Small-scale biogas upgrade for vehicle fuel

Transcription

1 Final Report driving innovation in AD small scale Small-scale biogas upgrade for vehicle fuel Evergreen Gas has investigated the feasibility and methodology of producing a methane-rich vehicle fuel from biogas on a small scale at a cost proportionate to the scale of production. Project code: OIN Research date: 2012 Date: April 2012

2 WRAP s vision is a world without waste, where resources are used sustainably. We work with businesses, individuals and communities to help them reap the benefits of reducing waste, developing sustainable products and using resources in an efficient way. Find out more at This report was commissioned and financed as part of WRAP s Driving Innovation in AD programme. The report remains entirely the responsibility of the author and WRAP accepts no liability for the contents of the report howsoever used. Publication of the report does not imply that WRAP endorses the views, data, opinions or other content contained herein and parties should not seek to rely on it without satisfying themselves of its accuracy. Written by: Evergreen Gas Front cover photography: The Evergreen Gas Caddy Ecofuel getting a fill of CNG at CNG Services filling station, Crewe While we have tried to make sure this report is accurate, we cannot accept responsibility or be held legally responsible for any loss or damage arising out of or in connection with this information being inaccurate, incomplete or misleading. This material is copyrighted. You can copy it free of charge as long as the material is accurate and not used in a misleading context. You must identify the source of the material and acknowledge our copyright. You must not use material to endorse or suggest we have endorsed a commercial product or service. For more details please see our terms and conditions on our website at

3 Executive summary Evergreen Gas has assessed three different upgrade technologies to produce a fuel derived from biogas with a methane concentration of 85% by volume that is suitable for use in vehicles. The technologies assessed originate from Finland, India and the UK. The Finnish technology supplied by Metener Oy was selected and a detailed appraisal of the technology presented. The report set out to evaluate upgrade at two scales: 5m 3 /h and 25 m 3 /h. The lower flow rate is for a pilot plant that would be installed at the Evergreen Gas digester in Shropshire, and the larger flow rate to represent the commercialised product once proof of concept had been demonstrated. 25m 3 /h of biogas can be produced from about 500 dairy cows or equivalent feedstock and represents a typical output from a small-scale farm AD plant. The capital cost for the design, build, installation, commissioning, monitoring and reporting of the pilot scale plant is 135,000 and this unit will produce approximately 50kg per day of vehicle fuel. The commercial scale plant has an output of approximately 250 kg of vehicle fuel per day. The report compared the value per cubic metre of biogas when used for heat, CHP or vehicle fuel, and the results indicate that at the 5m 3 /h scale, vehicle fuel is the most attractive use of biogas when there is either below 30% utilisation of surplus heat, or when the AD installation is unable to qualify for the renewable heat incentive. Economic analysis of a like for like substitution of CHP for vehicle fuel production requiring all biogas to be routed to the upgrade unit requires process energy for digester heating and maintenance to be bought in. Taking a typical farm AD plant as an example, at today s fuel prices, the payback period for the vehicle fuel only option is more than double the CHP output due to the high cost energy cost of digester operation. A scenario was developed where the 5m 3 /h upgrade facility was installed in parallel with a CHP and the two are operated at the same time. The findings are interesting, because the CHP provides digester heat and the electricity to run the upgrade plant is also generated by the CHP. Although there is additional capital cost for installing the upgrade unit, the advantage of this configuration is that it allows a farmer to become more energy selfsufficient as vehicle technology has been developed (thanks to the bridge provided by CNG) to utilise this fuel. Evergreen Gas proposes to purchase a complete upgrade unit from Metener in Finland as the demonstrator which will then be commercialised. Manufacture will be by Metener, and marketing, operation and commercialisation by Evergreen Gas.. Evergreen Gas anticipates that if WRAP gives the go-ahead for Phase II of the project, the time from receipt of the funding offer until delivery of the pilot prototype is in the order of 230 days. The potential market for biogas-derived vehicle fuel is huge, and small-scale AD is on the increase thanks to favourable FIT s and the emergence of technology providers to bring AD to the smaller operator. Production of vehicle fuel on-farm would be a leap towards reducing the carbon footprint of agriculture, reducing costs and getting closer to energy selfsufficiency. Small-scale biogas upgrade for vehicle fuel 1

4 Contents 1.0 Abstract Introduction and Background Evergreen Gas Biogas The Technology Metener Oy Green Brick Eco Solutions / IIT New Delhi Chesterfield Biogas Summary Application of the Technology Project Objectives Feasibility study Outcomes State of Technology Metener Green Brick Eco Solutions Legislation Relevant legislation Road fuel duty Detailed Technical Appraisal of the technology Metener simple upgrade system Process description Engineering scope Energy balance Mass balance Economics Operational parameters Green Brick Eco Solutions Process description Engineering scope Mass and energy balance Economics Operational parameters Chesterfield Biogas Process description Economics Conclusion Detailed Economic Analysis The economics of different biogas utilisation at 5m 3 /h and 25m 3 /h Overall Environmental Impacts The macro-economic picture The carbon footprint of agriculture Phase 2 Demonstration Methodology for the demonstration Project Timescale Project development Permiting and approvals Project financing Construction, operation and maintenance Monitoring and evaluation Decommissioning Small-scale biogas upgrade for vehicle fuel 2

