2020 has been a lost year for new anaerobic digestion plant capacity in the UK. A few years ago there were UK biogas plants starting construction at the rate of at least two a month, and the industry was even then disappointed and thought the rate ...
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"Anaerobic Digestion News" - 5 new articles

  1. 2020 A Lost Year for New Anaerobic Digestion in the UK
  2. In Sub-Saharan Africa Biogas Can Be A Replacement for Fossil Fuels
  3. Home Cooking with Gobar Gas - Biogas Stoves for Small Scale Digesters
  4. Biogas Potential Ignored in New UK Think Tank Report
  5. Make Biogas from Rice Crop Residues and Stop the Burning of Rice Straw Throughout Asia
  6. More Recent Articles

2020 A Lost Year for New Anaerobic Digestion in the UK

 

UK anaerobic digestion 2020 lost year

2020 has been a lost year for new anaerobic digestion plant capacity in the UK.



A few years ago there were UK biogas plants starting construction at the rate of at least two a month, and the industry was even then disappointed and thought the rate should be higher. It was hoped that at least in 2020 with the UK's Brexit departure set in stone at year's end, the UK industry might return (later in the year) to the rate of progress seen pre-2016.

It was in 2016 that the withdrawal of most UK government support for the technology began to stall new project starts which had been running at double that rate or higher for several years. Many will blame the COVID-19 pandemic for the poor performance this year, but in other industries such as in the UK wind-powered energy sector, turbine construction activity has continued.

In the last 2 to 3 years the UK government has made increasingly encouraging announcements about supporting the production of renewable energy production in areas of high potential such as the AD industry. But action seems to have been almost entirely lacking.

It seems that while Brexit talks continue to occupy the cabinet, much more important UK decisions will continue un-resolved, let alone will any real progress be made:
on climate change pledges, and
the benefits offered by a vibrant biogas industry.
The industry can also, let's not forget, generate many jobs at a time when these are so badly needed. At least 20 UK AD plants must be sitting with planning permission granted, and can surely be “shovel ready” in no time if only decisions are made to return confidence to the UK AD sector.

But, we are not about to let other European governments off the hook here. Their renewable energy performance when judged against the promises made during the Paris Accord 2015, and general statements made subsequently toward Net-Zero 2050 goals is also very disappointing.

To make our point more clearly, we are pleased to be able to republish the following article which explains the above statement and was first featured in the [RE]fuel Report, Issue 156, on 30 November:

[RE]fuel Article Starts:


EU countries remain far behind FQD requirements, EEA data shows


EU countries remain far behind on their requirement to reduce the intensity of greenhouse gases in the fuel they produce by 6% versus the 2010 level by the end of this year, according to figures released by the European Environment Agency in late November.

Although worrying, the figures are lagging and it will be two years from now before it is clear that countries have fallen short of the end-2020 deadline.

Figures published by the European Environment Agency (EEA) for 2018, the year that the most recent data is available, show that nearly all Member States are well behind Fuel Quality Directive (FQD) requirements, with data for the EU as a whole in 2018 showing that the greenhouse gas intensity of fuels across the EU have fallen by 3.7% compared to the 2010 baseline, mostly due to
the use of biofuels.
“Progress varied greatly across Member States, but almost all need to take swift action to meet the 2020 target of 6%,”

the EEA said in a statement to accompany the data.

The EEA said the fall in emission intensity of road transport fuels between 2017 and 2018 can be attributed mainly to a rise (from 4.5% to 5.2%) in the proportion of biofuels used, because biofuels
have a lower emission intensity than fossil fuels.

However, the heavy reliance on crop-based biofuels that year partly offset the benefits that could have been achieved, namely a 4% rather than a 3.7% reduction in emission intensity by 2018, the Commission added.
“This increase in biofuel emission intensity was due to an increase in the use of oil crops, which generally have a higher emission intensity than other feedstocks, in biofuel production.”
Compliance with the 6% FQD does not consider emissions from indirect land-use change (ILUC) but the EEA said that if ILUC is taken into account, the average GHG emission intensity of fuels consumed in 2018 is only 2.1% lower than in 2010.

[RE]fuel Article Ends:

It is clear that most of the reduction has been gained from crop-based biofuels, and this is itself a form of fuel production which although renewable by its general nature has been heavily criticized and is being phased-out globally due to the fact that:

  • while it is undoubtedly a lower carbon-emitting energy source than fossil fuel sources, including natural gas, it isn't particularly low carbon-emitting
  • government subsidies for crop-based biofuels have been heavily criticized for their suspected perverse effect in raising food prices. In principle, how can it make sense for governments which say they intend to keep food prices low, to continue to subsidize farmers to take a food crop (often maize -sweetcorn) off the food market to use it to make fuel?

The UK biogas industry, in particular, which produces a low output of crop-based biofuels which in recent years is considered to amount to no more than a 1% use of the national maize crop is tired of being roundly criticised for the use of food crops in this way.

