Exhibit 5.1

  Sheppard, Mullin, Richter & Hampton LLP 30 Rockefeller Plaza New York, New York 10112-0015 212.653.8700 main 212.653.8701 fax www.sheppardmullin.com

August 11, 2023

VIA ELECTRONIC MAIL

OPAL Fuels Inc.

One North Lexington Avenue, Suite 1450

White Plains, New York 10601

Re: Registration Statement on Form S-3

Ladies and Gentlemen:

We have acted as counsel to OPAL Fuels Inc., a Delaware corporation (the “Company”), in connection with the shelf Registration Statement on Form S-3 (as amended or supplemented, the “Registration Statement”), originally filed by the Company on August 1, 2023, as subsequently amended, with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”). The Registration Statement relates to the proposed issuance and sale from time to time pursuant to Rule 415 under the Securities Act, as set forth in the Registration Statement, the prospectus contained therein (the “Base Prospectus”) and one or more supplements to the Base Prospectus (each, a “Prospectus Supplement”), and any free-writing prospectus(es), of up to $200,000,000 in aggregate offering proceeds, of the following securities of the Company (collectively, the “Securities”):

● shares of Class A common stock, par value $0.0001 per share, of the Company (the “Common Stock”);

● shares of preferred stock, par value $0.0001 par value, of the Company, in one or more series or classes (the “Preferred Stock”);

● warrants to purchase Common Stock or Preferred Stock (the “Warrants”), which may be issued under warrant agreements (each, a “Warrant Agreement”), to be dated on or about the date of the first issuance of the applicable Warrants thereunder, by and between the Company and a warrant agent to be selected by the Company (the “Warrant Agent”); and

● units consisting of Common Stock, Preferred Stock or Warrants (the “Units”), which may be issued under unit agreements (each, a “Unit Agreement”), to be dated on or about the date of the first issuance of the applicable Units thereunder, by and between the Company and the other parties thereto (the “Unit Parties”).

We are delivering this opinion pursuant to the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.

In connection with this opinion, we have examined and relied upon originals, or copies certified to our satisfaction, of such records, documents, certificates, opinions, memoranda and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below. As to certain factual matters, we have relied upon certificates of officers of the Company and have not independently sought to verify such matters.

In rendering this opinion, we have assumed (i) the genuineness and authenticity of all signatures on original documents; (ii) the authenticity of all documents submitted to us as originals; (iii) the conformity to originals of all documents submitted to us as copies; (iv) the accuracy, completeness and authenticity of certificates of public officials; (v) the due authorization, execution and delivery of all documents where authorization, execution and delivery are prerequisites to the effectiveness of such documents; (vi) that the Registration Statement and any required post-effective amendment thereto have all become effective under the Securities Act and the Base Prospectus any and all Prospectus Supplement(s) required by applicable laws and any and all free-writing prospectus(es) related to the offer and sale of the Securities have been delivered and filed as required by such laws; (vii) that the issuance and sale of the Securities do not violate any applicable law, are in conformity with the Company’s then operative Certificate of Incorporation (as defined below) and Bylaws, do not result in a default under or breach of any agreement or instrument binding upon the Company and comply with any applicable requirement or restriction imposed by any court or governmental body having jurisdiction over the Company or its properties or assets; (viii) a prospectus supplement will have been prepared and filed with the Commission describing the Securities offered thereby; and (ix) a definitive purchase, underwriting or similar agreement with respect to any Securities offered will have been duly authorized and validly executed and delivered by the Company and the other parties thereto, as applicable.