5 9.3 Cost breakdown and milestones Project milestones Cost estimate Commercialisation of technology post demonstration Intellectual property Commercialisation plans going forward Key personnel Evaluation and monitoring Pilot: Commercial plant Health and safety Conclusion Appendices Glossary AD PSA PRV ATEX CHP CO 2 H2S GBES CNG OSR NFU ICL GRP BMAD IGE RHI FIT Anaerobic Digestion Pressure Swing Adsorption Pressure Relief Valve Official standard for applications in explosive atmospheres Combined Heat and Power Carbon Dioxide Hydrogen Sulphide Green Brick Eco Solutions Compressed Natural Gas Oil Seed Rape National Farmers Union Indian Compressor Ltd Glass Reinforced Polyester Barrett s Mill Anaerobic Digester Institute of Gas Engineers Renewable Heat Incentive Feed In Tariff Small-scale biogas upgrade for vehicle fuel 3

6 1.0 Abstract Biogas, which is generated from the anaerobic digestion of organic material, is rich in methane, typically 55% by volume, the balance volume being carbon dioxide with traces of other gases. Biogas can either be burned in its raw state in a boiler for the generation of heat, or in an engine coupled to a generator equipped with heat recovery equipment to produce heat and power. Biogas can also be scrubbed of carbon dioxide and impurities. It can then either be injected into the gas grid, or stored in bottles at pressure and used as a fuel for vehicles. This report evaluates the economic and operational feasibility of upgrading biogas for vehicle fuel at a small-scale. The driver is to improve the economics of on-farm AD and to broaden the options for energy utilisation increasing the potential for farms to become energy self-sufficient. Two scales are considered: 5m 3 /h and 25m 3 /h raw biogas input. A pilot plant will be constructed at the 5m 3 /h scale to prove the concept, and a commercialised model operating at 25m 3 /hour will be assessed. We have chosen 25m 3 /hour as this flow rate is achievable from a typical farm scale AD plant that would have an equivalent electrical output of 50kW. This report assesses three different upgrading technologies that are currently available. Two of the processes employ water scrubbing and the third uses a variant of pressure swing adsorption. While upgrading biogas to biomethane for grid injection can benefit from an economy of scale in regard to energy and capital cost, a purpose-built unit for production of vehicle fuel can be an attractive option to a farm-scale AD installation. Economic analysis of the different scales of biogas upgrade has shown that a combination of CHP and biogas upgrade at 5m 3 /h flow rate is more economically attractive than upgrade at 25m 3 /h requiring all of the biogas production from the AD plant for upgrade. The reason being that the process energy requirements of the AD plant are met by the CHP, alleviating the need to import energy. The capacity to generate heat, electricity and a significant quantity of vehicle fuel should be attractive to farmers looking to achieve a greater degree of energy self-sufficiency and to diversify their income. The potential market for a small-scale biogas to vehicle fuel upgrade facility is enormous, and once the concept has been demonstrated at the farm-scale, the flexibility of biogas upgrade in conjunction with CHP will become commonplace. 2.0 Introduction and Background 2.1 Evergreen Gas Evergreen Gas was founded in October 2011 by Michael Chesshire and Will Llewellyn to develop a range of value engineered, modular AD plants suitable for farms and rural communities. Evergreen Gas benefits from over 30 years experience in the design, construction, commissioning and operation of AD plants. Evergreen Gas is a British company, and the range of digesters covers electrical outputs from 20kW to 250kW, are designed to accommodate a range of feedstocks. For a small-scale AD project to be economically viable, the capital cost of installation must be proportionate to the plant s income. The Evergreen Gas design has enabled the Company to bring capital cost into line with income. The Evergreen Gas range of AD plants is based on a digester design that is partially buried and made of pre-fabricated concrete panels. Material is fed into the digester either by pump (if the feedstock is pumpable), or using an auger. The digester is built with a removable GRP roof. Gas is piped from the digester headspace into an above-ground dual membrane gasholder from where it is piped to the gas consumers, typically a CHP unit and a biogas boiler. The contents of the digester are mixed by recirculating biogas from nozzles set into Small-scale biogas upgrade for vehicle fuel 4

7 the digester floor. Digestate is discharged from the digester via a macerator, and the client can choose what method of digestate separation and storage they wish to employ. The background to our proposal is the perceived market demand for a means of making vehicle fuel from biogas at a small scale. Evergreen Gas currently owns a VW Caddy Ecofuel CNG-fuelled van. The closest CNG station is 60 miles from the office, so in the first instance, we would be able to avoid making unnecessary detours for refuelling. Figure 1:- Refuelling the Evergreen Gas Caddy Ecofuel at CNG Services, Crewe 2.2 Biogas Biogas is a mixture of methane and carbon dioxide with traces of hydrogen sulphide and other impurities. Hydrogen sulphide is a result of sulphur-containing organic material being digested and its sulphur being reduced by anaerobic sulphur-reducing bacteria. These bacteria are found in most anaerobic environments ranging from deep ocean vents to onfarm biogas plants. The amino acid Cysteine contains sulphur and is a component of many different proteins. Carbon dioxide is not damaging to an internal combustion engine but it does not contain any energy, so the purpose of removing it is to reduce the amount of energy compressing a gas with no energy value. Methane cannot be liquefied at temperatures above minus 160 o C, so must be compressed to enable the vehicle to have a useful range. Storage is optimised by ensuring that the gas contained is usable by the engine. Hydrogen sulphide must be removed from biogas before it is used as vehicle fuel. H 2 S reacts with oxygen during combustion and is converted to sulphur dioxide which in turn reacts with water to give sulphuric acid which is damaging to components in an engine. In the presence of oxidising agents and extremes of temperature (for example in the combustion chamber of an engine), solid sulphur can be generated. Sulphur build-up in the exhaust system and turbo chargers shortens the lifespan of these components. Once upgraded to above 95% methane, the gas is known as Biomethane and can either be stored at 250bar, or compressed directly into the fuel tanks attached to the vehicle. Evergreen Gas has investigated the potential for upgrading gas both to >95% and to 85% methane. The fuel specification for the VW Caddy is listed as H and L Grade CNG. Appendix 1 details the fuel specification of H and L grade CNG. Vijay et. al. successfully Small-scale biogas upgrade for vehicle fuel 5

