Biogas Magazine Edition 11

Page 1

Edition 11 | 2020

BI GAS Magazine

IBA’s commitment towards capacity building & awareness dissemination...Pg 08

Feed preparation for biogas plant............Pg 16

Waste management for better revenue generation...Pg 22

Innovative semi-aerobic hydrolysis pretreatment technology for fibrous substrate...Pg 25

Title Sponsor

Biogas Magazine | Edition 11 | 3

Biogas Magazine | Edition 11 | 4


IBA News IBA’s commitment towards capacity building and awareness dissemination


National Corner India’s nascent biomass supply industry turning reliable and


organised Feed preparation for biogas


plant Waste management


for better revenue generation Innovative semi-aerobic hydrolysis pretreatment technology for fibrous



International Corner Digestate – a valuable rest product from biogas production


Operation and Maintenance Essence of Operation and Maintenance in Biogas industry


in India

Printed by: The Color Impressions

Published by

Financed by

Coordinated by

In-Cooperation with

Foreword We welcome our readers to the 11th edition of Bio-

cessity of operation and maintenance in smooth

gas magazine!

running of a biogas plant with improved performance, and essence of pre-treatment technolo-

As the world is going through a critical-time,

gies for efficiently digesting fibrous substrates.

we should follow the guidelines of government to stop the spread of the pandemic caused by

This edition discusses possibilities of revenue gen-

“Covid19-Corona virus�. As a responsible citizen,

eration from managing organic-waste through

we need stay in our homes and protect ourselves,

anaerobic digestion along with effective utiliza-

family, community, and our nation.

tion of digestate, which in turn ensures financial viability of biogas plants thus making the industry

We have brought this informative magazine to

increasingly self-sustainable.

enrich your Biogas experience and look forward to continue doing the same.

The objective of the magazine is to cover every aspect of biogas value chain. We persevere to put

IBA is coming up with the Bio-Energy Pavilion

forth authentic and informative experiences from

from 23 -25 September, 2020, at REI Expo, India

the industry, and keep our readers apprised of the

Expo Mart, Greater Noida with the support of IC-

latest happenings world-wide.



ESN, Singapore and German Biogas Association. Your suggestions are always welcome. Stay Safe! The objective of the pavilion is to increase the visibility of Indian Bio-energy sector on international platforms leading to assured growth of the industry. More information can be seen on page no. 08 of this magazine. We keep emphasizing on wide spectrum of benefits that Biogas has on offer through our various channels including the Biogas App and the recently updated website. The present issue covers

Dr. Atma Ram Shukla

need for a reliable supply chain in the Biogas in-


dustry, importance of feedstock preparation, ne-

Indian Biogas Association



Learn from anywhere

Easy on pocket

Instructor-led Interac-

Online support

-tive training

Easy accessibility

Self-based learning

MODULES TO BE COVERED 01 Basic concepts of Biogas

02 Biogas Technologies

03 Biogas in India

04 Digestate as Fertilizer

05 Design and Control

06 Planning, O&M and safety

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Biogas Magazine | Edition 11 | 8

IBA’s commitment towards capacity building and awareness dissemination


BA is quite actively participating in various national and international conferences. In the recently concluded several conferences - be it 2nd Global Summit on Waste Management on 31st January 2020, MSMECCII Greentech Asia Exhibition on 3rd February 2020 or World Future Fuel Summit 2020 on 16 February 2020, we specifially debated and put forward Biogas case in a positive manner and emphasizing on the fact that the circular economy is incomplete without Biogas incorpration. Dr. A.R. Shukla is always in the opinion that if we play our card properly then in principle it is possible to even replace the whole imported crude with Biogas. Capacity Expansion of the Biogas Laboratory in IIT-BHU, Varanasi- Beginning 2020, the capacity of the commissioned biogas laboratory at IIT-BHU, Varanasi has been further augmented, and presently its scaled to carry out larger volume of tests simultaneously. The Biogas Lab at the premier institute was

set up by the institute in collaboration with the Indian Biogas Association and the German Biogas Association. The lab, which was set up in 2018, is equipped comprehensively with contemporary testing facilities, like determining composition and yield from various substrates, laboratory fermentation tests of co-substrates, determining environmental and nutrient requirements for substrate degradation, identifying potential inhibitors in biogas processes, evaluation and interpretation of the analysis results, and so on. Third edition of Biogas Training Tour to be organised in Eastern parts of India- The Indian Biogas Association (IBA) with its interest in promoting biogas in a sustainable manner has taken up the pursuit to provide the needful thrust towards capacity building in the field of biogas/CBG. IBA in collaboration with GBA plans to organize a training tour on “Basics of Biogas” in Kolkata, and Bhubaneshwar from 18th -20th May 2020. The exact venue

and dates will be announced soon and information on same shall be updated on our website. Continuing its trend of organising the event, previously in the Western and Southern parts of India, the idea this time around is reaching out to the eastern parts of India and disseminate awareness about biogas/ CBG in the region. Corporate Professionals, aspiring Entrepreneurs, Policy Makers, Financial Institutions, Environmental enthusiasts, research scholars, academicians and NGOs, can enhance their elementary information on the biogas. Bioenergy Pavilion, 2020 - IBA is coming up with the Bio-Energy Conference and Bio-Energy Pavilion in from 23rd to 25th Sept 2020 at REI Expo, Greater Noida. IBA have been organizing the bio-pavilion since last two years, with each successive event at larger scale than the former. Further, it has gathered wide acceptance from participants in the event. The pavilion and conference is expected to

