12. Stockholders’ equity

At-the-Market (“ATM”) Offering Program

On August 22, 2024, the Company filed a prospectus supplement under its effective shelf registration statement on Form S-3 authorizing an At-the-Market (“ATM”) offering program for the sale of up to $30,000,000 of the Company’s common stock. Under the ATM Sales Agreement (the “Sales Agreement”) with The Benchmark Company, LLC (“Benchmark”), acting as sales agent, the Company may offer and sell shares of its common stock from time to time in transactions that are deemed to be “at-the-market” offerings as defined in Rule 415(a)(4) of the Securities Act of 1933, as amended. Benchmark is entitled to compensation at a rate of 2.5% of the gross proceeds from each sale of common stock under the Sales Agreement. The Company has also agreed to provide customary indemnification and contribution to Benchmark with respect to certain liabilities, including liabilities under the Securities Act. During the nine months ended September 30, 2025, the Company sold 833,219 shares of common stock under the ATM program for net proceeds of approximately $5,921,000, after deducting sales commissions and offering costs. As of September 30, 2025, the Company had utilized the full amount permitted under its Form S-3 “baby shelf” limitations, and therefore had no remaining capacity to issue additional shares under the ATM program until such limitations are refreshed or additional availability becomes eligible.

Equity Line of Credit and Derivative

On May 15, 2025, the Company entered into an equity purchase agreement granting it the right, but not the obligation, to sell up to $10,000,000  of common stock to Lincoln Park Capital Fund, LLC over 24 months, at a discounted purchase price. On June 6, 2025, the Company registered 177,283 shares of common stock that the Company may elect to issue and sell under the ELOC. Additionally, on July 22, 2025, the Company’s shareholders voted to approve, for purposes of complying with Nasdaq Listing Rule 5635(d), the potential issuance and sale of up to $10,000,000 of common stock under the ELOC. Sales under the agreement are solely at the Company’s election and subject to various additional limitations, including pricing formulas, volume caps, and ownership percentage restrictions. The contract was concluded to be a purchased put option equity derivative which does not meet the indexation guidance for the scope exception for contracts in a company’s own equity under ASC 815‑40. As the shares are sold at fair value less a discount the Company has concluded the derivative asset does not have material fair value. During the nine months ended September 30, 2025, the Company issued 177,283 shares of common stock pursuant to the ELOC with Lincoln Park Capital Fund, LLC for net proceeds of $903,000, with approximately $9,097,000 remaining available for future issuance. On October 1, 2025, the Company filed a registration statement on Form S-1 covering the offer and sale, from time to time, of up to 1,000,000 shares of common stock to Lincoln Park under the agreement. During the nine months ended September 30, 2025, the Company also issued 22,717 shares of common stock to Lincoln Park Capital Fund, LLC related to a commitment fee under the ELOC.

Shares issued

During the nine months ended September 30, 2025, the Company issued 46,082 shares of common stock upon vesting of Restricted Stock Units ("RSUs") granted by the Company to management and employees, including 7,636 of reissued treasury stock. We withheld 12,541 shares to satisfy approximately $108,000 of employees’ tax obligations during the nine months ended September 30, 2025. We treat shares of common stock withheld for tax purposes on behalf of our employees in connection with the vesting of RSUs in a similar manner as common stock repurchases and reported as treasury stock. 

During the nine months ended September 30, 2025, the Company issued 5,017 shares of common stock upon vesting of RSUs granted to Board members and 4,568 shares of common stock to Board members related to director fees.

During the nine months ended September 30, 2025, the Company issued 22,717 shares of common stock to Lincoln Park Capital Fund, LLC related to broker fees.

During the nine months ended  September 30, 2024, the Company issued 12,986 shares of common stock upon vesting of Restricted Stock Units ("RSUs") granted by the Company to management and employees, including 4,426 of reissued treasury stock. We withheld 5,225 shares to satisfy approximately $552,000 of employees’ tax obligations during the nine months ended September 30, 2024. We treat shares of common stock withheld for tax purposes on behalf of our employees in connection with the vesting of RSUs in a similar manner as common stock repurchases and reported as treasury stock. 

During the nine months ended  September 30, 2024, the Company issued 2,011 shares of common stock for consulting services.

During the nine months ended September 30, 2024, the Company issued 733 shares of common stock upon vesting of RSUs granted to Board members.

During the nine months ended  September 30, 2024, the Company issued 660 shares of common stock to a former employee related to a severance agreement.

During the nine months ended September 30, 2024, the Company issued 344 shares of common stock pursuant to the employee stock purchase plan.

During the nine months ended  September 30, 2024, the Company issued 517 shares of common stock to Board members related to director fees.

During the nine months ended September 30, 2024, the Company issued 30,605 shares of common stock pursuant to the at the market issuance sales agreement for net proceeds of $2,820,000.

