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Panorama view of countryside with biogas plant. Yellow flowering
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Methanisation: converting CO2 from biomethane plants into useful products

Farah Doumit
PhD student at the Centre for Management Research (I³-CRG*) at École Polytechnique (IP Paris)
Key takeaways
  • Biomethane production emits biogenic CO2 and residual methane, the latter contributing to global warming.
  • To reduce this environmental impact, French regulations require plants to limit their methane emissions to between 0.5% and 1% by 2025.
  • Purifying biogenic CO2 could help to reduce methane emissions: it can be used in a variety of ways to promote a circular economy.
  • Biogenic CO2 can be used in fields as varied as the food industry and medicine.
  • Offering biogenic CO2 at a competitive price while improving the logistics and cost of capture technologies could make it a substitute for CO2 of fossil origin.

Methani­sa­tion, also called anaer­o­bic diges­tion, is a nat­ur­al bio­log­i­cal process where­by mate­r­i­al is bro­ken down by micro-organ­isms. In doing so, it releas­es ener­gy from organ­ic mat­ter. Indus­tri­al methani­sa­tion is the exploita­tion of this process, often in agri­cul­tur­al set­tings, as sus­tain­able source of ener­gy. Whilst methani­sa­tion is still grow­ing in usage, there remain sev­er­al unex­ploit­ed solu­tions to be explored, which could fur­ther improve its envi­ron­men­tal per­for­mance1

Purifying biogenic CO2 to reduce methane emissions 

The bio­gas pro­duced by methani­sa­tion gen­er­al­ly con­tains 50–70% methane (CH4) and around 30–50% CO2. Dur­ing the process that pro­duces the bio­methane, COis sep­a­rat­ed from the gas to deliv­er a flow with high methane con­cen­tra­tion. In this prac­tice of bio­gas purifi­ca­tion, off-gas­es are emit­ted to the atmos­phere. They main­ly con­tain 98% COand 1–2% resid­ual methane2. Accord­ing to the indus­try, this CO2, called bio­genic CO2, does not con­tribute to a net addi­tion of cli­mate gases.

Nev­er­the­less, the resid­ual methane released into the atmos­phere does con­tribute to glob­al warm­ing. There­fore, to reduce the envi­ron­men­tal impact of the plants in France, a new reg­u­la­tion has been issued. It requires bio­gas-to-bio­methane plants to lim­it their emis­sion of methane in the off-gas­es to 0.5–1% by 20253.

To abide by the new reg­u­la­tion, mature tech­nolo­gies (such as cryo-dis­til­la­tion, absorp­tion by sol­vent, pres­sure swing adsorp­tion) are avail­able and allow the sep­a­ra­tion of bio­genic CO2  from the resid­ual methane. Puri­fy­ing the bio­genic CO2  would allow plants to meet objec­tives and enhance the per­for­mance of the plant by rein­ject­ing the resid­ual CH4into the grid. Also, an addi­tion­al vir­tu­ous loop takes place. Indeed, the puri­fied bio­genic COcan be used to cre­ate val­ue through mul­ti­ple outlets.

Circular thinking could create novel synergies in the French market 

Using CO2  in spe­cif­ic set­tings can con­tribute to the cir­cu­lar econ­o­my4. The CO2  can be inject­ed into green­hous­es or applied direct­ly to crops. It can also be used in var­i­ous indus­tri­al appli­ca­tions, such as in the pro­duc­tion of plas­tics, chem­i­cals, and build­ing mate­ri­als like con­crete. COcan also be used for oth­er pur­pos­es, such as in the food and bev­er­age indus­try for car­bon­a­tion, in the med­ical indus­try for imag­ing, and in fire­fight­ing as a dry ice sub­sti­tute. E‑fuels and microal­gae are oth­er poten­tial out­lets that are also being investigated.