Biogas Magazine | Edition 11 | 9

spread the awareness about the Bio-Energy sector along with increased visibility of the sector upon convergence of corporates, entrepreneurs, academicians, Social organizations, lending institutions, and investors. This initiative is aimed at streamline scientific waste management practices, which is presently supported by various government schemes like Swachh Bharat, Sustainable Alternative Technology for Affordable Transportation (SATAT), New National Biogas and Organic Manure Program (NNBOMP), Waste-to-energy scheme, Ethanol Blending program, Compost promotional scheme, and other relevant schemes.

Last Year Photos of Biogas Training Tour

BIO-ENERGY PAVILION 2020 Biogas Magazine | Edition 11 | 10

Glimpse of Biogas Kumbh 2019


Business Meeting


23, 24, 25


Are you ignoring biggest market of Bio-Energy?

Part of Renewable Energy India 2020 Location : Greater Noida, India

“Three new Bio-CNG plants per day are planned”



-Goverment of India


Business Meeting



10,000+ Visitors



BOOK YOUR SPACE NOW! Contact us at M. +91 78384 47489, +91 70143 59823

Disclaimer : The figures mentioned in Bio Enegy Pavillion 2020 are expected figures. it should not be tajen as guaranted figures.

Biogas Magazine | Edition 11 | 12

India’s nascent biomass supply industry turning reliable and organised


he utilisation of cereal straws, like that of paddy, has always grabbed the headlines and attention of Biogas/ BioCNG sector owing to its vast potential to reshape the whole sector. Now, attempts to use crop residues, like Paddy Straw, for the purpose of BioCNG production have started gaining commercial traction, and the industry’s attempt to make it a major raw material, complemented with other biomass; like presmud, steadily looks achievable. Given the fact that Punjab and Haryana, the two major agrarian states adjacent to the capital city of India, together generates around 30 Million Tonnes of crop residue each year, thus making its availability in abundance w.r.t its demand by industries. Furthermore, this makes it a very low-cost fuel with moderate-to-high calorific value and a relatively stable price, in comparison with other CBG raw materials. The irony is that such a resourceful fuel is be-

ing openly burnt, and causing lethal air pollution in its catchment areas, due to lack of economic alternatives with farmers to manage it. These economical & ecological dynamics have led to the encouragement by industry and government for setting-up a large number of BioCNG, Biofuel plants and other industries to channelise the vast amount of crop residue into productive use and prevent its open burning. The push from Public Oil Marketing Companies, like HPCL and IOCL, to utilise crop residues in Bioethanol and BioCNG sectors is also fuelled by the concerns arising from high oil and gas import dependency of India. But, here in India, these crop residue-based industries have not been able to achieve the economic potential they possess, primarily owing to the lack of a reliable and integrated supply chain mechanism, which is quintessential for any bio-based industry to suc-

Biogas Magazine | Edition 11 | 13

they are dependent on expensive alternate fuels, due to huge commodity price risk associated with biomass fuels.

ceed. As reported by ‘Task Force on Biomass Management’, set-up by the Government of India’s think tank - NITI Ayog, power plants and industries are unable to utilise this residue due to fragmented and mismanaged biomass supply chain. The biomass supply sector in India has largely remained dependent on unorganised and unprofessional local players, who operate with a very low degree of reliability and supply inexpertly processed biomass thus negatively impacting its quality and thus energy output from the plants. This has caused viability issues for several major plants and subsequent shutdowns. While the currently operating plants are forced to operate at a very low capacity utilisation, at times,

But, now all these upcoming emboldened plants and industries have a solution in sight, as the biomass supply chain industry has started becoming professional and organised with the entry of innovative players like, RY Energies and others, providing reliable and integrated supply chain services. These companies undertake the responsibility of establishing the supply chain infrastructure in the vicinity of the plants and enable them to conveniently procure biomass at sustainable prices, with zero capital investment and zero downtime with assured biomass availability. This leads to an increase in profits of AD plants and enables them to fulfil their Renewable Purchase Obligations (RPOs). The supply chain companies work in close collaboration with farmers and regional agricultural departments to procure the biomass in a timely manner and prevent open burning of the crop residue, thus contributing to a greener and cleaner environment

Indeed, owing to agroresidues low cost, good properties and significant positive environmental impact, the crop residue biomass is the fuel of today and future for India and other developing agrarian economies.