8 demonstrated a Maruti 800 exhibiting a performance on biogas-derived fuel at 85% methane by volume that was comparable to commercially available CNG. 1 Evergreen Gas contacted VW UK in regard to this topic and was advised as follows by Volkswagen s technical department in Germany: In Sweden, for example, they are driving 100% bio-methan. However, for our vehicle use we stick to DIN Non conditioned gas in general do not correspond to this norm. Conditioned gas in general correspond to H-gas quality. If the Caddy Eco-Fuel work with 75% methan and 25% CO2 R&D do not know as not tested. We are excited by the opportunities the technology covered in the report may present to us. 2.3 The Technology Three different upgrading technologies have been assessed in this report. They originate from Finland, India and the UK. The companies are Metener Oy, Green Brick Eco Solutions (GBES) and Chesterfield Biogas Ltd. Metener and GBES have already developed a commercialised biogas to vehicle fuel system which they are actively marketing. Chesterfield Biogas has developed a prototype small-scale upgrade process that they are currently testing ahead of release onto the market Metener Oy Metener Oy, a Finnish company has developed a patented high-pressure water scrubbing process for converting biogas to vehicle fuel. Metener has containerised this process and is marketing the technology worldwide. There is an example of this technology at the Kalmari Farm in Luakaa, Finland where it is coupled to a dispenser to enable them to sell biomethane to the public. Figure 2 shows the filling station. Compressed biomethane is stored in bottles in the building behind the filling station. At present, there are over 30 cars regularly refuelling from Kalmari Farm filling station. Metener has also sold a containerised upgrading facility to China where it is installed on a pig farm. The standard Metener product is designed to process raw biogas with an inlet flow rate of between 30 and 100m 3 /h. 1 Biogas Purification and bottling into CNG cylinders: Producing Bio-CNG from biomass for rural automotive applications. The 2 nd joint international conference on Sustainable Energy and Environment (SEE 2006) November 2006, Bangkok Thailand Small-scale biogas upgrade for vehicle fuel 6

9 Figure 2:- Metener biomethane filling station, Finland Green Brick Eco Solutions / IIT New Delhi The Indian process uses high pressure water scrubbing and is similar to the simple Metener process, although the resulting biomethane requires further compressing before it can be stored and it is less automated. The process was developed by Professor VK Vijay in association with the Indian Institute of Technology (IIT), New Delhi which owns the patent. The technology has been commercialised by Green Brick Eco Solutions (GBES) for implementation throughout India. Prior to GBES, the IIT technology was marketed by Indian Compressors Ltd. The technology is producing vehicle fuel for auto rickshaws and cars across some cities in India. There is already a developed market for CNG vehicles in India, and recent changes to air pollution legislation have led to two-stroke petrol and some diesel engines being replaced by CNG / Biomethane powered units. Small-scale biogas upgrade for vehicle fuel 7

10 Figure 3:- IIT scrubbing column Figure 4:- ICL upgrade facility Figure 5:- Demonstration biomethane van Figure 6:- CNG-fuelled auto-rickshaw Chesterfield Biogas The British technology assessed is developed by Chesterfield Biogas. Chesterfield Biogas core market is the installation of biogas to grid upgrade facilities, and they are the license holder for Greenlane biogas upgrade units. Chesterfield Biogas has installed over 60 biogas to grid upgrade units in Europe including a unit for Thames Water in the UK at the Didcot Waste water treatment works. In addition to biogas upgrade facilities, Chesterfield Biogas manufacture CNG filling stations, some of which are sited at haulage depots in the UK. The newest offering from Chesterfield Biogas is a small-scale biogas to vehicle fuel scrubber that employs a version of pressure swing adsorption technology. The unit is aimed at the agricultural sector and food processor biogas plant installers. Chesterfield started development on this unit in 2011 and the prototype is currently undergoing testing. Small-scale biogas upgrade for vehicle fuel 8

11 2.3.4 Summary These biogas upgrade technologies have been chosen because they enable organic material, agricultural residues and wastes to be converted into vehicle fuel, and move farmers towards energy self-sufficiency. A reduction in agriculture s reliance on oil for transport, and crop production and fertilizer will reduce the overall carbon footprint of agriculture. 2.4 Application of the Technology Vehicle fuel production could be the next major gear change for the UK AD industry. AD has so far enabled plant developers to generate renewable electricity, a market driven both by Government-led renewable energy generation policy and a desire for energy self-sufficiency. High global demand for crude oil driven by emerging economies such as China and India keeps energy and fertilizer prices firm. The UK taxation policy of taxation levied on oil products contributes to the high prices, so if a viable replacement to oil can be found for transportation, then it will be attractive. Biogas is an attractive source of fuel as it can be derived from waste materials, and does not always require the growing of purpose grown crops for production. The NFU aspires to a figure of 1000 on-farm AD plants by 2020, so a small-scale biogas upgrade facility that is priced competitively and match the biogas output of a typical on-farm AD should attract strong interest. It is possible that in the future farmers will be under pressureto reduce the carbon footprint of their operations whether through restrictions on fugitive greenhouse gas emission or by more stringent emission controls imposed on their machinery. High high oil prices will impact on their costs of production as they are exposed to fuel and fertiliser price fluctuation. Both spark ignition engines and diesel engines can be modified to run on biomethane, although the latter requires a small amount of diesel to ignite the gas, so these engines must have dual fuel capability. The market for CNG vehicles is growing, and many manufacturers offer CNG variants of existing models across the spectrum of the road transport and agricultural fleet, Mercedes, Iveco, Valtra and VW to name just a few. Retrofit kits for petrol and diesel-engined vehicles are relatively inexpensive and available from companies like Tartarini Auto and Prins Autogas. The advantage of a methane-rich vehicle fuel derived from biogas is that the development of CNG infrastructure, handling and utilisation equipment has already been done and proven, so CNG acts as a bridge for biomethane. A competitively priced biogas to vehicle fuel technology increases the flexibility of AD, and enables the AD developer to choose how to utilise the energy in the biogas to optimise the efficiency of the biogas plant. A combination of vehicle fuel and CHP would be a very attractive proposition to a farmer with high onsite energy use and high fuel bills. Small-scale biogas upgrade for vehicle fuel 9