While some older farms in the UK continue to use some food crop in their feed mix, those are operations set-up many years ago and are grandfathered in upon funding agreements due to end in the next few years. Those AD plants are a small and diminishing part of the UK industry.

For many years the UK AD industry has been an industry based upon the use of AD technology to process all forms of waste biomass, and when maize is used as a feedstock it is used in such a way that the waste (stalks, leaves etc.) form the feed for the biogas process.

Let's be clear, the global biogas industry projections by bodies such as ADBA and the WBA for the contribution of up to 11% contibution (which we have reported previously here) that biogas can make to reducing carbon emissions from transport before 2050, are based upon biodegradable waste biomass feedstocks, and not food crops.

To explain this more fully, the energy industry distinguishes between the many sources of biofuel through the concept of “generations of biofuels”. Read on to find out more:


What are Crop Based Biofuels?

Crop Based Biofuels are first-generation biofuels.
These are fuels made from food crops grown on arable land. The crop's sugar, starch, or oil content is converted into biodiesel or ethanol, using transesterification, or yeast fermentation.

What Generation of Biofuels are Destined for Use in Producing Biogas and by Upgrading to Become Biomethane?

Those fuels will be the second generation biofuels using current and future anaerobic digestion process technologies.

Wikipedia defines second generation biofuels as:

Second-generation biofuels are fuels made from lignocellulosic or woody biomass, or agricultural residues/waste. The feedstock used to make the fuels either grow on arable land but are byproducts of the main crop, or they are grown on marginal land. Second-generation feedstocks include straw, bagasse, perennial grasses, jatropha, waste vegetable oil, municipal solid waste and so forth.

There are also third and fourth generation biofuels the technologies for which are not so far advanced in their development.

Image with text:


Conclusion

We hope that the sections following the [RE]fuel article above explain fully the fact that most of the reduction so far in carbon emissions by European nations has not been from anaerobic digestion and the use of upgraded biogas production (biomethane).

It is hoped that government actions throughout the globe will soon begin to remedy this by encouraging investment in their anaerobic digestion industries.

This post was originally published in the Anaerobic Digestion Blog.

    

In Sub-Saharan Africa Biogas Can Be A Replacement for Fossil Fuels

Biogas can have a central role in the replacement of fossil fuels in Sub-Saharan Africa and in providing affordable and clean energy as identified in the 2030 UN SDG 7.

Uniquely, biogas has a role in:

  • Image shows the key global issues and biogas, to explain How Biogas Can Be A Replacement for Fossil Fuels in Sub-Saharan Africa.
  • Environmental Security: being a cleaner fuel by far than the burning of fossil fuel so air pollution is reduced
  • Economic Security: reducing climate change and global warming due to its much-reduced greenhouse gas emissions and helping prevent the worst ravages upon crop production and human life with the resulting enormous cost to economic security throughout the region
  • Energy Security: by providing reliable and low-cost energy day and night from multiple distributed generation sources, biogas plants contribute to energy security
  • National Security: replacing fossil fuels can assist with providing jobs for and feeding the rising global population forecast to reach 9 Billion by 2050 (UN) which itself is essential for the maintenance of a stable society. National security requires a stable economy to pay for the police and army which can only exist when adequately supported by tax revenues.

The diagram above illustrates the inter-relationship between biogas and the 3 essential components of any civilized nation and the energy security which renewable biogas energy can provide. Biogas energy lies at the very heart of all three through its contribution to energy security and is required before any of the other forms of security can be achieved.

The Urgent Need to Decarbonize Every Economic Sector in Sub-Sharan Africa

Each of the following economic sectors presents a special challenge if society is to succeed in its aim for Net Zero Carbon Dioxide Emission to the Atmosphere by 2050:

  • Power and Electricity
  • Transport Fuel (land, sea and air)
  • Heat transfer (cookers, boilers)
  • Agriculture (compost, manure, crop residuals)
  • Waste management (landfills).

The Anaerobic Digestion and Bioresources Association has been attributed with the quotation which says it all: “There is no net-zero emissions without biogas” (EU).

What Is Biogas And What Are Its Benefits?

A composition table for biogas.

Biogas comprises 50 to 75% methane typically when produced plus Carbon Dioxide and small traces of Nitrogen, Hydrogen, Hydrogen Sulphide, and Oxygen. See image.