Biogas Magazine | Edition 11 | 14

Aru Mangla Director Reneyou Greentech Pvt Ltd

(Empowering RURAL COMMUNITIES to be Self-sufficient & Self-sustainable for their Electricity Needs)

     

Plot No.7,8 & 9, Sector-30B, IMT Rothak, Rohtak (Haryana), India Contact: Rejeesh, Mob: +91-7082828250 // E-Mail: // Demo Site, Bangalore :

Biogas Magazine | Edition 11 | 16

BHS Biogrinder near Ambala, India

Feed preparation for biogas plant


overnment of India is pushing vision of establishing 5000 Compressed Biogas plants in a phased manner by 2025. Such large capacity Biogas plants will require huge quantity of raw material as feedstock, so the plant operators have to get acquainted with various feedstock having potential for biogas generation. It will be imperative for the plant operators to set-up pre-treatment/ feed preparation system which can process the feed to the digestor on required large scale basis. Such systems should be capable of handling various raw materials so as the plant operator do not have to depend heavily on seasonal availability of particular raw material or shortage of raw material. Biogas has distinct advantage of being much greener bio-fuel compared to Ethanol and Biodiesel. Ethanol production requires specific feedstock with high fermentable carbohydrate level e.g. corn, sugarcane, sugar beet, cassava. Biodiesel production requires feedstock with high oil content (e.g. jatropha or any oil seed crop). Both technologies require complex feed preparation and extract yield only from portion of the feedstock. Biogas production uses wide range of agriculture waste as well as municipal sewage waste,

with relatively simple feed preparation. Proper design and planning should be done for the feed preparation to run the Biogas production efficiently on continuous basis with better yields. Biogas production traditionally started from dairy manure and sewage sludge. Though being easy digestible, the energy potential of manure/sewage/poultry litter is limited as animals have already consumed much of energy. This is the reason, various other feedstocks having high energy potential like grass, silage, food waste are used as co-digestion materials in modern Biogas plants. More than 2 or 3 substrates could be used at a time for co-fermentation. Table 1 shows energy potential for various raw materials. Any agricultural substrate or organic waste is fit for use in Biogas plant. Woody materials are not preferred due to high lignin content, which is resistant to decay in anaerobic digestion. Most Biogas plants use CSTR type anaerobic digestor with dry material content of 6% to 15%. It is preferred practice to mix manure/ poultry litter having better digestibility with

Biogas Magazine | Edition 11 | 17

high energy potential material from agriculture origins (grass, silage etc..). As generation of Biogas depends on anaerobic digestion of raw material, it is essential to pre-treat the feed to increase digestibility and in turn increase in yield of Biogas. BHS-Sonthofen GmbH have been working closely with European Biogas industry since last 10 years for the feed pre-treatment solutions. German Biogas plant owners were first to use Rotary Mill

Figure 1 BHS Biogrinder on platform structure

from BHS crushing equipment range for selective size reduction of the feed material. Aim of the selective size reduction of the raw material is to achieve defibering as well as comminute the material, which facilitates fast uptake of nutrients by the micro-organisms and achieve flocculent mass for better handling of the slurry. Based on continuous feedback from the Biogas industry, BHS developed Bio-Grinder which meets demands of Biogas industry for pretreatment for wide range of feed materials. BHS Biogrinder is based on rotary hammer mill principle, but with special design features to process substrates. Features like large opening allows feeding of substrates of various sizes. Crushing chamber is designed such as to facilitate maximum defibering and size reduction and

Neelesh Desai Managing Director BHS Sonthofen

Biogas yield in m3 per ton of fresh mass

Methane content

Corn silage



Grass silage






Sugar beet pressed pulp (dry chips)






Biowaste (food, kitchen, garden waste)



Chicken manure



Pig manure (bonded)



Cattle manure (bonded)



Brewery residues



Pig manure (slurry)



Cattle manure (liquid slurry)




Table 1

Biogas Magazine | Edition 11 | 18

Figure 3 Graph 1 Yield Comparison

run continuously choke free operation, even with moist substrates. There is possibility to use two different kind of hammers as well as change number of hammers to influence crushing result with variety of substrates. Motor KW power can be selected depending on the capacity required, customers have option to use VFD to change rotor speed to influence the output. Advantages of using Biogrinder for substrate pretreatment 1) Substantial increase in gas yield vis-Ă -vis normal cut feed materials. Refer Graph 1. 2) Stable fermentation process due to homogeneous mix, layer formation is avoided in the digester. 3) Less stirring power required due to easy and homogeneous mix of feed. 4) Short crushing time means all energy used for selective crushing. 5) Impurities like soil clods or stones also gets

crushed without any harm to the Biogrinder. 6) Biogrinder works on continuous process, thus meeting important aspect of integrating feed preparation with Continuous Digestors as well as providing large capacity handling of substrates. 7) Future proof investment as Biogrinder can be used for pre-treatment of varieties of substrate treatment, plant owners do not have to be dependent on just one feedstock material. Biogrinder in India:- BHS have supplied first Biogrinder in India in 2019 near Ambala for plant operated by Source Facility. This plant uses dairy manure for Biogas production. The plant operator have started processing vegetable waste from Agriculture market as additional feed material through the Biogrinder. This installation has successfully increased yield of Biogas from the plant with low operational cost. Increase in solid content also improved yield for digestate which can be used as a fertilizer.