12 Figure 7:- Cutaway view of VW Caddy Ecofuel showing gas storage bottles 1m 3 of methane at standard temperature and pressure has the equivalent energy content of 1.35 litres of diesel or 1.4 litres of petrol 2. The following table illustrates the methane yields of various feedstocks and their equivalence in litres of diesel or petrol. In this table, the data considers the equivalence in terms of at the wheels rather than energy value. The difference seen between these numbers and the relative calorific values stated above is related to the difference in efficiency between Otto cycle (spark ignition) and diesel cycle (compression ignition) engines. Table 1 compares methane yield per tonne of feedstock with litres of diesel /petrol on a like for like basis: For example, performance of two VW Caddies of the same power, one fitted with a diesel engine is compared to a similar VW caddy of the same age with a CNG-fuelled engine. Table 1:- Feedstock methane yields and vehicle fuel equivalent 3 Feedstock Nm 3 CH4/t Litres Diesel Eq. Litres petrol Eq. Cow Slurry Pig Slurry Sewage Sludge Potato Waste Horse Manure Grass Silage Maize Silage Fish Waste Household Foodwaste Slaughterhouse Waste Grease and Fat John Harwood, Project Manager, CNG Services 3 Metener Oy Small-scale biogas upgrade for vehicle fuel 10

13 A vehicle that is adapted for CNG can run on biomethane, and these are available all over Europe, India, Pakistan and the USA. CNG vehicles are available from new, but petrol and diesel cars can also be retrofitted with the necessary equipment to use CNG. Kazakhstan is currently investing in its domestic CNG infrastructure to take advantage of cheap natural gas. The upshot of this is that CNG is a bridge to the adoption of biomethane, so that modifying or buying a purpose built CNG vehicle is relatively inexpensive. Further development of this market will be stimulated by making the fuel more widespread. 3.0 Project Objectives 3.1 Feasibility study Evergreen Gas set out to evaluate the small scale biogas upgrade technologies offered by Metener Oy and by the Indian Institute of Technology and Chesterfield Biogas at scales of 5m 3 /h and 25m 3 /h raw biogas flow rate. Our aim is to develop a fundamental understanding of the process, engineering scope, mass balance, energy balance, capital cost, operational cost and maintenance cost for conversion of biogas to vehicle fuel. The feasibility study aimed to demonstrate that while biogas upgrade for grid injection is suitable for large scale AD projects, small-scale biogas upgrade can be well suited to the production of vehicle fuel. The feasibility study will open up further opportunities for farms to develop new income streams from small-scale AD plants. Evergreen Gas has learned that there are many farmers keen to install AD on their farms, but so far have been unable to find a technology provider that is at the right scale for their farming operations, so have been put off by the cost and operational requirements of large plants. Given that the NFU is hoping for 1000 on farm AD plants by 2020, there may be farms which could provide feedstock for AD restricted by the size of the grid connection, so cannot export power. A small CHP in conjunction with a small upgrade facility would both enable them to become energy self-sufficient and to diversify their income from sales of vehicle fuel. As part of this feasibility study, Will Llewellyn travelled to Finland to meet Metener and discuss the current state of their technology and work on a small-scale version that will be suitable for the pilot scale and commercial scale plants. 3.2 Outcomes The outcome of the feasibility study is to procure a pilot scale biogas upgrade plant and bring to market a simple upgrade process that can be sold in conjunction with the Evergreen Gas range of Small-Scale AD plants, and enable farmers and interested stakeholders to see for themselves the added flexibility of installing an AD plant. For the demonstration phase of the project, we will procure a 5m 3 /h pilot upgrade facility and incorporate it into BMAD, the 40m 3 digester we are building at our site in Shropshire. This AD plant is already designed to include a 7.5kW CHP, so we will use the pilot upgrade plant to provide fuel for our works van, a VW Caddy Ecofuel. The inclusion of biogas upgrade at a small-scale will prove that vehicle fuel is an example of the flexibility of AD and will open up the market for small-scale vehicle fuel production. Proof of concept will be demonstrated with the 5m 3 /h plant, and the work that we have undertaken at the 25m 3 /h scale will enable us to offer a larger vehicle fuel production facility should there be market demand. Small-scale biogas upgrade for vehicle fuel 11

