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Renewable Obligations Certificates

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THIS PAGE WAS LAST MODIFIED IN MARCH 2009 AND REQUIRES UPDATING – If you wish to provide an update then please contact:

In an e-mail message from Ofgem dated 1st July 2010 we read:

Ofgem is the administrator of the Renewables Obligation (RO). The RO policy and legislation is set by the Department of Energy and Climate Change (DECC) and Ofgem administers the scheme against the requirements set out in this legislation. It wouldn’t be in our remit to contact councils directly and discuss with them what decisions they are planning to make and/or influence those decisions.

To provide you with some brief background, in order for a generating station to be eligible to receive Renewable Obligation Certificates (ROCs) they must first seek accreditation from Ofgem. This accreditation confirms that the generating station is capable of generating electricity from a renewable source. The accreditation of ‘fuelled’ stations also requires the operator of the generating station to agree how the renewable proportion of their energy source will be monitored in order to meet the requirements set out in legislation. ROCs are issued to accredited generating station based on net renewable generation. For fuelled stations, the fuel is sampled using the process agreed during the accreditation process, factoring in the calorific value of the fuel being burnt, and this is then used to determine the renewable generation for ROC claim purposes.

You may be interested to read the RO generator guidance for more information on the operation of the RO:

You may also be interested to read more about fuel measurement in our FMS guidance:

The following update on Renewable Obligations Certificates was kindly supplied to UKWIN by Public Interest Consultant Alan Watson.

ENDS [1] reported on the outcome of the Renewable Obligations Certificates (‘ROCs’) consultation in January 2009:

The rest of the consultation response is dominated by technical changes to the obligation. However, two issues stand out:

Concerns have been raised that gasification and pyrolysis plants being developed to treat waste are no more efficient than conventional incineration.  BERR will now set eligibility criteria for such processes if they want to claim support under the RO. More efficient plants will receive 2 ROCs per megawatt hour of electricity produced; less efficient plants will receive only 1 ROC.

Unfortunately this short summary doesn’t explain why the Government is supporting such inefficient technologies.

A review by Fitchner for the Environmental Services Association shows that the Energos facilities are just 14% efficient plants [2]. A clue may be found in the recent news item reporting Energos are  celebrating the success of the lobbying on their behalf by minister Hazel Blears [3]. Incredibly Energos seem to think that the outcome is so successful that they may still be able to claim double ROCs…


The consultation on the Renewables Obligation 2009 included a report by AEA [4] which said:

Advanced Conversion Technology (ACT)

The reform of the RO will bring with it commercial pressures to classify processes as ACT, even where this could be considered marginal. In particular there is likely to be pressure to describe certain types of incinerator as ACT because of their combustion chemistry.

To succeed in its objective of support for ACT and to prevent overcompensation of conventional plant the RO needs more precise and practical definitions that allows for more efficient regulation. We understand that the intent behind support for ACTs is to encourage processes that produce a gas or liquid fuel that contain as much as possible of the waste’s heating value in its chemical energy so that it can be used effectively in an independent generator, be it engine, gas turbine or boiler.

For gasification and pyrolysis we propose that this is dealt with by setting a criterion that the gas or liquid fuel produced has a minimum gross calorific value that allows its independent use.

And in the text on page 6:

Differences between ACTs and incinerators

* Anaerobic digestion is a fundamentally different process based on biological processes.

* A combustion process will contain zones where the chemical reactions of pyrolysis and gasification take place but the products of these reactions are burned immediately within the apparatus. The calorific value of the waste is released into the apparatus and the sensible heat of the flue gasses coming from it. None of the calorific value is in the form of a fuel gas.

* A variant on the normal incinerator is the two stage incinerator where a substoichiometric first chamber feeds a hot gas into a second chamber where combustion is completed. Most of the energy in the waste is transferred into the sensible heat of the hot gas with little as chemical energy. The gas at the transition would not be capable of viable independent use if cooled and transferred.

This was a particularly useful clarification which deserved support – not least because it defines the crude old “starved air” plants like those promoted by Energos out of ACTs. The cross-section of the Energos plant shows that the grate and the secondary combustion chamber are closely linked and this is really a two stage incinerator.

The Government backed down significantly in their response [5] and set two thresholds for the energy of the gas “at the inlet to the generating station” . It is arguable, though not at all clear, that this maintains the requirement for the gas should be capable of independent use.  They have, however, also committed to carry on giving lifetime ROCs to “prebanded” existing plants which are really just standard incinerators.

The thresholds used for the syngas are incredibly low when compared with those from the Environment Agency BAT review [6]:


SLR reported [7] similar calorific values in their work for the GLA:

Three product gas qualities can be produced from gasification by varying the gasfiying agent; the method of operation; and the process operating conditions. The main gasifying agent is typically air but oxygen/steam gasification and hydrogenation are also used. Catalytic steam gasification is another mode of operation that influences both the overall performance and efficiency.

The three types of product gas have different CVs:
* Low CV: 4-10MJ/Nm3 using air and steam/air
* Medium CV: 12-18MJ/Nm3 using oxygen and steam
* High CV: 40MJ/Nm3 using hydrogen and hydrogenation

The typical net CV of syngas from gasification using oxygen is 10-15 MJ/Nm3 and 4-6 MJ/Nm3 using air: in comparison, natural gas is 38MJ/Nm3. Gasification offers the potential of using syngas for uses other than immediate combustion to produce heat, such as a fuel for gas engines/turbines, as feedstock for producing chemicals or for liquid fuel production.