The benefits of biogas production are many and varied, as follows:

  1. It is a low carbon emission fuel source which can be used at the point of creation or after transportation, for cooking heating and power creation.
  2. Waste biomass used for its production is used locally to produce biogas. This means that it is inherently a distributed energy source. When each biogas plant is located across the grid area, and power is fed into the grid locally, power line losses are low as the distance to the point of use is short., This contrasts with large output regional power stations where the energy is distributed from a single location. Much of the power must be transported long distances with consequently large power losses (up to approximately 30%). In this way, biogas has an energy efficiency advantage of large fossil fuel power stations.
  3. The process of anaerobic digestion which produces biogas produces an output (known as digestate) which is a natural fertilizer. Therefore, biogas use with the resulting fertilizer production displaces chemical fertilizers, which entail high carbon emissions in order to produce them.
  4. Using the fertilizer provides for the recycling of nutrients essential for the long-term health of soils, and by not adding those nutrients to landfills the damaging emissions of methane escaping from landfills are reduced.
  5. For the nations of sub-Saharan Africa which have little or none of their own fossil fuels to use, creating power at home reduces the need to import energy. This has a beneficial effect on their economies as they no longer forced to spend as much of their hard-won foreign exchange on energy imports.
  6. Decentralized biogas electricity generation means that populations remote from the grid and small communities which cannot afford the costs of grid connection can electrify their homes, farms, and business premises through self-help. This has the benefit of speeding up the connection of rural dwellings to electricity sources.
  7. Rural farming receives a welcome boost when a biogas plant is commissioned because much of the wealth created remains within the community. This cannot fail but boost incomes locally and provide rewarding employment for the skilled labour force needed to run and maintain each biogas plant.

Specific Challenges Experienced in Sub-Saharan Africa

Map of Sub Saharan Africa.

The region is characterized economically by huge unemployment and low GDP. Despite the low rainfall of parts of Sub-Saharan Africa, this represents a huge potential in terms of the available biomass which could be used in the anaerobic digestion process if fully developed.

At the moment too much of the region’s export income is spent on energy import, and most must buy in fuel from abroad. This is a huge burden, for example, over 50% of its transport fuels are imported currently. Increases in home-made energy production through new biogas plant output is desperately needed to reduce reliance on imported fuel. The money released to the exchequer of these nations could then be used to put right a legacy of poor infrastructural development which daily results in the spread of lethal diseases. Such domestic problems in Sub-Saharan Africa tend to result in unrest which all too often spills over into wars.

Biogas supplied straight from landfill or fermentation chambers can be used as fuel for cooking or heating; however, this is mostly seen in developing countries, such as India or Bangladesh. For biogas to be used as fuel in engines, it must be refined, i.e. purified from unwanted components, so that it consists of 96–98% methane.

This is of course achieved through chemical processes, such as absorption and adsorption. Once biogas is refined, i.e. converted to biomethane that has practically the same composition as the gas used in cookers, it can be compressed and used for various purposes, such as fuel for motor vehicles. via euinmyregion.blogactiv.eu

Biogas methane (biomethane) is ideally suited for use as a transport fuel with trucks available on the market which run reliably on purified and compressed biogas.

The range of a biogas bus is up to 250 miles - the same as a diesel bus. Reading Buses and Stagecoach both have their own compressed natural gas (CNG) refuelling stations and Nottingham City Transport will operate one from next year. via www.scania.com

Image text:

With financial support from the Swedish government, between 2006 and 2009 Skånetrafiken introduced 140 buses fuelled by a combination of natural gas and biogas to its network, making it the public transport company with the largest number of gas-fuelled buses in Sweden.

Since then the company has bought a further 300 gas-fuelled buses, which means that more than half of its fleet of 1,000 buses now runs on gas. These new buses already produce far fewer emissions of carbon dioxide than traditional diesel-fuelled buses but Skånetrafiken now wants to go further and has pledged that its entire fleet of buses will operate entirely on biogas by 2020. via www.smartcitiesdive.com

Biogas as a Raw Material Replacement for Oil

Biomethane can be used as the raw material instead of oil for many chemicals and plastic production. Methane is the precursor organic compound from which oil, products are produced in oil refineries. It is produced from fossil fuel oil as producer gas and can be a replacement organic material for most fossil fuel-based oil use.

Once again, biogas production particularly well matches the need of all Sub-Saharan nations to reduce imports. This could mean that a large proportion of foreign exchange currently being spent on oil as the raw material for refineries, could also be moved into each nation’s economy.

Conclusion - How Biogas Can Be A Replacement for Fossil Fuels in Sub-Saharan Africa

The potential for biogas in the Sub-Sharan Region is exceptionally large and the benefits of biogas production also closely match the most pressing needs of the area.

If governments will recognize the true merits of full implementation of biogas production from the anaerobic digestion process and provide initial help to develop the local biogas industry the resulting benefits will be enormous.

Plus, doing so simultaneously moves the biogas adopting nations toward a much-reduced rate of carbon emissions. This can, in turn, allow them to make big strides toward the goals globally set for reducing all carbon emissions (the emissions which raise Greenhouse Gas levels) to “Net -Zero” by 2050.