14 The proposed pilot scale upgrade plant will produce approximately 50kg day of biogasderived vehicle fuel. A typical 2 litre-engine car (VW Caddy) can average 10 miles per kg of CNG, so a farmer would be able to produce enough fuel to travel for 500 miles per day if he installed one of these small plants on his AD plant. The 25 m 3 /h unit would produce sufficient biogas for approximately 2500 miles per day, for example 10 vehicles each driving 250 miles per day. Finnish tractor manufacturer Valtra has developed a 140hp (104kW) dual fuel tractor with 24.4kg biomethane storage capacity (170 litres at 200 bar), sufficient fuel for 3 to 5 hours work depending on the activity. This tractor would use approximately 6kg of biomethane per hour. Figure 8:- Valtra T133 Biomethane-powered tractor Figure 9:- Valtra CNG bi-fuel schematic diagram Even the pilot-scale upgrade facility would produce sufficient vehicle fuel in a 24 hour period for 8 hours tractor operation. Clearly there is potential for additional diversification, significant fuel savings and even energy self-sufficiency on the farm. 4.0 State of Technology 4.1 Metener Low pressure water scrubbing was used in Finland during the Second World War, so is not a new technique. The difference between this approach and Metener s technology is the use of pressure to increase the rate of gas absorption into the water. Erkki Kalmari built his first high pressure scrubbing system in 2000 using a scrubbing column and components from a pressure washer. A more advanced, automated plant with was built in 2002 and the Kalmari Farm purchased their first CNG car in November of the same year. At the time of writing this report, there are over 30 cars regularly refuelling from the biomethane filling station on the Kalmari Farm including commuters, taxis, local delivery vehicles and the post van. The popularity of fuel derived from biogas is increasing in Finland because it costs approximately half of the price of petrol or diesel. Metener s process is centred around a pair of water scrubbing columns that alternate between filling and discharging phases. The unique attribute of the Metener process is that Small-scale biogas upgrade for vehicle fuel 12

15 upgraded gas leaves the scrubbing columns at 210 bar, and is further pressurised to 250 bar using a hydraulic booster before passing through a desiccating column and into storage. Keeping the upgraded gas at high pressure throughout the upgrade process removes the energy intensive step of re-pressurisation for storage post scrubbing. Water scrubbing also removes hydrogen sulphide, so alleviating the need for a consumable scrubbing medium. Metener has supplied biogas upgrade systems to customers including the University of Jyväskylä and abroad. The former is located on a landfill site and was the subject of a PhD thesis, and the latter has been installed on a pig farm in China where the upgraded gas is used for fuelling vehicles and for cooking. The plant in China will provide sufficient fuel for 1100 families to switch to renewable, clean fuel. Metener s typical containerised batch scrubbing facility has an input flow rate of 40-50m 3 /h and costs approximately 300,000. Figure 10:- Kalmari farm first bi-fuel vehicle: Volvo V70 Having already commercialised the technology on a large scale, Metener has agreed to work with Evergreen Gas to build an upgrade plant at a scale to match the budget and biogas production rate of the smaller operator. Figure 11:- Metener batch scrubbing columns and flash column (biomethane storage in background) Small-scale biogas upgrade for vehicle fuel 13

16 The cost of the small unit must be proportionate to the output so that it can earn a good return on capital. If this is unachievable then it will not be economically viable. 4.2 Green Brick Eco Solutions A variation of biogas scrubbing with water has been developed at the IIT by a team led by Professor Vijay. A patent was applied for (number is 161-del-2006), and initially the technology was designed for a raw biogas inlet of only 20m 3 /h. Initially, Indian Compressor Ltd (ICL) took the technology license from IIT Delhi and installed a small number of plants. Unfortunately these plants did not perform well. ICL is primarily a compressor company so dropped biogas upgrade from its portfolio to concentrate on its core compressor and CNG handling business. The licence has been taken over by Green Brick Eco Systems, founded by a group of IIT Delhi alumni who under the guidance of Professor Vijay have continued the R&D work on the technology. As a result of this collaboration, GBES has successfully developed an updated version of the technology that can handle a wider range of purification capacity. GBES are the official partner of IIT Delhi for commercializing and implementing biogas purification technology in India & abroad. The IIT technology was initially developed by a team led by Professor Vijay and implemented on a farm near Delhi. Michael Chesshire visited this farm in 2009 and saw the prototype in operation which was used for fuelling CNG adapted auto-rickshaws and small vehicles. Since this prototype, a larger scale application of the technology has been used to scrub, compress and bottle biogas for use in a small car. Vijay et al. published their work in a paper titled Biogas Purification and Bottling into CNG Cylinders: Producing bio-cng from biomass for rural automotive applications. The IIT technology is simpler than Metener s core product and is less automated. The upgraded gas is of a similar level of purity although a further compression step is required before it can be used as a vehicle fuel. 5.0 Legislation Production of biogas and upgrade of biogas to vehicle fuel is covered by various legislative frameworks to ensure that risks are kept to a minimum. Biogas is flammable and in some cases can be explosive. The AD facility should be designed and operated so that it poses no risk of pollution to the surrounding environment. The upgrade unit requires gas to be stored and handled at pressure so it must be fit for purpose both in terms of manufacture and suitably protected in the event of any unforeseen occurrences. 5.1 Relevant legislation The production of the biogas itself is governed by the Environment Agency permit or exemption certificate issued on a case specific basis for the anaerobic digestion facility. The upgrade and gas storage process itself is covered by the Pressure Systems Safety Regulations (2000). This is in line with the European Pressure Equipment Directive 97/23/EC (PED) sets out the standards for the design and fabrication of pressure equipment over one litre in volume and having a maximum pressure more than 0.5 bar. It sets the administrative procedures and requirements for the "conformity assessment" of pressure equipment, for Small-scale biogas upgrade for vehicle fuel 14