There­fore, cap­tur­ing the bio­genic COthat is oth­er­wise emit­ted into the atmos­phere could cre­ate nov­el syn­er­gies between bio­methane plants and COusers and thus pro­vide a sus­tain­able alter­na­tive to fos­sil-based CO2 in prod­ucts. There are sea­son­al ten­sions on the COmar­ket, induc­ing price volatil­i­ty asso­ci­at­ed with short­ages that can great­ly affect some con­sumers. In fact, the mar­ket price of COis high­ly vari­able: approx­i­mate­ly €50 to €200/t5. Thus, hav­ing local bio­genic COpro­duced by french bio­methane plants would make it pos­si­ble to meet these cur­rent challenges.

France is home to Europe’s fastest-grow­ing bio­methane sec­tor6. The num­ber of units pro­duc­ing bio­methane was a lit­tle over 500 at the end of 2022 in France7. There is a grow­ing inter­est in find­ing ways to fur­ther improve sus­tain­abil­i­ty of these plants. Puri­fy­ing bio­genic CO2  would help meet the envi­ron­men­tal guide­lines in 2025 and sub­sti­tute fos­sil-based CO2  use in France. In France, 800 Kt/year of CO2, are con­sumed, of which 70% by the agri-food indus­try8. The poten­tial of bio­genic COthat can be val­orised through these plants has been esti­mat­ed at around 700 to 800 Kt CO2/y. To date in France, less than a dozen bio­methane plants have imple­ment­ed this cir­cu­lar activ­i­ty9,10

Co-creating a circular business model is no simple task

While the poten­tial ben­e­fits of COval­ori­sa­tion in bio­methane plants are sig­nif­i­cant and pro­mote the devel­op­ment of a cir­cu­lar econ­o­my, there are still tech­ni­cal and eco­nom­ic chal­lenges to over­come in France. Depend­ing on the out­let cho­sen and the recov­ery tech­nol­o­gy of CO2, the process will impact the over­all ener­gy effi­cien­cy of the bio­methane chain and the cost of COcap­ture. Also, the biggest user of COin France remains the agri-food sec­tor. Spe­cif­ic qual­i­ty cer­ti­fi­ca­tions, such as the EIGA stan­dard, are need­ed for bio­genic COto be com­pli­ant with this indus­try. Fur­ther­more, in France, bio­methane units have an aver­age pro­duc­tion capac­i­ty of 1.8–2 kt CO2/year, where­as con­ven­tion­al sources of COcan sup­ply up to 200 kt CO2/year. Hence, mutu­al­iza­tion is need­ed in bio­genic COtrans­porta­tion to enhance economies of scale11.

Over the past years, the imple­men­ta­tion of a favourable reg­u­la­to­ry frame­work has sup­port­ed the expan­sion of the French bio­methane sec­tor. Case in point, the reg­u­la­tion to reduce CH4 in off gas­es will help improve its envi­ron­men­tal impact. Addi­tion­al­ly, it might cre­ate a poten­tial mar­ket for bio­genic COthat could sub­sti­tute the fos­sil-based one. Nev­er­the­less, if the process would make sense envi­ron­men­tal­ly, the busi­ness mod­el is still to be cre­at­ed. Efforts are required to co-cre­ate a viable val­ue propo­si­tion. Sure­ly enough, the local demand side is yet to be stim­u­lat­ed. Efforts from indus­tri­al play­ers can be pur­sued to pro­pose bio­genic COat a com­pet­i­tive cost while improv­ing logis­tics and cost cap­ture tech­nolo­gies. Oth­er levers can be iden­ti­fied, such as imple­ment­ing a reg­u­la­to­ry incen­tive for the pro­duc­ers and for the con­sumers of bio­genic CO2. How­ev­er, the lat­ter can be a dou­ble-edged sword because it can deter the reduc­tion of con­ven­tion­al COby imply­ing there is a need from the demand side. Last­ly, indus­tri­al play­ers are inves­ti­gat­ing nov­el finan­cial val­u­a­tion, such as the sell­ing of car­bon cred­its asso­ci­at­ed with the seques­tra­tion of the bio­genic COon the long term, through spe­cif­ic prod­ucts12.

