Anaerobic Digestion: Difference between revisions
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[[Category:Technologies & Solutions]] | [[Category:Technologies & Solutions]] | ||
[[Anaerobic Digestion]] ([[AD]]) is a process where biodegradable material is broken down by micro-organisms in the absence of oxygen in an enclosed vessel. The process produces a [[Biogas]] which can be used for generating renewable power and a nutrient-rich solid/liquor known as [[digestate]] which can be used as fertiliser and compost. Anaerobic Digestion uses biodegradable waste materials from [[Agricultural Waste]] such as manure and slurry, [[Food Waste]] and [[Sewage Sludge]]. Where the process utilises [[Animal By-product Material]], it must comply with the [[Animal By-Products (Enforcement) (England) Regulations 2011]] requirements. | |||
[[File:Biogen AD plant.jpg|400px|left|Biogen Ad Plant in Gwynedd 11,500 tonnes of food waste per year - source Biogen.co.uk]]__TOC__ | [[File:Biogen AD plant.jpg|400px|left|Biogen Ad Plant in Gwynedd 11,500 tonnes of food waste per year - source Biogen.co.uk]]__TOC__ | ||
__TOC__ | |||
==Overview== | ==Overview== | ||
'''Anaerobic Digestion''' (AD) is a process where biodegradable material is broken down by micro-organisms in the absence of oxygen in an enclosed vessel. [[Biogas]] is produced that can be used for the generation of power ( | '''Anaerobic Digestion''' (AD) is a process where biodegradable material is broken down by micro-organisms in the absence of oxygen in an enclosed vessel. [[Biogas]] is produced that can be used for the generation of power (electric and heat), or refined and used as a 'biomethane', and [[Digestate]] is produced which can be used as a 'biofertiliser'. | ||
[[File:NEW AD diagram LR.jpg|600px|left]]<ref>[http://www.abdabioresources.org/about-ad/what-is-it/ The AD Cycle - Reproduced from the [[ABDA]] website]</ref> | [[File:NEW AD diagram LR.jpg|600px|left]]<ref>[http://www.abdabioresources.org/about-ad/what-is-it/ The AD Cycle - Reproduced from the [[ABDA]] website]</ref> | ||
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The broad classifications by feedstock that can be used in AD are summarised in the table below including both waste and non-waste materials (with crops including maize, grass silage, energy beet and whole crop cereals) : | The broad classifications by feedstock that can be used in AD are summarised in the table below including both waste and non-waste materials (with crops including maize, grass silage, energy beet and whole crop cereals) : | ||
[[ | |||
{|class="wikitable" | |||
![[BEIS]]!![[NNFCC]]!![[ADBA]]!!Feedstock | |||
|- | |||
|rowspan=5| Anaerobic Digestion||rowspan=3|Farm AD||rowspan=3|Agriculture||[[Agricultural Waste]] (incl. manures and slurries) | |||
|- | |||
|Crops (incl. silage and whole crops) | |||
|- | |||
|[[Food Waste]] ([[MSW]] and [[Commercial Waste]] sources) | |||
|- | |||
|rowspan=2|Food AD||rowspace=1|MSW/Commercial Waste||[[Food Waste]] ([[MSW]] and [[Commercial Waste]] sources) | |||
|- | |||
|Industrial||[[Food Waste]] (at the origin of the waste, incl. [[Industrial Waste]]) | |||
|- | |||
|Sewage Sludge Digestion||Sewage Sludge AD||Sewage Sludge|| [[Sewage Sludge]] (at water treatment site) | |||
|} | |||
This classification can be further divided by the nature of the [[Food Waste]] (i.e. [[Animal By-product Material|ABPR]] and non-[[Animal By-product Material|ABPR]] material) - where the process utilises [[Animal By-product Material|ABPR]] materials, it must comply with the [[Animal By-Products (Enforcement) (England) Regulations 2011]] requirements and some Agricultural plants, for example, only utilise non-[[Animal By-product Material|ABPR]] material so as to avoid the need to comply with these requirements. Additionally, the three different feedstocks in the 'Agricultural' classification can be co-digested in different combinations to optimise plant productivity and yield of [[biogas]] and can be talked about in those terms.[[Sewage Sludge]] doesn't tend to be blended with other materials and tends to be a dedicated AD solution in its own right - primarily as it becomes impossible to to deliver [[End of Waste Criteria|End of Waste]] [[digestate]] with the introduction of [[Sewage Sludge]] as an input feedstock. | This classification can be further divided by the nature of the [[Food Waste]] (i.e. [[Animal By-product Material|ABPR]] and non-[[Animal By-product Material|ABPR]] material) - where the process utilises [[Animal By-product Material|ABPR]] materials, it must comply with the [[Animal By-Products (Enforcement) (England) Regulations 2011]] requirements and some Agricultural plants, for example, only utilise non-[[Animal By-product Material|ABPR]] material so as to avoid the need to comply with these requirements. Additionally, the three different feedstocks in the 'Agricultural' classification can be co-digested in different combinations to optimise plant productivity and yield of [[biogas]] and can be talked about in those terms.[[Sewage Sludge]] doesn't tend to be blended with other materials and tends to be a dedicated AD solution in its own right - primarily as it becomes impossible to to deliver [[End of Waste Criteria|End of Waste]] [[digestate]] with the introduction of [[Sewage Sludge]] as an input feedstock. | ||