[soc_panel color="orange"]This article is based upon a presentation given by Dr Vincent Ifeanyi Okudoh, Bioresources Engineering Research Group (BioERG), Department of Biotechnology, Cape Peninsula University of Technology, Cape Town, South Africa at the WBA Biogas Summit 2020.[/soc_panel]

    

Home Cooking with Gobar Gas - Biogas Stoves for Small Scale Digesters

An in-depth article about biogas stoves, covering everything for small scale digesters and home cooking with what in India is known as gobar gas. Read on for the info on biogas stoves:

What is a Biogas Stove?

A biogas stove is a specially adapted, stainless steel, countertop, or built-in, biogas fuelled stove.

Using a stove which is either intended or modified, to run on biogas (gobar gas) is the easiest method for home and small scale, biogas digester beginners. These stoves are small, most have no more than two burner rings, and are often portable. They can usually be positioned as needed in order to accommodate other kitchen appliances on the countertop.

They are most often manufactured from stainless steel or cast-iron. Some can be used as a built-in single burner stove specially adapted to cook with biogas. One brand of biogas stove is designed to slide into a stove range or be built into a countertop and is perfect for those who have limited kitchen space.

Biogas is the gaseous product of breaking down organic matter in the absence of oxygen (see "Anaerobic Digestion"). It can be used to meet the energy need for cooking and baking in individual households as well as in small businesses.

Stoves and ovens for biogas application are similar to conventional appliances that run on commercial fuels such as butane and propane. However, special modifications (particularly in the design of the burners) are required in order to ensure proper combustion and the efficient use of energy.

At this website, we have received so many queries regarding the non-availability of Biogas Stoves, and we are not quite sure why so few are on the market for sale. We assume that the reason is that the demand for biogas stoves is so low compared with other fuels that stores do not consider it worthwhile to stock them. It is difficult to buy biogas stoves both in rural areas and in big cities.

Close up of one of the biogas stoves discussed.
CC BY by Sustainable sanitation

However, not many people are aware that you can use a normal LPG stove to run on biogas with simple modifications. In fact, you will not find much difference if you look at both an LPG Stove and a Biogas Stove normally.

Most of these conventional appliances can be adapted for the use with biogas by the modification of the burners to ensure proper combustion and efficient use of energy.

Several grassroots and nonprofit organizations (such as Heifer International and it's partners) have in recent years started biogas fueled stove manufacturing projects to allow people in impoverished communities to have a sustainable way to cook their food and heat their homes.

Stoves for Small Scale and Home Biogas

By far the biggest demand for biogas stoves comes from the millions of small scale domestic and smallholding type biogas plants ranging in design from digesters based upon oil drum sized vessels all the way up to the community (e.g. village) biodigesters built in-pits with masonry walls and covers.

The gas pressure at which these stoves must operate is low and highly variable, and the same goes for the proportion of methane present.

One thing that doesn't change though, is that biogas burns over a narrow range of mixtures containing 9 to 17 per cent of biogas in the air. If the burning flame has too much gas, the burn will be poor and incomplete, giving off poisonous carbon monoxide and contain a lot of soot particles. via babiogas

A good biogas stove design aims to maximize the conversion of methane and to reduce unburned methane and soot from incomplete combustion. For this reason, a biogas stove design should burn on the lean side with a small amount of air to avoid the flame becoming rich. In a good biogas stove design, the air is mixed with the gas prior to when it is burned to ensure the correct air-gas mix is obtained. There are other problems to solve which are known as:

  • lighting back,
  • flame lift,
  • pressure drop at the burner manifold.

A successful biogas stove design must avoid those problems and deliver the flame where the heat of combustion can efficiently conduct its warmth into the cooking vessel.

Cooking on a biogas stove.
Potential Improvements from Biogas Stoves

Stoves and ovens using biogas have the potential to improve the wellbeing of marginalised people. They offer an excellent opportunity to put an end to the indoor air pollution generated in the kitchens of many poor families around the world, as well as treating organic waste that commonly represents health and environmental threats.

Local manufacturers of biogas stoves are, therefore, emerging in many countries. There appears to be significant potential to improve the combustion efficiency and overall quality of the stoves which are currently being offered on the market. It is hoped that as sales increase competition will become greater and the sellers with then match the quality of today's best gas stove brands.

Domestic Appliances Running on Biogas

As a gaseous fuel, biogas can be used for many domestic tasks. A common practice is the adaptation of commercial appliances that originally ran on fossil fuel gases, such as liquefied petroleum gas (LPG) or natural gas.

Biogas from small digesters may contain carbon dioxide and water vapour and is at low pressure flows out of burner holes. It flows through stoves with less volition and therefore has a lower calorific value than LPG (or natural gas) and therefore cannot be used to run normal LPG gas appliances. Regular appliances can be modified to run on biogas by enlarging apertures (theoretically a simple process, but a lot more tricky in practice).

