Hot was­hed

Lithi­um is the gold of the 21st cen­tu­ry. The modern world deman­ds its use on a mas­si­ve sca­le, for examp­le in lar­ge-volu­me bat­te­ries. How nice it would be if the crum­bly metal could be extrac­ted from domestic depo­sits. And in an envi­ron­ment­al­ly com­pa­ti­ble way, too. Can that real­ly be true?

Geo­ther­mal power plant in Bruchsal

To cla­ri­fy this ques­ti­on, we made an appoint­ment on site. In Karls­ru­he. With both feet, so to speak, abo­ve the Upper Rhi­ne Gra­ben, which runs through here. And with someo­ne who should know. Pro­fes­sor Jochen Kolb con­ducts rese­arch on this topic at the Karls­ru­he Insti­tu­te of Tech­no­lo­gy (KIT). The expe­ri­en­ced geo­sci­en­tist and mine­ra­lo­gist knows exact­ly what is true about the report that the gold of e‑mobility comes out of the ground in this regi­on vir­tual­ly by itself.

The white gold

Lithi­um does not occur in natu­re in pure form; the alka­li metal is far too reac­ti­ve for that. As pure lithi­um oxi­de, it loo­ks like crum­bly cream cheese. But this reac­ti­ve light metal is in gre­at demand becau­se it gives mobi­le ener­gy sources, i.e. rech­ar­ge­ab­le bat­te­ries, a long and robust life that can be rech­ar­ged again and again. The pro­blem is that it cur­r­ent­ly comes main­ly from Aus­tra­lia or Chi­le and does not necessa­ri­ly enjoy the most envi­ron­ment­al­ly friend­ly repu­ta­ti­on due to its extrac­tion methods. 

Depen­ding on the type, bat­te­ries requi­re about 80 to 130 grams of che­mi­cal­ly pure lithi­um per kilo­watt hour of stored ener­gy. About 10 kilo­grams of the rare metal are instal­led in a Tes­la Model S. The­re are still far too few bat­te­ries that are recy­cled, as the power sources for e‑cars sim­ply last too long. The­re­fo­re, lithi­um must be extrac­ted from eit­her rock (Aus­tra­lia) or bri­ne (Chi­le). Or …

The tre­a­su­re under the Upper Rhine

… it bub­bles up at you. Becau­se the­re are pla­ces in the shell of Mother Earth whe­re ther­mal­ly hea­ted deep water not only relea­ses ener­gy, but also car­ri­es dis­sol­ved lithi­um and ple­nty of other cove­ted sub­s­tan­ces. Exact­ly this situa­ti­on pre­vails in the Upper Rhi­ne Gra­ben. Even the anci­ent Romans knew how to make them­sel­ves com­for­ta­ble here thanks to ther­mal baths.

The­se days, there’s less of a call for a warm foot bath. Ins­tead, the focus is on tap­ping deep lay­ers of rock for geo­ther­mal power plants. In Bruch­sal, the bore­holes reach down to a depth of 2,500 meters, in neigh­bo­ring Alsace a good twice as deep. The­re are geo­ther­mal power plants in Bruch­sal, Land­au, Ins­heim and in Soultz-sous-Soultz, Rit­ters­hof­fen and La Want­zen­au on the French side.

The 160-degree hot water from the depths is tap­ped by means of two bore­holes. In the first bore­ho­le, the hot water is pum­ped upwards and injec­ted back down through a second bore­ho­le at a pres­su­re of up to 50 bar. Ide­al­ly, this is an almost clo­sed cir­cuit, becau­se the hot water relea­ses its ener­gy through a sys­tem of heat exch­an­gers. This is eit­her fed direct­ly into a district hea­ting net­work or used to dri­ve tur­bi­nes that gene­ra­te electri­ci­ty. “Howe­ver, this only makes sen­se if the tem­pe­ra­tures are very high, such as in Ice­land,” says Jochen Kolb. 

Con­vey­ing with filters

Kolb and his team are at their best when it comes to the hot water from the depths. The hot bri­ne con­tains a con­si­derable con­cen­tra­ti­on of lithi­um. Enough to pro­du­ce about 20,000 bat­te­ries each year from just one well for Tes­la, for examp­le. That makes inte­res­ted par­ties sit up and take noti­ce: Tog­e­ther with EnBW, the­re is the Unli­mi­ted pro­ject, which is finan­ced by the BMWi and runs for four years.

Pro­fes­sor Kolb is an expert on depo­sits. Befo­re taking up his pro­fes­sor­s­hip in Karls­ru­he in Octo­ber 2016, he spent ten years working on raw mate­ri­als geo­lo­gy in Green­land. In Karls­ru­he, around 40 peop­le work in his team and con­duct rese­arch on topics rela­ted to the extrac­tion of gold, cop­per, cobalt, rare earths or even lithi­um. “We are an app­lied branch of sci­ence. We deve­lop models that indus­try can use to search for and extract raw mate­ri­als.” In neigh­bo­ring Bruch­sal, Kolb and his col­leagues are on the trail of lithi­um in ther­mal water.