===Definition by Output=== | ===Definition by Output=== | ||
The broad classifications by output are summarised in the table below: | The broad classifications by output are summarised in the table below (broadly by [[ADBA]] on their on-line map<ref name="Map">[http://adbioresources.org/map ADBA AD Map]</ref>, but primarily by [[Ofgem]] via the different subsidy scheme requirements, but also [[BEIS]] via the Digest of UK Energy Statistics<ref name = "DUKES">[https://www.gov.uk/government/statistics/digest-of-uk-energy-statistics-dukes-2019 National Statistics: Digest of UK Energy Statistics (DUKES) 2019]</ref> and the [[DOT]] via the reporting on Road Transport Fuels<ref>[https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/790538/rtfo-annual-report-2017-2018-web.pdf RTFO Annual Report 2017-18]</ref>): | ||
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* consists of both of the above (i.e. Farm AD that is multi-streamed). | * consists of both of the above (i.e. Farm AD that is multi-streamed). | ||
The banding levels shown for the various subsidies relate to different subsidy rates in each band and are referred to in this page and the associated subsidy pages and links. | The banding levels shown for the various subsidies relate to different subsidy rates in each band and are referred to in this page and the associated subsidy pages and links. | ||
The Statutory Guidance for AD facilities including the use of the resultant biogas can be found here<ref>[https://www.gov.uk/government/publications/sr2021-no-6-anaerobic-digestion-facility-including-use-of-the-resultant-biogas-installations?utm_medium=email&utm_campaign=govuk-notifications-topic&utm_source=9ca610e6-b14a-4823-bb2b-77175d62080c&utm_content=daily SR2021 No.6: anaerobic digestion facility, including use of the resultant biogas - installations]</ref>. | |||
===The Chemical Process of AD=== | ===The Chemical Process of AD=== | ||
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==Growth in Anaerobic Digestion== | ==Growth in Anaerobic Digestion== | ||
Whilst the introduction of the [[Renewables Obligation]] in 2002 started to stimulate growth in larger AD projects (including 'Food AD' and 'Sewage Sludge AD') it was only really with the introduction of The [[FIT]] scheme in 2010 that the AD market really started to grow, stimulating smaller projects and especially 'Farm AD' based on crops, [[Agricultural Waste]] and in some cases [[Food Waste]]. This was also enabled by investment tax benefits for investing in these projects ([[EIS]] and [[SEIS]] especially, which reduced in impact with changes to the schemes in 2015/16 leading to less investment stimulus. | Whilst the introduction of the [[Renewables Obligation]] in 2002 started to stimulate growth in larger AD projects (including 'Food AD' and 'Sewage Sludge AD') it was only really with the introduction of The [[FIT]] scheme in 2010 that the AD market really started to grow, stimulating smaller projects and especially 'Farm AD' based on crops, [[Agricultural Waste]] and in some cases [[Food Waste]]. This was also enabled by investment tax benefits for investing in these projects ([[EIS]] and [[SEIS]] especially, which reduced in impact with changes to the schemes in 2015/16 leading to less investment stimulus). | ||
With greater focus on the collection of separate [[Food Waste]] from 2011 onwards this also stimulated the market at the time by making materials available with gate fees payable. The roll-out of [[Food Waste]] collection, however, slowed and the stimulation provided by the [[FIT]] scheme was reduced in 2017, leading to projects relying on the creation of biomethane, which in turn relied on the [[RHI]] (for injection to the gas grid) and [[RTFO]] (for use in vehicles) | |||
With greater focus on the collection of separate [[Food Waste]] from 2011 onwards this also stimulated the market at the time by making materials available with gate fees payable. The roll-out of [[Food Waste]] collection, however, slowed and the stimulation provided by the [[FIT]] scheme was reduced in 2017, leading to projects relying on the creation of biomethane, which in turn relied on the [[RHI]] (for injection to the gas grid) and [[RTFO]] (for use in vehicles) which has generally led to a slowing in the growth of the market. | |||
