to achieve biogas reactor mixing, some solutions are generic and have been around for many years. But, many of the best now, which are now avialable are compartaively cheap to run and provide the closest approximation to perfect mixing, are proprietory.

Xergi for example has its own in-house mixing technology to ensure that the mixing function is reliably available to provide something like the features of a fully-mixed reactor (fermenter).

5. Remote Control of Operating Systems

Biogas plants need to be readily accessible by remote control to operational managers 24/7, including at times while off-duty. Production of power has to continue all the time, so remote control must not only be available, but capable of being used easily on multiple computing device types, including from a small smartphone 

For further information visit the Xergi website here: www.xergi.com

Sunday, October 05, 2014

Many UK Anaerobic Digester Planning Applications Still Public Relations Disaster

Objections are Understandable After UK AD Plant Leaks
New anaerobic digestion plant projects are being put forward for planning permission in increasing numbers in the UK, but many are facing heavy local opposition.

In fact it isn't unreasonable to label many of these planning applications as a public relations disaster. 

In this post we have highlighted just three biogas plant applications to provide a flavour for the public reactions received. In the first example, it is clear that the residents of the quiet market town of Whitchurch in Shropshire are very concerned about the possible negative impacts of this anaerobic digestion project.

1000 sign petition against Whitchurch anaerobic digester - shropshirestar.com

"1000 sign petition against Whitchurch anaerobic digester. Shropshirestar.com - One of the group's campaigners Sue Whitson said:
“We have been collecting signatures against the proposed digester for some weeks now and have had petitions in a number of business premises in the town as well as collecting signatures on-line."
In the article it becomes clear that an incident at an AD Plant not far away, is on the minds of many of the people of Whitchurch. We reported upon that tank collapse and digestate leak here:
"So far, Whitchurch Town and Parish Councils have objected to the plans on the grounds of potential smell and negative environmental impacts. Many have noted the problems caused by another plant at Harper Adams University in Newport. The plant’s process tank collapsed earlier in the year following a small explosion, with slurry spilled onto the site."
That incident resulted in the smell of digestate being present for several days while a mopping-up operation took place, and it hard not to sympathize with the objectors about that, especially when the perpetrator was a university run plant where most would expect the very highest standards of maintenance to be used.
To find out more about "1000 sign petition against Whitchurch anaerobic digester - shropshirestar.com" and anaerobic digestion, click here

Planning experts always say that the secret to avoiding objections to any controversial project is early consultation, and spending time with the locals to make the case for the AD Plant and allay fears, if necessary modifying your proposals before the full application for planning permission is submitted. The next link suggests that this may be the approach being used in this case, but it is unclear whether the plannign application has yet been made:

More than 120 Wimblington people have their say on Fengrain ... - Wisbech Standard
"Wisbech Standard - GALLERY: More than 120 Wimblington people have their say on Fengrain ...Wisbech Standard - Public meeting about the Anaerobic digestion for Fengrain, Held at Wimblington parish hall. Left: Mick Knight resident and organiser of the meeting. Cllr David Connor, Chairman David Green,Speaker Charlie Graham-Cameron.Picture: Steve Williams.and more »" http://news.google.com/news/url?sa=t&fd=R&ct2=uk&usg=AFQjCNFQJEhjv3-8ekI8q9HBa9IuNSMTUQ&clid=c3a7d30bb8a4878e06b80cf16b898331&cid=52778602410076&ei=J6cxVOCnEuG9igaK-4DACg&url=http://www.wisbechstandard.co.uk/news/gallery_more_than_120_wimblington_people_have_their_say_on_fengrain_anaerobic_digester_plans_at_public_meeting_1_3759096
Clearly, the UK anaerobic digestion industry needs to do better with its public relations. That the public are against this AD Plant going ahead is evident from the following quotation from the article:
"Mr Barclay revealed the result of the contrasting petitions he put on his website for and against the digester – 151 voted against it, 11 people were in favour."
Finally, there are yet more biogas plant planning permission problems currently evident in the following example:
Developer appeals over green belt anaerobic digestion plant refusal - PlanningResource (subscription)
"Place North West - Developer appeals over green belt anaerobic digestion plant refusal. The developers behind a planned anaerobic digestion plant on a green belt site in Greater Manchester have appealed against a council's decision to turn down the application. Ramsbottom: developer to appeal energy plant refusal. The application, for the ...Controversial digestion plant developers lodge appeal against refusal. Bury Times: Appeal launched for Ramsbottom energy plant. Place North Westall 2 news articles »" http://news.google.com/news/url?sa=t&fd=R&ct2=uk&usg=AFQjCNHPd0gZeUrS6D4MNMRI33FKvIRH-w&clid=c3a7d30bb8a4878e06b80cf16b898331&cid=52778601344343&ei=J6cxVOCnEuG9igaK-4DACg&url=http://www.planningresource.co.uk/article/1310815/developer-appeals-green-belt-anaerobic-digestion-plant-refusal
However, it is clear that there will be many more AD Plants built in the near future throughout the UK if the following news, of a regulation that has been simplified, is anything to judge by:

Changes to UK's waste regulations favour anaerobic digestion industry - Renewable Energy Focus

"Changes to UK's waste regulations favour anaerobic digestion industry: Renewable Energy Focus - Biogas producers will no longer need to pay for permits or waste handling controls to use fruit and vegetable by-products in the anaerobic digestion (AD) process, the Environment Agency confirmed earlier this week.1 This resolves a long-standing ...and more »" http://news.google.com/news/url?sa=t&fd=R&ct2=uk&usg=AFQjCNGKDNO2Ub_ErMuL2Gv-G_2l-1KKDw&clid=c3a7d30bb8a4878e06b80cf16b898331&cid=52778607361466&ei=J6cxVOCnEuG9igaK-4DACg&url=http://www.renewableenergyfocus.com/view/39984/changes-to-uk-s-waste-regulations-favour-anaerobic-digestion-industry/
Taking the above reports into account does we suggest fully justify our view that many current UK Anaerobic Digester Planning Applications are still a Public Relations disaster. Does anyone have any suggestions as to how this situation can be improved?