17 the free placing on the European market without local legislative barriers. It has been mandatory throughout the EU since 30 May The Institute of Gas Engineers (IGE) SR25 document contains guidance on leakage and dissipation data from joints. This document must be referred to during the design of the upgrade plant. The Dangerous Substances and Explosive Atmospheres Regulations (2002) govern the inspection and auditing of pressure vessels at both the design and routine inspection level. 5.2 Road fuel duty Duty is currently set at per kg of CNG and will increase on 1 st August 2012 to per kg. This duty figure is based on CNG with an energy content of 14.26kWh/m 3. Interestingly, the calorific value of CNG is variable, but duty is not levied against calorific value, only by mass based on a standard quality. At present it is unclear whether the Government will levy duty against the energy content of the vehicle fuel, so a small-scale upgrade plant should be equipped with a suitable flow meter to satisfy inspection. 6.0 Detailed Technical Appraisal of the technology 6.1 Metener simple upgrade system Water scrubbing of biogas relies on the greater solubility of carbon dioxide and hydrogen sulphide than methane in water. Both the Metener and IIT processes rely on these gasses dissolving into water under pressure. Carbon dioxide dissolves in water to form Carbonic acid as per the following equation: CO 2 + H 2 O H 2 CO 3 Figure 12:- Adsorption and desorption of carbon dioxide in water: A reversible reaction The amount of a gas that can be dissolved in water is described by Henry's Law. Higher gas pressure and lower temperature enable more gas to dissolve in the liquid. When the temperature is raised or the pressure is reduced (as happens when a container of carbonated water is opened) the dissolved gasses come out of solution, in the form of bubbles. As discussed previously the core Metener upgrade plant is a containerised, batch upgrade plant. Metener have drawn on their expertise to develop a simple system for Evergreen Gas. The details of the simple system are considered in this appraisal, based on a flow rate of 5m 3 /h of raw biogas. Will Llewellyn visited Metener at their offices at the Kalmari Farm near Laukaa, Finland to discuss the requirements of the DIAD feasibility study, to see first-hand how the process was managed, and enhance Evergreen Gas fundamental understanding of biogas upgrade to Vehicle Fuel. Will spent a day in the company of Jussi Lantela, process engineer and designer of both the commercial scale and simple upgrade processes, and Juha Luostarinen, process engineer and biogas specialist. Will was delighted to meet Erkki Kalmari, inventor of the Metener High pressure upgrade system, and while on site, vehicles came and filled up at the filling station. Small-scale biogas upgrade for vehicle fuel 15

18 6.1.1 Process description Raw biogas is compressed to between 4 and 10 bar and stored in a buffer tank. The compressed biogas flows into the scrubbing column. The scrubbing column maintains a continuous counter current flow of water and biogas. Biogas enters from the bottom of the column and water is sprayed in from the top Purified gas flows continuously out from the top of the column.. It is compressed to 250 bar either straight into a vehicle or into storage Downstream of the high pressure compressor the product gas then passes through a desiccating column to remove any remaining traces of moisture. After the desiccating column, the dry gas enters an odourisation unit to add odour so that leaks can be detected, before entering the vehicle or storage tanks. Used water flows to a flashcolumn to desorb any dissolved gasses. The pressure is reduced so that the methane desorps preferentially to the carbon dioxide and hydrogen sulphide. The off gas from the flash column contains between 5 and 10% methane by volumeso is recycled to the front end of the process to optimise scrubbing efficiency From the flash column, water flows to the main desorption column where the bulk of the carbon dioxide and hydrogen sulphide are released. To enhance gas desorption, the column can be operated under negative pressure, or air can be passed through the bottom of the column. The water is pumped by a 1.1kW pump from the desorption column to a buffer tank and is cooled from 8 degrees to 5 degrees before returning to the scrubbing cycle. Before being vented to atmosphere, the off gas can be passed through a biofilter to remove the hydrogen sulphide, but if the plant is not located near odour receptors, offgas is vented safely direct to atmosphere. Figure 13:- Metener simple upgrade process flow diagram Table 2:- Metener simple upgrade major components list 1 Inlet biogas stream 10 Product gas outlet to storage / vehicle 2 Inlet flow meter 11 Flash column 3 Primary biogas compressor 12 Desorption column 4 Pressure regulator 13 Off gas blower 5 Non-return valve 14 Off gas outlet to biofilter 6 Packed media scrubbing column 15 Water recirculation pump Small-scale biogas upgrade for vehicle fuel 16

19 7 Pressure relief valve 16 Water buffer and cooling tank 8 Product gas flow meter 17 High pressure water pump 9 High pressure compressor Engineering scope The Metener simple upgrading plant (capacity 5m 3 /h and 25m 3 /h) is skid-mounted and designed for easy access to major components. It has been developed for plug and play installation. The process pipelines and columns are manufactured from Class D or E PVC pipe. The compressor for compressing the raw biogas is a modified workshop-type compressor that is equipped with a cast iron cylinder and stainless steel reed valves. The columns are packed with an appropriate medium sized for the application. Low pressure pipelines are made from 1 PVC pipe, and high pressure pipes will be 10mm stainless steel pipe. If upgraded biogas is stored, the storage cylinders are seamless steel and pressure rated in excess of 250 bar. The plant is equipped with PLC control, full instrumentation to enable automatic operation and gas monitoring instrumentation. The upgrade plant user interface is a touch-screen scada system with data logging capacity. The percentage of methane in the upgraded gas from the main scrubber column is determined by the flow rate of water through the column and can be varied as required. This can be between 85 and 97%. The upgraded gas passes either to storage or to an additional compression phase depending on what the final use will be Energy balance The upgrading process requires energy input, and the amount of energy used is influenced by the degree of purity of the upgraded gas. Table 5 illustrates the two scenarios: They are for upgrading to 85% methane from 55% methane with an input rate of 5m 3 per hour and 25m 3 per hour. Small-scale biogas upgrade for vehicle fuel 17