Biogas Magazine | Edition 11 | 19

Various Substrates Input vs Output from Biogrinder

Figure 4: Banana Plant Input - Output

Figure 5: Vegetable waste Input - Output

Figure 6: Rice Grass Input - Output

Figure 7: Corn Cobs input - Output

Biogas Magazine | Edition 11 | 20

Figure 8: Coconut Shells Input - Output

Figure 9: Corn Silage Input - Output

Figure 10: Sugar Beet Input - Output


Articles published in the newsletter are indivdual views of respective authors. IBA has only provided to share their views. IBA is not responsible for the content/images of the articles.

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Biogas Magazine | Edition 11 | 22

Waste management for better revenue generation


he increasing industrialization, urbanization and changes in the pattern of life, which accompany the process of economic growth, give rise to generation of increasing quantities of wastes leading to increased threats to the environment. In recent years, technologies have been developed that not only help in generating substantial quantity of decentralized energy but also in reducing the quantity of waste for its safe disposal or rather use it for better revenue generation. The definition of waste,� which is useful resource laying at wrong place “itself suggests that it must be utilized properly. In current scenario, environmental concerns rather than energy recovery is the prime motivator for waste-to-energy facilities, which help in treating and disposing / reusing of wastes. Energy in the form of biogas, heat or power is seen as a bonus, which improves the viability of such projects. A common feature in most developed countries is that the entire waste management system is being handled as a profitable venture by private industry or non-government organizations with tipping fee for treatment of waste being one of the major revenue streams. The major advantag-

es for adopting technologies for recovery of energy from urban wastes is to reduce the quantity of waste and net reduction in environmental pollution, besides generation of substantial quantity of energy. Poultry industry is major food supplement provider in India and across the world, it’s a major boost to farmers also for side business and earn good money out of it. As per recent census The total poultry livestock in the country is 851.81 million in 2019, and registered an increase of 16.8% in the total poultry. The total birds in the backyard poultry in the country is 317.07 million. The backyard poultry has increased by around 46% as compared to previous Census. The total Commercial Poultry in the country is 534.74 million in 2019, increased by 4.5% over previous Census. But in recent period this industry is facing serious challenges due to increase in feed rate , power rate , very less production of feed due to draught , heavy rain , steep drop in selling prices of eggs , meat etc. The social nuisance of near by villagers ( to the poultry set up ) is also reached to alarming level.

Biogas Magazine | Edition 11 | 23

M/s. AVEE Broilers, Nashik also face those serious issues and find it difficult to focus on daily activities and rather scratch head from those non value added activities. AVEE Broilers came in contact M/s. Urja Bio System Pvt Ltd, Pune with one of major player in waste management system provider. After a fruitful discussion, it was agreed to set up Biomethanation plant at Broilers premises. Based on the available 2,00,000 birds, he proposed for 22 TPD litter based biogas plant. The plant is set up for 22 TPD litter which is able to generate @ 2000 m3/day raw biogas. This litter initially undergoes suitable primary treatment, basically the challenge in litter is its heavier silica (grit) and lighter feather content, Urja has made in built design to handle such problems and sorted out this issue and also facts for needful provisions for their anticipated challenges. Thus, a proper well functional plant is set up at the site. The farm is being provided with 2500 kWH/day electricity (200 kw x 14-16 hrs per day), thus reducing major dependency on MSEB (State Electricity Board Power), which provided interrupt, power supply leading to usage of diesel gensets. The digested slurry also bringing very good revenue, as the Broiler is generating @ 7 TPD dry manure, which is very good soil conditioner and useful for bat crop. The heavy monetary loss due to usage of diesel genset is completely stopped, which was draining @ 25,000 Rs per day.

Following is highlighted some of the major achievements through this project: 1. Completely stopped the social nuisance of nearby people who were always complaining about the obnoxious litter smell. 2. Zero requirement of diesel in genset. 3. Usage of green power, which brings good subsidy from state as well as central govt. 4. Better revenue generation through sale of digested slurry as organic manure. Seeing the better revenue generation model through manure sale, Avee Broilers is further planning to go for value added organic fertilizer plant.

Gajanan Patil Managing Director Urja Bio System Pvt. Ltd.