With respect to our opinion as to the Common Stock or other Securities convertible into, exercisable for, or including Common Stock, we have been advised by the Company and for purposes of this opinion we have assumed that, at the time of issuance and sale, a sufficient number of shares of Common Stock are authorized and available for issuance and that the consideration for the issuance and sale of the Common Stock (or for Preferred Stock convertible into Common Stock, or for Warrants exercisable for Common Stock, or Units consisting of or including Common Stock) is in an amount that is not less than the par value of the Common Stock. With respect to our opinion as to the Preferred Stock or other Securities convertible into, exercisable for, or including Preferred Stock, we have assumed that, (a) at the time of issuance and sale, a sufficient number of shares of Preferred Stock are authorized, designated and available for issuance and that the consideration for the issuance and sale of the Preferred Stock (or for Warrants exercisable for Preferred Stock or for Units consisting of or including Preferred Stock) is in an amount that is not less than the par value of the Preferred Stock, and (b) the rights, preferences, privileges and restrictions, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation privileges of each series of Preferred Stock will be set forth in a certificate of designation to be approved by the Company’s Board of Directors, or in an amendment to the Company’s then operative certificate of incorporation (the “Certificate of Incorporation”), to be approved by the Company’s Board of Directors and stockholders, and that one or both of these documents will be filed either as an exhibit to an amendment to the Registration Statement to be filed after the date of this opinion or as an exhibit to a Current Report on Form 8-K to be filed after the Registration Statement has become effective. We have also assumed that (i) with respect to Securities being issued upon conversion of any convertible Preferred Stock, the applicable convertible Preferred Stock will be duly authorized, validly issued, fully paid and nonassessable; and (ii) with respect to any Securities being issued upon exercise of any Warrants or relating to any Units, the applicable convertible Warrants or Units will be valid and legally binding obligations of the Company, enforceable against the Company in accordance with their terms, except as enforcement may be limited by applicable bankruptcy, insolvency, reorganization, arrangement, moratorium or other similar laws affecting creditors’ rights, and subject to general equity principles and to limitations on availability of equitable relief, including specific performance. We have also assumed with respect to the Warrants offered under the Registration Statement, that (a) such Warrants will be issued pursuant to a Warrant Agreement, (b) the Warrant Agreement will be filed either as an exhibit to an amendment to the Registration Statement to be filed after the date of this opinion or as an exhibit to a Current Report on Form 8-K to be filed after the Registration Statement has become effective, and (c) the particular terms of any series of Warrants will be set forth in a supplement to the prospectus forming a part of the Registration Statement. We have also assumed with respect to the Units offered under the Registration Statement, that (a) such Units will be issued pursuant to a Unit Agreement, (b) the Unit Agreement will be filed either as an exhibit to an amendment to the Registration Statement to be filed after the date of this opinion or as an exhibit to a Current Report on Form 8-K to be filed after the Registration Statement has become effective, and (c) the particular terms of any series of Units will be set forth in a supplement to the prospectus forming a part of the Registration Statement.

Notwithstanding anything to the contrary, our opinion herein is expressed solely with respect to the federal laws of the United States and the Delaware General Corporation Law. We express no opinion as to whether the laws of any jurisdiction are applicable to the subject matter hereof. We are not rendering any opinion as to compliance with any federal or state law, rule or regulation relating to securities, or to the sale or issuance thereof. We express no opinions concerning the validity or enforceability of any provisions contained in Warrant Agreements or Unit Agreements that purport to waive or not give effect to rights to notices, defenses, subrogation or other rights or benefits that cannot be effectively waived under applicable law.

On the basis of the foregoing and in reliance thereon, and subject to the qualifications herein stated, we are of the opinion that:

1. With respect to the Common Stock offered under the Registration Statement,provided that (i) the issuance of the Common Stock has been duly authorized by all necessary corporate action on the part of the Company; and (ii) the certificates for the Common Stock have been duly executed by the Company, countersigned by the transfer agent therefor and duly delivered to the purchasers thereof against the requisite payment therefor, which the Company has received, the Common Stock, when issued and sold as contemplated in the Registration Statement, the Base Prospectus and the related Prospectus Supplement(s) and any related free-writing prospectus(es) and in accordance with any applicable duly authorized, executed and delivered purchase, underwriting or similar agreement, or upon conversion of any convertible Preferred Stock in accordance with their terms, or upon exercise of any Warrants in accordance with their terms, will be duly authorized, validly issued, fully paid and nonassessable.