20 Table 3:- Energy balance for Metener simple upgrade system. All gas volumes are normalised. Biogas flow rate 5m 3 /h 25m 3 /h Raw biogas CH 4 concentration % Upgraded biogas CH 4 concentration % Upgrading Pressure bar Input biogas flow rate m 3 /h 5 25 Total system power kw Product gas flow rate m 3 /h Product gas flow rate kg/h Energy consumption /unit volume of product gas kwh/ m Energy consumption /product gas kwh/kg Energy produced /energy consumed The bottom row refers to the ratio of energy produced in terms of kwh per kg of product gas relative to the amount of energy consumed by the upgrade facility in kwh Mass balance Table 4:- Mass balance for Metener simple upgrade system. All gas volumes are normalised. Biogas flow rate 5m 3 /h 25m 3 /h Methane content of biogas % (v/v) CO 2 content of biogas % (v/v) Total Moisture and H 2 S content of biogas % (v/v) 1 1 Density of biogas kg/m Mass flow-rate of biogas kg/h CH 4 content of upgraded gas (before dryer) % (v/v) CO 2 content of upgraded gas (before dryer) % (v/v) H 2 O content of upgraded gas (before dryer) % (v/v) H 2 S content of upgraded gas (before dryer) ppm <10 <10 Density of upgraded gas kg/m CH 4 input flow rate as a component of biogas m 3 /h CH 4 loss during upgrade process % (v/v) 1% 1% Volume flow rate of product gas m 3 /h Mass flow rate of product gas kg/h CO 2 released to the environment m 3 /h CO 2 released to the environment kg/h CH 4 slip (volume flow rate) m 3 /h CH 4 slip (mass flow rate) kg/h Water flow in (no recycle) m 3 /h Water flow out (no recycle) m 3 /h Water flow in (recycle) m 3 /h Water flow out (recycle) m 3 /h Small-scale biogas upgrade for vehicle fuel 18

21 The mass and energy balance figures have been provided by Metener Oy. Slight differences appear between the mass flow rate of product gas given in the energy balance and the mass balance, but the two figures are well within range of each other so are representative of expected values Economics a) Cost of construction Item Cost ( ) 5m 3 /h Cost ( ) 25m 3 /h Low pressure compressor 5,000 6,000 Scrubbing columns and packing materials 20,000 20,000 Proportional valves 5,000 5,000 Instrumentation 10,000 10,000 Main water scrubbing pump ( 4,000 6,000 Desorption column water discharge pump 500 1,000 Containerisation, insulation and installation 4,000 4,000 Compressor to 250 bar 6,500 10,000 Cost of materials 55,000 62,000 Cost of labour 10,000 10,000 Total cost 65,000 72,000 b) Operational and maintenance costs: both scales Labour Spare Parts Desiccating Medium 0.05/kg product gas 0.05/kg product gas Dry every 3000kg product gas The desiccating medium is dried by placing on a tray in an oven for 1hour at 250 degrees C so the cost is negligible. Hydrogen sulphide is generally vented to atmosphere, although where necessary a simple filter or activated carbon scrubber could be fitted. The cost of this item was not investigated as the quantity of hydrogen sulphide released is negligible. Plant water consumption is also minimal as the water can be re-used through the process several times Operational parameters The raw biogas flow must be maintained at constant rate as the upgrade process is continuous. The gas composition must not vary and a supply of replacement water should be available to the plant. The upgrade unit is equipped with gas monitoring equipment to enable the product gas quality to be kept constant, as it is water throughput that governs the purity of the product gas. The upgrade facility has an automatic shutdown facility in the event that the storage capacity is reached or a problem is detected. In the event of shutdown, the upgrade unit sends a fail signal to the AD plant control system to allow biogas to be diverted elsewhere on Small-scale biogas upgrade for vehicle fuel 19

22 the biogas plant, either in a CHP unit or burned safely to prevent fugitive methane emissions to atmosphere. 6.2 Green Brick Eco Solutions Water scrubbing technology as patented by IIT Delhi is one of the cheapest and most viable solutions for biogas purification, and multiple purification plants are in operation throughout India. GBES did not provide the degree of process detail by comparison to the other technologies assessed, but we are able to give a thorough overview of the core process and engineering scope Process description The IIT Delhi upgrade unit s core components are a scrubbing column, a water supply system, a low pressure compressor, a buffer storage vessel, and a high pressure compressor for bottling the product gas. Raw biogas is pressurised and stored in a buffer tank before entering the scrubbing column from the base. Water is pumped into the scrubbing column from the top and carbon dioxide and other impurities dissolve into the water. The water is removed from the base of the scrubbing column to prevent flooding of the packed media. The water is channelled to a desorption tank for the carbon dioxide and hydrogen sulphide to diffuse out of solution before being returned to the scrubbing column. The process is considered to be a closed loop, and GBES did not specify the degree of water loss / replenishment required during the scrubbing operation. GBES describe the product gas as having a methane content >95%. Figure 14:- IIT / GBES schematic diagram Small-scale biogas upgrade for vehicle fuel 20

23 6.2.2 Engineering scope In addition to the above core of the upgrade unit, the GBES purification system contains the following equipment 4 :- Knock-out drum on incoming biogas line Biogas compressor Biogas receiver-1 Scrubbing tower Knock-out drum-2 Purified gas receiver-2 High pressure compressor Heat exchanger Water pump Dryer (dehumidifier) Two-cylinder set for purified biogas filling/storage Dispensing unit for vehicle filling Instruments: flow-meters/pressure gauges etc. Ball-valves/safety valves/check-valves etc. Piping/fittings/strainers etc. Electrical fittings/panel etc. Gas analysers for: CH 4, CO 2, H 2 S, moisture content Table 5:- GBES/IIT drive specifications Biogas Flow Rate 5m 3 /h 25m 3 /h Biogas Compressor Specification Flow rate 6m 3 /h 25m 3 /h Medium Biogas Biogas Input pressure Atmospheric Atmospheric Output pressure 10 bar 12 bar Water Pump Specification Flow rate 1.2 m 3 /h 4 m 3 /h Delivery pressure 10 bar 10 bar Medium Water Water High Pressure Compressor Specification Flow rate 3.5 m 3 /h 16 m 3 /h Medium Product gas Product gas Input pressure 8 bar 8 bar Output pressure 200 bar 200 bar 4 Vijay et al. The 2nd Joint International Conference on Sustainable Energy and Environment (SEE 2006) November 2006, Bangkok, Thailand Small-scale biogas upgrade for vehicle fuel 21