Biogas Magazine | Edition 11 | 24

Biogas Magazine | Edition 11 | 25

Innovative semi-aerobic hydrolysis pretreatment technology for fibrous substrate


iogas has emerged as a promising renewable technology to convert agricultural, animal, industrial and municipal wastes into energy. Quite like any renewable energy technology, biogas offers a range of benefits such as reduction in Greenhouse Gas Emissions (GHG), ensures energy security and offers a sustainable alternative to conventional energy sources. Stubble burning in the regions of Punjab and Haryana is one of the major sources for Delhi Air Pollution. Converting bio-mass to compressed biogas and bio-CNG will not only help curb the menace of stubble burning but also create additional income for farmers. India consumed close to 20 million tonnes of LPG in 2016-17 and is expected to grow to at whopping rate 23.7 in the next upcoming years. Of the total consumption in 2016-17, close to 11 million tonnes was imported. Biogas can serve to offset a significant portion of this import requirement. The current biogas potential is estimated at 60,443 million m3 (raw biogas) which is equivalent to 26 million tonne LPG per year. Biogas produced is further purified and processed, to bio-compressed natural gas (bio-CNG) which is similar to natural gas in terms of its composition and properties, and is a cleaner alternative to fuels such as petrol and diesel Thus Fuel from Agrowaste can be a better al-

ternative to LPG and other fossil liquid fuels (Petrol and diesel) Supporting policies in india – BioCNG It is planned to roll out 5,000 CBG plants across India in a phased manner; 250 plants by the year 2020, 1,000 plants by 2022, and 5,000 plants by 2025 with expected production of 15 million tonnes of CBG per annum, which is about 40 per cent of current CNG consumption of 44 million tonnes per annum in the country. The National Policy on Biofuels, 2018, emphasised on active promotion of advanced biofuels, including CBG. The Government had launched the GOBAR-DHAN (Galvanising Organic Bio-Agro Resources) scheme earlier to convert cattle dung and solid waste in farms to CBG and compost. The scheme proposed to cover 700 projects across the country in 2018-19. CBG networks can be integrated with city gas distribution (CGD) networks. Later, the retailing from OMC fuel stations could be injected into CGD pipelines, too, for efficient distribution and access. The potential for CBG production from various sources in India is estimated at about 62 million tonnes per annum. Problems Associated with Feedstock Most of the agro wastes like Paddy straw are highly fibrous, which makes it difficult to di-

Biogas Magazine | Edition 11 | 26

gest as they are highly resistant to anaerobic digestion. The fibrous feedstock contains non-edible plant material so called lignocelluloses and is mainly composed of cellulose, hemicellulose, and lignin. Hemicelluloses is present as the matrix that surrounds the cellulose skeleton, while lignin is present as an encrusting material and serves as a protective layer. All three components have covalent cross-linkages between the polysaccharides and lignin, therefore, making biomass a composite material

Fibrous Feedstock






Different Feedstock and their composition


Cellulose (%)

Hemi-Cellulose (%)

Lignin (%)

Rice straw








Maize straw




The retention time and the speed of decomposition vary greatly based on the composition of feed. As per the graph, the fibrous material which has higher portion of lingo-cellulose requires more retention time to decompose.

Anaerobic digestion has been extensively used for treating highly biodegradable wastes like fibrous waste. Pretreatment is an important tool for cellulose conversion processes, and is essential to change the structure of cellulosic biomass to make cellulose more available tothe enzymes that convert the carbohydrate polymers into fermentable sugars. The pretreatment step is referred to as the technological bottleneck and is cost effective.

Atleast 20% of the total production cost is represented by the pretreatment phase Long decomposition time, Low biogas conversion rate, particularly less gas yield rate, formation of the floating layer in the system and clogging problems makes it less feasible for anaerobic digestion and no suitable digestion technologies for pure straw substrate. Physical pretreatment Physical pretreatment methods, including

Available Pretreatment Methods Several pretreatment methods have been followed to decompose fibrous rich agro waste.

mechanical operations, different types of irradiation and ultrasonic pretreatment, have been utilized to enhance the accessibility to hydrolysable polymers within lignocellulosic material. Among the physical pretreatments, (below beneath) mechanical pretreatment is widely used for waste materials, such as agricultural residues or any other crops and forestry residues. 1. Mechanical Treatment 2. Steam Explosion 3. Microwave radiation

Physio Chemical pretreatment Steam explosion Steam explosion (SE) is a well-known technique for the pretreatment of various biomass feedstocks. During SE pretreatment, lignocellulosic material is exposed to ahigh-pressure saturated steam at a temperature of 160–260 °C and a corresponding pressure of 5–50 atm for afew minutes. The pressure is gradually released, and the steam expands within the lignocellulosic matrix, causing individual fibers to separate and the cell wall structure to be disrupted. Acid can be added as a catalyst during steam explosion Chemical pretreatment Chemical treatment methods are used more than biological or physical pretreatment methods because they are more effective and enhance the biodegradation of complex materials. Common chemicals used in chemical pretreatment methods for improving the AD performance of agricultural residues are sulfuric acid (H2SO4), hydrochloric acid (HCl),acetic acid (CH3COOH), sodium hydroxide (NaOH),potassium hydroxide (KOH), lime (Ca(OH)2), aqueous ammonia (NH3H2O),

Biogas Magazine | Edition 11 | 28 and hydrogen peroxide. 1. Alkali pretreatment 2. Acid hydrolysis Biological pretreatment The deconstruction of lignin structures in the cell wall using microbes and/or enzymes as catalysts is usually referred to as biological pretreatment and occurs in the first stage of hydrolysis with other pretreatment processes. It can be done by manure addition as well as by adding certain microbes like actinomycetes 1. Microbiological treatment 2. Manure Addition