Why on earth should support at 1 ROC/MWh be given to plants which have syngas that is just 40% of the lower level of the BAT guidance?

And why should the Minister intervene to support ROCs subsidy for a technology which the Government’s consultants have made clear is just a two stage incinerator?

Can it be because the Minister intervened on behalf of Energos?

And why, if Energos and ENER-G PLC are so proud of their technology, have they refused to release copies of their own response to the consultation? [8]


1 ENDS (2009): More biomass co-firing allowed under Renewables Obligation Report 408, January 2009, p 51
2  Fitchner Consulting Engineers Ltd (2004). The Viability of Advanced Thermal Treatment of MSW in the UK London, for the Environmental Services Association (ESA).
3   New Energy Focus (2009)  Gasification firm celebrates securing renewable energy subsidies 17-02-09
4   AEA Energy & Environment (2008). Renewables Obligation: Defining the different types of electricity generation using biomass and waste  2 June 2008
Issue Number 1 ED43479 Restricted Commercial Final Report to The Department for Business, Enterprise and Regulatory Reform.
5   Department of Energy and Climate Change (2008). Reform of the Renewables Obligation – Government Response to the Statutory Consultation on the Renewables Obligation Order 2009 December 2008.
6 Higham, I., I. Palacios, et al. (2001). Review of BAT for New Waste Incineration Issues Part 1 Waste Pyrolysis & Gasification Activities Technical Report P4-100/TR November 2001, AEA Technology Environment for the Environment Agency.
7 SLR Consulting for GLA (2008). Costs of incineration and non-incineration energy-from-waste technologies.
8 Leah, G. (2009): DECC, Personal correspondence 18th February. “Whilst we did receive responses from ENER-G PLC and ENERGOS Limited respectively, they requested in both cases that these remain confidential.  “

The full Government Response was:

2.13 In the statutory consultation we set out our proposals for a revised definition of gasification/pyrolysis to replace the current definition of ACT. The definition reflects our policy intent to provide gasification/pyrolysis (along with anaerobic digestion) with an increased level of support (2 ROCs/MWh) where it presents potential advantages in efficiency for using biomass and waste over standard incineration4.

2.14 Given our policy intent, the definition of gasification/pyrolysis needs to ensure that it can be clearly differentiated from standard incineration. The revised definition, was based on a report commissioned by us from AEA Technology and included in the statutory consultation, took both these objectives into consideration in setting a minimum gross calorific value for the gas produced allowing it to be used effectively in an independent generator.

2.15 The majority of respondents on this topic agreed with the need to differentiate between gasification/pyrolysis and standard incineration. However, some felt that the threshold proposed in the new definition was too high and would not only exclude incineration but also gasification/pyrolysis generating stations that produce syngas of a lower calorific value, but are currently supported by the RO.

2.16 Those affected argued that such a change would remove support for technologies in which they have invested in expectation of ROC support and could encourage wasteful processing of feedstock simply to meet the qualifying criteria. Following further analysis of the efficiencies of various incineration, gasification and pyrolysis technologies we remain of the view that gasification/pyrolysis which does not meet the minimum threshold is likely to have little or no efficiency gains over incineration.

2.17 However, we understand that investor confidence is critical – especially in the current financial situation – and we have therefore decided to introduce two definitions for gasification and pyrolysis, in addition to the pre banded (ACT)
definition. The first (”advanced gasification/pyrolysis”) will reflect the recommendations of the AEA report that technologies receiving 2 ROCs/MWh will need to demonstrate that the syngas at the inlet to the generating station when measured at 25 Celsius and 0.1 megapascals has a gross calorific value of at least 4 megajoules per cubic metre. The second (“standard gasification/pyrolysis”) will mean that those that have already invested in gasification/pyrolysis technologies that produce syngas of a lower calorific value will receive support of 1 ROC/MWh where they can demonstrate that the syngas at the inlet to the generating station has a gross calorific value of at least 2 megajoules per cubic metre when measured at 25 degrees Celsius and 0.1 megapascals. No ROCs will be granted for electricity generated from fuel that does not meet the requirements of the “Standard” or “Advanced” gasification or pyrolysis bands, unless the generating station meets the accreditation deadlines for the “Pre-banded Gasification/Pyrolysis” bands.

2.18 We will, continue with our intention to phase out the current definition of ACTs. However, stations which have been accredited under this definition, now called Pre-banded Gasification/Pyrolysis, or have achieved preliminary accreditation
by 31st March 2009 and full accreditation by 31st March 2011, will continue to receive 1 ROC/MWh. No ROCs will be awarded for electricity which is produced by a generating station which does not meet the above accreditation deadlines. The ROO includes drafts of the new definitions of the “Advanced”, “Standard” and “Prebanded” gasification and pyrolysis bands. The draft ROO will be further amended to provide that ROCs will not be issued in respect of electricity produced from gasified or pyrolysed fuels which does not qualify for any of these bands.