There are a number of domestic appliances in addition to Stoves and Cookers which can be fuelled biogas. These are:

Cost of Household Biogas Systems

Costs for any plant require initial investment costs and once built, they also incur running costs. Considering the initial capital cost versus the financial and environmental benefits is important. It is estimated that an 8 m3 household biogas tank can treat the manure from 4 to 6 pigs, yielding around 385 m3 biogas annually. That suggests that such a plant can save 847-1,200 kg of coal-based on the calculation of effective heat equivalent. According to the methodology recommended by IPCC in 2006, if a household biogas digester treats the manure of 4 pigs, it can reduce GHG of 1.5~5.0 tonnes CO2e.

The initial equipment purchase and installation costs of each household biogas digester (8-16 m3) range from US$500 to US$1,000 depending on the digester size. Most rural households within developing countries have low disposable income and weak financial capacity for making such a large investment. In addition, the household will continue to pay a biogas digester maintenance cost. By contrast, the current practice of deep-pit treatment method is by far considered the most attractive option for manure treatment given that it requires very limited additional investment and labour input. via www.ctc-n.org

The cost functions for a biogas plant are thought of by one research group as being:

  1. The economies of scale
  2. The ratio of the cost of a given size of the plant to the cost of a reference plant (this remains almost constant over time)
  3. The effect of retention time and other factors on the capital cost
  4. The costs of the material (if it must be brought in from outside the farm or home).

Using a Biogas Stove

Biogas can be used in gas appliances for energy production which is then used for heating, lighting, the supply of steam plants, in water boilers, gas stoves, infrared radiators and internal combustion engines.

The simplest method of biogas utilization is using it in burners, as it can be directly supplied from low-pressure gas holders, but it is more preferable to use biogas for mechanical and electrical energy production. The best biogas stove sellers offer designs that are specifically developed for the low-pressure gas burners needed to burn biogas direct from small digesters or from storage holders containing biogas.

Gas pipes are also needed that can effectively connect the point where you collect the accumulated biogas and the stored gas through gas lines to the home stove.

The stainless steel, built-in single burner stove is specially adapted to cook with biogas. The HomeBiogas stove is designed to slide into a stove range or be built into a counter-top and is perfect for those who have limited kitchen space.

After selecting the type of digester, the retention time, which is a key parameter in determining digester size, is chosen to maximize the percentage of production of biogas with respect to the retention time. 10 to 30 days is often chosen as the minimum amount of time for sufficient bacterial action to take place to produce biogas and to destroy many of the toxic pathogens found in human waste, considering the diameter and height of the mixing pit are equal.

At the household level, biogas systems can also be used to produce fertilizer and for providing energy for cooking and lighting.

Safety pilot and air filter Biogas-fueled radiant heaters should always be equipped with a safety pilot, which turns off the gas supply if the temperatures go low i.e. the biogas does not burn any longer.

Biogas consumption can be calculated from assuming that household burners consume 0.2 to 0.45 m3 of biogas per hour and industrial burners – from 1 to 3 mof biogas per hour. Biogas volume, necessary for food preparation can be determined from the time spent on daily cooking.

Using a Regular LPG Stove

Using 1-2 burners for biogas in addition to your current LPG stove is a good way to set up a kitchen to use biogas whenever possible. If a user chooses to connect a "HomeBiogas"™ digester to a regular stove, the user should be aware of the energy requirement of the stove.

The Biogas stove is different from the LPG regular stove since low compressed bio-methane is a far less compressed gas than LPG, the gas burner flame openings need to be wider for better combustion.

The first time that a new digester set-up is used, the gas in the tank won't burn as it contains Carbon Dioxide gas. If, fortunately, it burns then good, or else wait for the second time after draining the first tank-load of gas. The second use will be likely to be much better quality biogas, and thereafter will usually be good methane. You can detect how much gas there is in the system when the gas holder tank rises up as the gas is produced.

How to Modify a Normal LPG Stove to Run on Biogas

So it is very difficult biogas stoves in big cities. However, you can use a normal LPG stove to run on biogas with simple modifications. You will not find much difference if you look at both LPG Stove and Biogas Stove normally.

The Biogas Burner I am showing has 3 mm holes in it. Take an LPG stove, unscrew and remove the nozzle, and this may be enough, also close any air-entraining/ mixing gap provided for LPG use. You can control the pressure and required amount of biogas with the gas control knob provided.

Check by comparison with existing burner the operation of it with biogas after removing the nozzle. If it is burning properly, then leave it as it is otherwise necessary to search for a burner of the same diameter. Burners are of different sizes. So take your LPG burner when searching. In our locality, there are hardware stores fabricating and selling local-made stoves for biogas use.