The table shows the increased gas generation rate of anaerobic digestion based on the type of pre-treatment method preferred

Pre-treatment Type

Mechanical Pre treatment

Chemical Treatment (Various on type of Method) Biological Treatment (Adding Manure) Our Technology - Semi Aerobic Hydrolysis The fibrous raw materials are being decomposed step by step into simpler compounds using a multistage microbiological process. The first two stages, pre-digest and acidification are usually often described as hydrolysis. Process Flow

Percentage of Increased Gas generating Capacity (%) 11-13


40.7 Semi-aerobic pre-digestion is the microbiological pre-decomposition of the hardly accessible parts, especially of the fibers in the substrates. Thereby the gas yield is being increased and the use of fibrous substrates is made more economical.

Biogas Magazine | Edition 11 | 29 lose is small and the activity is low.

Working Principle The Semi aerobic hydrolysis unit provides an aerobic and anaerobic mixed flora (facultative species) with different biochemical reactions in which the Aerobic and anaerobic bacteria could work together to decompose the lingo-cellulose structure. 1. Support aerobic microorganisms to rapidly secrete large amounts of hydrolase to convert cellulose into soluble sugar 2. Support anaerobic microorganisms to produce small amounts of alcohol 3. Support aerobic production of acetic acid 4. Supports the internal disintegration of molecular chains and reduces material viscosity while rapid polymer degradation In the conventional system, the hydrolyzed microorganism is a dedicated anaerobic microorganism, and its living environment is limited by the methanogen, and the amount of the enzyme capable of acting on the cellu-

Technology - Advantages 1. No chemical agent added, lower operation cost 2. Hydrolysis completed within 1-2 days, hydrolysate input to the digester and complete the biogas conversion within 25 days 3. Volume of digester decreased, lower investment 4. Easily pumpable and less floating layer, lower agitating power consumption 5. Possible for gas conversion of pure dry straw, deeply utilize gas yield potential 6. A higher CH4 concentration is obtained, as some CO2 released from hydrolysis 7. Many inhibiting chemicals can be broken down in hydrolysis(such as phenols, Ammonia etc), keeping the digester(methane production) running more stable. Semi Aerobic Hydrolysis of Rice Straw – Case Study

Results for Various Feedstocks

The normal anaerobic digestion of paddy straw produces very less biogas. Average specific biogas production is in the range of 248 m3 /tonne of total solids fed to the plant whereas the semi aerobic Hydrolysis of Rice straw produced around 400 Nm3/tonne.

Biogas Output for 45 TPD Feed – 12000 Nm3/day The semi hydrolysis treatment of Fibrous feedstock has proven to produce more biogas than general Anaerobic digestion Conclusion

Biogas Magazine | Edition 11 | 30

Substrate Characteristics and feeding amount


Annual feeding amount (t/a)

Daily amount (t/d)


TS input (t/d)


OTS input (t/d)








Process Water







Rice straw







Pretreatment alters the various feedstock characteristics at the fiber, fibril and micro fibril level. The extent and rate of LM hydrolysis are affected by biological pretreatment, chemical pretreatment, physical pretreatment, and its morphological characteristics. The mechanism behind semi aerobic hydrolysis is initiated by the increased facultative bacteria growth rate and enzymatic activity and the greater cellulase production under micro aerobic conditions. It is an efficient and cost-effective pretreatment method that meets most of the requirements for industrial applications, such as the formation of reactive cellulosic fiber for enzymatic attack, avoidance of the formation of possible inhibitors to the fermenting microorganisms and hydrolytic enzymes, reduced energy demand and reduced cost of size reduction of the

feedstock. Other benefits include the reduction in the cost of material for construction of the pretreatment reactor and the generation of fewer residues due to zero consumption of chemicals, all of which makes this technology as one of the most promising and environmentally friendly techniques in the long run.

P. Dev Anand Chairman & MD Kankyo Group of Companies

Biogas Magazine | Edition 11 | 31

Biogas Magazine | Edition 11 | 32

Figure 2

Figure 1 Figure 3

Digestate - an undervalued resource turned problem? Experiences of a Norwegian researcher in India


am a Norwegian researcher working at the Norwegian Institute of Bioeconomy Research. One of the projects I work on is a collaboration between Norway and India. The research focus of the collaboration is use of digestate, the organic rest from biogas production, as a fertiliser in rice production. In Norway I have worked on use of digestate as fertiliser for other crops, primarily wheat. We have found that digestate is a good fertiliser, with a lot of nutrients that are available to plants. And the biogas process improves the fertiliser value of animal manure, nutrients are mineralised and made plant available in the process. The Indian counterpart in the collaboration is KIIT university in Bhubaneswar, Orissa. KIIT university runs a biogas training centre and helps farmers in the area set up and run household sized digestors. As part of the collaboration I have been taken out to see the digestors in two villages, Salepur and Kakatpur. This was very interesting for me. The digestors seem to be running well and provide clean burning fuel for cooking for the villagers, and the trainers from KIIT appear very satisfied. However, there has not been much attention to digestate. I noticed a few problems, and I think at least in some cases, simple and cheap measures could make a lot of difference.