24 6.2.3 Mass and energy balance GBES provided Evergreen Gas with details of both the 5m 3 /h and 25m 3 /h upgrade plants upgrading to a product gas purity of >95% CH 4. The mass balance is as follows, although it does not take into account water losses from the closed loop system which requires topping up at a rate of litres per cubic metre of raw biogas upgraded. Water flow rate is in the range of 0.7m 3 to 1m 3 per hour for 5m 3 /h biogas inlet rate, but GBES did not advise what this figure would be for the 25m 3 /h variant, although given that the water circuit is a closed loop and we know what the water losses to evaporation are per cubic metre of raw biogas, this will not overly affect the mass balance. We would expect the flow rate for the scrubbing water to be five times faster for the 25m 3 /h variant. Table 6:- IIT / GBES mass balance at 5m 3 /h and 25m 3 /h biogas input. All gas volumes are normalised. Biogas flow-rate 5m 3 /h 25m 3 /h CH 4 content of biogas % (v/v) CO 2 content of biogas % (v/v) Total H 2 O and H 2 S content of biogas % (v/v) 1 1 Density of biogas kg/m Mass flow rate of biogas kg/h 6 30 CH 4 content of upgraded gas (before dryer) % (v/v) CO 2 content of upgraded gas (before dryer) % (v/v) 4 4 H 2 O content of upgraded gas (before dryer) % (v/v) 1 1 H 2 S content of upgraded gas (before dryer) ppm <20 <20 Density of upgraded gas kg/m CH 4 input flow rate m 3 /h 3 15 CH 4 loss during the upgraded process % (v/v) ~ 0 ~ 0 Volume flow-rate of upgraded gas m 3 /h Mass flow rate of upgraded gas kg/h ~2.41 ~12.1 CO 2 released to the environment m 3 /h CO 2 released to the environment kg/h The above figures make the assertion that there is no methane slip through the upgrade process. Methane slip is the expression to describe methane that is lost from the product gas and is released to atmosphere with the carbon dioxide and other impurutues that are removed through the scrubbing process Economics a. Capital Cost 5m 3 /h inlet gas flow rate: INR 4,000,000 EXW ( 50,000) 25 m 3 /h inlet gas flow rate: INR 6,500,000 EXW ( 81,250) b. Operational and maintenance costs Small-scale biogas upgrade for vehicle fuel 22

25 GBES recommend that a single semi-skilled operative can operate both sizes of plants. The only details of consumables given are water which must be topped up at a rate of m 3 per m 3 of raw gas. Minimal maintenance is required for this type of plant, and a budget has been given (basis India) as INR 150 ( 1.60) per day for the smaller plant and INR 200 ( 2.50) per day for the larger plant. Electricity consumption given by GBES for upgraded product gas compressed to 250bar for the 5m 3 /h plant is 1.86kWh/kg and 0.80kWh/kg for the 25m 3 /h raw biogas plant. The difference is due to the fact that equipment for such low capacity (i.e. 5n.m 3 /hour) is not readily available in India. The exact figures for above values are subject to availability of equipment for particular flow-rate/capacity Operational parameters We do not know a great deal about the operational parameters of the IIT plant, as there are no examples of this type of plant that we are aware of in Europe, so operational data is drawn from numerous scientific papers authored by Professor Vijay that document the performance and development of the process. Please see Appendix 2 for further details. A spokesman from GBES has told us that GBES has co-developed an improved version of the upgrade process in collaboration with IIT. 6.3 Chesterfield Biogas Initially, Evergreen Gas set out to assess the feasibility of small-scale biogas upgrade to vehicle fuel using Metener and IIT/GBES technology at 5m 3 /h and 25m 3 /h raw biogas flow rate. During the research, we became aware that Chesterfield Biogas is developing a small scale biogas to vehicle fuel upgrade unit that fitted our requirements. While the unit is currently at the prototype testing stage, it deserves a mention as Chesterfield Biogas is a well-established company with extensive experience of biogas upgrade. Rather than using water scrubbing, the Chesterfield Biogas technology employs a variant of Pressure Swing Adsorption (PSA) to scrub the gas Process description Raw biogas at a flow rate of between 5m 3 /h and 40m 3 /h enters the upgrade unit from the AD plant at low pressure (20-50mbar). The incoming gas is compressed to a working pressure of 1 bar. The system is a 5 vessel system comprising buffer storage, gas processing and stripping, recirculation and outgoing buffer storage vessels. Hydrogen sulphide is removed from the incoming biogas stream in a scrubbing vessel using a replaceable scrubbing medium. This medium must be replaced every six months. A vacuum pump is used to strip the carbon dioxide from the scrubbing medium, and hydrogen sulphide is removed by adsorption into a scrubbing medium. Outgoing upgraded gas is piped to a refuelling compressor for direct vehicle refuelling, or alternatively compressed into bulk cylinder storage for future dispensing requirements. Process pipework is 10 bar-rated PVC and gas routes are controlled with solenoid valves. The plant is equipped with a remote panel that consists of a gas analysis panel, main control panel and variable speed drive control panel. The pressure vessels are Small-scale biogas upgrade for vehicle fuel 23