[caption id="attachment_4664" align="alignleft" width="500"]Featured image text biogas stoves CC BY by DFID - UK Department for International Development[/caption]

Once you did the modifications, Connect Biogas pipeline to your stove and check your stove and it should run on biogas properly. via ww.instructables.com

Do not add anything other than cow dung slurry and organic waste. Once gas formation starts, you can feed organic waste in small quantities. Make sure there is no leakage. Also, be aware that the initial gas produced will not burn as it will be mostly carbon dioxide.

Release the gas 2 to 3 times before testing. Use a Bunsen burner to test and DO NOT use a lighted match stick for testing. If the gas pressure is too low to fuel the bunsen burner, add some weight on top of the gas holder to get a better pressure.

LPG Stoves Versus Biogas Stoves

Almost any gas stove can be converted to support biogas by removing the pressure nozzle. However, one stove cannot supply both LPG and biogas.

For an LPG stove versus Biogas stove, the LPG stove wins for its low cost for a high-quality product. Lightweight and portable. Check that the one you buy has easy to use heat adjustment dials.

Against this background, for the biogas stove, you will most likely need a match to light the stove. In addition, heat adjustment is not precise.

If you're looking for something simple on holiday, a butane stove can be perfect for you. It's our favourite, for a solo camper looking to make a simple but delicious meal is a cheap LPG stove.

However, for the poor and any environmentally aware person, the biogas stove is considered far better with its wonderfully "green" environmental benefits and its value in reducing the unhealthy smoke found in so many developing nations in houses where wood would be the only economically alternative cooking fuel.

Methane Used in Puxin Biogas Stove

From its first decade, the Puxin methane program was a success. It installed more than 20,000 biogas stoves (or biodigesters) in that period. Digesters that enable rural households to turn the waste of their cows and pigs into a methane-rich gas suitable for both cooking and lighting, as well as bio-slurry (predominantly used as a substitute for fertilizer).

To begin explaining biogas stoves, it is probably useful to first think about what "biogas" is? biogas is essentially another word for

For instance, the 5,000l package comes with the digester, one purifying biogas (methane purifier) MP 12 135 (PVC), a gas holder with a capacity of 5 m3, one generator bg 2500 w (biogas power generator 2500 watts), bacterial methane activators gp-7 for 1 month, installation of equipment, and stoves. a gas mixture that is predominantly made up of methane (CH4) and carbon dioxide (CO2).

Puxin Biogas Oven

Cookstoves and ovens for biogas application are similar to those of conventional appliances running on commercial gas-fuels. A biogas stove usually has a single or double burner with varying gas consumption rates, which is influenced by the pressure provided by the biogas plant and the diameter of the inlet pipe.

Stoves and ovens for biogas application are similar to conventional appliances that run on commercial fuels such as butane and propane.

Biogas Fuel Stove with Single Burner

Biogas combustion is so much cleaner than other fuels, such as solid biomass and kerosene, that it must be considered. However, for these advantages to make it worth buying a biogas stove it depends on the quality of the biogas stove (particularly the burner).

The HomeBiogas™ stainless steel, built-in single burner stove is specially adapted to cook with biogas. This stove is designed to slide into a stove range or be built into a countertop and is perfect for those who have limited kitchen space.

    

Biogas Potential Ignored in New UK Think Tank Report

An influential Think-Tank report has now been published by experts who should know better, and which completely misunderstands and ignores the full scope and potential of the anaerobic digestion and biogas industry “on the road to recovery”.
Road to recovery graphic from
Only 1 mention of AD in the whole report: Click on the image above to enlarge it to read small text.


Referring to AD solely as a technology for the treatment of food waste and only once in the entire report, shows such a lack of knowledge that it simply has to be called out for the nonsense it is.

But, it doesn't stop there as unfortunately the omission of any proper recognition of the potential of biogas, results in a conclusion which lacks any reference to action on energy from waste by anaerobic digestion.

ADBA (The Anaerobic Digestion and Bioresources Association) has published their own reaction to this report, which is reproduced below:

It is time to understand AD: ADBA responds to Policy Connect report


ADBA Press Relase Posted on 06 Aug, 2020 by Giulia Ceccarelli:

Out of the 674 anaerobic digestion (AD) plants in the UK, just over 100 treat solely food waste, over three times as many treat agricultural wastes and 164 wastewater, while the rest treat a combination of different organic wastes. All are turning what we perceive as ‘waste’ organic material that would otherwise be causing a health hazard and emitting harmful methane emissions, into green energy and natural bio fertilisers, demonstrating AD’S role at the heart of the circular economy of organic wastes. AD, therefore, has a central role to play in waste policy in the UK. The first step is to understand this ready-to-use technology.

In mentioning AD, the latest Policy Connect report, which calls for a Scandinavian approach to waste policy in the UK and argues in favour of Energy from Waste (EfW) versus landfilling, commits the mistake of referring to AD solely as a technology for the treatment of food waste.