The most serious problem I noticed was that the digestate was stored in open tanks in most places (Figure 1). In my country all storage of manure and digestate needs to be covered, but digestate stored like this is particularly problematic because there will usually be some methane potential left in it. How much will vary, but for household sized digestors it is probably difficult to balance the input to exactly match the need, so that sometimes there will be quite a bit left. In many cases I could see bubbles forming (Figure 2), indicating that gas production was still going on. As methane is a powerful greenhouse gas (about 21 times stronger than CO2), any climate benefit from the digestors are therefore quickly negated this way. Ammonia is also lost to the air. That represents a loss of nutrients, and it can result in eutrophication elsewhere. In addition, open tanks could be a danger for children or animals to fall in. Only in one place saw I the tank covered. The cover was made of some twigs partly covered with plastic (Figure 3). We do not know which cover is best, but any cover is a lot better than no cover. Farmers should be encouraged to cover their digestate storage tanks and keeping them covered as much as possible. They can use whatever is available to them to cover it, so that this should not need to incur large extra cost.

Biogas Magazine | Edition 11 | 33

Figure 5

Figure 4

In the storage tank, the solid will sink to the bottom, so the solid is separated out to some extent. The liquid overflows at the top. At intervals, the tank is emptied and the solid taken out from the bottom. This solid is composted in open piles (Figure 4). At present it is mostly this compost that is used in the field as fertiliser or soil improver. This compost will contain organic matter and organic nitrogen and therefore improve soil fertility in the longer term. However, the content of readily plant available nitrogen is relatively low. It is the liquid digestate that contains the most readily available nutrients, in fact it is almost like diluted mineral fertiliser. For big biogas plants it is often difficult to use the liquid optimally. The large volumes make transport to areas that need it expensive, and in many countries, including India, there are restrictions on the use of it. The reason for the restrictions is mainly fear of spreading pathogens. However, in small farm-sized plants, these problems should be easy to overcome. There are no restrictions on the use of it, because there is little or no risk of spreading any pathogens the farm doesn’t already have. And the transport should also be a small problem as it is usually not necessary to transport it more than a few hundred metres. Even with very simple

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means of transport that should be possible. Currently, the overflowing liquid digestate represent a problem because it flows into the surrounding environment (Figure 5), where it becomes a pollution problem. In many cases it was led directly into ponds or streams, and here it leads to eutrophication and overgrowing (Figure 6). Some tanks were placed further away from water and close to trees or banana plantations, and that reduces the problem as much of the nutrient can be taken up by the plant, as well as directly providing nutrients to the crops. So that is the first thing to consider where the tank is placed. It should drain into a field with a large need for nutrient, and not be close open water. Figure 6 The most important is to still to try use the liquid better as fertliser. In India, farmers usually apply fertiliser multiple times during the growth of the crop. It should therefore be recommended to take out the liquid digestate often and apply to the field as often as possible. In this way farmers can also save money as liquid digestate can substitute mineral fertilisers. Farmers are sometimes reluctant to substitute mineral fertilisers with organic ones, because not all nutrients are immediately available in organic fertiliser, and the fertiliser effect can therefore be difficult to predict. However, liquid digestate contains a lot of mineral nutrients. Substitution should be based on ammonium concentration, as this is known to be immediately available to the crop. In this way we can be sure that the crop will get at least as much nitrogen as with mineral fertilisers. Our project will provide better data on ammonium concentration and fertiliser value of this digestate. Our current

Biogas Magazine | Edition 11 | 34 data suggest 0.19-0.26 gN/L. In conclusion, I think these villages have managed the biogas production well, but there is still room for improvement when it comes to the management of the digestate. I believe they could improve it a lot at very low cost, or even at negative cost. It is important to always think about the management of digestate when biogas plants or project of biogas introduction are planned. Biogas plants produce two valuable resources, one is biogas energy, the other is digestate where the nutrients have been made more plant available than in the feedstock. Making use of both resources will improve the economy of the plant. In this magazine, I have read a few articles about how big plants can make marketable products from digestate. However, for small plants it is actually much easier to turn this waste into a valuable resources, and this opportunity should not be wasted.

