Biogas


The case for biogas upgrading in the UK


Should the UK consider the option of biogas upgrading? Dr Adam Read and Frank Hofmann explore the potential opportunities of biogas upgrading and make reference to two exemplar projects in The Netherlands and Germany where this technology is being used successfully on a large scale.


Dr Adam Read (right) Global practice director for resource efficiency and waste management, AEA Frank Hofmann, Ecofys


D


EFRA’S RECENTLY published anaerobic digestion strategy and action plan reiterated the UK government’s commitment to increasing energy from waste through anaerobic digestion


(AD) in the UK. Through the application of AD a versatile


form of energy in the form of biogas becomes available, something that the UK is keen to exploit given its target for renewable energy generation. A number of options are available for its use. It can be used to fire boilers for heat production, as a fuel for cogeneration (CHP) units to produce heat and electricity or it can be upgraded to natural gas quality and injected into the gas grid or used directly as a vehicle fuel. In a country where purchasing fuel, heat or


power from such AD sources is not obligated on energy suppliers, any investor needs to tread with care and ensure that the chosen market and the technologies are compatible with the proposed project. For specific waste treatment projects the final choice of AD treatment option will depend on a number of considerations. For example: • Is it possible to match the demand for energy with a steady production of biogas?


• Is it possible to use the heat with sufficient effectiveness in case of cogeneration?


• What is the distance to the gas grid and what is the capacity that can be replaced by upgraded biogas (biomethane)? The points mentioned above are all


linked to biogas production, site and market characteristics, all of which provide insight into the technical, economic and commercial feasibility. In turn the way that financial incentives for AD are structured in the form of the feed-in tariff (FIT), the renewables obligation, the renewable heat incentive (RHI) and the renewable transport fuel obligation (RTFO) also have great influence. The fact file above shows how the financial incentives in place for AD vary according to the end- use application. In this example, the tariff available for biomethane injection to the grid is up to twice that for electricity generation. The revenues from biomethane production


can therefore be up to 70% higher than for electricity production alone. The available experience with upgrading in the UK, however, is limited and this lack of track record may be considered a serious barrier to short term investment. However, looking at the wider picture and including European experience, the outlook changes significantly. In Europe over 10,000 biogas plants are


running at a commercial scale. Production of biomethane is realised in over a 100 operational upgrading plants, some of which have been in operation for more than 20 years. Two case studies of biogas upgrading


plants are presented here to demonstrate the potential relevance of this technology for the European market and could serve as examples for new opportunities in the UK.


Recycling & WA S T E W O R L D www. r e c y c l i n gwa s t ewo r l d . c o . u k


Carbiogas Plant near Eindhoven, the Netherlands One of the pioneering plants in this field has been the Carbiogas Plant near the city of Eindhoven in the Netherlands. The unit was designed by the company


Cirmac in 1989 and has been operational since 1990. The technology applied is known as vacuum pressure swing absorption (VPSA). The unit operates on landfill gas extracted


form the second largest landfill site in the Netherlands. At its peak the plant handles more then 13 of landfill gas per year, yielding of pseudo natural gas (PNG).


million m3 eight million m3 This scale is equivalent to the upper range


of the AD applications we are likely to see in the UK (8MW biogas; ~3 MWe). Presently production is lower, since the landfill operation ended in 2003 and the amount of landfill gas is now decreasing. Similar uncertainties as those being


experienced in the UK played a role in establishing this project. Factors to overcome included:


• A European subsidy of 500 kEuro was provided, which represented 25% of the overall investment in the upgrading plant; and


• The stakeholders actively participated in the project and together formed an operating company, including the landfill operator, the party responsible for the design and operation of the gas extraction system, Cirmac as supplier of the upgrading plant, and the local utility company that accepted the upgraded biogas in its network. The plant is still in operation today and is looking for ways to extend the input of biogas


to compensate for the decreasing quantities of landfill gas. Construction of an AD facility at the site is being currently considered. It should be noted that the natural gas


quality distributed in the Netherlands is somewhat lower than that in the UK (~88% vs ~97%). This means that the requirements for upgrading are less stringent and that higher quantities of PNG per m³ of biogas can be produced. In Germany, the requirements for accepting


upgraded biogas are similar to those that apply in the UK. To meet these requirements an almost complete removal of the CO2


contained


in the biogas is required in addition to a small injection of propane to reach the demands for caloric value and the Wobbe-index.


Biogas upgrading plant in Könnern, Germany In Könnern, Germany, a biogas plant is running with a capacity of 3,300 m³/hr biogas production and is one of the largest biogas upgrading installations worldwide (pictured below). The biogas production is approximately twice that of the Carbiogas plant discussed in Eindhoven. The plant mainly uses energy crops and some manure as a feedstock (14%). The biogas is upgraded to biomethane in an amine scrubbing facility. The strong point of this technology is the


low internal energy demand and the very high efficiency with which biogas is converted into biomethane. The overall loss of methane is less then


0.1%. Additionally, the amine scrubbing technology offers methane purity of up to 99%, which meets the UK gas grid specification. Amine scrubbing can also be used to upgrade biogas from waste treatment


The biogas plant in Könnern, Germany, is one of the largest biogas upgrading installations worldwide and mainly uses energy crops and some manure as a feedstock. The overall loss of methane is less than 0.1%


Fact File


THE TARIFF for biomethane injection to the grid in the RHI is currently set at 6.5 p/kWh per m3


m³ of biogas, 0.5 m3


of biogas (55% methane). From 1 of biomethane can be


separated, taking the heat demand of the digester of 10% of the biogas into account. This 0.5 m3


energy content of 4.9 kWh, which converts to a revenue of 32 p per m3


of biomethane represents an of biogas.


large scale AD (>500kWe) is currently set at 9.4 p/kWh per m3


For comparison, the FIT for electricity from of biogas. Around 2.2


kWh of electricity can be produced, of which 90% (2kWh) can be exported to the grid. This gives a revenue of up to 19p per m3 biogas.


of


or agricultural biogas plants, as well as for landfill gas and sewage gas. This plant is capable of generating around


166 GWh biomethane per year (~17 million m3


) which can be injected into the gas grid.


The typical investment costs of such an upgrading plant are about £2.6m (€2.6m), on top of the £21.7m (€25m) for the biogas plant itself. The specific costs for biomethane


production are about 6.5 p/kWh (7.5 ct/kWh), while the upgrading costs are about 1.1 p/kWh (1.3 ct/kWh). Clearly the UK is in a state of flux with


significant government policy and financial support being directed at AD development as a form of renewable energy generation and waste treatment.


Considering the biogas production option Significant development is expected with numerous plants in the planning process and a number of local authorities out to procurement. With much planned growth in the sector, perhaps the UK needs to look more closely at the option of biogas production, something which remains off the UK policy agenda at present? Clearly, the choice of AD technology type


for any project/site will be dependent on the guaranteed feedstock quality and supply, and decisions regarding biogas production will inevitably be informed by the availability of suitable and local end users for the biogas, the length of contracts that can be secured for the AD products and the ongoing availability of government subsidies. There will always be conflicting priorities


when selecting AD technology type and process, with the inevitable one in the UK being future potential for heat use or grid gas injection, and the need for smaller and more local solutions with secure feedstock’s and end markets and larger facilities that have variable inputs and outputs. Clearly, the market is developing and the


role of biogas upgrading needs closer attention during these developmental times. If it is good enough for Europe then it should be good enough for the UK.


Plant costs have been converted from Euros to GBP using an exchange rate of 1.15:1.


December 1 2011 7 RWW


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