In   May 2024, the Company completed a public offering of 100,625 shares of its common stock at the public offering price of $78 per share. In connection with the sale of common stock, the Company issued warrants to purchase shares of common stock at the rate of one warrant for every share of purchased common stock, at the offering price of $2 per warrant. After the deduction of the underwriter’s discount and expenses payable by us, we received net proceeds of $7,306,000. The Company used the relative fair value method to allocate the net proceeds of approximately $7,306,000 between the common stock and the warrants. As presented below, the Company recorded the fair value of the warrants of $3,081,000 and common stock of $4,225,000.

Warrant issued

In connection with the above-described  May 2024 public offering, the Company issued a warrant to purchase 3,912 shares of the Company's common stock to the underwriter of the Company's public offering, equal to 2% of the shares and the number of shares underlying the warrants sold in the offering, for relative fair value of $0.1 million. The warrants are exercisable at $97.50 per share on the closing date,   May 14, 2024. The warrants have an expiration date of 5 years from the date of issuance and will expire on   May 14, 2029. The relative fair value of the warrants was recorded in the condensed consolidated balance sheet in additional paid-in capital in stockholders' equity as the warrants are indexed to the Company’s common stock and meet the conditions for equity classification.

In  May 2024, in conjunction with the Company's public offering, the Company issued a warrant to purchase up to 100,625 shares of the Company's common stock, for the relative fair value of $3 million. The warrants are exercisable at $78 per share. The warrants have an expiration date of 5 years from the date of issuance and will expire on  May 14, 2029. The relative fair value of the warrants was recorded in the condensed consolidated balance sheet in additional paid-in capital in stockholders' equity as the warrants are indexed to the Company’s common stock and meet the conditions for equity classification.

Stock-based compensation

The stock-based compensation expense was allocated as follows (in thousands):

2019 Stock Incentive Plan

In 2019, our board of directors adopted the Aqua Metals, Inc. 2019 Stock Incentive Plan (the “2019 Plan”). On May 23, 2024, 47,500 shares of common stock were authorized and added to the plan. A total of 140,000 shares of common stock was authorized for issuance pursuant to the 2019 Plan. Subsequently, on July 22, 2025, 260,000 shares of common stock were authorized and added to the plan, bringing the total shares authorized for issuance under the 2019 Plan to 400,000 shares. The 2019 Plan provides for the following types of stock-based awards: incentive stock options; non-statutory stock options; restricted stock; restricted stock units, or RSUs; and performance stock units, or PSUs. The 2019 Plan, under which options  may be granted to employees and directors under incentive and non-statutory agreements, requires that the option price may not be less than the fair value of the stock at the date the option is granted. Option awards are exercisable until their expiration, which may not exceed 10 years from the grant date. 

Restricted stock units

During the first quarter of 2025, the Company granted 535 RSUs to an employee, all of which were subject to vesting, with a grant date fair value of $10,000. The shares vest in three equal installments over a three-year period.

On  October 3, 2024, the Company approved a supplemental retention program designed to retain business-critical resources essential to ongoing operations and strategic initiatives. Participation in the program is contingent upon management achieving specified fundraising targets and subject to the continued service of eligible employees. The program established specific funding tranches tied to cumulative fundraising milestones, which must be achieved on or before  March 7, 2025. The grant terms included a fixed dollar, variable share, structure with potential settlement valued from $0 to $925,014 dependent upon satisfaction of performance conditions. Once performance conditions are met, the shares to be granted are fixed and subject to an additional six-month service condition. During the first quarter of 2025, the first funding tranche was achieved, triggering the issuance of 11,847 RSUs to qualified employees in accordance with the program’s terms. These shares have been granted subject to continued service requirements.

During the first quarter of 2025, the Company granted 2,500 RSUs to an employee, all of which were subject to vesting, with a grant date fair value of $49,000. The shares vest over a six-month period.

During the second quarter of 2025, the Company granted 10,204 RSUs to an employee, all of which were subject to vesting, with a grant date fair value of $100,000. The shares vest in three equal installments over a three-year period.

During the second quarter of 2025, the Company granted 21,739 RSUs all of which were subject to vesting, with a grant date fair value of $250,000 to Board Members. The shares vest in four equal installments over a twelve-month period.

During the second quarter of 2025, the Company granted 4,567 RSUs to Board Members as compensation for board services. These RSUs vested immediately upon grant and had an aggregate grant-date fair value of $85,000, which was recognized as stock-based compensation expense in the period.

During the third quarter of 2025, the Company granted 99,606 RSUs to employees, all of which were subject to vesting, with a grant date fair value of $377,000. The shares vest in three equal installments over a three-year period.

During the third quarter of 2025, the Company granted 11,250 RSUs to an employee, all of which were vested immediately, with a grant date fair value of $46,350.