Biogas Magazine | Edition 11 | 35

Biogas Magazine | Edition 11 | 36

Essence of Operation and Maintenance in Biogas industry


ood Operation and Maintenance (O&M) practices at any plant has significance not only in terms of achieving high levels of performance parameters, but also for ensuring the good health of the equipment running in the plants thus improving plant’s overall durability and longevity. Talking specifically of the biogas plants, its operation can be comprehended as easy as digestion of food consumed by cow to as complex as numerous series of reaction steps, interdependent, facilitated by a large variety of microorganisms, whose functioning can be extremely sensitive to its exposed ecosystem. In other words, setting up a biogas plant is relatively easier than to run it efficiently and effectively over its operating years. Thus, appropriate O&M is a crucial factor for longer life and sustainability of biogas plants. Over the years, a typical biogas plant shows deterioration in its performance due to ageing factor. The conditions aggravate further, if proper O&M practices are not followed in its operation. The biogas plants in India display a wide spectrum of operational practices without a well-planned, or no O&M strategy be-

ing in place leading to reduced plant performance including efficiency, production, and capacity utilization. The principal underlying reasons are inadequate planning at inception, i.e. improper or no-feasibility studies); missing methodological approach, like absence of a differentiated but common approach for each piece or category of equipment and inappropriate production plan, leading to increased equipment downtime in the long run; lack of returns to plough it back into the system; and organizational concerns, i.e. to be placated with make shift arrangement thus missing futuristic vision. Of the above-mentioned concerns, the most vital one relate to inefficient use of financial resources with minuscule fraction of entire budget allocated towards well planned O&M activities. O&M activities of a biogas set-up includes all work and inspections needed to ensure its smooth functioning and long service life. It doesn’t only encompass technical issues, but also managerial, social, financial, and institutional issues. Evidently, many failures are not technical ones, as they may result from poor planning, upfront. The ease of opera-

tion and maintenance of a facility is central to its sustainability and must be given careful consideration at the inception stage. Preferably, a higher mix of indigenous components in overall plant set-up is suggested as it bereaves the necessity to hold costly inventory as spare parts for onward maintenance. But, this should be well balanced with appropriate mix of import component, deemed necessary to ensure safety and reliability is not jeopardised at any cost. After all, what’s the point in saving few bucks upfront with economical procurement that leads to exorbitant costs later. Biogas Installations particularly require strengthened O&M practices, which includes continual monitoring, periodic inspection, standard operating procedures, scheduled preventive maintenance, enhancement in technical and managerial skills of O&M personnel, and necessary infrastructure/facilities improvement. These actions address uncertainty and risks associated with outages, reactive maintenance, abrupt start-ups and shut-downs, and ensures long term up-time, performance, and economic viability. Additionally, there lies a significant scope for improving overall performance of the under-

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performing biogas plants through strengthening their O&M practices. Improving performance through interventions aimed at strengthening of O&M practices is the quickest and least cost alternative, rather than fixing the situation with fresh capital investment. Although, such restoring exercise would require multiple interventions across various aspects, as per the situation, including people, technology, process and infrastructure etc. Underneath is highlighted few aspects, which are necessary for efficient O&M management in biogas projects: • Appropriate accountability mechanisms with an organised O&M strategy - Accountability is essential to the success of any biogas project. Having a written O&M plan, manual, or similar guidance in place helps ensure that management is aware of and can be held accountable for O&M responsibilities, which in turn ensure the long-term viability of a project. • Sturdy Documentation and tracking systems -Tracking systems, such as maintaining log books, keeping records, trend analysis of process parameters not only ensures that a given project is performing as designed, but facilitates continual improvement of O&M activities, by identifying opportunities for more effective strategies. • Training and capacity building - Local technicians and operators need to be trained for the proper operation of a given biogas setup, more so for a new installation. Hands-on training is desired to ensure full understanding and the implications of the new system. In-house operators or outsources local engineering companies, whomsoever will take care of the maintenance of the systems, should be also trained in the type of maintenance activities that have to be carried out periodically. Effective O&M training should be provided in an easy-to-understand format, should occur at regular intervals, and is targeted to the relevant employees or volunteers, who are expected to carry out the corresponding activities.

Biogas Magazine | Edition 11 | 38 so. This neglect or delay in applying proper O&M has adversely affected the credibility of the investments made, the functioning of the services, the well-being of residents in vicinity, and most importantly loss of prospective projects. This turns out to be a vicious cycle. A comprehensive approach needs to be adopted, emphasising not only on the design and construction in the beginning, but also appropriate planning towards post-construction activities in form of an appropriate O&M strategy, upfront in the planning stage.

• Outsourcing of O&M - Sometimes, it makes sense to bring on board experienced O&M providers, who are fully equipped to provide ongoing operations and maintenance services to ensure peak efficiency of biogas plants. Such engagement ensure that the necessary resources are in place. There are several models like BOO, BOOT, BOWT that can be judiciously carved out to meet the requirement of a given project. • Establishing vehicles for compliance assurance – Its recommended to have some type of cross-functional team (including mechanical, electrical, instrumentation, process operation, fire and safety) in place to monitor and ensure that needful activities are being performed without any discrimination across departments. • Dedicated funding/ budgetary allocation for O&M- A dedicated source of fund or allocation of needful budget shall provide means to cover justified costs pertaining to prudently adopted O&M strategy. Often, in the Indian scenario, appropriate O&M practices in biogas set-up has been completely ignored in past, or in some cases introduced only after compulsion to do

Abhijeet Mukherjee Project Head Indian Biogas Association