But how do you get the raw mate­ri­al of the ener­gy tran­si­ti­on? Using a bypass sys­tem, the geo­lo­gists want to tap into the cir­cuit of the ther­mal power plant in Bruch­sal. Here, around 30 liters per second flow from the depths through the plant. The water is very sal­ty, car­ry­ing about 150 grams of dis­sol­ved sub­s­tan­ces per liter, about four and a half times more par­ti­cles than in sea­wa­ter, for examp­le. Of the­se, about 160 mil­li­grams are lithi­um. That is much less than in the sali­na­ries of the Andes, whe­re up to 1,000 mil­li­grams are pre­sent. But the high flow rates in the plants, ran­ging from 30 to 70 liters per second, make extrac­tion interesting.

Raw mate­ri­al from the bypass

Initi­al­ly, only a small por­ti­on of this is to be diver­ted and then run through the pilot plant. Lithi­um and other raw mate­ri­als from the natu­ral­ly hea­ted solu­ti­on are che­mi­cal­ly and mecha­ni­cal­ly fil­te­red out here by means of a man­ga­ne­se oxi­de, then the bri­ne flows back into the sys­tem and is pum­ped back to depth. The man­ga­ne­se oxi­de is freed from its lithi­um load and reco­ve­r­ed. The reco­ve­r­ed lithi­um chlo­ri­de can then be used in pre­ci­pi­ta­ti­on reac­tions to pro­du­ce eit­her lithi­um car­bo­na­te or lithi­um hydro­xi­de for bat­te­ry production.

ARTIS-Uli Deck// 12.05.2021 EnBW Geo­ther­mie­kraft­werk Bruchsal 

What worked in the labo­ra­to­ry in a test tube as part of a master’s the­sis must work in a flow-through in the pilot plant. That’s also the big chal­len­ge: “The sys­tem is instal­led down­stream of the heat exch­an­ger, but works with water that is still 60 to 80 degrees hot and lar­ge amounts of unwan­ted solutes. 

For Bruch­sal, we expect lithi­um extrac­tion that should be enough to pro­du­ce a bat­te­ry in an e‑bike every two minu­tes and a Tes­la bat­te­ry every 40 minu­tes or so. Howe­ver, we can­not yet esti­ma­te the size of the depo­sit. We don’t know the con­di­ti­ons under­ground well enough yet that we know when salt reduc­tion will dilu­te the deep water and give us less yield. Howe­ver, we assu­me that the depo­sit will be reco­ver­a­ble for at least 20 years,” says Pro­fes­sor Kolb optimistically.

Pro­fit and loss

Geo­ther­mal ener­gy is usual­ly an addi­tio­nal busi­ness in pla­ces whe­re the­re is no vol­ca­no hea­ting the earth’s crust to the soles of your shoes. “Here in Bruch­sal, it only works with sub­si­dies, becau­se the heat exchan­ge and thus the heat out­put is still too low. The power plant in Rit­ters­ho­fen, Fran­ce, howe­ver, is used to dry crops for a starch fac­to­ry. In Munich, an incre­a­singly lar­ge part of the district hea­ting net­work is cur­r­ent­ly being sup­plied by deep geo­ther­mal ener­gy. It’s working out excel­lent­ly there.”

But it gets real­ly inte­res­ting when the “white gold of elec­tro­mo­bi­li­ty” falls off as a by-pro­duct, so to speak. And with mini­mal impact on the envi­ron­ment. “If you do it right, even the risk of ear­th­qua­kes is safe­ly mana­ge­ab­le.” Com­bi­ne the heat genera­ti­on with the lithi­um yiel­ds from the geo­ther­mal plants, and the eco­no­mic sce­n­a­rio chan­ges drastically.

Pro­fes­sor Dr. Jochen Kolb

This does not always have only posi­ti­ve con­se­quen­ces. The sci­en­ti­fi­cal­ly moti­va­ted gold miner knows all about the hun­ger for rare metals: “The demand for them is a bit like a gold rush. A lot of small com­pa­nies are rus­hing into it, which are some­ti­mes on the edge of respec­ta­bi­li­ty, whe­re the stock mar­ket meets the mar­ke­ting specta­cle. That can work, but it can also be a pure air act.”

So no repre­sen­ta­ti­ve of the auto­mo­ti­ve indus­try has yet to set off for Karls­ru­he: “In EnBW, we have found a part­ner who will work with us to build this first pilot plant, which is sche­du­led to go into ope­ra­ti­on in 2023. If it works, then it will be up to the indus­try to get lar­ger plants up and run­ning. I expect that such a lar­ge-sca­le plant will then requi­re ano­t­her five to ten years of deve­lo­p­ment.” Anyo­ne who is now impa­ti­ent with the oppor­tu­nities that the fire of the earth holds in store in terms of rene­wa­ble ener­gies and new raw mate­ri­als: For geo­lo­gists, who other­wi­se cal­cu­la­te in mil­li­ons of years, this peri­od is a pie­ce of cake!

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