1Bré­mond, U.; Bertran­dias, A.; Stey­er, J.-P.; Ber­net, N.; Car­rere, H. A Vision of Euro­pean Bio­gas Sec­tor Devel­op­ment towards 2030: Trends and Chal­lenges. Jour­nal of Clean­er Pro­duc­tion 2021287, 125065. https://​doi​.org/​1​0​.​1​0​1​6​/​j​.​j​c​l​e​p​r​o​.​2​0​2​0​.​1​25065.
2Cor­do­va, S. S.; Gustafs­son, M.; Eklund, M.; Svens­son, N. Poten­tial for the Val­oriza­tion of Car­bon Diox­ide from Bio­gas Pro­duc­tion in Swe­den. Jour­nal of Clean­er Pro­duc­tion 2022370, 133498. https://​doi​.org/​1​0​.​1​0​1​6​/​j​.​j​c​l​e​p​r​o​.​2​0​2​2​.​1​33498.
3Arrêté du 17 juin 2021 mod­i­fi­ant l’arrêté du 12 août 2010 relatif aux pre­scrip­tions générales applic­a­bles aux instal­la­tions classées de méthani­sa­tion rel­e­vant du régime de l’enregistrement au titre de la rubrique n° 2781 de la nomen­cla­ture des instal­la­tions classées pour la pro­tec­tion de l’environnement – Légifrance. https://​www​.legifrance​.gouv​.fr/​j​o​r​f​/​i​d​/​J​O​R​F​T​E​X​T​0​0​0​0​4​3​7​14543 (accessed 2023-05-08).
4Inter­na­tion­al Ener­gy Agency. Putting CO2 to Use: Cre­at­ing Val­ue from Emis­sions. Sep­tem­ber 2019.
5CTBM. https://​atee​.fr/​e​n​e​r​g​i​e​s​-​r​e​n​o​u​v​e​l​a​b​l​e​s​/​c​l​u​b​-​b​i​o​g​a​z​/ctbm (accessed 2023-05-08).
6Euro­pean Bio­gas Asso­ci­a­tion. Track­ing Bio­gas and Bio­methane Deploy­ment across Europe. 2023.
7Synthese_methanisation_2022_1.Pdf. https://www.methafrance.fr/sites/default/files/2022–11/synthese_methanisation_2022_1.pdf (accessed 2023-05-08).
8ADEME. Val­ori­sa­tion du CO2 Quels béné­fices ? Sous quelles con­di­tions ? Sep­tem­bre 2021.
9L’usine inno­vante de Sanamethan vers une val­ori­sa­tion de Biogaz et de CO2 à bilan car­bone négatif, instal­lée par Clarke Ener­gy. https://​www​.clarke​-ener​gy​.com/​f​r​/​2​0​2​2​/​s​a​n​a​m​e​t​h​a​n​-​b​i​o​g​a​s​-​c​o​2​-​r​e​c​o​v​e​r​y​-​p​lant/ (accessed 2023-05-17).
10Pre­mière en France, Métha­Treil val­orise le CO₂ d’épuration de son bio­méthane – MAGAZINE ET PORTAIL FRANCOPHONE DES BIOÉNERGIES. https://​www​.bioen​ergie​-pro​mo​tion​.fr/​8​9​8​0​1​/​p​r​e​m​i​e​r​e​-​e​n​-​f​r​a​n​c​e​-​m​e​t​h​a​t​r​e​i​l​-​v​a​l​o​r​i​s​e​-​l​e​-​c​o​2​-​d​e​p​u​r​a​t​i​o​n​-​d​e​-​s​o​n​-​b​i​o​m​e​t​hane/ (accessed 2023-05-17).
11GRDF – Pro­jet Méthani­sa­tion | La val­ori­sa­tion du CO2 biogénique issu de l’épuration du biogaz. pro­jet-methani­sa­tion. https://​pro​jet​-methani​sa​tion​.grdf​.fr/ (accessed 2023-05-08).
12Euro­pean Bio­gas Asso­ci­a­tion. Bio­genic CO2 from the Bio­gas Indus­try. Sep­tem­ber 2022.

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