Summary of significant accounting policies - Narrative (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) model segment asset_group $ / shares shares	Jan. 31, 2022 $ / shares	Jan. 11, 2022 shares	Oct. 31, 2021 $ / shares	Aug. 10, 2021 $ / shares
Accounting Policies [Abstract]
Number of operating segments | segment	1
Number of reportable segments | segment	1
Restricted cash	$ 9.7
Security deposit	2.9
Restricted cash, bank guarantee for future recycling services	$ 5.5
Number of asset groups | asset_group	2
Long-lived asset, asset group, undiscounted cash flow model, useful life	40 years
Long-lived asset, asset group, remaining useful life	49 years
Long-lived asset, asset group, cash flows supporting carrying value, term	16 years
Number of cash flow models | model	2
Sensitivity analysis of fair value, commodity, favorable change in price, percent	15.00%
Sensitivity analysis of fair value, commodity, adverse change in price, percent	15.00%
Sensitivity analysis of fair value, commodity, favorable change in payables, percent	10.00%
Sensitivity analysis of fair value, commodity, adverse change in payables, percent	10.00%
Sensitivity analysis of fair value, metal recoveries, adverse change in price, percent	5.00%
Sensitivity analysis of fair value, metal recoveries, favorable change in price, percent	5.00%
Sensitivity analysis of fair value, operating costs, favorable change in price, percent	10.00%
Sensitivity analysis of fair value, operating costs, adverse change in price, percent	10.00%
Sensitivity analysis of fair value, construction costs, favorable change in price, percent	5.00%
Sensitivity analysis of fair value, construction costs, adverse change in price, percent	5.00%
Class of warrant or right, number of securities called by each warrant or right (in shares) | shares	1		0.253
Class of warrant or right, exercise price of warrants or rights (in dollars per share) | $ / shares	$ 11.50	$ 11.50		$ 3.57	$ 2.10