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2. With respect to the Preferred Stock offered under the Registration Statement, provided that (i) the terms and issuance of the Preferred Stock have been duly authorized by all necessary corporate action on the part of the Company; (ii) appropriate certificates of amendment to the then operative Certificate of Incorporation relating to the terms and issuance of Preferred Stock have been duly approved by the Company’s Board of Directors and been filed with and accepted by the State of Delaware; and (iii) the certificates for the Preferred Stock have been duly executed by the Company, countersigned by the transfer agent therefor and duly delivered to the purchasers thereof against the requisite payment therefor, which the Company has received, then the Preferred Stock, when issued and sold as contemplated in the Registration Statement, the Base Prospectus and the related Prospectus Supplement(s) and any related free-writing prospectus(es) and in accordance with any applicable duly authorized, executed and delivered purchase, underwriting or similar agreement, or upon exercise of any Warrants in accordance with their terms, will be duly authorized, validly issued, fully paid and nonassessable.

3. With respect to the Warrants issued under a Warrant Agreement and offered under the Registration Statement, provided that (i) the Warrant Agreement has been duly authorized by the Company and the Warrant Agent by all necessary corporate action; (ii) the Warrant Agreement has been duly executed and delivered by the Company and the Warrant Agent as described in the Registration Statement, the Prospectus and the related Prospectus Supplement(s); (iii) the issuance and terms of the Warrants have been duly authorized by the Company by all necessary corporate action; and (iv) the Warrants have been duly executed and delivered by the Company and authenticated by the Warrant Agent pursuant to the Warrant Agreement and delivered against the requisite payment therefor, which the Company has received, and assuming that the Warrants are then issued and sold as contemplated in the Registration Statement, the Prospectus and the Prospectus Supplement(s), then the Warrants, when issued and sold in accordance with the Warrant Agreement and a duly authorized, executed and delivered purchase, underwriting or similar agreement, will be valid and legally binding obligations of the Company, enforceable against the Company in accordance with their terms, except as enforcement thereof may be limited by applicable bankruptcy, insolvency, reorganization, arrangement, moratorium or other similar laws affecting creditors’ rights, and subject to general equity principles and to limitations on availability of equitable relief, including specific performance.

4. With respect to the Units issued under a Unit Agreement and offered under the Registration Statement, provided that (i) the Unit Agreement has been duly authorized by the Company and the Unit Parties by all necessary corporate action; (ii) the Unit Agreement has been duly executed and delivered by the Company and the Unit Parties as described in the Registration Statement, the Prospectus and the related Prospectus Supplement(s); (iii) the issuance and terms of the Units have been duly authorized by the Company by all necessary corporate action; and (iv) the Units have been duly executed and delivered by the Company and authenticated by the Unit Parties pursuant to the Unit Agreement and delivered against the requisite payment therefor, which the Company has received, and assuming that the Units are then issued and sold as contemplated in the Registration Statement, the Prospectus and the Prospectus Supplement(s), then the Units, when issued and sold in accordance with the Unit Agreement and a duly authorized, executed and delivered purchase, underwriting or similar agreement, will constitute valid and legally binding obligations of the Company, enforceable against the Company in accordance with their terms, except as enforcement thereof may be limited by applicable bankruptcy, insolvency, reorganization, arrangement, moratorium or other similar laws affecting creditors’ rights, and subject to general equity principles and to limitations on availability of equitable relief, including specific performance.

The foregoing opinions are qualified to the extent that the enforceability of any document, instrument or the Securities may be limited by or subject to bankruptcy, insolvency, fraudulent transfer or conveyance, reorganization, moratorium or other similar laws relating to or affecting creditors’ rights generally, and general equitable or public policy principles.

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We hereby consent to the filing of this opinion as an exhibit to the above-referenced Registration Statement and to the use of our name wherever it appears in the Registration Statement, the Base Prospectus, and any Prospectus Supplement. In giving such consent, we do not believe that we are “experts” within the meaning of such term as used in the Securities Act or the rules and regulations of the Commission issued thereunder with respect to any part of the Registration Statement, including this opinion as an exhibit or otherwise.

This opinion is expressed as of the date hereof unless otherwise expressly stated, and we disclaim any undertaking to advise you of any subsequent changes in the facts stated or assumed herein or of any subsequent changes in applicable laws.

Very truly yours,

/s/ SHEPPARD, MULLIN, RICHTER & HAMPTON LLP

SHEPPARD, MULLIN, RICHTER & HAMPTON LLP

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