AD is a widely available circular economy technology (indeed it has been treating our sewage here in the UK for decades), which has been recognised as the preferred technology for managing residual food waste, as acknowledged in the Policy Connect report. However, its role in recycling wastes to generate energy goes far beyond that. AD treats, and most importantly, recycles, a much greater range of organic wastes into green renewable energy and a low carbon biofertilizer, digestate, that recovers nutrients and organic matter to help restore our depleted soils.

When pledging to achieve Net Zero by 2040, the National Farmers Union identified AD as a key technology to meet its ambitious target.


“AD has a role in agriculture across all scales”, said NFU Chief Renewable Energy Adviser Jonathan Scurlock, “using animal manures, crops and crop by-products to create low-carbon gas to replace fossil fuels and petrochemicals, while returning nutrients and organic matter to land – and perhaps in the future to actively remove CO2 from the atmosphere.”

AD is also a vital technology for the treatment of wastewater.

“EFW plants certainly have a role to play in recycling some wastes”, said Howard Burton from leading pump and mixer manufacturer, Landia, – “But with the increasing amount of digester mixing equipment that we are supplying to UK water companies, we can see first-hand just how valuable a feedstock wastewater sludge is for Anaerobic Digestion plants. AD/Biogas provides a tremendous opportunity to bolster both electricity and gas supplies, whilst also recycling a wide range of organic wastes (not just food waste), and producing a valuable fertilizer.” 
ADBA Chief Executive Charlotte Morton said:
“AD and the specificity of our sector remain widely misunderstood. Since this technology by definition has application in many different sectors, AD is often grouped with other technologies under various labels – EfW, Renewables, Bioenergy, Biofuels – without a clear understanding of AD’s role at the heart of the circular economy and its enormous potential. Lack of awareness is often the underlying cause, therefore we at ADBA call on the Government, civil servants and local authorities to attend ADBA’s L&D event “Introduction to AD” on 25th August to educate themselves on this incredible technology which can deliver a 6% reduction of total UK carbon emissions today, and with it 30,000 new green jobs.”
– ADBA Press Release ENDS –

Why The Policy Connect report “No Time to Waste” Needs Re-thinking to Add the Role of Anaerobic Digestion and Biogas Where It Should Be

    

Make Biogas from Rice Crop Residues and Stop the Burning of Rice Straw Throughout Asia

Rice straw biogas production from rice crop residues is a proven technology that is still completely untapped and at the same time stop the smoke from burning rice fields after each crop.

Around 300 million tonnes of waste rice straw is burnt in fields across Asia every year. Rice accounts for 48% of all greenhouse gas emissions from crops globally, or 1,000 MT of CO2e/yr. Straw burning is producing smoke so thick it can block out the sun for days on end in the main rice-producing regions. This comes at great cost in respiratory ailments and early deaths.

As the global population grows, more rice is produced, leading to yet more straw burning every year. And the sooty “black carbon” particles in the smoke are far more potent global warmers than the gases most people worry about, such as carbon dioxide.

Rice straw biogas diagram showing the CO2 reduction possible.

Straw Innovations

One company which believes it has the answer to this problem is Straw Innovations Limited, with biogas operations in Laguna in the Philippines.

What Straw Innovations are saying is revolutionary, because if implemented globally their plans for the anaerobic digestion of rice straw would transform this major waste into:
A major asset as a renewable fuel source: locally produced 24/7
Valuable compost or fertiliser that can build soil fertility
Increased rice productivity, enabling three crops per year instead of just two
A means of rural development and job creation, right where they are so much needed in the midst of the developing nations.

A Global Vision for Rice Straw Biogas from Anaerobic Digestion


It is hard not to be impressed by the vision of their Director, Craig Jamieson, who recently presented to the World Biogas Association's eFestival attendees stating that:

“If all available rice straw were to be digested, it would reduce global CO2 emissions enough to offset all of the CO2 currently emitted by the entire global aviation industry (918 MT of CO2e/yr), leaving the resulting biogas from the anaerobic digestion process to power their farms and localities.”

“It would also save a huge problem with rice straw stubble burning where 300 million tons are now being burnt every year, just in Asia. If you have ever visited cities such as Delhi in India during the rice straw burning season you will know just how appalling it is to have to live with the smoke that creates.”

“Governments are progressively banning the burning, but farmers frequently don't see any alternative, and therefore aren't complying. The race is on to find ways of using all global rice-waste in a way that doesn't simply end-up causing another problem to further impoverish the world's poor”.
Many local jobs would also be created to serve the biogas industry locally, and the need for importing energy from abroad in these nations would be greatly reduced.

Diagram of rice straw removal and use.

Rice Agronomics and “To Burn or Not to Burn”

The most obvious solution would seem to be simply returning the rice straw back into the soil. The problem is that it then rots in waterlogged ground, producing methane emissions. Methane is a greenhouse gas, approximately 25 times more potent than CO2.

Another disadvantage of returning it to the land is that waiting while the previous crop decomposes delays the establishment of the next rice crop.

