As filed with the Securities and Exchange Commission on July 5, 2022

Registration Statement No. 333-262431

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Amendment No. 6

to

Form S-4
REGISTRATION STATEMENT

UNDER
THE SECURITIES ACT OF 1933

CLEANTECH ACQUISITION CORP.

(Exact name of registrant as specified in its charter)

207 West 25^th Street, 9^th Floor
New York, NY 10001
(212) 494-9005
(Address, including zip code, and telephone number, including area code, of Registrant’s principal executive offices)

Eli Spiro
Chairman and Chief Executive Officer

CleanTech Acquisition Corp.

207 West 25^th Floor, 9^th Floor
New York, NY 10001

(212) 494-9005

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of this registration statement and the satisfaction or waiver of all other conditions under the Merger Agreement described herein.

If the securities being registered on this Form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box: ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering: ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b–2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

The Registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

CleanTech Acquisition Corp. is filing this Amendment No. 6 to its registration statement on Form S-4 (File No. 333-262431) (the ’‘Registration Statement”) as an exhibits-only filing. Accordingly, this amendment consists only of the facing page, this explanatory note, Item 21 of Part II of the Registration Statement, the signature page to the Registration Statement and the filed exhibits. The remainder of the Registration Statement is unchanged and has therefore been omitted.

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 21. Exhibits and Financial Statement Schedules

SIGNATURES

Pursuant to the requirements of the Securities Act, the registrant has duly caused this Amendment No. 6 to the Registration Statement on Form S-4 to be signed on its behalf by the undersigned, thereunto duly authorized, on the 5^th day of July, 2022.

Pursuant to the requirements of the Securities Act of 1933, this Amendment No. 6 to the Registration Statement on Form S-4 has been signed by the following persons in the capacities and on the dates indicated.

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