Depending on the view taken on load factors in operational plants (i.e. the amount of power/gas production vs the plated capacity) there is presently an excess of AD capacity in relation to the feedstocks available to the plants, especially for separately collected [[Food Waste]]. | |||
An analysis of the data provided by National Statistics<ref>https://www.gov.uk/government/statistics/monthly-small-scale-renewable-deployment</ref> for the monthly [[FIT]] commissioned installations over the period of the schemes existence shows an increase from 1 plant prior to 2010 to 427 plants by March 2019, generating 294.9MW of power. | An analysis of the data provided by Office for National Statistics (ONS)<ref>[https://www.gov.uk/government/statistics/monthly-small-scale-renewable-deployment National Statistics: Monthly Small Scale Renewables]</ref> for the monthly [[FIT]] commissioned installations over the period of the schemes existence shows an increase from 1 plant prior to 2010 to 427 plants by March 2019, generating 294.9MW of power. | ||
{| class="wikitable" | {| class="wikitable" | ||
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| Total || 427||100%||294.9||100% | | Total || 427||100%||294.9||100% | ||
|} | |} | ||
The table shows that by 2019, whilst the size of plants were relatively evenly distributed amongst the 3 bands of measurement/scales of plant, the larger scale projects had a | The table shows that by 2019, whilst the size of plants were relatively evenly distributed amongst the 3 bands of measurement/scales of plant, the larger scale projects had a dis-proportionally large installed capacity. | ||
==Number of UK Sites== | ==Number of UK Sites== | ||
At December 2018 | At December 2018 the ONS reported the following key statistics for the number of AD sites generating electricity (extract from table 6F)<ref name = "DUKES"/>: | ||
{| class="wikitable" | {| class="wikitable" | ||
|- | |- | ||
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|Total||419<sup>1</sup>||393||812 | |Total||419<sup>1</sup>||393||812 | ||
|} | |} | ||
# noted as 427 by the [[Ofgem]] reported figures above (these figures appear to be reporting December 2016 figures despite | # noted as 427 by the [[Ofgem]] reported figures above (these ONS figures appear to be reporting December 2016 figures for FIT projects, despite stating December 2018 in the table) | ||
[[ADBA]] maintain the national database of AD plants in the UK as an online tool<ref | [[ADBA]] maintain the national database of AD plants in the UK as an online tool<ref name="Map"/>. The online tool captures those plants which are based on four different feedstock configurations and three different power output configurations. A summary of the total plants listed is set out below, with an extract in the map to the right of MSW/Commercial [[Food Waste]] AD facilities generating electricity: | ||
[[File: | [[File:AD Map Biogas-info.png|800px|thumb|right|AD Map from Biogas-info.co.uk ]] | ||
{| class="wikitable" | {| class="wikitable" | ||
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| Matching Total|| 503 || 42 ||102 || || | | Matching Total|| 503 || 42 ||102 || || | ||
|} | |} | ||
[[ABDA]] most recently suggested<ref>Article in January 2021 for [[MRW]] magazine referring to data</ref> that in 2021 there were 686 [[AD]] plants in operation in the UK and a further 269 in development. | |||
The table below is reproduced from table 4.3 in the Renewable Obligation Annual Report 2017-18 by [[Ofgem]] and shows the consignments reported | ==Feedstock== | ||
The table below is reproduced from table 4.3 in the Renewable Obligation Annual Report 2017-18 by [[Ofgem]] and shows the consignments (i.e. the feedstock flows reported to AD plants, not the number of AD plants) reported as AD against the sustainability criteria required by the [[Biomass Sustainability]] reporting, although those with <1MW are not formally linked to a [[ROC]] issue<ref>[https://www.ofgem.gov.uk/system/files/docs/2019/03/ro_annual_report_2017-18_final.pdf Renewable Obligation Annual Report 2017-18]</ref> : | |||
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|- | |- | ||
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|} | |} | ||
There are currently 100 AD stations with a Greenhouse Gas Emission installed capacity less than 1MW | There are currently 100 AD stations with a Greenhouse Gas Emission installed capacity less than 1MW | ||
The difference between the | The difference between the ONS data and the [[Ofgem]] data above, i.e. 213 sites (adjusted from the 221 sites with the time error data highlighted above), can be inferred to be those AD plants that are producing biomethane rather than electricity (assuming their other datasets align). | ||
The same [[Ofgem]] data shows that the smaller projects are primarily fed by silage, manures and slurries (i.e. Farm based AD). | |||
==References== | ==References== | ||
<references /> | <references /> | ||