Burning the rice crop-waste in the fields reduces methane emissions by 50%, but results in local air pollution, including black carbon which also traps heat in the atmosphere.

“Upland rice” or “aerobic rice” can be grown instead, where the fields are not flooded. Then the straw can be returned to the soil without the high methane emissions. However, upland rice suffers from lower yields and much greater weed problems, which require hand-weeding or the use of herbicide chemicals.
Other Solutions – Alternate Wetting and Drying (AWD)

A compromise is to alternate between flooding and draining rice fields. This can enable higher yields and reduced weed growth (as with flooded fields), but with reduced water use and lower methane emissions (because it’s not continuously flooded).

However, AWD can increase emissions of N2O – one of the most potent greenhouse gases – especially if not well managed, and the drying phase is not always possible in countries with heavy rain seasons.


Sheeting over the dry straw for digestion.
Covering a new batch of rice straw to exclude air and produce biogas.

The “Straw Innovations Limited” Biogas Plant Solution

Straw Innovations Limited has been researching and developing rice straw biogas technology since 2017, partnering with Universities and other biogas companies keen to innovate in what, if their voice is heard, will become a $multi-billion industry.

Financial assistance has been provided by the UK Government, which has enabled them to trial an innovatively simple and low-cost dry anaerobic digestion process, with support from British universities and QUBE Renewables.

Their solution is to remove the rice straw from the fields and co-digest it with manure. With most crops, removing all the crop residues would lead to loss of organic matter in the soil, but with flooded rice-rice systems, this is not a problem. The lack of oxygen reaching the soil means that any organic matter breaks down more slowly.

Just leaving the crop roots in the soil after harvest provides enough organic matter to retain soil fertility; hence all the straw can be safely removed and used for other things. That being the case the collection and use of rice straw in the anaerobic digestion (AD) process can truly be a sustainable process.


straw-burning-in-vietnam
At the end of every growing season, rice farmers burn off all the leftover rice straw on Vietnam's fields. This process produces huge amounts of carbon emissions. – CC BY-NC-ND by Ratclimaa

Anaerobic Digestion of Rice Straw: a Big Opportunity

Anaerobic digestion has so far been adopted mostly in three areas of activity, using “wet AD technology” these being:

– Domestic and small community waste: in developing nations – especially China where several million low-tech biogas plants have been built and operated. They continue to provide much needed clean fuel and fertiliser to rural communities.

– Municipal Wastewater Sludge Treatment from the Activated Sludge Process: in industrialised nations, these have been in use for more than 50 years but are being installed now at an ever-increasing rate to enable water companies to decarbonise their operations. The best of them are using their AD plant biogas to help power operations and move rapidly toward corporate goals for compliance with global decarbonisation targets arising from the 2015 Global Accord signed in Paris.

– Commercial: Large CSTR type “Wet AD” Reactors for agricultural and food waste applications originally developed to be fed by specially grown food crops, but this has now become rare due to the removal of government subsidies and tax-breaks from food crop use. Nowadays such plants are fed with crop wastes instead, digesting what remains after the food has been harvested.

The numbers of these plants globally are rising each year and the pace of development is accelerating. The decomposed contents of the digester are returned to the land as fertiliser, creating a sustainable, ‘closed-loop’ cycle.

All 3 “wet AD” applications above are now well-proven and attracting mainstream investment. However, Straw Innovations are using a novel, “Dry AD” batch process.
Dry Anaerobic Digestion

“Dry AD” refers to biogas production using less water (20% dry matter or above) and is also now a mature technology, used until now mostly for local government-funded MSW pre-treatment. “MSW pre-treatment” is essentially anaerobic digestion/ biogas extraction which governments require to reduce the biological activity of the waste before the organic content of mixed MSW is allowed to be disposed to landfill.

Straw Innovations has adapted the dry AD process for rice straw biogas and if they have their way dry digesters will become far more popular.

Rice straw and biogas article featured image.

Rice Straw Biogas – The Next Big Opportunity for Anaerobic Digestion

The view of everyone at Straw Innovations Limited, is that now is the time for the AD industry to move into the Anaerobic Digestion of rice straw, and by so doing the rice-producing nations can also join with the rest of the world in using AD technology to decarbonise their economies at little or no net cost.

Dry AD technology is well-proven and should attract investment from banking institutions, as Straw Innovations prove its application for rice straw.

While implementing this technology for rice straw biogas they will also benefit from the many spin-off advantages of anaerobic digestion processes.

Not least will be the benefit in removing the deathly annual palls-of-smoke from straw burning, now blighting the rice-growing nations of the world.

The anaerobic digestion of rice straw must surely be a massive opportunity right in front of our eyes!
For more information, see Straw Innovations' at www.strawinnovations.com or on Facebook https://www.facebook.com/StrawInnovations/
    

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