“Public opinion is a major obstacle to underground CO2 storage”

The cap­ture and sto­rage of car­bon dioxide is a tech­no­lo­gy that could make it pos­sible to conti­nue using fos­sil fuels during much of the 21^st cen­tu­ry. It par­ti­cu­lar­ly concerns coal, a cen­tral resource for many coun­tries since there are still more than 2,500 ther­mal power plants in the world. This ener­gy is used for the pro­duc­tion of elec­tri­ci­ty and heat (coge­ne­ra­tion) for indus­trial and domes­tic pur­poses. Coal-fired and gas-fired ther­mal power plants are rela­ti­ve­ly abun­dant, affor­dable, avai­lable and loca­ted all over the world. As such, they streng­then the secu­ri­ty and sta­bi­li­ty of ener­gy systems.

Eco­no­my and demo­gra­phics being what they are, the ener­gy tran­si­tion will take time – seve­ral decades at least. While we wait for the green hydro­gen eco­no­my, we must none­the­less conti­nue to live, all the while bat­tling against the green­house effect cau­sed by CO₂ emis­sions. As such, car­bon cap­ture and sto­rage offers a solu­tion to help buy us some valuable time. CO₂ emis­sions represent approxi­ma­te­ly 270 mil­lion tons eve­ry year but today only 0.1% of indus­trial emis­sions are cap­tu­red. Need­less to say, there is work to be done !

Nor­mal­ly, under­ground sto­rage of CO₂ is achie­ved through various methods of phy­si­cal or che­mi­cal cap­ture, and it requires strict geo­lo­gi­cal condi­tions. As such, only very pre­cise geo­lo­gi­cal envi­ron­ments can be used. In par­ti­cu­lar, the geo­lo­gi­cal for­ma­tions must not only be capable of contai­ning the CO₂ but must also prevent late­ral and/or ver­ti­cal migra­tion of the gas. Any leaks could conta­mi­nate potable ground­wa­ter at low depths, infil­trate the ground, or more impor­tant­ly reach the atmosphere.

The geo­lo­gi­cal for­ma­tions used for CO₂ sto­rage are main­ly oil and gas reser­voirs, as well as deep saline aqui­fers found in sedi­men­ta­ry basins. The sto­rage of gas (inclu­ding CO₂) in these envi­ron­ments has been pro­ven to work on a large scale. It can even be per­for­med during oil extrac­tion ope­ra­tions (secon­da­ry reco­ve­ry), natu­ral gas sto­rage, and aci­dic gas removal.

Some of the risks asso­cia­ted with CO₂ cap­ture and sto­rage are simi­lar and com­pa­rable to those of any other indus­trial acti­vi­ty for which safe­ty and regu­la­to­ry pro­to­cols are alrea­dy esta­bli­shed. At the moment, there are only few ope­ra­tions in the world where CO₂ is injec­ted and sto­red in the ground (USA, Aus­tra­lia, Cana­da, Chi­na and UK). Most of the time, if not exclu­si­ve­ly, it is done in the context of an ope­ra­tion moti­va­ted by dri­vers other than cli­mate change, such as oil pro­duc­tion or regu­la­to­ry requi­re­ments for the use of hydro­gen sul­fide (H₂S).

Exis­ting ope­ra­tions show that there is no major tech­no­lo­gi­cal obs­tacle for the geo­lo­gi­cal sto­rage of CO₂. Chal­lenges and blocks thus lie elsew­here. They main­ly stem from the high cost of the ope­ra­tion, par­ti­cu­lar­ly for dilu­ted flows, like those from power plants and indus­trial com­bus­tion processes.

Spe­ci­fic risks asso­cia­ted with CO₂ sto­rage relate to the ope­ra­tio­nal phase (the injec­tion, to put it sim­ply) and the post-ope­ra­tio­nal phase. The grea­test concern is lin­ked with the pos­sible risk of CO₂ lea­kage in the short or long term. Nega­tive effects include the glo­bal cli­mate impact of the return of CO₂ in the atmos­phere, as well as the local health and envi­ron­men­tal risks, which must the­re­fore be cor­rect­ly asses­sed and managed.

The other obs­tacle is the­re­by more media-dri­ven. We are concer­ned that public opi­nion might reject this tech­no­lo­gy and that it could affect the large-scale imple­men­ta­tion of CO₂ geo­lo­gi­cal sto­rage. Indeed, who will accept such a sto­rage site in their town ? The risks asso­cia­ted with the trans­por­ta­tion and injec­tion of car­bon dioxide are rea­so­na­bly well unders­tood. Howe­ver, there exists a small pos­si­bi­li­ty that the CO₂ sto­red under­ground could leak from a reser­voir, either by an uni­den­ti­fied migra­tion path­way, or because of a well defect.

The threat that it could represent must be asses­sed in com­pa­ri­son with vol­ca­nic CO₂ emis­sions, which are natu­ral. Dif­fuse CO₂ emis­sions from the soil or via car­bo­na­ted sources in vol­ca­nic areas do not seem to represent a threat, pro­vi­ded that the CO₂ can dis­perse in the atmos­phere. Howe­ver, CO₂ is dan­ge­rous when it accu­mu­lates in clo­sed spaces. Thus, large clouds of CO₂ lin­ked with sud­den emis­sions coming from vol­ca­nic vents or cra­ters are a dead­ly threat. The Lake Nyos disas­ter in 1986 in Came­roon, which resul­ted in 1,800 deaths from CO₂ asphyxia­tion, serves as a reminder.

Even if few ana­lo­gies exist bet­ween such an event and a pos­sible CO₂ leak from a reser­voir, the risk is not null. This disas­ter is the­re­fore like­ly to come up in the media and will arouse hos­ti­li­ty in popu­la­tions living in proxi­mi­ty of a poten­tial sto­rage site. Murphy’s law will pre­vail over any other consideration.

In this case, only one option remains viable : sto­ring CO₂ in the open sea. In Europe, the Nor­we­gian Sea is often cited. Howe­ver, this does not mean that there would not be any impact in the event of a release of CO₂. Lea­kage of gas under the sea would result in water aci­di­fi­ca­tion around the sto­rage site, with pos­sible damage for fau­na and flo­ra close by. This has been exa­mi­ned in eco­toxi­co­lo­gy stu­dies. But in any case, this CO₂ release – even in the event of a signi­fi­cant leak – would not direct­ly affect human health since it would be under the sea. This is the­re­fore reas­su­ring for the public. Social accep­tance of this alter­na­tive is the­re­fore the only variable capable of acce­le­ra­ting the imple­men­ta­tion of tech­no­lo­gies for redu­cing anthro­po­ge­nic CO₂ emis­sions in the atmosphere.